Scotland’s Dotterel: still hanging on

blogpic brooding

Dotterel brooding chicks

Within the UK, the Dotterel now only breeds on plateaux in the highest Scottish mountains, restricted by habitat that is more commonly found in the arctic or arctic-alpine regions. 

As soon as climate change became apparent, the Dotterel turned into a focal species for ornithologists who were interested in how species would be affected by climate heating. Their fate seemed to be sealed; put simply, there is nowhere colder in Britain to which to retreat when faced with changing habitats and/or breeding conditions.

A 2020 paper by Steven Ewing, Alistair Baxter and colleagues explores the potential ways that changing environmental conditions may be driving the Dotterel’s decline.

Life history

Scottish Dotterels don’t actually spend much time in Scotland, with most birds arriving in early May and leaving within three months. The large part of the year is spent in North Africa, and the plains to the northwest of the Atlas Mountains in Morocco seem to be a particularly important wintering grounds for Scottish birds. Migration north and south appears to be direct, with few European reports of ringed birds in spring and autumn. There is some evidence that Dotterel move further south within North Africa as winter progresses (Whitfield et al 1996), perhaps responding to rainfall patterns.

blogpic map

In May, the numbers of males and females on Scottish breeding sites are roughly equal but many females leave their males sitting on a first clutch of eggs and then depart, leading to an observed drop in sex ratios to about 10:1. Females ringed in Scotland have been spotted breeding with Norwegian males later in the same season and this onward movement to areas with later snow-melt may well be a normal pattern. Indeed, many Dotterels seen on passage in May, often on traditionally used fields or mountain tops south of the Scottish Highlands, may loop north, passing through Highland nesting haunts and then heading northeast into Scandinavia.

A species in decline

blogpic Alistair

Alistair Baxter points to a Dotterel nest that’s right next to a path following the line of a ridge

Dotterels in Britain are at the south-western limit of the species’ global range. They breed almost exclusively in arctic-alpine habitats above 750 m, particularly on Racomitrium moss-heaths that are so characteristic of the flatter topped mountains. These habitats are of high conservation concern, with a tapestry of nationally-rare alpine and arctic plant species.

Scottish Dotterel have been well-studied for over eighty years, a process that was started by Desmond Nethersole-Thompson in the 1940s (detailed in his classic monograph The Dotterel, 1973) and has involved the authors of the Global Change Biology paper since 1987. Some of the areas featured in this paper were studied by Nethersole-Thompson.

An earlier WaderTales blog (Dotterel numbers have fallen by 57%) suggested a number of possible reasons for declines – habitat changes, increased predation and increased disturbance in the Scottish Highlands, compounded by issues affecting the wintering population in North Africa. In the 2020 paper, Ewing et al look in more detail at the potential roles of these changes

Climate and habitat change in Scotland’s mountains

Mountains in Britain are subject to a range of environmental drivers of change that may potentially influence Dotterels, but the logistical challenges presented by working in these environments means that there is rarely good data documenting these changes. This study focuses on snow cover and nitrogen deposition.

blogpic change

The amount of snow-cover is important for cold-adapted species of plants and animals; it insulates the ground in winter and slows up warming in spring, thereby creating a relatively stable environment.  Potential consequences of changes in winter snow-lie for alpine birds might include:

  • A longer growing season for plants, with taller vegetation that reduces the suitability of these areas for species that favour shorter swards.
  • Fewer snow patches, around which Dotterel feed, perhaps also leading to a reduction in peak insect abundance that may not match feeding requirements of chicks.

blogpic nestLots of research carried out in the UK shows that nitrogen deposition is an important driver of upland vegetation change.  Higher deposition of nitrogen tends to result in a reduction of alpine specialist plants, including species of mosses that form key breeding habitats for Dotterel.

The earlier WaderTales blog (Dotterel numbers have fallen by 57%) suggested other possible reasons for Dotterel declines on the breeding grounds, including increased predation and increased disturbance in the Scottish Highlands. While these potential drivers of change could not be tested, due to a lack of data, they are considered in the paper’s Discussion.

