Curlews and foxes in East Anglia

blog chicksWith Curlew populations in free-fall across much of the British Isles, researchers are trying to understand the reasons for poor breeding performance. At the same time, several groups are trialling emergency interventions, such as predator control and predator exclusion, to try to boost the number of fledged chicks. Sharing knowledge is crucial, so it’s great that a 2020 paper by Natalia Zielonka and colleagues in Bird Study adds to our understanding of nest-site selection and the reasons for nesting failures.

Breckland Curlew

When we think of Britain’s breeding Curlew, the traditional image that comes to mind is moorland, where displaying birds deliver their haunting, bubbling call across upland heather moor and sheep pasture. In lowland East Anglia, in the east of England, things are very different. Some Curlew nest on Breckland heaths, which are structurally similar to moorland, but you can also find nests in sugar-beet field, in military training areas and around airfields.

The Eurasian Curlew is now categorised as Near Threatened by IUCN & BirdLife International, due to populations declines (see Is the Curlew really near-threatened?). Figures from the Breeding Bird Survey for the period 1995-2017 show that the situation in England (30% decline) is less bad than Scotland (down 61%) or Wales (down 68%). The species is now too thinly spread to be monitored in Northern Ireland but we know that the breeding population in the Republic of Ireland dropped from 3,300 pairs to just 138 pairs in 30 years (more in Ireland’s Curlew Crisis). In this context, the hot-spot in Breckland (see left-hand map from Bird Atlas 2007-11) is significant, as is the fact that there are four 10-km squares in East Anglia where an increase in density was noted between 1988-91 and 2008-11 (right).

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Problems for Curlew

The main driver of UK Curlew decline is low breeding productivity, attributable to predation and reduced quality of breeding habitats (see review by Franks et al., summarised in Curlews can’t wait for a treatment plan). Research has informed habitat provision and demonstrated that legal predator control (of foxes, crows, stoats and weasels) can increase Curlew breeding success and abundance – but not in all cases.

blog flyingMuch of the research underpinning the above review was conducted in upland areas. What is happening in the flatlands of East Anglia and might any differences explain the apparent resilience – or even growth – of this population? Most lowland Curlew breed on dry grasslands and heathland, where physical ground-disturbance is increasingly advocated as a land management technique for other rare, scarce and threatened species, such as Stone-Curlew and Woodlark. How do these interventions affect breeding Curlew in the same areas?

Study site

Natalia and her colleagues studied Curlew in two extensive grass-heath sites that differed in predator density and management. Across both sites, vegetation structure had been modified, using ground-disturbance plots, as part of a wider multi-taxa experiment, aimed at increasing biodiversity and supporting key species such as Woodlark (paper in Ibis) and Stone Curlew (paper in Biol. Conserv.).  This disturbance involved creating  2 to 4 hectare plots of deep- or shallow-cultivated ground within the wider grassland/heathland environment.

Before the experiment began, and based on previous research elsewhere, it was assumed that Curlew would avoid physically-disturbed areas, given that Curlew have been shown to prefer to nest in rougher habitats with longer grass swards.  Wherever the Curlews decided to nest, it was predicted that nest survival would be higher on the site with lower predator density, that most clutches would be taken at night and that success would decrease through the season.

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The study was carried out in 2017 and 2018 across the Stanford Military Training Area (STANTA) and Brettenham Heath. Both sites contain extensive areas of dry grassland and grass-heath, surrounded by arable farmland and woodland. Generalist predator control on STANTA was largely carried out around Pheasant release pens, with little or none in most of the surrounding, open arable farmland and woodland. In contrast, Brettenham Heath was subject to continuous predator control across the whole site and in surrounding arable farmland (but not woodland). Brettenham Heath is also enclosed by a two-metre high deer fence with a single electric strand set 50 cm above the ground. There is more about the two sites in the paper (link below).

blog Brettenham

Across both sites, 64 experimental ground-disturbance plots were established in early 2015 and subsequently disturbed annually, using a variety of management techniques. Areas on STANTA that might have contained unexploded ordinance could not be disturbed – and were trickier to survey! In both years, nests were located between mid-April and late June, by visiting any area where Curlew had been seen and looking for adults sitting on, or walking back to, a nest.

