Godwits and godwiteers

This blog tells a few stories about individual colour-ringed Black-tailed Godwits and the ‘godwiteers’ who watch them on the estuaries of the east coast of England. They’re part of an international network of 2000 birdwatchers, contributing to some fascinating science. 

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The dots on graphs within scientific papers hide fascinating stories about individual birds. With the help of a small number of colour-ring readers, here’s an opportunity to eschew the statistics and to focus on a few of the Black-tailed Godwits that have been recruited to help answer scientific questions. The next colour-ringed godwit that you spot may have been hundreds of miles away just 24 hours ago or could break the longevity record for the species of 25 years. At the end of this blog there’s a list of 18 published papers, most of which could not have been written without the help of colour-ring observers – our ‘godwiteers’.

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WeBS data from 2009-14 illustrate how numbers change over the winter season (figures not adjusted to reflect a few gaps in coverage)

Over the last two decades, Dudley and Carol Hird have seen over 500 individual colour-ringed Black-tailed Godwits in Kent, Graham Catley has witnessed a huge expansion of the wintering flock on the Humber, David and Pat Wileman have co-ordinated daily counts and sightings at Cley, while Simon & Pat Cox, Ed Keeble and Mark Nowers have collected data in Essex – and turned the Mistley flock on the Stour estuary into an open-air migration display for the public.

There has been a fantastic rise in the number of Black-tailed Godwits on the east coast of England since the 1990s. Work led by Prof Jennifer Gill and published in Nature in 2001 showed that this expansion was an example of a buffer effect, with newly colonised winter sites being of lower quality than sites further south in the range. As you will read, winter flocks rarely experience the bitingly-cold weather that they did twenty years ago and birds have learned to take advantage of feeding opportunities on grassland, particularly on the Ouse Washes. Life on the east coast may well now be easier than it once was but it is still a lot colder than the sunny conditions experienced by godwits wintering in Portugal, for instance, as shown in this paper in Ecology.

Graham Catley on the Humber estuary

Graham has witnessed a huge expansion in the number of Black-tailed Godwits on the Humber. Many of the birds that are seen on this estuary in autumn and early winter turn up at Welney, on the Ouse Washes, in the period February through to April, where they moult into their summer finery prior to a migration of more than 1500 km to Iceland.

My old notebooks tell me that I saw 11 Black-tailed Godwits at North Killingholme Haven pits on August 20th 1969 but it was autumn 1989 before there were more than 50 recorded. Little did we know at that time just how things would change over the next 27 years. In autumn 1995 the peak count at North Killingholme was 178 on August 28th but significantly on that date I saw a bird with colour rings. Subsequent enquiries revealed that it had been ringed on the Eden Estuary in Fife in 1993 – and a second bird was seen the following week from the same scheme. In 1996 new birds were seen from a scheme in the Wash and my first contact was made with Jenny Gill, who has furnished me with detailed ringing and recovery information on what are now over 300 different birds seen on the Humber since those initial sightings. Autumn passage can see a high tide roost of up to 6400 birds at North Killingholme (probably about 10% of the Icelandic population) but seeing leg rings can be problematic, as birds often stand in deep water and flocks are spooked by local Sparrowhawks and Peregrines.

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This juvenile bird was ringed in northern Iceland on 17 July 2007 and photographed at Killingholme 2 months later. It returned to Iceland in 2009, to breed in the next fjord.

The Humber Estuary started to hold wintering birds in the late 1980’s and now there are up to 2500 birds from November through to February. Checking colour-ringed birds has shown us that there are complex movements of birds around the estuary but also around Europe. Some of our autumn birds appear for quite short periods before moving on south while others seem to move to the Wash and then come back up to the Humber for the winter. Many wintering birds move south to the Ouse Washes in late winter and early spring, before heading off for Iceland, while others have been shown to move cross-country to Lancashire and Ireland. We’ve seen individuals from schemes in Portugal, France, Ireland, Scotland, Suffolk, Hampshire and of course the Wash and Iceland. It is always great to catch up with a bird you have not encountered for a few years and bumping into individuals with new types of rings or combinations begs the question – is it from a new scheme or have they run out of combinations?

In practical conservation terms, observing the colour-ringed godwits on the Humber has provided a large amount of information on the birds’ favoured roosting and feeding areas and how different individuals use the estuary during the course of the year. It also adds a little spice to a day’s birdwatching – trying to get an accurate count of a large and mobile flock of charismatic waders, identifying old friends and new acquaintances and finding out what other exotic and not-so-thrilling parts of the continent they have visited on their phenomenal migrations.

David & Pat Wileman at Cley, Norfolk

Working our way south, the next site with a long-run of colour-ring sightings is Cley, on the North Norfolk coast. Not only do David & Pat Wileman collect daily counts and observations, they also record individual moult patterns, as birds change in and out of their summer plumage.

There’s already a blog about the Black-tailed Godwits of Cley here.

Godwit moulting

Three pictures of the same bird at Cley, moulting out of its breeding plumage. Photographs by Chris Cook, Pat Wileman & Richard Chandler

Ed Keeble on the Stour estuary, Essex

Ed Keeble is one of an enthusiastic team of colour-ring readers on the Stour. He combines observations with photography and evocative art-work. The Stour held large flocks of waders long before sites such as the Wash and Humber, with birds using the estuary in the autumn, winter and spring.

I’m lucky enough to have have been born and bred on a farm on the banks of the Stour, so my earliest birding memories are of watching godwits roosting on our fields in the mid -1970s, through a leather-bound brass telescope . We were very proud of the godwits because, at that time, the Stour flock was one of only two in the UK that regularly approached 1000. With no colour-rings we knew very little about them. The godwits used to endure ferocious winter weather in those days. I’ve even seen them “legless”- flying with their legs folded forward into their breast feathers to conserve heat.

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White rings can sometimes look orange, due to staining

Fast forward to the present day and I am still birding intensively on the Stour, but with improved optics. I had noticed colour-rings on the godwits for many years but had assumed that there were some scientists somewhere who busied themselves reading them and therefore that there was nothing to report. The moment of revelation for me was a talk by Jenny Gill, when I was surprised to hear that the scheme was dependent on public sightings and that we were positively encouraged to pester her, Pete Potts and other colleagues with sightings!

One of the most rewarding aspects of reading colour-rings on the Stour at Mistley is how common it is to find a casual birdwatcher who has seen a ringed godwit, has sent the sighting in and been absolutely thrilled to get an email back with details.  I’ve been told countless times with great pride that “I got an email back from a professor and my godwit came from Iceland.”   There’s no doubt that one of the things which sets this scheme apart is the prompt response to sightings and the willingness to spend time unravelling confused and inconsistent ring-readings from the likes of me. This must take ages, but generates a great deal of goodwill.

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YO-B/B connected university friends in Scotland and England

One of my favourite regulars is a bird I know as the Yob (Yellow Orange – Blue over Blue), who was ringed by an old University friend in Scotland and sent down south for my entertainment. I’m still very much in my apprenticeship when it comes to the dark arts of colour-ring reading, but beginning to learn the difference between faded red and orange, and that things which look orange or yellow may in fact be stained white.

One of the most fascinating local insights from the colour-ring returns is the number of godwits using the Stour.  Based on counts of flocks alone, we know that we have about 1,000 wintering in a normal season.  But, with over 50 colour-ringed individuals per year, we have learned that there is a high degree of turnover and that the river is probably used by more than 3,000 birds, including those stopping over in the autumn on the way to France, Portugal or Spain.  We also get periodic influxes of 1000 birds or more when the Ouse Washes flood in the winter. So, whilst we may not offer top-grade wintering habitat (not enough wet meadows), we are a very much a hub for godwits on the move.

Mark Nowers on the Stour estuary, Essex

Mark is one of many UK-based colour-ring readers to have followed the Black-tailed Godwits to Iceland. He happily shares his love of the birds with the many promenade-walkers, birdwatchers and swan-feeders at Mistley, engaging them with stories of the travels of ringed individuals – a bit like the Ancient Mariner, who ‘stoppeth one of three’.

Black-tailed Godwits have taken over my ornithological life since moving to work and live around the Stour Estuary in 2002. It was obvious from very early on that dedicated people were spending a great deal of time and effort ringing these birds and I felt honour-bound to let them know what I was seeing.

The platform for watching Godwits is Mistley, which is so good that the RSPB ran engagement events there for several years. Mistley is a popular promenade so, as well as people with a specific interest turning up, we have also collared passers-by who showed the merest hint of interest. It only took a few moments, having begun to explain the godwits’ migration story, for them to realise that it was worth their while stopping. We were able to crystallise things with the story of “Billy the Boomerang” (he keeps coming back!) – or LY-YW to his ringing friends. Almost without fail, every autumn and spring he reappears on the Stour Estuary; between times he spends the mid-winter period with Dudley & Carol Hird in Kent.

LYYW

LY-YW – photographed on the Stour by Liz Cutting, appearing in Mark Nower’s Iceland notebook in April 2004 and digi-scoped by Jenny Gill in April 2008, to illustrate a BBC blog

In 2004, I spent a week in Iceland with Pete Potts and a godwit ringing and resighting team. On the 20th April, one of the birds seen was our friend “Billy” from Mistley. Four years later, in 2008, I saw ‘Billy’ on 14th April at Mistley and he was seen by Jenny Gill and Graham Appleton at Eyrarbakki, on the south coast of Iceland, four days later. His arrival was described in a live broadcast by Graham for the World on the Move BBC radio series. Billy was ringed as an adult on The Wash in 1998, so being at least two years old at the time of ringing, he is currently 19 and still going strong. I know that, among the godwit ringing community, this is quite a regular occurrence but to the wider public, when you tell the story of the very same bird that you have seen in two different countries, the look of disbelief and amazement says it all.

Simon & Pat Cox on many Essex estuaries

As a ringer with some 55 years of experience, Simon Cox realises just how valuable each report of a ringed bird can turn out to be.  Working with his wife, Pat, makes it significantly easier to collect data from big flocks of birds.

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Team photo: Pat & Simon Cox, Mark Nowers & Ed Keeble. [Most colour-ring readers will be jealous of the facilities on offer at Mistley]

The Essex coast is a very convenient base for watching Black-tailed Godwits, as our estuaries hold some 4,000 to 5,000 birds in winter (out of an estimated total of only 50,000 Islandica birds – Bird Study, 2005) and higher numbers during peak spring and autumn passage. The Stour, Colne and Blackwater estuaries have been my principal ‘godwit sites’ and I have to date recorded over 300 colour-ringed individuals, with just a few at more distant locations on my various travels, usually accompanied by my wife Pat, who has been very helpful in spotting ringed birds, especially when we have been confronted by a large flock all feeding actively in various depths of water! We sometimes take turns in keeping a ‘scope’ fixed on those frustrating birds that stand on one leg so that the full colour combination is only partly visible!

We find the movements of individuals fascinating, especially when the precise timing of the movements can be demonstrated:

GO-OfW  Green orange – orange-flag white was ringed in France near La Rochelle on 23/09/09 and had been seen on 30 more occasions, twice in Iceland and the remainder in France before I saw it in Alresford Creek on 27/07/14. Vincent Lelong kindly emailed me to say it was back in France the following day.

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R8-GW

WO-L/W  I recall Jenny Gill asking me the time of my sighting of white orange – lime over white in Alresford Creek on 22/09/05. It transpired that approximately three hours earlier it had been at Freiston Shore, on the Lincolnshire section of The Wash!