Study system

The data that lie at the heart of the Global Change Biology paper have been collected over three decades. Two different but complementary data sources were used in the study.  Firstly, Dotterel were counted at between 128 and 198 alpine sites in the UK during three national surveys in 1987-88, 1999 and 2011.  These censuses focused upon suitable breeding habitats, especially Racomitrium heath, with the latter two surveys successfully covering more than 50% of identified breeding areas.  Secondly, between 1987 and 1999, a smaller cohort of alpine sites were surveyed with far greater frequency (between 40-60 times) as part of SNH’s Montane Ecology Project, where the aim was to study the Dotterel’s breeding ecology in far more detail. The 2020 paper contains detailed information about site use and the parameters that were measured/assessed (elevation, slope, area, snow cover, nitrogen deposition, summer temperature etc.)

blogpic surveyEach site visit involved a lot of climbing, so many of the sites were visited only once per season, with more frequent visits to just 15% of the sites. Having accompanied Phil Whitfield (one of the authors) up one mountain, on one day, I have huge respect for the effort that each data-point represents.  Once up on the tops, observers covered the study areas thoroughly, passing within 100 m of every point and scanning frequently. This has been shown to provide a good count of breeding males.

The authors used their data to investigate whether key potential drivers of environmental change in Scottish mountains (snow-lie, elevated summer temperatures and nitrogen deposition) may have contributed to the population decline of Dotterel.  They also consider the role of rainfall on the species’ wintering grounds in North Africa. The key questions they address are:

  1. Is there evidence of an uphill shift in the elevation of the Dotterel’s breeding range during the study period (1987-2014)?
  2. Are changes in the density or site occupancy of breeding male Dotterels associated with the size, connectedness or topographical aspect of alpine sites?
  3. Does spatial variation in atmospheric nitrogen deposition account for variation in density or occupancy of breeding males at alpine sites?
  4. Are patterns of snow cover or late summer temperatures associated with density or occupancy of male Dotterels at alpine breeding sites?
  5. Do densities of breeding male Dotterels on alpine sites vary with conditions on the North African wintering grounds, as reflected by winter rainfall?

blogpic gloaming

What has changed?

The results are presented in two ways. Data from the period of intensive studies, between 1987 and 1999, are used to try to understand factors influencing annual changes in the number of nesting males. Examination of changes between 1987-90 and 2011-14 gave some indication of factors affecting longer-term trends – something that is important to understand when Dotterel can live for at least ten years.

Densities of breeding male Dotterel in mountainous regions of Scotland declined between 1987 and 1999 and, over the longer-term, site occupancy fell from 80% in 1987 to only 36% in 2014. Densities of breeding males declined disproportionately from lower-lying sites, which resulted in the Dotterel’s breeding range retreating uphill at a rate of 25 m per decade.

Geographically isolated sites appear more likely to lose breeding Dotterel. This makes sense; playback studies in Russia have shown that passing flocks of Dotterel respond to calls, suggesting that birds will be attracted to already-occupied locations.

Settlement patterns were linked to snow-cover.  Generally, Dotterels appear to prefer to settle on higher sites, but late-lying snow at higher elevations appears to deprive them of suitable breeding habitat.  Rather than delay nesting, it seems that these birds then choose to move to lower snow-free sites to breed. Long-term changes in snow cover are poorly documented in high-elevation habitats in Scotland, so it is difficult to know whether the substantial declines observed for Dotterel in recent decades reflect systematic changes in snow-lie.

blogpic snow patch

Nitrogen deposition was shown to be negatively associated with densities of males nesting at lower and intermediate elevations.  The primary impact of nitrogen deposition on Dotterel is likely to be via effects on the species’ favoured Racomitrium moss-heaths, with greater nitrogen levels increasing the rate of moss decomposition and favouring accelerated grass growth.  This presumably results in these habitats becoming increasingly unsuitable for breeding Dotterel.

blogpic chick

Will this chick makes it to Morocco? If it does, how will the conditions it experiences in the non-breeding season affect its probability of return to Scotland?

High rainfall in North Africa seems to lead to higher densities of breeding male Dotterel two springs later, suggesting that wintering ground conditions can potentially influence population dynamics of this alpine-breeding bird.  Similar positive impacts of North African rainfall have also been seen in Ring Ouzels that breed in the UK (Beale et al. 2006).