Evidence of nest success

blog chickTo determine the date and timing of nest failure, temperature sensors were placed under the eggs. Nests were remotely checked every three-to-seven days, to confirm adults were still incubating, and the scrape was visited once a week to record any predation events (e.g. partial clutch predation). From three days before the predicted hatch date, nests were remotely monitored daily to accurately determine their fate. After hatching, the nest site was visited every three-to-five days, to observe adults and chicks from a vehicle, continuing until the chicks fledged or the breeding attempt had failed.

Three types of evidence can help to reveal the outcome of a nesting attempt:

  • Small chicks or alarming adults are seen in the vicinity of an empty nest.
  • Small shell fragments are found in the nest cup, indicating that chicks have hatched.
  • The temperature sensor reveals that adults kept the eggs warm for the whole incubation period.

A sudden drop in nest temperature can reveal the timing of predation and hint at the culprit. Other studies have shown that nocturnal visits are usually by foxes or badgers, or occasionally hedgehogs. In 2018, infra-red cameras, triggered by movement, were used on ten nests.

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Where to nest?

Unexpectedly, given that breeding Curlew in the uplands are usually associated with areas with longer grass, Breckland pairs were five- to six-times more likely to select disturbed plots than undisturbed grassland. Nearly half of nests were located on disturbed grassland across both years, which only occupied about 8% of the grassland area. Curlew are long-lived and site-faithful, so disturbed plots may have been created within already-established breeding territories. Whilst physical-disturbance interventions are unlikely to bring birds in from the wider landscape, this study shows that nest placement was more likely to occur on disturbed grassland within a pair’s home range. This suggests that local-scale management can influence nest placement within established breeding sites.

Disturbed grassland is characteristically bare and short compared to uncultivated grassland. Curlew may have placed nests in this habitat because it allows greater vigilance and/or because there is a greater abundance of some important prey for chicks than the surrounding grassland (information in paper by Hawkes et al.). Most nests were on shallow-cultivated plots (created with a rotary rotovator), with few on the barer deep-cultivated plots (created with an agricultural plough). There was taller vegetation and more ground cover in the shallow-cultivated plots.

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Nest survival rates                                                                                                                       

Over the course of the two summers, 44 Curlew nests were monitored, of which 32 failed. 29 nests were predated, one was trampled by livestock, one was mown and one pair deserted (and then renested). Mean overall nest survival probability from start of incubation to hatching was 0.70 ± 0.18 SE at Brettenham Heath (where there was intensive predator control and fencing) and 0.16 ± 0.06 at STANTA (where predator control was patchy and the site was open). Overall breeding productivity was 0.16 ± 0.01 SE fledged chicks per nesting attempt. As predicted, daily nest survival rate decreased through the course of the nesting season.

The figure for STANTA represents low nesting survival, especially when compared to other lowland sites in England, and re-nesting following failure appeared infrequent. Productivity here is likely to be substantially below that required to maintain a stable population. Importantly, nest survival across the two sites was not influenced by ground-disturbance, which suggests that this management intervention did not increase nest exposure to predators.

Identifying the predators

D4_sheep_predation_20May

Sheep versus Curlew

Of the ten 2018 nests with nest cameras:

  • Three nests survived through to hatching.
  • Four were predated by fox (one during the day and three at night).
  • One nest was predated by an unknown predator (following camera malfunction).
  • One nest was predated by a sheep (two out of four eggs remained but incubation was not resumed and the other eggs were later taken by a crow).
  • A single-egg, late-season re-nesting attempt was abandoned three days after camera deployment (egg was later taken by a crow)

There was no effect of nest cameras on daily nest survival rate.

G1_Fox_predation_20May

Fox versus Curlew

Parent Curlews removed some of the temperature loggers but there were sufficient data to identify the timing of predation events for 23 nests. Of these, 17 events were during the night (13 nocturnal, four crepuscular) and six during the day. This nocturnal timing of nest predation was consistent with mammalian rather than avian predation, with camera traps and other evidence suggesting that foxes were the main perpetrators.

As expected, from the levels of predator control, nest survival was lower at STANTA than Brettenham Heath. The latter site was both fenced and subject to lethal fox control, delivering a breeding productivity well above that considered necessary for a sustainable population of Curlew. It is possible that a few fenced sites and others with high levels of predator control might be disproportionately responsible for the fact that Curlew appear to be doing better in the Brecks than in other areas.