R8-GW  Red eight (on white) – green white has been seen several times on the Blackwater. He winters on the Exe estuary in Devon but visits Kent during spring and autumn passage, which seems a long way round to get to and from Iceland but works for him.

Dudley and Carol Hird in Kent

The southeast corner of England is an interesting area in which to observe the comings and goings of Black-tailed Godwits. The proximity to French estuaries and position on flightlines between Iceland and Spain/Portugal add extra possibilities for godwit watchers. Many people have provided sightings from this area but Dudley and Carol Hird are the godwiteers par excellence.

On June 29th 2006 we sighted OR-W//W at Oare Marshes and reasoned that this must have been ringed for some scientific purpose and that we should check it out and report it.  Thank goodness for the Internet in helping us to find the source and setting us on the path to over 5,000 colour ring combination sightings of a range of species, up to the end of 2015.  As time went on we realised it was useful, even important, to understand the different schemes in use by ringers if we were to play our part in the study of migration.

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Feeding godwits on the rising tide at Conyer, on the Swales Estuary, with Elmley on the far shore (Dudley Hird)

We are lucky, here in Kent, in having a beautiful estuarine system at Oare and Conyer on the Swale, Funton and the whole Motney Hill area on the Medway and the large Allhallows area on the Thames, which can all contain large numbers of waders throughout the year.  Our main concern is with the Black-tailed Godwits, as Kent must be of major importance to them on passage and over-wintering.  Oare is primarily a roost site (much harder to check for rings) while all our other sites are used for feeding (both legs in full view).

With the help of Pete Potts, godwits have been caught and colour-ringed by Swale Ringing Group in Kent; at Kingsnorth Power Station on the Medway estuary and on the Swale estuary at Harty.  As a consequence of this, nearly 40% of our sightings are of Kent colour-ringed godwits.  It is quite exciting in that they ring one day at Harty and we see them the next day at Oare.

Our total number of individual Black-tailed godwit sighting records cover 479 individual birds, which must mean our estuaries service a lot of godwits in total.  In addition to the Kent-ringed birds, 23% have been ringed in Iceland, 10% in France and 10% on the Solent.  We also have sightings of godwits from Norfolk, Lincolnshire, Suffolk, Devon, Scotland, Northern Ireland, Portugal, Spain and the Netherlands.

One very interesting godwit was Y8-WG sighted at Oare on July 16th 2012. This adult male was in active primary moult when ringed in Iceland on July 10th, just six days previously. He had flown nearly 2,000 km with only seven out of ten main primary flight feathers – an extraordinary feat of migration.  He obviously came to no harm as we have seen this bird back in 2013, 2014 and 2015.  We have never seen this bird on Spring passage and, to our knowledge, do not know where it winters or the route it takes back to Iceland. There’s still plenty to find out.

As I write this, in January, we are approaching one of our busiest times, with godwits arriving from the south and staying for nearly three months, as they build up to almost full breeding plumage before departing towards the end of April to their breeding grounds in Iceland.  It will be exciting to see which birds have returned to Kent again.

John Parslow on the Ouse Washes

The flooded grassland of the Ouse Washes attract thousands of Black-tailed Godwits, especially in the late winter and early spring.

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Well-used field guide

There will be a separate blog about this critical area in due course but we would like to pay tribute to John Parslow (one of the authors of the Heinzel, Fitter & Parslow field-guide, published in 1972), who was the area’s most prolific colour-ring reader for over a decade.  John passed away in November 2015, having spent many a winter day scanning flocks of Black-tailed Godwits, particularly at Fen Drayton, which is not an easy site to work. He has left behind over 1600 records of nearly 300 individual godwits, which is a significant part of the database for the Ouse Washes. His data live on.

Sharing the science

Here’s a list of papers to which colour-ring readers have contributed – so far. Each one comes with a link to the paper:

  1. Gill, J.A., Norris, K., Potts, P.M., Gunnarsson, T.G., Atkinson, P.W. & Sutherland, W.J. (2001) The buffer effect and large-scale population regulation in migratory birds. Nature, 412, 436-438. DOI: 10.1038/35086568
  1. Gunnarsson, T.G., Gill, J.A., Sigurbjörnsson, Þ. & Sutherland W.J. (2004) Arrival synchrony in migratory birds. Nature, 431, 646-646. DOI: 10.1038/431646a
  1. Gunnarsson, T.G., Gill, J.A., Potts, P.M., Atkinson, P.W., Croger, R.E., Gélinaud, G., Gardarsson, A. & Sutherland, W.J. (2005) Estimating population size in Icelandic Black-tailed Godwits Limosa limosa islandica by colour-marking. Bird Study, 52, 153-158DOI: 10.1080/00063650509461385
  1. Gunnarsson, T.G., Gill, J.A., Petersen, A., Appleton, G.F. & Sutherland, W.J. (2005) A double buffer effect in a migratory population. Journal of Animal Ecology, 74, 965-971. DOI: 10.1111/j.1365-2656.2005.00994.x
  1. Gunnarsson, G., Gill, J.A, Newton, J., Potts, P.M. & Sutherland, W.J. (2005) Seasonal matching of habitat quality and fitness in migratory birds. Proceedings of the Royal Society of London B, 272, 2319-2323. DOI: 10.1098/rspb.2005.3214 
  1. Gunnarsson, G., Gill, J.A., Appleton G.F., Gíslason H., Gardarsson, A., Watkinson, A.R. & Sutherland, W.J. (2006) Large-scale habitat associations of birds in lowland Iceland: implications for conservation. Biological Conservation, 128, 265-275. DOI 10.1016/j.biocon.2005.09.034 
  1. Gunnarsson, T.G., Gill, J.A., Atkinson, P.W., Gélinaud, G., Potts, P.M., Croger, R.E., Gudmundsson, G.A., Appleton, G.F. & Sutherland, W.J. (2006) Population-scale drivers of individual arrival times in migratory birds. Journal of Animal Ecology, 75, 1119-1127. DOI: 10.1111/j.1365-2656.2006.01131.x
  1. Gunnarsson, T.G., Gill, J.A., Goodacre, S.L., Gélinaud, G., Atkinson, P.W., Hewitt, G.M., Potts, P.M. & Sutherland, W.J. (2006) Sexing black-tailed godwits: a comparison of behavioural, molecular, biometric and field-based techniques. Bird Study, 53, 193-198. DOI: 10.1080/00063650609461433
  1. Gill, J.A., Langston, R.H.W., Alves, J.A., Atkinson, P.W., Bocher, P., Vieira, N.C.,  Crockford, N.J., Gélinaud, G.,  Groen, N., Gunnarsson, T.G., Hayhow, B., Hooijmeijer, J., Kentie, R., Kleijn, D., Lourenço, P.M., Masero, J.A., Meunier, F., Potts, P.M., Roodbergen, M., Schekkerman, H., Schröder, J., Wymenga, E. & Piersma, T. (2008) Contrasting trends in two Black-tailed Godwit populations: a review of causes and recommendations. Wader Study Group Bulletin, 114, 43-50. 
  1. Alves, J.A., Lourenço, P.M., Piersma, T., Sutherland, W.J. & Gill, J.A. (2010) Population overlap and habitat segregation in wintering Black-tailed Godwits. Bird Study, 57, 381-391. DOI: 10.1080/00063651003678475 
  1. Gunnarsson, T.G., Sutherland, W.J., Alves, J.A., Appleton, G.F., Potts, P.M., & Gill, J.A. (2012) Rapid changes in the distribution of phenotypes in an expanding population of a migratory bird. Proceedings of the Royal Society of London B, 279, 411-416. DOI: 10.1098/rspb.2011.0939 
  1. Alves, J.A., Gunnarsson, T.G., Potts, P.M., Gélinaud, G., Sutherland, W.J. & Gill, J.A. (2012) Overtaking on migration: does longer distance migration always incur a penalty? Oikos, 121, 464-470. DOI: 10.1111/j.1600-0706.2011.19678.x 
  1. Alves, J.A., Sutherland, W.J. & Gill, J.A. (2012) Will improving wastewater treatment impact shorebirds? Effects of sewage discharges on estuarine invertebrates and birds. Animal Conservation, 15, 44-52. DOI: 10.1111/j.1469-1795.2011.00485.x 
  1. Alves, J.A., Gunnarsson, T.G., Hayhow, D.B., Potts, P.M., Sutherland, W.J. & Gill, J.A. (2013) Costs, benefits and fitness consequences of different migratory strategies. Ecology, 94, 11-17. DOI: 10.1890/12-0737.1
  1. Alves, J.A., Gunnarsson, T.G., Potts, P.M., Sutherland, W.J. & Gill, J.A. (2013) Sex differences in distribution and resource use in a sexually-dimorphic migratory shorebird. Ecology and Evolution, 3, 1079-1090. DOI: 10.1002/ece3.503 
  1. Gill, J.A., Alves, J.A., Sutherland, W.J., Appleton, G.F., Potts, P.M. & Gunnarsson, T.G. (2014) Why is timing of bird migration advancing when individuals are not? Proceedings of the Royal Society of London B, 281, 20132161. DOI: 10.1098/rspb.2013.2161 
  1. Gill, J.A. (2015) Encountering extreme weather during migration: individual strategies and their consequences. Journal of Animal Ecology, 84, 1141-1143DOI: 10.1111/1365-2656.12412 
  1. Gunnarsson, T.G., Arnalds, O., Appleton, G.F., Méndez, V. & Gill, J.A. (2015) Ecosystem recharge by volcanic dust drives large-scale variation in bird abundance. Ecology & Evolution, 5, 2386-2396. DOI: 10.1002/ece3.1523 

Please send reports of colour-ringed Black-tailed Godwits to Jenny Gill (j.gill@uea.ac.uk). She will reply with full details of any birds ringed on the Wash or forward your e-mail to colleagues running other schemes.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

 

Prickly problems for breeding waders

Spoiler alert – hedgehogs are the killers

Machair thinner (JC)

Hedgehogs – an unwelcome addition to the unique machair habitat  (Photo: John Calladine)

The chain of Hebridean islands from the northern tip of North Uist to the southern tip of South Uist are special places to visit in the summer. Nowhere else in the UK will you find higher concentrations of breeding waders. In 1983, Fuller et al. estimated that this region held a third of the UK’s breeding Dunlin and a quarter of its Ringed Plover. (Populations of breeding waders and their habitats on the crofting lands of the Outer Hebrides)

Catley Hedgepig

Photo: Graham Catley

The islands are still special but, as a consequence of the spread of hedgehogs, following the introduction of just seven individuals in 1974, numbers of breeding birds have dropped dramatically. The addition of this extra predator, which can feed by day and night and possesses a coat of spines that can withstand aerial attacks by parent birds, has long been associated with the decline.  But how much of the blame lies with the hedgehog and what can be done to support wader populations?

Brief history

close up RP TGG

A quarter of the UK’s breeding Ringed Plover nest within the Outer Hebrides (Tómas Gunnarsson)

The Outer Hebrides, in north west Scotland, used to be a haven for breeding waders, many of which nest on machair, fertile coastal grasslands along the west coast.  It’s a mosaic of habitats that includes arable and pastoral farmland, pools and sand dunes. The waders that nest here have been subject to predation, from gulls, corvids, rats etc. but the hedgehog was an unwelcome addition. With no foxes or badgers to eat them, no fleas to carry diseases and a good supply of easily-accessible eggs, hedgehogs have thrived and spread.