Dotterel inhabit open farmland and sub-desert steppes in North Africa, where seasonal rainfall brings a flush of vegetation growth and insect abundance. Higher winter rainfall may increase prey availability and Dotterel survival rates but that would be reflected in the arrival numbers in the next spring. The lag of an extra year suggests that low rainfall levels may mostly affect young birds, perhaps delaying recruitment of some Dotterels until their second breeding season.

Conclusions

blogpic juvvyPopulation declines and site abandonment by Dotterel in Scotland during the last three decades have largely occurred at lower elevations, fitting with the traditional idea of climate change limiting the available climate space for alpine breeding species. However, this study found relatively limited evidence that the decline in the breeding population is being driven by climatic factors on the breeding grounds.

Snow cover does seem to influence year-to-year variation in the species’ elevational distribution in Scotland, potentially because a smaller population may now be increasingly settling on higher sites that perhaps were previously unavailable, due to extensive snow cover.  There was also some evidence that greater nitrogen deposition reduced breeding densities of Dotterel at low to intermediate elevations, perhaps by decreasing the suitability of Racomitrium moss heath breeding habitats.  It is also possible that there may have been a redistribution of birds, with newer generations moving further north, to more suitable sites in Norway. (There is a WaderTales blog about this sort of Generational Change mechanism in waders, focusing on Black-tailed Godwit).

Given that Dotterels spend so little time in Scotland, a big gap in our understanding is what is happening in Morocco, where adult Scottish Dotterel spend three-quarters of the year and where young birds may also spend their first summer. How are factors such as rainfall and land-use (particularly farming methods) affecting Dotterels? Might changes in these areas affect other species of migrant that leave northern Europe at the end of the breeding season? Perhaps conservation scientists need to head south for the winter to find out?

Read more in the paper

Clinging on to alpine life: investigating factors driving the uphill range contraction and population decline of a mountain breeding bird. Steven R. Ewing, Alistair Baxter, Jeremy D. Wilson, Daniel B. Hayhow, James Gordon, Des B. A. Thompson, D. Philip Whitfield & René Van der Wal. Global Change Biology.

blogpic dewy


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

@GrahamFAppleton

 

Nine red-listed UK waders

blog rpIf you ask British birdwatchers to name the nine wader species that are causing the most conservation concern in the UK, they would probably not include the Ringed Plover. Curlew may well be top of the list, even though we still have 58,500 breeding pairs in the UK*, but would people remember to include Ruff? This blog is written to coincide with the publication of Red67, an amazing collaboration of artists and essayists that highlights and celebrates the 67 species on the current UK red list, nine of which are waders.

*Avian Population Estimates Panel report (APEP4) published in British Birds

What’s a Red List?

The UK Red List is made up of a strange mixture of common and rare species. Nobody will be surprised to see fast-disappearing Cuckoo, Turtle Dove and Willow Tit, but why are 5.3 million pairs of House Sparrow in the same company? The list is very important because it helps to set the agenda for conservation action, the way that money for research is distributed and focuses attention during planning decisions. The main criteria for inclusion are population size – hence the inclusion of species that are just hanging on in the UK, such as Golden Oriole – and the speed of decline of common species. Data collected by volunteers, working under the auspices of the British Trust for Ornithology, measured a population decline for House Sparrow of 70% between 1977 and 2017, which is worrying enough to earn this third most numerous breeding species in the UK a place in Red67.

blog bookIn his foreword to Red67, Mark Eaton, Principal Conservation Scientist for RSPB, explains how listing works. The Birds of Conservation Concern (BOCC) system, through which the Red List and Amber List are determined, uses a strict set of quantitative criteria to examine the status of all of the UK’s ‘regularly’ occurring species (scarce migrants and vagrants aren’t considered), and uses a simple traffic light system to classify them. There are ‘Red’ criteria with thresholds for rates of decline in numbers and range, historical decline and international threat (if a species is considered globally threatened it is automatically Red-listed in the UK), together with a range of other considerations such as rarity, international importance of UK populations, and how localised a species is. If a species meets any of the Red List criteria it goes onto the Red List.