Conservation implications

blog bare nestThe key finding of this project is that physical ground-disturbance, which is advocated as a conservation measure within lowland dry grassland and grass-heath for many rare, scarce and threatened species, also provides suitable Curlew nesting habitat, with no reduction in nest survival. Implementing ground-disturbance, particularly through shallow-cultivating, in areas with few or no mammalian nest predators, could provide a useful management tool for attracting breeding Curlew to safer areas.

An intervention to help Stone Curlew and Woodlarks was never designed to assist Curlew. Indeed, there was a prediction that Curlew would actively avoid areas that had been rotovated, in order to create bare patches in which the target species could nest and feed. In a rare case of serendipity, experimental research by Rob Hawkes, Paul Dolman and others has delivered a way of encouraging Curlew to nest in relatively small plots (2-4 hectares) around which it may be possible to run an electric fence. One of the big questions “How can we protect Curlew nests when they have such big territories?” might have become easier to answer. If ‘Curlew plots’ can be created within known territories, or even areas that seem good for Curlew, then they can potentially become the focus for protection.

Having spotted that Curlew seemed to be attracted to disturbed areas it is great that Natalia Zielonka was able to study this population, in order better to understand constraints that seem to be restricting productivity. Her research was undertaken as part of her MSc in Applied Ecology and Conservation at the University of East Anglia,

Further reading

blog RARThe paper at the heart of this blog is:

Placement, survival and predator identity of Eurasian Curlew Numenius arquata nests on lowland grass-heath. Natalia B. Zielonka, Robert W. Hawkes, Helen Jones, Robert J. Burnside & Paul M. Dolman.

Bird Study. DOI 10.1080/00063657.2020.1725421


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.

 

Which Icelandic Oystercatchers cross the Atlantic?

blog ringed birdMost Icelandic Oystercatchers leave Iceland in the autumn, crossing the Atlantic and arriving in Ireland, the UK and mainland Europe. Despite much shorter day-length and colder conditions, 30% spend the winter in Iceland, as discussed in this blog (Mission Impossible).

A 2020 paper from Verónica Méndez and colleagues asks whether birds that stay in Iceland or cross the Atlantic differ in sex, body-size or breeding location (within Iceland) and whether birds behave differently in different years. Interestingly, they were also able to test whether there is assortative mating – do Oystercatchers that stay in Iceland pair with other stay-at-home birds?

Iceland’s Oystercatchers

Iceland lies at the northern edge of the breeding range of Eurasian Oystercatchers. The country supports an unusually high proportion of wintering Oystercatchers, given its latitude and winter temperatures (Þórisson et al. 2018), and this may be influenced by the trans-oceanic flight of at least 700 km that migratory individuals must undertake to reach the European wintering sites. Individuals that migrate or stay within Iceland could differ in body size, for example if size influences the capacity to survive adverse winter conditions. Females tend to be slightly larger, and thus any sex differences in migratory behaviour could potentially reflect differences in body size.

It would be easy to imagine a scenario in which Oystercatcher pairs try to breed as early as possible, as this could increase the number of potential nesting attempts, as discussed in Time to nest again, based on Morrison et al. 2019. Does this mean that stay-at-home birds pair off at the start of the season, before migrants arrive? Given that most birds will choose the same mate in successive years, what happens in mixed pairs if a resident is waiting around for a delayed migrant? Is divorce likely to occur, as discussed in the importance of synchrony for Black-tailed Godwits, and could this mean that mixed pairs are rare?

Colour-marks and isotopes

blog map of sightingsA huge amount of the evidence that was used to answer the questions posed by Verónica and her colleagues was provided by volunteer birdwatchers, who reported colour-ringed Oystercatchers in their wintering areas, in the period through to April 2018. There’s an impressive set of dots on the map alongside, from the north of Scotland through to Spain, and the number of sightings continues to rise. It’s perhaps unsurprising, given the direction of travel from Iceland, that there is a strong westerly bias to the distribution across the British Isles.

The sample size from colour-ring observations was not big enough to answer all of the questions posed above, especially relating to whether pairs mate assortatively. To provide one data-point, it’s necessary to know the winter locations of both members of the pair. Might feather isotope ratios provide some help?