Work in 1998, led by Digger Jackson, showed that the hatching success for Dunlin, Lapwing, Redshank and Snipe clutches was 2.4 time higher in areas from which hedgehogs had been excluded. This was published in the Journal of Applied Ecology in 2000.

Breeding waders were surveyed in 1983, when hedgehogs were restricted in their distribution to small parts of South Uist. By the time of the next extensive survey in 2000, hedgehogs were well-established across South Uist and Benbecula, and the first individuals had reached the southern end of North Uist Uist. In just 17 years, numbers of breeding waders declined by 39% in the areas with hedgehogs, while there was an increase of 9% in North Uist. There were differences for all wader species but particularly for Redshank and Lapwing. The results were published in Biological Conservation in 2004. A subsequent control programme, to assess whether eradication might be a practical option, was expected to arrest the decline in wader numbers and promote recovery. Sadly, population levels have not recovered as well as expected which begs the question – ‘are hedgehogs the only problem?’

Further large-scale surveys were carried out in 2007 and 2014

Walking transect cropped (JC)

Rob Fuller, walking a transect (John Calladine)

The 2007 survey is written up in Bird Study. (Changes in the breeding wader populations of the machair of the Western Isles. Scotland, between 2000 and 2007).

The 2014 survey is written up in Scottish Birds (Calladine, J., Humphreys, E.M. & Boyle, J. (2015). Changes in breeding wader populations of the Uist machair between 1983 and 2014. Scottish Birds 35: 207-215).

In the period between 1983 and 2014, the greatest overall proportional declines were of Dunlin and Ringed Plover (72% and 70% respectively). Snipe declined overall by 45% and Lapwing by 14% while, in contrast, Redshank increased by 8% and Oystercatcher by 74%. The changes were not the same in the zones with and without hedgehogs. The deviation in trends was most marked for Redshank (which increased by 91% in the northern zone, with fewer hedgehogs, while decreasing by 22% in the southern zone) and Snipe (much bigger decreases in the south). Dunlin and Ringed Plover declined markedly in both zones, though less so in the northern zone. Any difference in trends was less apparent for Lapwing, although it did appear that they may have fared less well in the southern zone.

Are hedgehogs the main problem?

Predation event 1 (SNH video grab)

A hedgehog ignores nest defence efforts of pair of Lapwing (screen-grab from SNH surveillance camera)

A report, prepared for Scottish Natural Heritage by a consortium comprising the British Trust for Ornithology, the James Hutton Institute and MacArthur Green Ltd., aims to quantify the importance of predation by hedgehogs, relative to that by other predators.  The report includes a summary of the changes in numbers for the various wader species during a forty-year period, based on occasional broad-scale surveys and more regular monitoring of specific study sites.  The focus, however, is on results from studies using nest cameras, temperature loggers and fixed point observations in the 2012, 2013 and 2014 breeding seasons, measures of disturbance, transect work to assess productivity, and some land use and habitat recording.

report coverCalladine, J., Gilbert, L., Humphreys, E.M., Fuller, R.J., Robinson, R.A., Littlewood, N.A., Mitchell, R.J., Pakeman, R.J. & Furness, R.W. 2015. Predation studies on breeding waders of the Uist machair: Final report covering fieldwork undertaken in 2012-14. Scottish Natural Heritage Commissioned Report No. 811. 

 

Hog on machair (JC)

A hedgehog in the half-light (John Calladine)

The principal aim of the study was to quantify the importance of predation by hedgehogs, relative to that by other predators, work that could support arguments in favour of continued and enhanced removal of these introduced predators. Cost-effective solutions may require lethal control, instead of or in addition to translocation. These are tricky decisions, especially when considered alongside the rapid decline in numbers of hedgehogs across much of the UK.

Main findings

survival table

Clutch survival rates

The latest study provides further evidence that predation by hedgehogs is having an ongoing impact on breeding success of wader nest on the Uist machair, at least some of which is additional to that of gulls, which take both eggs and chicks.

In North Uist (low density of hedgehogs) clutch survival rates were higher than on South Uist (high density of hedgehogs) for the four main study species – see table. Overall, in North Uist, 74% of

predation table

Confirmed and probable causes of predation

wader nests, where outcome was confirmed, successfully hatched chicks.  In South Uist only 45% of nests successfully hatched chicks.  Most observed losses in both areas were due to predators.

Hedgehogs were the most numerous nest predators identified using nest cameras and other evidence, accounting for over half of occurrences, with all confirmed instances of predation by hedgehogs occurring in the ‘high hedgehog density’ areas. In these high density areas, hedgehogs were responsible for 35% of nest failures. Although summer nights are shorter than in much of the UK, 45% of clutch incubations ended during darkness in high hedgehog density areas, compared to 29% in low density areas, again suggesting that mammals are the main predators, with hedgehogs the most likely culprits.

Predation event 2 (SNH video grab)

This Common Gull takes an egg – and may be back for more (screen-grab from SNH surveillance camera)

Although avian predators (gulls, raptors and corvids, which are diurnal predators) were recorded most frequently in the high hedgehog density areas, observers did not find a difference in the frequency of predation attempts by avian predators between these areas and areas with fewer hedgehogs. The number of successful attacks by avian predators witnessed during fixed point observations was small (24 in 460 hours of observations spread over three years) and more successful avian predation events were recorded in low hedgehog density areas (n = 15) than in high hedgehog density areas (n = 9), despite lower abundance of avian predators in the low hedgehog density areas. There is a suggestion that avian predation may, to some extent, replace hedgehog predation in areas with low hedgehog density, especially at the chick stage, but this interpretation is based on a small sample size.

Other potential causes of wader declines may be associated with land use changes within the machair. These are discussed in a 2014 Bird Study paper by Calladine et al.

Conclusions

hog-predated nest (David MacLennan)

Evidence of hedgehog predation (David MacLennan)

It is pretty clear that hedgehogs are causing significant problems for nationally and internationally important populations of breeding waders, two of which are red listed species of conservation concern (Lapwing and Ringed Plover) and the rest of which are amber-listed.  It is also clear that efforts to control hedgehogs have had limited success.

Eradication is a contentious issue. Hedgehogs may have been introduced but, having become established on the Uists, the species has attracted significant support from a number of animal protection organisations, members of which don’t want lethal control methods to be employed. Translocation – the current control method – is a costly alternative.

SNH has demonstrated a political will to try to tackle the hedgehog issue and has applied to the EU for funding for an eradication programme. There’s more about the Uist Wader Project  on the Scottish Natural Heritage website.

Given current financial constraints, EU funding seems to be the most likely way to deal with this man-made predation issue. Any eradication programme may rely on proving that translocated hedgehogs survive. If they don’t, then there is probably a choice between using lethal control or further losses of red-listed and amber-listed wader species. At that point, is there going to be the political resolve to embark on a plan to remove all of the hedgehogs? Wader biologists hope that funding can be found to tackle this prickly issue.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Tracking waders on the Severn

Birdwatchers are being asked to help with some cutting-edge science, simply by reporting sightings of colour-dyed Dunlin and colour-ringed Curlew and Redshank.

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The Severn: an empty estuary or a food-rich haven? (Corinna Blake)

The tides that create unique feeding opportunities for waders and other waterbirds on the Severn can potentially be harnessed to produce large amounts of clean energy. New impact assessment work aims to see how a development that would bring big benefits to the local economy might be carried out with as little negative environmental side-effects as possible.

Colour ringed Curlew by Kane Brides

Birdwatchers are asked to look out for colour-ringed Curlew and Redshank (Kane Brides)

The Severn is a great place for birds, especially waders, attracted to the area by mud that has high densities of mud-loving invertebrates such as ragworms. It is designated as an SPA, because of its importance to wintering species such as Bewick’s Swan, Curlew, Dunlin, Pintail, Redshank and Shelduck, and the spring passage of Ringed Plovers. There’s more about the SPA on the JNCC’s website.

The British Trust for Ornithology and Wildfowl & Wetlands Trust scientists have been awarded a contract to undertake an Environmental Impact Assessment for the proposed Cardiff Tidal Lagoon  by Tidal Lagoon Power, with BTO focusing on waders and WWT on ducks. It’s a unique opportunity not only to inform conservation planning but also to answer questions about the winter ecology of some key species. The team aims to:

  • Validate and refine methods developed by Richard Stillman (Bournemouth University) that predict bird distributions from food availability. (It’s easier to map food distribution than to follow bird movements)
  • Understand patterns of movement of species that use the proposed development area and other key sites, such as the Gwent Levels.
  • Track birds in order to identify feeding and roosting areas that are used when birds are hard to observe – in poor weather, at night and at all stages of tide.
  • Work out how mobile birds are, in order to propose ways in which lost feeding opportunities might be replicated as close by as possible.

Tagging

Tag on Curlew back (head covered to keep bird calm) by Lucy Wright

Tags like this should reveal how waders and ducks use the Severn estuary. Curlew by Lucy Wright.

Tagging is an important part of the project. Four-gramme Pathtrack tags are being glued to the backs of a sample of Curlew, Redshank, Shelduck and (hopefully) Shoveler. These should stay on for a couple of months, during which time movements will be logged every 90 minutes and downloaded using UHF receiving stations set up around the Severn. These four species have been chosen because, for each, more than 10% of the estuary’s population lies within the proposed footprint of the tidal lagoon.

Colour-rings

Colour ringed Redshank by Emily Scragg

This colour-ringed Redshank may well breed in Iceland but which areas of mud-flat does it use in the winter? (Emily Scragg)

Tagged Redshank and Curlew are also being colour-ringed, alongside others that are not being tagged. By collecting reports of colour-ringed birds from birdwatchers, the BTO team will be able to monitor the efficacy of the tag down-load process and keep a track of movements when the tags stop transmitting. As an added bonus, the colour-rings may generate some new information about the breeding sites of waders that winter on the Severn.

Sightings of colour-ringed birds would be very much appreciated. Five rings have been used on both Redshank and Curlew. Please submit sightings (date time and ideally a six-figure grid reference) to Emily.scragg@bto.org who would also be interested in “ratio counts” of flocks of birds – simply the number of colour-rings and the size of the flock.

Colour-dyed Dunlin

The Severn Estuary holds an estimated 3.2% of the European wintering population of the alpina race of Dunlin, birds that breed from Siberia across to northern Scandinavia. Dunlin are too small to carry transmitters that can be used with base stations so the team has gone back to traditional picric dye in order to look at the mobility of flocks. Any sightings of colour-marked Dunlin will be appreciated by emily.scragg@bto.org. Where possible, please submit ratio counts broken up into yellow/orange on breast (adults), yellow/orange on the rump (juveniles) and unmarked birds, together with date, time and location (ideally with six-figure reference).