The Red67 book – words meet art

Red67 is the brainchild of Kit Jewitt, a.k.a. @YOLOBirder on Twitter. It’s a book featuring the 67 Red-listed birds, each illustrated by a different artist alongside a personal story from a diverse collection of writers. Proceeds will support Red-listed species conservation projects run by BTO and RSPB. Kit describes Red67 as 67 love letters to our most vulnerable species, each beautifully illustrated by some of the best wildlife artists around, showcasing a range of styles as varied as the birds in these pages. My hope is that the book will bring the Red List to a wider audience whilst raising funds for the charities working to help the birds most at need.

This blog is about the nine waders in the book, but there are 58 other fascinating species accounts and wonderful artworks. Each species account starts with a quote from the story in the book and is accompanied by a low-resolution version of the artwork (Ringed Plover is illustrated above).

Lapwing

blog l“It’s the crest that does it for me – that flicked nib stroke, the artist’s afterthought” – Lev Parikian

The Lapwing used to nest across the whole of the United Kingdom and was a common bird in almost every village. It’s still the most numerous breeding wader in the UK, with 97,500 pairs (APEP4), beating Oystercatcher by just 2,000 pairs. Numbers dropped by 54% between 1967 and 2017, according to BirdTrends 2019, published by BTO & JNCC. Huge losses had already occurred over the previous two centuries, as land was drained and vast numbers of eggs were collected for the table. The Lapwing is now a bird associated with lowland wet grasslands and the uplands, rather than general farmland.

Red-listing has been important for Lapwing, increasing the profile of the species and encouraging the development of specific agri-environment schemes targeted at species recovery. These include ‘Lapwing plots’ in arable fields and funding to raise the summer water tables in lowland grassland. Several WaderTales blogs describe efforts to try to increase the number of breeding waders in wet grassland, especially Toolkit for Wader Conservation. The loss of waders, and Lapwings in particular, from general farmland is exemplified in 25 years of wader declines.

Ringed Plover

blog rp graph“They gather at high tide like shoppers waiting for a bus: all facing the same direction, and all staring into the distance” – Stephen Moss

One of the criteria that the BOCC panel takes into account, when constructing the Red List, is the responsibility the UK has for a species or subspecies in the breeding season, during winter or both. The Ringed Plovers we see in the UK in the winter are almost exclusively of the hiaticula subspecies; birds that breed in southern Scandinavia, around the Baltic, in western Europe and in the UK. There are only estimated to be 73,000 individuals in this subspecies, so the 42,500 that winter in the UK constitutes a large percentage of the Ringed Plovers that breed in many of these countries.

The Wetland Bird Survey graph alongside shows a decline of over 50% between 1989 and 2014. At the start of the period, Ringed Plover numbers were at an all-time high but this is still a dramatic and consistent drop. Numbers have stabilised and may even have increased slightly but Ringed Plovers need some good breeding years. Disturbance is an issue for breeding Ringed Plovers, which share their beaches with visitors and dogs, and could also potentially be a problem in the winter (see Disturbed Turnstones).

Dotterel

blog dot“I want you in the mountains. Summer breeze. At home. Doing your thing. So don’t go disappearing on us, okay?” – Fyfe Dangerfield

The Dotterel is a much clearer candidate for Red67 – there’s a small population in a restricted area and numbers have fallen. The detailed reasons for decline may still need to be nailed down but candidate causes such as declining insect food supplies and the increasing numbers of generalist predators are probably all linked to a changing climate – squeezing Dotterel into a smaller area of the mountain plateaux of Scotland.

There’s a blog about the decline in Dotterel numbers called UK Dotterel numbers have fallen by 57%, based upon a paper that uses data up until 2011. At this point, the population was estimated at between 280 and 645 pairs. There has been no suggestion of improvement since that blog was written. Interestingly, Dotterel may have a way out of their predicament, as we know that marked individuals move between Scotland and Norway in the same breeding season.