Oystercatchers that winter in Iceland use a restricted number of coastal sites (as inland sites are frozen during winter) and forage on marine prey. Elsewhere in Europe, a much wider range of marine and freshwater resources is available, with birds readily moving between the shoreline and fields, golf-courses, football pitches and road-side verges. Previous studies have shown that terrestrial diets produce different carbon and nitrogen isotope ratios, based on salinity and trophic level of prey items.  Are differences in habitat use and diet of Oystercatchers reflected in carbon (δ13C) and nitrogen (δ15N) isotope ratios of feathers grown during late winter?

blog isotope chest

Oystercatchers moult their chest feathers in late winter

The research team hoped that isotopic signatures from resighted colour-marked migrants and residents would be sufficiently different to be able to predict the probable wintering areas (Europe or Iceland) of marked birds not seen away from their breeding sites. If so, this would greatly increase the sample size, by enabling the combination of data from observations of colour-marked individuals with information on birds that could be assigned as Icelandic or European winterers using the isotopic composition of their feathers. They predicted that it would then be possible to:

  • Identify migratory strategies of individual Oystercatchers and explore whether the likelihood of migrating or staying in Iceland is related to gender, body size or breeding location.
  • Assess how consistent these individual strategies are between years.
  • Quantify spatial variation in the distribution of migrants and residents across the Icelandic breeding range.
  • Determine whether Oystercatchers mate assortatively in relation to migratory behaviour.

The work covered in this paper was conducted between 2013 and 2017. Full details of the study areas and methods are available in the paper – link below.

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Early nesting is not always a good idea – still incubating after sudden snow-fall

Migrant or resident?

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An Icelandic Oysterctaher spending the winter in Co. Sligo in Ireland

Of the 537 colour-ringed adults in the study, 58 were seen away from Iceland and 55 were shown to be resident in Iceland. Oystercatchers undertake a partial moult at the end of the winter period, when they grow new feathers on the neck and chest. The isotopic signature of a tiny piece of one of these feathers, taken from each adult at the time of ringing or recapture, was determined. The values of δ13C, which relates to habitat salinity, and δ15N, which relates to trophic level of diet, varied between residents and migrants but there was an overlap (details in paper).  There was enough of a difference, however, for it to be possible to allocate two-thirds of ringed birds that had not been seen in the winter period to the resident and migratory categories, with sufficient certainty, thereby increasing the sample size for other tests.

Consistency of migratory tendency

The 18 individuals that were observed in more than one winter were all consistent in migratory behaviour (10 residents and 8 migrants) and each was seen in the same specific location (Iceland or western Europe) in both winters. Where feather samples were taken in more than one year, there was no evidence of any bird changing its habitat or diet.

Factors influencing individual migratory programmes

Females and males were equally likely to migrate and there was no evidence that bigger (or smaller) birds were more likely to leave Iceland. Most Oystercatchers that winter in Iceland are in flocks in the west of the country, where the coast is warmed by the Gulf Stream. Unsurprisingly, westerly breeders were more likely to be resident than those in the south or northeast of Iceland (see figure below).

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Assortative mating

Vero and her colleagues were able to assign the migratory strategy to both members of the pair for 162 pairs (either by resightings or using predictions from isotopic signatures). Among these, 75 pairs (46%) were both migrants, 32 pairs (20%) were both residents and 55 pairs (34%) were mixed. The frequency of full-migrant, full-resident or mixed pairs varied significantly among regions, which was to be expected, given the differences in the likelihood of migrating from different parts of Iceland. There was no evidence of assortative mating; the likelihood of a particular individual pairing up with a migrant was as expected from the proportion of migrants in the area; it was not influenced by whether the particular individual was itself a migrant (see figure above).

To migrate or remain in Iceland

The consistency of adult migratory behaviour suggests that migratory strategy is determined in early life, and the regional variation in the frequency of migrants and residents may thus reflect variation in the conditions encountered by individuals during this life stage. As noted above, the frequency of residency is greatest amongst Oystercatchers breeding in the west of Iceland, which are the areas closest to the main wintering locations. Juveniles from the northwest and west are more likely to encounter these flocks of adult and sub-adult birds when moving south, than juveniles from the south, north-east and east, which are more likely to encounter migrating adults.

blog gen chThe regional variation in migratory strategy could arise through the influence of social cues, with juveniles adopting the behaviour of Oystercatchers they encounter and then recruiting back into their natal locations (more about this in Generational Change, focusing on Black-tailed Godwits). Birdwatchers across Europe will hopefully help to test this theory, by tracking colour-ringed juveniles during the early years of life. This is all part of a quest to identify the conditions that influence migratory behaviour and to understand the consequences, in terms of survival rates and productivity, of adopting different migratory traits.