Colour-dyed Shelduck

shelduck Kane Brides

The neck of this tagged Shelduck will be dyed yellow before release (Kane Brides)

It’s not just waders.  Over 3,000 Shelduck winter on the Severn, which is more than 1% of the European population. A sample has been caught by WWT. Ringed birds have a yellow/orange dye mark on the normally white plumage on the neck/upper breast (between the dark green head and the brown breast band). No Shoveler have been caught yet but the aim will be to put a similar dye-mark on these birds too.  Sightings of dye-marked ducks should be reported to Ed.burrell@wwt.org.uk

Impact Assessment

The consortium of organisations that is working on this new tidal-power study is well placed to combine impact assessment with high quality wader science. By focusing on Curlew and Redshank, both red-listed species of conservation concerned, it is to be hoped that more will be learnt about the winter feeding ecology of these two species. The BTO team has already discovered that Redshank fly further at night than was previously thought and hope to get to understand some of the pressures facing Curlew, now classified as globally near-threatened (see separate WaderTales blog)

Severn 4 WWT

The Severn – Gareth Bradbury/WWT

This is not the first impact assessment work that has managed to incorporate research that increases the scientific understanding of wader behaviour and ecology. Two other examples are given below:

The Wash: Back in the 1970s, a plan to build huge reservoirs on the mud flats of the Wash, in which to store fresh water that might meet the growing demands of southeast England, led to a doubling of wader catching activity, intensive studies of their feeding ecology and complementary work on other taxa. Much was learned about the mobility of species within this huge estuary and the turn-over of birds within the annual cycle. A draft copy of the report is available on line at the NERC website 

Cardiff Bay: In the period 1989 to 2003, long-term studies took place to try to understand the impacts of closing Cardiff Bay and hence reducing the amount of tidal feeding area for waders. Following the development, it was shown that Redshank that had been displaced from the Bay were in poorer condition and had lower survival rates in subsequent winters.  There’s a summary on the JNCC website. The papers listed at the bottom of this JNCC web-page are essential reading for anyone trying to counter the ‘birds will simply go elsewhere’ arguments, which are sometimes put forward in favour of development work.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Black-tailed Godwits expand their range in Russia and Iceland

Birdwatchers and farmers plot range-changes of Black-tailed Godwits

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The Back-tailed Godwit has expanded it range in Iceland (above) and in western Russia (Tómas Gunnarsson)

A recent paper by Igor Popov and Dmitry Starikov in Wader Study, the journal of the International Wader Study Group, provides a glimmer of good news for those concerned about the huge losses of the nominate limosa subspecies of the Black-tailed Godwit.  At the same time as limosa numbers in the west of the range have been dropping by an average of 5% per year, there has been colonisation of areas of Russia that are beyond what was thought to be the northern edge of the subspecies’ range.  Over a similar time period there has also been a well-documented range expansion of the islandica subspecies, about which more later.

Popov I. & Starikov D. 2015. Recent northward expansion of breeding Black-tailed Godwits Limosa limosain NW Russia. Wader Study122(3): 173–183.

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Wader Study is the journal of the International Wader Study Group

Black-tailed Godwit is classified as near-threatened by IUCN/BirdLife, as a result of widespread and rapid declines in numbers of limosa, the most numerous subspecies (Gill et al 2007).  These declines have been linked to agricultural intensification and changes in the timing of farming operations on grass fields in the breeding season, habitat changes and the destruction of wetland habitats in Europe and western Africa, where limosa birds spend the winter, and possibly hunting effects.  In contrast, the Icelandic subspecies has been increasing.  Tómas Gunnarsson and colleagues had previously mined long-term datasets, provided by Icelandic farmers, the Icelandic Natural History Institute and others, to show that the range of the islandica subspecies has expanded hugely over the last century.  Now Igor Popov and Dmitry Starikov have used similar detective work to show that the northern edge of the limosa subspecies is moving north.

Russia

Russian site

One of the new habitats used by Black-tailed Godwits in the Nizhnesvirsky Reserve (Igor Popov)

In some ways, the Russian research is quite conventional, in that the records upon which the study is based were collected by scientists and birdwatchers.  The region under consideration belongs to five administrative areas of the Russian Federation but the focus is the area surrounding St Petersburg, where reports go back to at least the end of the 19th century.  By delving into the records from the libraries of the Russian Academy of Sciences, the Russian National Library and the libraries of various local institutions, the authors were able to pull together a list of observations and to establish that Black-tailed Godwits were absent from other lists.  At the heart of the study is the Nizhnesvirsky Reserve where systematic observations have been made for fifty years.

In the late 1980s, four pairs of Black-tailed Godwits were observed in the Nizhnesvirsky Reserve with other records between 1997 and 2003.  At the same time, there were increasing numbers of sightings in the wider study area and from beyond its borders, where there had been reports from as early as the late nineteenth century through to the 1940s and 1950s, with the first breeding record in the 1970s.  There is now a small but apparently stable population in the reserve, an area in which mean April temperatures have risen from +2.2°C to +4.8°C over the period 1880 to 2015.  Within the larger study area, Igor Popov and Dmitry Starikov feel that it is likely that there have been similar colonisations in other locations, as birds have settled in small numbers within dispersed areas.  One factor that may have contributed to the ability of Black-tailed Godwits to expand their range northward in recent years is the replacement of large areas of the taiga forests across the whole of Northern Russia with more open habitats that suit the species.

Iceland

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A male Black-tailed Godwit, glowing in the late afternoon sun (Nigel Clark)

The documentation of the range epansion of islandica Black-tailed Godwits in Iceland owes more to the inquisitive nature of Icelandic farmers than to the observations of birdwatchers.  This is fortunate, as farmers operate throughout Iceland, whilst birdwatchers are few and far between.  As the species spread into new coastal areas, farmers could not help but notice the arrival of these noisy russet-red birds, feeding in hay fields, perched on fence-posts and careering around the skies in their acrobatic display flights.  The key thing that farmers did was to tell someone.  Many of their observations ended up at the Icelandic Institute of Natural History in Reykjavík, which encourages and collects submissions of natural history records from across Iceland.  Tómas Gunnarsson collated these records, together with others, in order to date the major patterns of colonisation of breeding sites by black-tailed godwits.  In total, 118 records were obtained from these sources, which enabled identification of dates of first or recent breeding for 65 individual breeding sites within 39 individual basins throughout Iceland. The earliest breeding date of these sites was used as the colonisation year for each basin and the general pattern of colonisation is summarised in the figure below.

godwit spread

2017 chick surveyAs in Russia, one of the drivers of the increasing Black-tailed Godwit population in Iceland could well be changes in spring temperatures. In this blog about the effect of temperature and volcanic eruptions on breeding success, there is a clear relationship between the number of successful broods and the temperature in May, as you can see in the figure alongside. You can read more about this in the paper:

Effects of spring temperature and volcanic eruptions on wider productivity. Tómas Grétar Gunnarsson, Lilja Jóhannesdóttir, José A AlvesBöðvar Þórisson & Jennifer A Gill. IBIS (2017) DOI: 10.1111/ibi.12449

There was an even warmer spring in 2017 – which explains the orange dot (top-right) in the figure above. There’s more about wader research in Iceland during the summer of 2017 in this blog.

Conservation implications of range expansion

Numbers of the islandica race of Black-tailed Godwits are still rising but their European cousins (limosa) are in serious decline, especially in the Netherlands. This blog reveals a 75% decline in numbers since 1967 and concludes with: “Although enormous amounts of money and effort have been expended to conserve continental godwits, our findings make clear that these have been ineffective or insufficient.”

The recent colonisation of new areas in Russia does not necessarily mean that the limosa Black-tailed Godwit will become abundant in its north-eastern territories.  It is still rare, and its numbers are only increasing slowly.  In Finland, which lies at a similar latitude, the breeding population was estimated at 20 pairs in the 1980s, 25–35 pairs in the 1990s (Vaisanen et al. 1998), and 40–60 pairs in the 2000s (Jensen 2007).  Such detailed estimates are not yet possible for the new breeding areas in Russia but, because all reports concern only small numbers, Igor Popov and Dmitry Starikov conclude that no rapid population growth has taken place to date.   Sadly, it appears that colonisation of northern areas is unlikely to be much compensation for losses elsewhere in the limosa range.

Layout 1To read more about the Russian range expansion:
Popov I. & Starikov D. 2015. Recent northward expansion of breeding Black-tailed Godwits Limosa limosain NW Russia. Wader Study122(3): 173–183.

Icelandic colonisation data are used in five papers:

When Icelandic farmers sent in their Jadrakan (Black-tailed Godwit) observations to the Natural History Institute the term ‘citizen science’ had not been invented.  Nearly 100 years after the first records, their sightings have not only chronicled the spread of the species, they have also facilitated the publication of some interesting – and varied – papers.

cover pics

Grabbing the front cover: citizen science is at the heart of research into the range expansion of Black-tailed Godwits

Double buffer effect: As the population of Icelancic Black-tailed Godwits has increased, birds have moved into areas of poorer quality breeding habitat as well as areas of poorer quality winter habitat. Gunnarsson T.G., Gill J.A., Petersen A., Appleton G.F. & Sutherland W.J. A double buffer effect in a migratory shorebird population. J Animal Ecology 2005, 74:5 965-971.

Seasonal matching: Black-tailed Godwits that breed in newly-colonised, poorer-quality breeding habitats tend to winter in poorer-quality wintering sites. Gunnarsson T.G., Gill J.A., Newton J, Potts P.M. & Sutherland W.J. Seasonal matching of habitat quality and fitness in a migratory bird. Proc. Biol. Soc. B 2005 Nov 7; 272(1578): 2319–2323.

Arrival times in spring: Individual godwits from traditionally used breeding areas, where average habitat quality and spring temperatures are higher, arrive in Iceland earlier than those which breed in recently occupied areas, where average habitat quality and spring temperatures are lower. Gunnarsson T.G., Gill J.A., Atkinson P.W., Gélinaud G., Potts P.M., Croger R.E., Gudmundsson G.A., Appleton G.F. & Sutherland W.J.  Population-scale drivers of individual arrival times in migratory birds. Journal of Animal Ecology 2006 75, 1119–1127

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Small males tend to occupy territories in traditional breeding areas (Tómas Gunnarsson)

Selection pressure: The size of male Black-tailed Godwits is highly variable and varies strongly in relation to the timing of colonisation across Iceland, with small males being absent from recently-colonised sites.  This is most likely to be a consequence of preferences females may have for small males (and good quality habitats). Gunnarsson T.G., Sutherland W.J., Alves J.A., Potts P.M. & Gill J.A.  Rapid changes in phenotype distribution during range expansion in a migratory bird. DOI: 10.1098/rspb.2011.0939

Migration strategies: Individuals experiencing more favourable winter conditions had higher survival rates, arrived on the breeding grounds earlier, and occupied better quality breeding areas, even when migration costs are substantially higher. Alves J.A., Gunnarsson, T.G., Hayhow D.B., Appleton G.F., Potts P.M., Sutherland W.J. & Gill J.A. Costs, benefits, and fitness consequences of different migratory strategies Ecology, 94(1), 2013, pp. 11–17


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

 

How well do Lapwings and Redshanks grow?

There has been an assumption that managers of nature reserves know how to provide the right foraging conditions for Lapwing and Redshank chicks.  This paper in Wader Study shows that they do.

Lapwing chick Andy Hay rspb-images (2)

How quickly will this Lapwing chick grow? Photo: Andy Hay/RSPB images

For conservationists looking to increase wader populations, attracting birds to a chosen site is a good first step, but only if pairs can breed more successfully than they would have done elsewhere.  To understand whether a species recovery prescription works or, if it does not, to understand what is going wrong, it’s necessary to measure nest success, chick growth and fledging rates.  In their paper in the journal Wader Study, Lucy Mason and Jen Smart focus on the middle of these – how well chicks grow – to check whether the right feeding conditions are being provided.