Whimbrel

blog whim“How often do Whimbrels pass overhead nowadays? Unseen and unheard, their calls mean nothing to most of us” – Patrick Barkham

Most British and Irish birdwatchers think of Whimbrel as spring migrants, enjoying seeing flocks of Icelandic birds when they pause on their way north from West Africa (see Iceland to Africa non-stop). There is a small, vulnerable population nesting almost exclusively on Shetland. The latest estimate is 310 pairs (2009), down from an estimate of 530 pairs, published in 1997. Many pairs have been lost from Unst and Fetlar and this blog about habitat requirements, based on RSPB research, might give clues as to why: Establishing breeding requirements of Whimbrel.

The curlew family is in trouble across the Globe, potentially because these big birds need so much space (see Why are we losing our large waders?)

Curlew

blog cu“… achingly vulnerable in a world that is battling to hold onto loveliness” – Mary Colwell

What more can be said about Curlew, ‘promoted’ to the red list in 2015 and designated as ‘near threatened’ globally. Most significant is the story from Ireland, where 94% of breeding birds have disappeared in just 30 years. These blogs provide more information about the decline and review some of the reasons.

There are more Curlew-focused blogs in the WaderTales catalogue.

Black-tailed Godwit

blog blackw“A glimpse of terracotta is obscured by ripples of grass, dipping gently in the breeze” – Hannah Ward

Winter Black-tailed Godwit numbers are booming but these are islandica – birds that have benefited from warmer spring and summer conditions in Iceland, as you can read here in: From local warming to range expansion. Their limosa cousins are in trouble in their Dutch heartlands (with declines of 75%) and there have been similar pressures on the tiny remaining breeding populations in the Ouse and Nene Washes. Here, a head-starting project is boosting the number of chicks; so much so that released birds now make up a quarter of this fragile population. Red-listing has shone a spotlight on this threatened subspecies, attracting the funding needed for intensive conservation action.

Ruff

blog ruff“They look a bit inelegant – a small head for a decently sized bird, a halting gait, and that oddly vacant face” – Andy Clements

There are two ways for a species to be removed from the Red List – extirpation (extinction in the UK) and improvement. Temminck’s Stint came off the list in 2015, having not been proven to breed since 1993, and Dunlin was moved to Amber at the same time. Ruff are closer to extirpation than they are to the Amber list. There is a spring passage, mostly of birds migrating from Africa to Scandinavia and the Baltic countries, and some males in glorious breeding attire will display in leks.

250 years ago, Ruff were breeding between Northumberland and Essex, before our ancestors learnt how to drain wetlands and define a hard border between the North Sea and farmland. Hat-makers, taxidermists and egg-collectors added to the species’ woes and, by 1900, breeding had ceased. The 1960s saw a recolonisation and breeding Ruff are still hanging on. There are lekking males causing excitement in sites as disparate as Lancashire, Cambridgeshire and Orkney, and there are occasional nesting attempts. Habitat developments designed to help other wader species may support Ruff but the situation in The Netherlands does not suggest much of a future. Here, a once-common breeding species has declined to an estimated population of 15 to 30 pairs (Meadow birds in The Netherlands).

Red-necked Phalarope

blog rnp“… snatching flies from the water in fast, jerky movements, droplets dripping from its slender beak” – Rob Yarham

Red-necked Phalaropes that breed in Shetland and a few other parts of northern Scotland appear to be an overflow from the Icelandic population; birds which migrate southwest to North America and on to the Pacific coastal waters of South America. This BOU blog describes the first track revealed using a geolocator.

The Red-necked Phalarope was never a common breeder and came under pressure from egg-collectors in the 19th Century. Numbers are thought to have recovered to reach about 100 pairs in Britain & Ireland by 1920. Numbers then fell to about 20 pairs by 1990, so the latest estimate of 64 pairs (The Rare Breeding Birds Panel) reflects conservation success. Given the restricted breeding range and historical declines, it is unlikely that the next review will change the conservation status from Red to Amber, despite the recovery of numbers.

Woodcock

blog wk“… taking the earth’s temperature with the precision of a slow, sewing-machine needle” – Nicola Chester

The presence of Woodcock on the Red List causes heated debate; how can this still be a game species? Red-listing is indisputable; the latest survey by BTO & GWCT showed that there was a decline in roding males from 78,000 in 2003 to 55,000 in 2013, with the species being lost from yet more areas of the UK. Each autumn, the number of Woodcock in the UK rises massively, with an influx of up to 1.4 million birds. Annual numbers depend upon seasonal productivity and conditions on the other side of the North Sea. A recent report on breeding wader numbers in Norway, Sweden and Finland, shows that breeding populations of Woodcock in this area are not declining (Fennoscandian wader factory).