Paper

Please click on the title below to access the paper:

Individual variation in migratory behavior in a sub-arctic partial migrant shorebird by Méndez V., Alves J.A., Þórisson, B., Marca, A., Gunnarsson, T.G., Gill, J.A.  Published in Behavioral Ecology (2020).  doi.org/10.1093/beheco/araa010 

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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

 

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.

 

 

Disturbed Turnstones

blog facingIn a 2020 paper, Mark Whittingham and colleagues show that, in one area of northeast England, the decline in Turnstone numbers is more obvious on mainland sites that are subject to human disturbance than on offshore refuges. Whilst national declines are probably linked to factors affecting productivity in breeding areas in Greenland and Canada, it is interesting that Turnstone seem to be withdrawing into areas where they are subject to less winter disturbance.

Turnstones – some background

The Turnstones that we see around the coastline of Britain and Ireland in the winter are almost exclusively birds that fly here from Greenland and eastern Canada, as you can read in this blog about wader migration (Which wader, when and why?). Britain’s wintering Turnstone numbers are falling, as are populations of several other species, such as Curlew, Oystercatcher, Knot and Redshank (see Do population estimates matter?). Turnstones are opportunist feeders; although traditionally thought of as rocky coast specialists, they can also be found on muddy estuaries and around beach-bars in the Caribbean (Why do Turnstones eat chips?).

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Measuring disturbance

Assessing the effects of disturbance during the winter is not easy. Feeding waders may be flushed by bait-diggers, kayakers, dog-walkers etc. but is this an issue if the food that they were attempting to eat becomes available later? To demonstrate that disturbance is a real problem, one would ideally demonstrate reductions in fitness measures such as survival, recruitment and/or productivity. This is discussed in a paper by Jenny Gill and colleagues, who studied the potential effects of disturbance on feeding Black-tailed Godwits (paper in Journal of Applied Ecology) and in another paper by Colin Beale and Pat Monaghan that shows that well-fed Turnstones were quicker to respond to disturbance than birds that had not received supplementary food supplies (Animal Behaviour).  Birds may be quicker to fly if they are well-fed or there is somewhere else where they can feed. The ones that have no choice and are still hungry may be the last to leave. The issue is discussed more widely in Why behavioural responses may not reflect the population consequences of human disturbance.

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It’s not just waders : Little Egret being chased  along the shores of the River Bann SPA and (below) the last few Brent Geese being removed from saltmarsh on the Exe Estuary (SPA)

Potentially, roosting waders could be more prone to disturbance than feeding birds, because of the wasted energy associated with flying around over the high-tide period or relocating to an alternative roost site (see A place to roost). An interesting modelling paper by Mark Rehfisch and colleagues showed that 90% of Dunlin, Grey Plover and Redshank on the Wash could be serviced by roost sites that were 2 km, 2.5 km and 3.5 km apart, respectively (Applied Ecology). These numbers may or may not be comparable for Turnstone but do suggest that small- to medium-sized waders feed within relatively short distances of their preferred roosting areas.

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Turnstone in this study

Turnstone is a species of qualifying interest for the Northumbria Coast Special Protection Area (SPA) and for several Sites of Special Scientific Interest (SSSI) in the region. On this 140 km stretch of coast, the population of Turnstone declined by 27% between 2004/5 and 2009/10, during a period when the wintering number within England declined by 9%. There was concern that human disturbance may be one of the drivers of the population decline of wintering Turmstone within the SPA. Potentially such conditions could become more challenging towards the end of the winter, when food supplies may be less and birds are preparing for migration, or during periods of very cold weather. Given an increase in the local human (and canine) population and a marked rise in tourism within the region, it was suggested that the potential for disturbance may have increased.