Mason, L.R. and Smart, J. Wader chick condition is not limited by resource availability on wader-friendly lowland wet grassland sites in the UK. Wader Study 122:3 Dec 2015

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Tags make it easier to find ringed Redshanks. Photo: Kirsty Turner

Breeding success for Lapwing and Redshank can be poor, even on protected sites, which often leads site managers and policymakers to ask whether low food availability might be limiting chick survival, despite management aimed at providing optimum foraging conditions. Although this question is difficult to answer on a large scale, Lucy and her team were able to monitor and compare wader chick body condition and rates of growth across a range of UK sites.  If food availability is an issue, they expected to find that chicks would grow slower and weigh less than might be expected – or hoped.

_D062084 Lapwing

Photo: Kevin Simmonds

One of the main reasons RSPB scientists published this research was because site managers often ask for support to monitor invertebrates, in order to make sure that there is enough food for waders.  There are lots of reasons why this is extremely difficult – i) what is enough? ii) chicks are catholic in their choice of prey, going for whatever is abundant and available at the time, so what do you measure and when? iii) linking food availability to growth and survival is inevitably tricky.  The great thing about this paper is that it shows that, in general, well-managed sites will provide enough food.  If managers are worried about food availability then monitoring the growth rates of chicks and comparing their data to the published information is far easier than measuring an invertebrate resource that varies hugely in space and time.

To understand the growth rates of Lapwing and Redshank chicks, a total of 130 tags were deployed across 15 lowland wet grassland nature reserves and protected sites, within the UK, during 2009, 2010, 2012 and 2013.  This enabled family parties to be tracked and helped to yield a total of 750 monitored individuals.  All sites were managed with the aim of providing optimum conditions for breeding Lapwing and Redshank (both nesting and chick rearing).  Chicks were ringed, tagged and measured when captured and subsequently about every eight days.  Relocating the chicks involved tracking the tagged individuals and, through them, their ringed siblings.  It was harder to recapture Redshanks, which are more cryptically coloured and move around more.

Lapwing Fledglings

Two well-grown Lapwings on a wet day. Photo: Jen Smart

Lucy and her colleagues demonstrated that, on average, Lapwing and Redshank chicks achieved growth rates similar to those calculated for larger samples of chicks studied in The Netherlands and the UK, and achieved better conditions more quickly than those measured in a standardised Dutch study.  This suggests that food availability for wader chicks on well-managed lowland wet grassland sites is unlikely to be limiting chick survival and population recovery.

To understand why populations of species such as Lapwing and Redshank are failing to recover, the focus should be on other potential causes of chick mortality, such as predation or agricultural activities.  The positive message is that, if these other causes of chick mortality can be reduced, well-managed wader sites are likely to be successful in producing healthy fledglings and to facilitate population recovery.

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Body condition of tagged Lapwing chicks (centre) did not differ from that of untagged chicks in other broods, indicating that the tags (representing 2-3% of a tagged chick) and recapture frequencies did not aversely affect chick body condition or growth. Photo: Jen Smart

More feeding opportunities for chicks

There are several management options which are being used by conservation organisations and land-owners who are keen to try to support species that breed on lowland wet grasslands.  The first suite increases feeding opportunities for chicks:

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Long grass is important to nesting Redshank and their chicks. Photo Kevin Simmonds

Grazing regimes need to be adjusted to create the correct sward height, heterogeneity of structure etc. See, for instance, McCracken, D. & J. Tallowin. 2004. Swards and structure: the interactions between farming practices and bird food resources in lowland grasslands. Ibis 146: 108–114.

Increasing the height of the water table provides better feeding opportunities for adults and chicks.  See, for instance: Eglington, S.M., M. Bolton, M.A. Smart, W.J. Sutherland, A.R. Watkinson & J.A. Gill. 2010. Managing water levels on wet grasslands to improve foraging conditions for breeding northern lapwing Vanellus vanellus. Journal of Applied Ecology 47: 451–458.

Providing more wet habitat features, in the form of pools or foot-drains. See, for instance: Eglington, S.M., J.A. Gill, M. Bolton, M.A. Smart, W.J.Sutherland & A.R. Watkinson. 2007. Restoration of wet features for breeding waders on lowland wet grassland. Journal of Applied Ecology 45: 305–314 and Smart, J., Gill, J.A., Sutherland, W.J., Watkinson, A.R., 2006. Grassland-breeding waders: identifying key habitat requirements for management. Journal of Applied Ecology 43: 454-463.

Using agri-environment schemes to achieve these habitat goals. See, for instance: Smart, J.A., Wotton, R., Dillon, I.A., Cooke, A.I., Diack, I., Drewitt, A.L., Grice, P.V. & Gregory, R.D. 2014. Synergies between site protection and agri-environment schemes for the conservation of waders on lowland wet grasslands Ibis 156: 576-590. 

Reducing predation risks

A reduction in predation can be effected by direct control of species such as corvids, mustelids and foxes but other tools are also available:

Carrion crow Andy Hay rspb-images

Andy Hay/RSPB images

Removing isolated trees, telegraph posts and wires that are used as look-out perches by corvids:  Berg, A., Lindberg, T. & Kallebrink, K.G. 1992. Hatching success of Lapwings on farmland – Differences between habitats and colonies of different sizes. J. Anim. Ecol. 61: 469-476 and MacDonald, M.A. & Bolton, M. 2008. Predation on wader nests in Europe. Ibis 150: 54-73.

Using electric fences to keep out foxes and badgers. Malpas, L. R., Kennerley, R. J., Hirons, G. J., Sheldon, R. D., Ausden, M., Gilbert, J. C. & Smart, J. 2013. The use of predator-exclusion fencing as a management tool improves the breeding success of waders on lowland wet grassland. Journal for Nature Conservation: 21, 37-47.

Designing the lay-out of water features so as to reduce fox/nest interactions: Bellebaum, J. & C. Bock. 2009. Influence of ground predators and water levels on Lapwing Vanellus vanellus breeding success in two continental wetlands. Journal of Ornithology 150: 221–230.

Diversionary feeding – providing areas of long grass which act as refuges for small mammals: see other WaderTales Blog.

Decisions for the future

Lapwing nest Andy Hay rspb-images

Andy Hay/RSPB images

The majority of the chicks monitored in this study were predated before fledging.  If this mortality can be reduced then sites which are managed with wader chicks in mind have the potential to support population recovery.  Decisions upon how to reduce predation will need to be based upon the effectiveness and costs of the suite of solutions that are available, as well as ethical decisions as to which predators can be controlled and when – a potentially tricky issue for those managing nature reserves.

Mason, L.R. and Smart, J. Wader chick condition is not limited by resource availability on wader-friendly lowland wet grassland sites in the UK. Wader Study 122:3 Dec 2015


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

 

NEWS and Oystercatchers

It’s amazing what you can find when walking along a beach with a pair of binoculars

Curlew in snow

Curlews waiting for the tide to drop: Graham Catley

Thousands of British and Irish birdwatchers visit estuaries but there’s a lot of coastal habitat that gets little attention.  That’s where you’ll find 87% of the UK’s Purple Sandpipers, over half of the Turnstones and nearly half of the Ringed Plover – or those were the figures nine years ago.  It’s time to update these estimates, which is where NEWS-III came in. That’s the catchy name for the third Non-estuarine Waterbird Survey, which operated in the UK and Ireland over the period 1 Dec 2015 to 29 Feb 2016.

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We’ll be looking out for colour-ringed Oystercatchers: Tómas Gunnarsson

We covered 6 beach sections as our contribution to NEWS-II over the Christmas period 2006/07: three horrible stretches right next to the main A78 along the Clyde coast and three lovely beaches on the island of Cumbrae. We found 57 waders on the first set, while dodging the traffic, and 184 on a very relaxed day trip from Largs by ferry. There were comparable numbers of Curlew, Turnstone and Redshank but more Oystercatchers on the wider, island beaches.  That’s where we also found our only Ringed Plover, as well as 11 Purple Sandpipers and 3 Lapwing.

cumbrae comparisonThis year, we found far fewer waders than nine years ago. The table alongside provides a comparison for the three sections that we covered on Cumbrae for NEWS II and NEWS III. We failed to find any Purple Sandpipers in any of the 17 sections of the Clyde coast that we covered but were surprised to see a total of 5 Greenshanks. There seemed to be far fewer seabirds too. This is just a tiny snap-shot that may not be representative of the picture across the whole of the coastline of Britain & Ireland. Let’s hope that, despite the stormy weather, there was sufficient coverage for robust anlayses to be carried out by BTO staff.

RP WeBSWe know that wader number on estuaries are changing.  For instance, in the last few years, numbers of Ringed Plover in the UK have been falling (see figure).  The declining line indicates a significant drop but it won’t be quite such a concern if this year’s NEWS-III surveyors find that there are now more Ringed Plovers on open coasts.  That may seem like an optimistic suggestion, unless you look at changes between NEWS (1997/98) and NEWS-II (2006/07).  During this period, at the same time that WeBS counts of estuaries were falling, there was actually a 25% increase in Ringed Plover numbers on open coast.  Perhaps this redistribution from estuaries to open coasts has continued?

NEWS tableTwenty-one species of wader were recorded during NEWS-II, with Oystercatcher being the most numerous with an estimated total of 64,064 for the whole non-estuarine coastline of the UK. The full report is available on the BTO website .  With support from hundreds of volunteer birdwatchers it was possible to make population estimates for the 12 most numerous species, including the non-estuarine specialists, Ringed Plover, Sanderling, Purple Sandpiper and Turnstone.  These four species accounted for estimates of 15,230, 6,295, 11,306 and 30,122 individuals respectively.  The table alongside shows the intertidal-zone totals and the percentage of the total UK population that each estimate comprises, based on Population estimates of birds in Great Britain & the United Kingdom by Musgrove et al which was published in British Birds.

Five of the species that were in the top 12 for NEWS-II have been categorised as near-threatened by IUCN/BirdLife.  Oystercatcher is the most numerous of the five, with over 64,000 in intertidal areas of the open coast, representing nearly 20% of the national wintering population.  There are relatively small numbers of Bar-tailed Godwit, Lapwing and Knot but 26,744 Curlew is equivalent to 17.8% of the UK total.   There’s a WaderTales blog about the near-threatened designation of Curlew.

Turnstone Belsey

59% of the UK’s Turnstone ar found on the open shore: Derek Belsey/BTO

Unfortunately for the scientists who organised NEWS-III there is a huge disparity between the distribution of birdwatchers and the number of coastal stretches that would ideally be surveyed, so let’s hope a good number of English birdwatchers decided to spend a few days in Scotland over the survey period.  Three-quarters of the open coast in the UK is in Scotland (all those crinkly bits, sea-lochs and islands) with Northern Ireland, England and Wales respectively having approximately 2.3%, 16.0% and 6.6%.  Taking account of the spread of the available sites, there’s a relatively uniform UK-wide distribution of most species, although  Sanderling has a southerly bias to its distribution and Purple Sandpiper a strong northern bias.