The UK’s breeding Woodcock population is under severe threat from things such as increased deer browsing and drier ground conditions but winter numbers appear to be stable. The difference in conservation status between breeding and wintering populations is reflected in the fact that Woodcock is on both the Red List and the Quarry List, for now. There is a WaderTales blog (Conserving British-breeding Woodcock) that discusses ways to minimizes hunting effects on British birds. These guidelines from GWCTemphasise the importance of reducing current pressures on British birds.

In conclusion

blog bookThe Red List creates some strange bedfellows. In the book, Turtle Dove follows Herring Gull; a bird with links to love and romance and another with at best the charm of a roguish pirate. But the List works; it creates an evidence-base that help those who devise agricultural subsidy systems, advise on planning applications, license bird control and prioritise conservation initiatives.

Red67 seeks to raise awareness of the UK’s most at-risk bird species, nine of which are waders, and to raise money for BTO and RSPB scientists to carry out important research. It’s a lovely book that captures the thoughts and images of a generation of writers and artists. You can learn more about the project, order the book and buy some Red Sixty Seven products by clicking here.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

 

Scottish Wader Woes

The report on Scotland’s terrestrial bird species, covering the period 1994-2016, did not make easy reading for wader lovers. All but one species was contributing negatively to the upland bird indicator, with declines of over 40% for breeding Lapwing, Curlew, Dotterel, Oystercatcher and Golden Plover. In this short blog, there are links to information that helps to explain what might be going wrong for Scotland’s waders.

The figures from the report have been update in the Breeding Bird Survey for 2018 (published 2019) and these figures are now included below. Golden Plover is no longer part of the ‘over 40%’ club.

The full report is available on the SNH website (https://www.nature.scot/information-library-data-and-research/official-statistics/official-statistics-terrestrial-breeding-birds)

The updated Breeding Bird Survey results are available on the BTO website (https://www.bto.org/our-science/projects/bbs/latest-results)

One species has been increasing – Snipe up 22% *

snipe abundance change* BBS results for Snipe for 1995-2017 revise the change figure to show an increase of 32%.

The one spot of good news is that breeding Snipe numbers in Scotland have risen over the period 1994 to 2016. This is particularly encouraging, given declines in much of the rest of Britain and Ireland, as you can see in the map alongside and read in this WaderTales blog Snipe and Jack Snipe in the UK and Ireland.

In the map, produced for Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC), pink colours show abundance increases and grey areas show decreases.

Lapwing declines largest – down 63% *

GHH picture* BBS results for Lapwing for 1995-2017 revise the change figure to show a decrease of 55%.

When a widespread species such as Lapwing is in decline this is bad news. Subtle difference in the way that lowland valleys are farmed may be part of the problem, as illustrated in this WaderTales blog, based on work by Mike Bell, written up with the help of John Calladine, of BTO Scotland: 25 years of wader declines.

Curlew down 62% *

Blog Jill P* BBS results for Curlew for 1995-2017 revise the change figure to show a decrease of 61%.

The Curlew is causing huge concerns in Ireland and Wales, where conservationists are contemplating its disappearance as a breeding species. Scotland holds much larger numbers but a decline of nearly two-thirds suggests that there are major problems here as well.

Two WaderTales blogs tell the Curlew story. Is the Curlew really near-threatened explains why we should be so worried about what is happening and Curlews can’t wait for a treatment plan summarises a BTO-led paper from Sam Franks and colleagues which attempts to explain the patterns we are seeing in the species’ decline.

Dotterel down 60%

IMG_2123

Alistair Baxter

Most of the information about Scotland’s breeding birds comes from annual data collected by volunteers contributing to the Breeding Bird Survey (BBS), organised by the BTO, in partnership with JNCC and RSPB. Dotterel is different; here the counts are dependent on dedicated surveys of Scotland’s high-mountain plateaus. Concern for the species is very much linked to climate change but this blog, based on a paper by the RSPB’s Daniel Hayhow and colleagues, shows that there may well be other reasons for the species decline: UK Dotterel numbers have fallen by 57%. The figure for the decline may be slightly out-of-date but the blog isn’t.