 

study area

The aim of the study was to compare wintering Turnstone densities and changes in counts across time from sites with differing levels of human disturbance. This was possible because long-term Wetland Bird Survey counts of waders had been made in the period between 1998/99 and 2015/16. Counts were available for two offshore refuges and 17 mainland sites that were subject to higher levels of human disturbance. No direct measure of human disturbance was available so questionnaires were used to determine the behaviour of beach users, in terms of distance travelled to visit the coast. The paper contains full detail of this methodology.

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Results

After controlling for the extent of preferred habitat (rocky shore) at each site the authors found that:

  1. The closer each of the 19 sites was to the nearest offshore refuge the higher the density of Turnstones, where density is calculated as birds per hectare of suitable feeding habitat.
  2. Turnstone counts at the four sites closest to, or containing, offshore refuges showed no significant declines. Despite the national decline in the number of wintering Turnstones, the counts on the Farne Islands and on St. Mary’s Island (both offshore islands) rose during the study period, although the rate of increase was not statistically significant from zero. There were declines at 15 of the 17 non-refuge sites. These results are consistent with the idea that, as populations decline generally, the sites of the highest quality (in this case those subject to less human disturbance) will show no, or slower, declines.
  3. 65% of the walkers interviewed on beaches were exercising their dogs, 83% having travelled 6 km or less to get to the beach. No relationship was found between Turnstone counts and human population densities. There is more information in the paper about the amount of time that people spend on different types of beaches.
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Graph showing Turnstone densities at different distances from refuges on the coast of northeast England. Figure from paper in Bird Study.

 

Implications

The authors of the Bird Study paper have not sought to explain declines in Turnstone numbers, but they have provided some useful references in the Discussion that highlight how improved water treatment and warmer winters might have affected regional distributions. They also remind us that Turnstone numbers are declining – as is the case for several High Arctic species. Having established that there are declines, they use the pattern of change to ask questions about whether disturbance is an issue for this species.

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Seahouses, looking out towards The Farnes – not far, as the Turnstone flies

The results of the research suggest that Turnstones make greater use of relatively undisturbed areas (offshore refuges) than those subject to greater disturbance by humans and their four-legged friends. Previous work has shown that excessive disturbance prevents the use of roosts and that disturbance can have serious energetic consequences (see A place to roost). Although the paper does not distinguish between birds that are foraging or roosting, this study suggests greater provision of undisturbed sites (refuges) within, or close to, protected areas is important for Turnstones, especially if there is also a drive to build more houses and attract more tourists.

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Beaches at Seaburn (County Durham) and Ross Back Sands (Northumberland). Proximity to human settlement makes a big difference! There are 15 dogs in the left-hand picture.

When looking at the planning process for developments close to SPAs, Mark Whittingham and his colleagues suggest that three issues need to be considered in some detail:

  1. While it is valuable to consider the SPA as a whole, it is also important for decision-makers to consider the vulnerabilities of constituent parts of the site.  Thus, for planning decisions based upon environmental impact assessments, there is clearly a need to consider pressures on particularly vulnerable areas, e.g. those used for roosting.
  2. blog tagged

    One of the tagged individuals that was tracked as part of a complementary study

    Studying the behaviour of marked individuals might help to pinpoint areas that are of critical importance. A separate, small-sample study of radio-tagged Turnstones in the area showed that these birds avoided mainland feeding and roosting areas at night, with at least some of the tagged Turnstones being found on offshore sites.

  3. Species need to be considered separately when assessing disturbance issues because habitat use and resource distribution varies widely. The focus for Turnstones is on rocky coasts and this determines their choice of roosting sites. The requirements of red-listed Ringed Plover (for instance) may be very different, especially as they spend a lot of time feeding on the sort of open beaches that look great for exercising dogs.

Paper

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Dogs are an important part of the disturbance issue.

The paper at the heart of this blog is:

Offshore refuges support higher densities and show slower population declines of wintering turnstones by Mark J. Whittingham, Ailsa J.  McKenzie, Richard M. Francksen, David Feige, Tom Cadwallender, Matthew Grainger, Nadheer Fazaa, Caroline Rhymer, Catherine Wilkinson, Pauline Lloyd, Ben Smurthwaite, Steve M. Percival, Tammy Morris-Hale, Clare Rawcliffe, Claire Dewson, Sarah Woods, Gavin B. Stewart & Elizabeth Oughton. Bird Study DOI  10.1080/00063657.2020.1713725


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.