NEWS-III was not just about waders; volunteers were asked to record other waterbirds too. Our counts for NEWS-II covered Cormorant and Shag, Mute Swan, Eider, Red-breasted Merganser, Wigeon, Mallard, Guillemot and Grey Heron.

oyc table

Data from BTO ringing report

Whilst I was delighted to use WaderTales to promote NEWS-III, there was an ulterior motive. We wanted counters to look out for Oystercatchers wearing colour rings. Icelandic Oystercatchers can be encountered almost anywhere but the ones in England are very much outnumbered by those from Norway, the other main source of wintering birds. The table alongside gives an idea of the north-westerly distribution of birds with an Icelandic origin.

oycmap.pngColour-ringed Icelandic Oystercatchers are part of a new project to look at how climate change might be affecting migration patterns. There’s a blog about the project here. The map alongside shows where colour-ringed birds from the study areas in Iceland have already been found, with most in Scotland and Ireland.  Birds will either be wearing 3 colour-rings and a green or white flag or two colour-rings and an engraved darvik.

NEWS only happens every few years so this was a great opportunity to contribute to our understanding of the conservation status of some important species, several of which are now near-threatened. I am looking forward to the results with interest, and a little concern.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Why is spring migration getting earlier?

In Iceland, young trend-setting Black-tailed Godwits are changing the timing of spring migration

Flocks of up to 5000 Black-tailed Godwits gather in Alftafjordur in spring: Tómas Gunnarsson

Flocks of up to 5000 Black-tailed Godwits arrive in Alftafjordur (East Iceland) in spring: Tómas Gunnarsson

In recent years, earlier arrival of spring migrants has been widely reported in birds as diverse as swallows and waders but it’s not a universal trend; species such as British Cuckoos and Icelandic Whimbrels have not changed their arrival dates.  Interestingly, many of the species that have not advanced timing tend to be those that are declining.  By thinking about the mechanisms that enable some species to take advantage of earlier spring warming it might be possible to explain how timings and population changes may be linked.

Are individual Black-tailed Godwits arriving earlier each spring? (Photo: Nigel Clark)

Are individual Black-tailed Godwits arriving earlier each spring? (Photo: Nigel Clark)

The simplest way for spring migration to advance would be for individual birds to change their arrival dates, arriving earlier now (either because they have departed earlier or migrated faster) than they did in previous years.  These changes could be facilitated by changes to weather conditions before, during or after migration.  In general, the arrival of short-distance migrant species has advanced more than long-distance species, which has led to suggestions that individual birds are able to assess conditions on their breeding grounds from afar, and to ‘fine-tune’ arrival accordingly. This could explain why long-distance migrants seem less well able to change their schedules than species which have less far to travel.

Figure 1: Changes in first spring arrival dates of six species of waders in southern Iceland from 1988 to 2009 (reproduced from Gunnarsson & Tómasson 2011)

Figure 1: Changes in first spring arrival dates of six species of waders in southern Iceland from 1988 to 2009 (reproduced from Gunnarsson & Tómasson 2011)

This pattern of advances in arrival dates, and greater advances in short-distance migrants is seen in birds arriving into Iceland each spring (Gunnarsson & Tómasson).   By monitoring the first dates of a range of migratory breeding species to the area around Laugarás, an inland village in southern Iceland, over the period 1988 to 2009, Tómas Gunnarson and Gunnar Tómasson showed that species which spend the winter further south than France showed no change in arrival, whilst those from further north in Europe were returning earlier.  The southern group included the only wader in the Gunnarsson & Tómasson study which uses this migration strategy, Whimbrel (see diagram).

GL-YX on a windy day in western Iceland. He has been seen in eleven years. Despite the vagaries of spring weather, his arrival dates have only been spread over nine days (standard deviation 3.5 days) and have not advanced over the period 2003-2015

GL-YX on a windy day in western Iceland. He has been seen in eleven years. Despite the vagaries of spring weather, his arrival dates have only been spread over nine days (standard deviation 3.5 days) and have not advanced over the period 2003-2015

One of the species that has advanced spring arrival (by about two weeks in the last two decades) is the Black-tailed godwit.  Since 2000, we have been recording arrival dates of individually colour-ringed godwits into coastal Iceland – giving us the opportunity to assess whether individuals have indeed brought forward their time of arrival.  By making regular visits to the same sites we have discovered that the dates when we first come across individuals are remarkably consistent.  Although the arrival of the whole population is spread over a five or six week period, the window in which a specific Black-tailed Godwit appears is generally predictable, whether he or she is a bird that we tend to first see in mid-April or mid-May.  There are annual differences, of course, which appear to be linked to periods of adverse weather during the period of the sea-crossing (Gunnarsson et al 2006), from departure points in The Netherlands, The UK Ireland, France and Portugal, but there is no significant trend.

Dates of spring arrival into Iceland of 54 individually marked black-tailed godwits recorded on arrival in between 4 and 8 years, from 1999 to 2012 (reproduced from Gill et al. 2014). Whether an individual arrives early (left-hand birds) or late (right), the sighting dates for each bird are highly consistent.

Dates of spring arrival into Iceland of 54 individually marked black-tailed godwits recorded on arrival in between 4 and 8 years, from 1999 to 2012 (reproduced from Gill et al. 2014). Whether an individual arrives early (left-hand birds) or late (right), the sighting dates for each bird are highly consistent.

timing pop v indivAlthough the arrival date for the population has been advancing at ~0.8 days per year (Gunnarsson & Tómasson 2011), there has been no trend in individual arrival dates (not significantly different to zero days per year); Gill et al. 2014.

Most of the godwit chicks were ringed by groups of volunteers led by Pete Potts and Ruth Croger (Photo: Tómas Gunnarsson)

Most of the Black-tailed Godwit chicks were ringed by groups of volunteers led by Pete Potts and Ruth Croger (Photo: Tómas Gunnarsson)

If individuals are consistent in arrival but the population is advancing, the advance must presumably result from new birds recruiting into the population being earlier-arrivers than recruits from previous years?  Fortunately, there is a second long-running set of data that’s available to answer this question, in a large part because of the efforts of Pete Potts and Ruth Croger of Farlington Ringing Group.  In the period 1999 to 2014, they organised teams of volunteers to ring Black-tailed Godwit chicks in Iceland, with the support of the Icelandic Natural History Museum.  Significant contributions to the total of over 350 colour-ringed chicks were also made by Tómas Gunnarsson and José Alves, while researching the breeding ecology of Black-tailed Godwits for the Universities of East Anglia and Iceland.

Dates of spring arrival into Iceland of 46 individuals hatched in different years and subsequently recorded on spring arrival (reproduced from Gill et al. 2014)

Dates of spring arrival into Iceland of 46 individuals hatched in different years and subsequently recorded on spring arrival (reproduced from Gill et al. 2014)

Wader chick mortality is quite high and there are further losses in the eighteen-month period between autumn departure from Iceland and the first return trip, eighteen months later, so it was wonderful to have a sufficiently big cohort of marked recruits to look at patterns and trends.  For this study, arrival dates for 46 individuals of known hatch year were available for analysis.  As can be seen from the graph, arrival dates of new recruits have been getting earlier, with birds hatched in the last decade arrive around two weeks earlier than individuals hatched in the 1990s.

There are several reasons why recent recruits may be arriving earlier than in previous years, but the most likely is that this is a knock-on effect of advances in godwit laying dates that have occurred in recent decades.  Icelandic godwits nest earlier in warmer springs, and the frequency of warmer springs has increased.  Early fledging may benefit new recruits, by increasing the time available for them to migrate south, locate a good winter site and be in condition to return early when they recruit into the breeding population (Alves et al. 2013 http://www.esajournals.org/doi/abs/10.1890/12-0737.1  http://dx.doi.org/10.1890/12-0737.1). As their arrival date will be consistent thereafter, the overall timing of arrival of the population will advance.

Will this young Black-tailed Godwit contribute to our understanding of the timing of migration? (Photo: Tómas Gunnarsson)

Will this young Black-tailed Godwit contribute to our understanding of the changing timing of migration? (Photo: Tómas Gunnarsson)

Many other studies of different species in which individuals are tracked during migration are showing similar levels of consistency in individual timing of migration.  What then is causing the variation among species in rates of advance?  Long-distance migrants typically arrive later on the breeding grounds and breed quite soon after arrival, while short-distance migrants can have quite large time gaps between arrival and laying, depending on conditions for breeding. Short-distance migrants therefore have more capacity to advance laying dates (because they are on the breeding grounds waiting for suitable conditions), while long-distance migrants, such as Whimbrels in Iceland, arrive later and so cannot breed earlier even in a warmer year. Advances in spring arrival dates may therefore result from advances in laying dates and associated benefits of early fledging for recruits, and lack of advance in long-distance migrants may be a consequence of arriving late and hence being unable to take advantage of early, warm spring conditions.

In the Icelandic subspecies of Black-tailed Godwit, which is expanding in both number and distribution, it is clear that young recruits to the breeding population are driving the advance in timing of migration.  We only know this because of the long-term programme of chick ringing by volunteers and because we have been able to record the timing of individual birds’ migratory activities over a large number of years.  Funding for this work has been provided by the volunteers themselves, NERC , Icelandic Research Council  and EU TMR.

This blog is based upon research presented in the following open access paper:

Gill, J.A., Alves, J.A., Sutherland, W.J., Appleton, G.F., Potts, P.M. & Gunnarsson, T.G. 2013 Why is timing of bird migration advancing when individuals are not? Proceedings of the Royal Society B. , 281, 20132161

Please send reports of colour-ringed Black-tailed Godwits to Jenny Gill (j.gill@uea.ac.uk). She will reply with full details of any birds ringed on the Wash or forward your e-mail to colleagues running other schemes.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Is the Curlew really ‘near-threatened’?

If a Curlew can live for over 32 years and there are flocks of 1000 in Norfolk, how can they be described as near-threatened? 

Dark times lie ahead for Curlew? (© Graham Catley)

Dark times lie ahead for Curlew? (© Graham Catley)

Thirty years ago there were eight members of the world-wide curlew family but now we may well be down to six.  The planet has lost one species, the Eskimo Curlew, with no verified sightings since the 1980s, and probably the Slender-billed Curlew as well.  Of the others, Far Eastern Curlew and Bristle-thighed Curlew are deemed to be endangered and vulnerable, respectively, and our own Curlews are classed as near-threatened, which is the next level of concern. This may seem strange, especially when flocks of 1000 can be seen on the Norfolk coast.  However, evidence suggests that we should take heed of what is happening to other members of the curlew family, as we consider the future of this evocative species with its wonderful bubbling curl-ew calls.

Threat levels for the eight members of the Curlew family (based on IUCN BirdLife assessments)

Threat levels for the eight members of the Curlew family (based on IUCN/BirdLife assessments)

Our Curlew – more properly called the Eurasian Curlew – was until relatively recently a locally popular game species in Britain, especially in September and October, when birds are reputed to be particularly flavoursome.  A male Curlew is equivalent in weight to a Wigeon (or two Teal) and the bigger female may well be as heavy as a Mallard, so it is not surprising that they were worth targeting.  They came off the British quarry list in 1981.