TGG OycOystercatcher down 44% *

* BBS results for Oystercatcher for 1995-2017 revise the change figure to show a decrease of 38%.

In England, the latest BBS report shows an increase of 49% in Oystercatcher numbers but, in Scotland, where there are far more breeding pairs, the species is in decline. Oystercatchers: from shingle beaches to roof-tops looks at the history of the species’ spread from the shoreline, into the hills and onto roofs and considers the role of predation in recent declines.

Golden Plover down 43% *

* BBS results for Golden Plover for 1995-2017 revise the change figure to show a decrease of 10%.

As noted in the press release about the SNH report ‘The golden plover population has declined by 43% since 1994 and stands at its lowest point since the BBS survey began. Declines may be linked to climate change, in part due to impacts on the abundance of craneflies during the breeding season”. There are two interesting papers about this by James Pearce-Higgins and colleagues.

golden ploverPearce-Higgins, J.W., Yalden, D.W. & Whittingham, M.J. 2005. Warmer springs advance the breeding phenology of golden plovers Pluvialis apricaria and their prey (Tipulidae). Oecologia 143: 470–476.

Pearce-Higgins, J.W., Dennis, P., Whittingham, M.J. & Yalden, D.W. 2010 Impacts of climate on prey abundance account for fluctuations in a population of a northern wader at the southern edge of its range. Global Change Biology 16: 12–23.

Common Sandpiper down 39% *

* BBS results for Common Sandpiper for 1995-2017 revise the change figure to show a decrease of 23%.

The Breeding Bird Survey does not properly capture trends for species found mostly along rivers. Data for Common Sandpiper are derived from the BTO Waterways Bird Survey and the Waterways Breeding Bird Survey.

Why no Redshank?

Unfortunately, breeding Redshank are now patchily distributed across Scotland, with too few being picked up by BBS surveyors to make a contribution to Scottish population indices. Across the UK, the latest published BBS decline is 38%. UK graphs for Oystercatcher, Redshank and Curlew are shown below.

UK BBS


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

 

WaderTales: a taste of Scotland

11 Dec RK LWhy is Scotland losing its breeding waders? The latest WaderTales blog with a Scottish flavour is a story from Strathallan, based on observations by Mike Bell.

“If you’ve taken the A9 north of Stirling, through Strathallan, perhaps you might have noticed displaying Lapwing, Oystercatcher, Curlew and Redshank? Over a 25-year period, the number of breeding waders in this valley and another one that runs northwest and that can be seen from the B827 has dropped from 600 pairs to just 76 – that’s a loss of 87%, or over 20 pairs per year.”

Click here for a link to the blog

 

And here are five more uniquely Scottish WaderTales blogs

headerWaiting for the wind – spring flocks of Black-tailed Godwit on Scotland Observations from Tiree by John Bowler and others gave a unique insight into what happens if northerly winds set in at migration time.

scottish-wadertalesEstablishing breeding requirements of Whimbrel  focuses on the different habitat needs of adults and chicks in Shetland.

Oystercatchers: from shingle beach to roof-tops details significant declines in Scotland, at least partly explained by predation. An increasing number have now taken to nesting on roofs.

UK Dotterel numbers have fallen by 57% presents the results of an RSPB survey that was published in Bird Study.

Prickly problems for waders explains how SNH are trying to deal with introduced Hedgehogs in the Outer Hebrides, where they are a major problem for breeding waders.

And here are another nine which may well appeal to Scottish birdwatchers:

  • NEWS and Oystercatchers focuses on the waders that  winter on coasts, instead of estuaries. It was written to promote the 205/16 coastal survey run by BTO.
  • A place to roost discusses the importance of safe, high-tide roosts, especially in terms of energetics. What are waders looking for?
  • The not-so-Grey Plover focuses on the moult of the Grey Plover but the principles are relevant to determining the ages of birds of other species.

There are over 40 WaderTales blogs. The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published.


GFA in IcelandGraham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

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