Map showing movements of ringed curlews. Purple dots indicate where British/Irish ringed birds have been recovered and orange dots show ringing sites of birds found here and wearing foreign rings. Maps of movements can be found on the BTO website at http://www.bto.org/volunteer-surveys/ringing/publications/online-ringing-reports

Purple dots indicate where British/Irish ringed Curlews have been recovered and orange dots show ringing sites of birds found here and wearing foreign rings. Maps of movements can be found at http://www.bto.org/volunteer-surveys/ringing/publications/online-ringing-reports

The Curlews that we see on the Norfolk coast in autumn and winter are drawn from a wide breeding area; some are of British origin but many are from Scandinavia, Finland and Russia.  The Wash Wader Ringing Group recently received a report of a bird that was ringed in Norfolk in September 2000 and recovered in Izhma in Russia in May 2014.  At 3300 km (2000 miles) this is nearly as far away as the furthest east dot on the map of Curlew recoveries, shown here and published on the website of the British Trust for Ornithology.  The bird was an adult when ringed so must have been at least 15 years old when shot.  This seems like a good age for a Curlew but is less than half of the British longevity record, set by a chick ringed in Lancashire in 1978 and found dead on the Wirral in 2011.

Curlew mortality is higher in severe winters (© Graham Catley)

Curlew mortality is higher in severe winters (© Graham Catley)

Curlew numbers on the Wash, which sits between the counties of Norfolk and Lincolnshire, increased dramatically when shooting ceased in 1981, although milder winters could have also have been influential.  In the five years immediately before the ban, the average maximum, winter Wetland Bird Survey count on the Wash was 3281, rising to 9642 in the period 2006/07 to 2010/11.  There were similar increases on the North Norfolk coast and a bit further south at Breydon Water.  The broader, national picture is one of increase between 1981 and 2001, although generally at a lower level to that seen in Norfolk, followed by a steady, shallow decline.  If numbers are higher than they once were does this mean that we should be less concerned about Curlews – and what is the justification of the species’ near-threatened designation?

Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Curlews fly vast distances to spend the winter on the estuaries of Britain & Ireland (© Graham Catley)

Conserving migratory species is difficult because individuals rely on different resources in different countries at different stages of the year.  For Curlews, there is evidence that breeding season problems are at the heart of large decreases in numbers in Russia, through the Baltic and into The Netherlands – the countries from which much of the wintering population on the east coast is drawn.  According to the European Commission’s species management plan, drivers of decline include wide-scale intensification of grassland management for milk production, land-abandonment and increased predation in some areas.  Autumn, winter and spring hunting is thought to have had a lesser but contributory effect to the long-term losses, with hunters across the European Community shooting between 3% and 4% of the population each year.  In the last twenty years, within the EC, hunting of Curlew has been confined to Ireland, Northern Ireland and France.  Much of this shooting pressure was and is in France, where coastal hunting of Curlew was reinstated after a five year moratorium. Read blog about this here.

curlew webpageFocusing on Britain and Ireland, we have seen major losses in our breeding populations.  In Ireland, the Curlew population is estimated to have dropped from 5000 to 200 pairs in the twenty years between 1991 and 2011 (with further declines since – see Ireland’s Curlew Crisis blog below). There has been an 80% decline in Wales and other losses elsewhere.  There’s more about these distributional changes in a 2012 article written for the BTO website.

Curlew productivity in several areas appears to be very low and it is possible that the adults we are seeing are part of an ageing population.  As has been shown in seabirds, counts of adults can give a false sense of security, as it is easy not to notice that there is little recruitment of new, breeding adults into the population, with obvious long-term consequences.

Graph shows the changing Curlew population in Great Britain (Wetland Bird Survey)

Graph shows the changing Curlew population in Great Britain (Wetland Bird Survey)

The decline in the number of breeding Curlew in Great Britain is clearly reflected in monthly, winter counts undertaken by volunteers on west coast estuaries.  On the Dee, for instance, the average peak-winter count dropped from 6109 in the early 1970s to 4348 in the five years after the shooting ban, rose to 5081 in the late 1990s but then slipped back to 3802.

In Ireland and Northern Ireland, a total ban on shooting Curlew was announced in 2012, brought in once it was clear that the estimated November harvest of between 6% and 8% was unsustainable and set against a background of the collapse of the local breeding populations.  The same local reasoning lies behind continuing protection in Wales, western England and in much of Scotland, especially at a time when financial support to land-managers is being used to try to bolster British breeding numbers.  In eastern England, Curlew conservation has a more international flavour, as we provide a safe haven for birds from as far away as Russia.

With relatively few continental birds, the Wetland Bird Survey trend reflects more local declines

With relatively few continental birds in Northern Ireland, the Wetland Bird Survey trends probably reflect local declines

Britain & Ireland, between them, provide winter homes for half of the Europe-wide population of Curlews (about 210,000 out of 420,000), with the Netherlands holding 140,000 birds.  There are also significant flocks in Germany and about 20,000 in France.  These may seem like reasonable numbers but, given that fewer chicks are being raised, the number of adults is declining, two close relatives have been driven to extinction and other curlew species are in trouble, the label of near-threatened seems highly appropriate.

We should be proud of our wintering Curlews in Great Britain, where numbers have stabilised, albeit at a level that is 20% lower than at the turn of the century, but there is no room for complacency in Northern Ireland, where the decline continues.

Update: Curlew was added to the red list of the UK’s Birds of Conservation Concern on 3 December 2015

Other WaderTales blogs about Curlew

  • Why are we losing our large waders? takes a look at a review of the common threats faced by the 13 Numeniini species (godwits, curlews and Upland Sandpiper).
  • Curlews can’t wait for a treatment plan focuses on the primary drivers of the species’ breeding decline in Great Britain.
  • Sheep numbers and Welsh Curlew looks at habitat associations within a large site  in the Welsh uplands; getting the grazing regime right seems to be very important.
  • Curlew Moon has at its heart a review of Mary Colwell’s book of the same name but also summarises some of the issues being faced by Curlew in Ireland and the UK.
  • Ireland’s Curlew Crisis focuses on the nationwide breeding survey between 2015 and 2017, which revealed a 96% decline in the number of pairs in just 30 years.
  • Curlews and foxes in East Anglia suggest that ‘curlew plots’ may be helpful in the fight to conserve the species.
On autumn high tides, flocks of Curlew roost on east coast stubble fields (© Graham Catley)

On an autumn high tide, a flock of Curlew roosts on an east coast stubble field (© Graham Catley)


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

UK Dotterel numbers have fallen by 57%

Research from RSPB Centre for Conservation Science, with University of Aberdeen (School of Biological Sceinces), Scottish Natural Heritage (SNH) and Natural Research Ltd

Male Dotterel brooding chicks: Alistair Baxter

Male Dotterel brooding chicks: Alistair Baxter

I have only once climbed a mountain to count Dotterel, with Phil Whitfield decades ago, but that is enough to appreciate how many hundreds of hours of hard work lie behind the statement, “The number of Dotterel breeding in the UK declined by over half between 1987/88 and 2011”. This is the headline in a paper published in the November 2015 issue of the BTO journal, Bird Study:

Changes in the abundance and distribution of a montane specialist bird, the Dotterel Charadrius morinellus, in the UK over 25 years. Daniel B Hayhow, Steven R Ewing, Alistair Baxter, Andy Douse, Andrew Stanbury, D Philip Whitfield & Mark A Eaton Bird Study 62:4, 443-456

As Des Thompson and Phil Whitfield wrote at the conclusion of their account for the 1988-91 Breeding Atlas, “The Arctic affinities of the British Dotterel, its beauty, its rarity and its likely sensitivity to habitat and climate change secure its place as one of our most fascinating breeding birds”.  Well-documented stories of females laying clutches in Scotland, to be brooded by their male partners, and then flying on to Norway to lay second clutches add an air of mystery too.

The 2011 Dotterel Survey was carried out under the Statutory Conservation Agencies/RSPB Annual Breeding Bird Survey (SCARABBS) programme and was funded by the RSPB and SNH (Alistair Baxter)

The 2011 Dotterel Survey was carried out under the Statutory Conservation Agencies/RSPB Annual Breeding Bird Survey (SCARABBS) programme and was funded by the RSPB and SNH (Photo: Alistair Baxter)

The population estimate of 423 breeding male Dotterel in 2011 represents a decline of 43% since 1999, when the comparable total was 747 pairs, and of 57% since 1987/1988 (981 pairs).  All regions except the West Highlands had lower numbers in 2011 than in 1999, with the core area of the East Highlands (the Grampians east of the A9) experiencing a significant decrease of 32% since 1999 and 56% since 1987.  This massif has become increasingly important, with 60% of the pairs in what amounts to 30% of the potential breeding habitat for Scottish Dotterel.

No Dotterel were recorded outwith Scotland during the systematic national survey but Bird Atlas 2007-11 fieldwork did add a record from Northern England.  In the absence of annual monitoring, a national survey can only provide a snapshot for a species.  However, information gathered during the four summers of the Bird Atlas project and as part of an ongoing detailed study suggests that the results for 2011 are representative of the current UK Dotterel population – and that the declines are therefore very much real.

Population changes across the range

Large-scale surveys of Dotterel are difficult, due to the remoteness of many of their breeding sites, and monitoring elsewhere across their European breeding range tends to be based on visits to particular sites or using transects.  Given the plasticity shown by the females – including an ability to nest in two countries in one year – changes in apparent numbers could potentially reflect the fact that birds breed further north in some springs than in others.  The best series of data come from Swedish Lapland, where Svensson & Anderson reported no changes in the population over the period 1972 to 2011.

In, Finland, Pulliainen & Saari observed that most females left their study area after egg-laying and hypothesised that this was in order to secure more mates further north. Lucker et al. have found evidence for higher rates of shared incubation by females at the more northern extent of the species’ breeding range than those breeding further south, providing some evidence to support this hypothesis.  Saari had previously estimated the Finnish population to be 90% less than in the early 1900s and suggested that hunting in early 20th century and overgrazing by reindeer may have been to blame.   Since the 1960s, the tree line has advanced and large areas of the mountain heath are now covered by scattered Scots Pines, making the habitat largely unsuitable for Dotterel.  Similar processes, associated with warmer conditions, could have major, negative impacts the number of Dotterel breeding in Scotland.

Is the SPA network working for Dotterel in Scotland?

Racomotrium heath is an important and increasingly rare habitat (Alistair Baxter)

Racomotrium heath is an important and increasingly rare habitat (Alistair Baxter)

The designation of Special Protected Areas (SPA), based on the results of the 1987/88 survey has been a key tool in the efforts to conserve Dotterels in Scotland.  This network of montane sites has helped to provide a focus for research funding and planning considerations.  Encouragingly, SPAs have supported between 50% and 60% of the population since designation.

The decline in numbers of Dotterel within and outwith the SPA network is of concern, but in terms of site occupancy, sites in SPA/SSSIs were more likely to be occupied than those outside the protected area network.  Protected area designation has been shown to be good for a group of northern species at the trailing edge of their distribution in the UK, although this effect decreased at higher latitudes and altitudes (Gillingham et al. 2015).

Explaining the declines

The well-referenced, discussion section of the paper looks at the potential reasons for the changes to Dotterel populations and assesses the available evidence.

Habitat change in the high mountains: Racomitrium moss heath has been shown to provide important foraging opportunities for Dotterel of all ages; this is a habitat that has been in a long-term decline over the last half century.   Studies have outlined how overgrazing and levels of atmospheric nitrogen interact, resulting in changes to the composition and extent of montane heaths.

A frequent prey of both adult and juvenile Dotterel is Tipulid (cranefly) larvae which require dense mats of moss vegetation.  Changes in composition and extent of Racomitrium heath could result in reduced prey availability, potentially affecting settlement decisions and breeding success for Dotterel.

Raven abundance has increased across much of the Dotterel's range (Map from Bird Atlas 2007–11, which is a joint project between BTO, BirdWatch Ireland and the Scottish Ornithologists’ Club)

Raven abundance has increased across much of the Dotterel’s range (Map from Bird Atlas 2007–11, which is a joint project between BTO, BirdWatch Ireland and the Scottish Ornithologists’ Club)

Predation in the breeding season: Predation of Dotterel eggs by Ravens can cause localised declines, and lower return rates have been reported for adult male Dotterel after clutch loss by predation. The period of decline in Dotterel is coincident with an increase in range and abundance, of Ravens in Scotland.  Although previous work has found no significant negative associations between Raven numbers and upland wader populations, this interaction may well warrant further investigation.

Disturbance: There is little strong evidence for widespread effects of increased visitor numbers, despite negative impacts of such activities on heath condition.

Pressures in wintering areas: Pesticide use and hunting on the wintering grounds, North Africa and Spain, have been suggested as possible factors in the decline.

More attractive conditions further north: Upland species, such as Dotterel, are cold-adapted and may well find northerly areas more conducive to breeding.  Without a flyway approach to Dotterel monitoring it is not possible to distinguish between a northerly shift in the breeding area of Dotterel and population-scale declines.

What next?

The 2011 Dotterel survey clearly shows the decline in numbers of Dotterel breeding in the UK and contraction to core sites in the East and Central Highlands.  Further, detailed work is required to understand the mechanisms driving the observed population trends, which may well involve studies in wintering areas and migration hot-spots, as well as a mixture of ecological research and ongoing monitoring in the mountains of Scotland.

The 2011 Dotterel survey has provided a spring-board for detailed research by Alistair Baxter, which is being written up as part of his PhD at the University of Aberdeen.  By repeating studies carried out during the 1980s by SNH, he hopes to see whether changes in habitat availability, habitat quality and invertebrate abundance can help to explain the decline in numbers in the last thirty or so years.

Ptarmigan is another montane species that will be targeted by

Ptarmigan is a key montane species that is being targeted by “What’s Up?” (Alistair Baxter)

Given how much effort has to go into any survey of upland species and the relative infrequency of national surveys, it is great that two recent initiatives are making the most of the calories burned to climb our highest peaks.  Many volunteers involved in the annual Breeding Bird Survey of upland squares now add an adjacent square to the original, randomly-selected plots, in order to increase the sample size in these sparsely populated but special bird areas.  Another valuable contribution is being made by mountain-lovers who know their birds and who are now contributing to the BTO Scotland led “What’s Up?” project.  This focuses on species that are sensitive to climate change and disturbance, such as Ptarmigan, Snow Bunting and Dotterel.

In an era of ever tightening budgets, it is unclear when it might be possible to organise another national survey for Dotterel.  Let’s hope that, until then, “What’s Up?” can help to alert us to distribution changes and that annual surveys of key sites might provide indications of national population changes. 

Dotterel was moved onto the red list of species of conservation concern on 3 December 2015.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Conserving British-breeding Woodcock

To help to take the pressure off declining and now red-listed British-breeding Woodcock, many estates are already delaying the start of the Woodcock shooting season.  How might this make a difference?

This is a modified version of an article published in Shooting Times on 30 Sep 2015. There are updates at the end, reflecting changing advice provided by the Game & Wildlife Conservation Trust.

Photo: Richard Chandler

Photo: Richard Chandler

Each autumn, the British population of Woodcocks is swamped by the arrival of up to a million birds, returning from northern Europe and Scandinavia. The exact timing of their migration is very much influenced by weather, with birds crossing the North Sea as early as October or as late as December.  The numbers each year are thought to vary markedly, reflecting peaks and troughs in the size of the European breeding population, annual chick production, the amount of frost and snow on the other side of the North Sea and the timing of periods of cold weather.

A quick look at the bag index for Woodcock, produced by the Game & Wildlife Conservation Trust (GWCT), shows annual variation in the numbers shot each winter but no downwards trend.  Hunting appears to be sustainable (but see note at the bottom giving advice from GWCT about shooting in winter of 2017/18).  Unfortunately, there is a problem; British-breeding Woodcock are in serious decline and there is no way to differentiate between a local bird and one from continental Europe.  As the GWCT Woodcock tracking project has shown, birds share the same woodland habitats during winter months.  Mara and Jack, for instance, two birds caught in March 2014 on Islay, have very different annual stories to tell, with Mara breeding locally and Jack migrating to Russia.

A shrinking distribution

Bird Atlas 2007-11, published by the British Trust for Ornithology (BTO), confirmed that our Woodcock are in trouble.  Between 1968-72 and 1988-91, the number of 10×10 km atlas squares where Woodcock were present fell from 1439 to 917, representing a decline of 36%.  By 2008-11, the number was down to 632, a further drop of 31%.  In the 1968-72 Atlas, Woodcocks were generally widespread, with birds absent only from parts of southwest England and Wales and easy to find from the North Midlands through to northern Scotland, other than in the highest mountains.  Fragmentation that was becoming apparent in 1988-91 was glaringly obvious in 2008-11, especially in the south and west.  In Ireland the situation, if anything, looked worse.

Bird Atlas 2007-11, published by the BTO, in association with the Scottish Ornithologists’ Club and BirdWatch Ireland, shows that breeding Woodcock are disappearing from southern and western Britain, as well as from Ireland. Downwards pointing black arrows show losses, with bigger symbols indicating recent changes.

Bird Atlas 2007-11, published by the BTO, in association with the Scottish Ornithologists’ Club and BirdWatch Ireland, shows that breeding Woodcock are disappearing from southern and western Britain, as well as from Ireland. Downwards pointing black arrows show losses.

Early results being contributed to the Bird Atlas 2007-11 project confirmed that there was an urgent need for a special Woodcock survey, to try to assess numbers as well as distribution, and this was organised for the summer of 2013.  The GWCT and the BTO wanted to replicate the survey they had organised in 2003, which suggested that the breeding population across Scotland, Wales and England included just over 78,000 territorial males.

Andrew Hoodless of GWCT has shown that the number of Woodcocks observed during a standard evening watch period provides a good index of local abundance.  The national survey called for the deployment of hundreds of birdwatchers, who were asked to visit chosen sites, many of which had been visited ten years previously.  Standing at dusk and listening to the distinctive roding calls of male Woodcocks, as they patrol the boundaries of their territories, provides magical moments for lucky birdwatchers.  However, the chance of success in many parts of the country was far lower in 2013 than it had been in 2003.  A paper, with a full regional analysis was published in 2015, revealing an estimated fall in numbers of 30%, to just over 55,000 roding males.  As suggested by the Atlas distribution maps, percentage losses were higher in Wales and England than in Scotland.

Current status and recent trend of the Eurasian Woodcock Scolopax rusticola as a breeding bird in Britain, by Christopher J Heward, Andrew N Hoodless, Greg J Conway, Simon Gillings & Robert J Fuller, in Bird Study Nov 2015

The main aim of the 2013 Woodcock survey was to assess the population, rather than to understand the causes of decline, but it is interesting to note that there were smaller losses in the largest areas of woodland.  More detailed studies have suggested that larger woods may offer a greater diversity of habitats and damper micro-climates in which to feed.  Booming deer populations are having major effects on a lot of woodlands; by browsing the vegetation they can open up the understorey, thereby removing nesting habitat and drying out soils.  There are probably several factors driving down the breeding population and it has been suggested that recreational disturbance and over-winter hunting of resident birds could each be playing a part in declines.

Changes to the hunting season?

BirdTrack is coordinated by the BTO, in partnership with RSPB, BirdWatch Ireland, the Scottish Ornithologists’ Club and the Welsh Ornithological Society. These lists provide fascinating information about the timing of migration, annual breeding patterns and species’ abundance. See www.birdtrack.net to learn more.

BirdTrack is coordinated by the BTO, in partnership with RSPB, BirdWatch Ireland, the Scottish Ornithologists’ Club and the Welsh Ornithological Society. These lists provide fascinating information about the timing of migration, annual breeding patterns and species’ abundance. See www.birdtrack.net to learn more.

Although the main pressures may well occur during the summer months, one way to help British breeding Woodcock may be to change the start of the shooting season.  The season currently opens on 1 September in Scotland and 1 October across the rest of the UK.

Looking at BirdTrack data, collected from species lists sent in by thousands of birdwatchers across Britain & Ireland, it is clear that there are virtually no continental Woodcock in these islands during September and few until at least the second half of October.  In the graph alongside, the red line shows average rates of occurrence on birdwatchers’ lists.  The blue line for 2014 indicated a pulse of arrivals in early October, largely as observed by birdwatchers on the east coast.  These birds will have moved inland and disappeared into woodland and farmland.  The main arrival in this particular year appears to have been in late October with later spikes in the graph suggesting further bursts of east coast activity in November and December.

The 2013 Woodcock survey was funded by the Game & Wildlife Conservation Trust, the Shooting Times Woodcock Club and a charitable trust. Photo: Richard Chandler

The 2013 Woodcock survey was funded by the Game & Wildlife Conservation Trust, the Shooting Times Woodcock Club and a charitable trust. Photo: Richard Chandler

The BirdTrack pattern will come as little surprise to gamekeepers and shoot-owners, many of whom already restrict Woodcock shooting to the winter months, in order to minimise losses of local, resident birds.  GWCT scientists have been encouraging restraint in the autumn months for some while.  Now, having analysed the results of the GWCT/BTO 2013 Woodcock survey, and shown a further decline of nearly a third in just ten years, they are researching the potential impact of shooting on resident birds. This will include an assessment of whether a formal change to the timing of the hunting season for Woodcock is required, in order to add an extra level of protection to resident birds.

Update: 28 July 2017

New GWCT  guidance: ‘generally we recommend not shooting woodcock before 1 December’ and not at all if ‘numbers have been low in the area’. More information is available at https://www.gwct.org.uk/media/696047/Pocket-woodcock-guide.pdf

Update: 11 December 2017

Migrant Woodcock appear to have had a poor breeding season and GWCT is advising restraint:

Dr Hoodless has issued the following statement: “GWCT and the Woodcock Network are advising shooters across the UK to rethink their woodcock shooting for this season and reduce their bags. This echoes moves being taken by organisations in several other European countries. A further update will be issued in early January, once more information is available.”

“Although similar events will have happened many times in the past, this is the first time that monitoring of woodcock age ratios by ringers, and improved communication across Europe, has been able to offer shooters an early warning system. Populations normally rebound after such events, but most shooters understand the importance of preserving breeding stocks when there are signs of adverse natural events and are prepared to minimize shooting pressure in order to aid population recovery.”

Read more here

Update: 16 March 2018

Woodcocks are severely affected by cold weather. Research by GWCT suggest that Woodcock start to suffer when the ground has been frozen for relatively short periods of time. They propose restraint after four days of freezing conditions, with birds being given a recovery period of seven days once a thaw commences. There’s more in this blog here and the paper can be found here.

Update: September 2020

There is no suggestion that the numbers of Woodcock breeding in Finland, Sweden and Norway are changing. This blog summarises survey data for breeding waders during the period 2006 to 2018.


 GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton