The waders of Northern Ireland

blog CU postNorthern Ireland is a great place for wintering waders but the same can no longer be said for its breeding species. There are far too few places left in which Curlew bubble and Snipe drum.

Waders provide some of the best birdwatching spectacles in Northern Ireland, as flocks swirl around coastal estuaries, when the tide rises on a winter’s day. Birds fly in from as far away as Canada and Russia but there are particularly strong links to Iceland, about which there will be more later. Every year, winter counts by volunteers, who help with the Wetland Bird Survey, alert us to the ups and down in wintering populations on loughs and estuaries. Unfortunately, we know much less about breeding species such as Lapwing, Redshank, Snipe and Curlew – four species that feature in a new Northern Ireland survey in the summer of 2019. Although the annual Breeding Bird Survey monitors birds such as Song Thrush and Willow Warbler, waders are just too thinly spread in Northern Ireland for it to be possible to pick up any year-to-year changes. That’s why they need a special survey.

blog L flightWe know that there were some great wader hot-spots in the years 1985 to 1987, when a major Northern Ireland survey took place, and that large drops in numbers were reported in 1999 and again in 2013, after other dedicated surveys, but what is happening now? Are there still places where Snipe drum and Curlew bubble? The BTO in Northern Ireland is asking local and visiting birdwatchers to revisit some of the best places that were identified in previous surveys, to look for breeding waders and to assess the habitats that remain. This work complements work being undertaken by RSPB Northern Ireland. If you think that you may be able to help click here to find more information.

Not looking good?

Although it would be nice to be proved wrong, the expectation is that breeding wader numbers will have declined still further. This means, of course, that any remaining sites that still hold species such as Redshank and Lapwing, are going to be even more important than they were thirty years ago. Pessimism is based on trends elsewhere; numbers of breeding waders are falling throughout the UK and increased agricultural intensification within the Republic of Ireland has caused sharp declines in the focal species of this survey – Lapwing, Redshank, Snipe and Curlew. The following notes give some highlights about Northern Ireland’s waders and point out some of the things that we don’t know (yet).

Lapwing

blog Lap mapThe Lapwing has quietly disappeared from much of Northern Ireland over the last fifty years. The black triangles in the map alongside represent 10-km squares that lost their breeding Lapwings between the two atlases of 1968-72 and 2008-11. Previous Northern Ireland surveys of breeding waders in 1985-87 and 2013 suggest that the number of pairs dropped from an estimated total of 5250 to a total of 860 – that’s a loss of 5 out of 6 pairs. The new survey this summer will update breeding numbers in the species’ heartland areas, as long as sufficient volunteers step forward to help with coverage. (Here’s a link to the results of the 2013 Northern Ireland wader survey.)

Redshank

blog RKThere is no recent estimate for the number of breeding Redshank in Northern Ireland. Across the UK, the Breeding Bird Survey suggests that we have lost 41% of breeding birds since 1995, and the decline was well underway by then. The survey this year provides a good opportunity to learn as much as possible about this threatened species.

In the late summer, the tiny Northern Ireland population is joined by Redshank from Iceland and Scotland. There are also small a number of movements linking Northern Ireland with Wales and England; some of these might be of birds from further east in Europe that were ringed in Britain. Strangford Lough peak counts of over 2000 in October illustrate just how much of an influx there is each autumn.

Snipe

blog SN mapThe lowland wader survey in 1985-87 suggested that the Northern Ireland population of Snipe was about 5725 pairs. By the time of the next survey in 1999, that number had dropped to 3993 and then to 1123 in 2013. That’s a drop of 80%. Snipe seem very sensitive to habitat change, especially drainage. The map alongside shows the change in abundance between 1988-91 and 2008-11 across Britain & Ireland. There is an interesting mix of losses (grey) and increases (orange) in Northern Ireland. It will be great if the 2019 survey picks up some new Snipe hot-spots. One of the key elements of the fieldwork this year is to record habitat data and field-use. What habitats do Snipe still breed in and can these be expanded and replicated elsewhere within Northern Ireland?

blog SN groundThere’s a WaderTales blog about Snipe & Jack SnipeMany of the birds that are seen in Northern Ireland in the winter have flown across the Atlantic to escape the snow and cold of Iceland but there are also large numbers from Scandinavia and continental Europe

Curlew

The Curlew is in huge trouble across the whole island of Ireland. Surveys of random squares in 1985-87, 1999 and 2013 suggest that the number of breeding pairs in Northern Ireland dropped from 5000 to about 500 over the period. There is talk about potential extinction as a breeding species in Ireland and Wales. This may seem ridiculous when you can see flocks totalling 2000 birds around Lough Foyle, on a winter’s day. However, these are almost exclusively migrants, from Finland, Scandinavia and Scotland. One of the hopes is that the new survey will pinpoint new hot-spots for Curlew. There is already concerted action to try to bolster numbers through the Lough Erne Landscape Partnership.

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Other Northern Ireland waders

Oystercatcher: Many wintering Oystercatchers leave Northern Ireland in the spring, heading for Iceland, Scotland or perhaps Norway (more in this wader migration blog). By that time, resident adults will already have moved inland or onto beaches to breed and other birds will have returned from southern wintering areas.

blog RPFlocks of young birds are found on estuaries in the summer, as Oystercatchers typically don’t breed until three years old. We know that the number of breeding Oystercatchers in Scotland dropped by 38% between 1994 and 2017 but English numbers rose by 49% (read more here). We don’t know what’s happening in Northern Ireland.

Turnstone: Wintering birds are mostly thought to come from Greenland and Canada but a December capture of a bird from Sweden suggests that there might be a link to the east as well.

Ringed Plover: The new survey in Northern Ireland is not designed to monitor beach-nesting Ringed Plover. The most recent UK-wide survey of the species was in 2007, when the Northern Ireland population estimate was 147 pairs, similar to the estimate at the time of the previous survey, in 1987. In the same period, numbers dropped in Scotland (-42%) and England (-29%). Link to summary of paper.

blog GP mapGolden Plover: Ireland is a winter destination of choice for many Golden Plover that breed in Iceland. The recovery of a Belgian-ringed bird in 2006 suggests that some birds may arrive from the east as well. Wintering numbers are half what they were 25 years ago, according to WeBS data for Northern Ireland. A few breeding birds can still be found in the western parts of Northern Ireland but they have been lost from most other areas.

Grey Plover: It’s a long way from Siberia to Northern Ireland, so perhaps it is not surprising that not many Grey Plover make it this far west!

Knot: The best place to see Knot is in Strangford Lough, where numbers peak at over 4000 in some winters. The only two foreign-ringed birds were shot wearing Icelandic rings in 1957 and 1975 (when shooting them was legal). Northern Ireland’s wintering Knot probably breed in Greenland or Canada and migrate via Iceland.

Sanderling: The Sanderling that are seen around the coast in winter months, in small numbers, will almost certainly breed in Greenland. Numbers are higher in spring, when birds from further south stop off on their way to Iceland and then Greenland.

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Dunlin: This year’s survey of Lapwing, Redshank, Snipe and Curlew should really include Dunlin, as they share similar breeding habitat. However, it will be a very lucky volunteer who finds a displaying adult. Birds of the schinzii (green arrows) and arctica (yellow) race pass through in spring and autumn but the wintering birds are of the alpina race (orange).

blog WK mapWoodcock: The black triangles in the map opposite show the parts of Northern Ireland that have lost breeding Woodcock in the last 50 years. Data are from Bird Atlas 2007-11 (BTO, BirdWatch Ireland & SOC). In late autumn, birds fly in from counties such as Germany, Norway and Russia. See this blog.

Black-tailed Godwit: All is not gloom and doom in the world of waders; there are six times as many Black-tailed Godwits wintering in Northern Ireland as there were 30 years ago. Great views of these Icelandic visitors are provided at the RSPB reserve at Belfast’s Window on Wildlife. This blog explains why numbers have taken off in recent years.

Bar-tailed Godwit: The Bar-tailed Godwit that are seen in Strangford Lough and elsewhere are birds from northern Norway and Russia. There seems to have been little change in numbers, according to Northern Ireland WeBS counters.

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Whimbrel: A few Whimbrel drop in during autumn passage but far more appear in spring. Most Icelandic Whimbrel can fly straight to West Africa in the autumn but 80% stop off on the way north, many in Northern Ireland (see graphic above). You can read more here.

From Avocet to Pectoral Sandpiper

There is a supporting cast of waders that visit Northern Ireland. This blog provides more information on wader migration: Which wader, when and why?

A call for help

blog habitatAs must be obvious by now, BTO Northern Ireland is looking for volunteers to help with wader surveys in 2019. Sites are discrete lowland wet grassland areas, small enough to survey in one morning. At least two or ideally three visits to each site are required between mid-April and mid-June, with at least two weeks between each visit.

Each field or sub-unit needs to be covered on foot and the number of Lapwing, Curlew, Redshank and Snipe are counted per field. Some additional habitat recording is required, e.g. recording grazing, rush cover and estimating dampness.

blog mapSites are located in five broad areas (see map):

  • Loughs Neagh and Beg
  • Blackwater Catchment
  • Tyrone Fairy Water Bogs
  • Upper Lough Erne
  • Lower Lough Erne (these sites will be covered by the RSPB)

More details are available here, on the BTO Northern Ireland website. There will be a free training session on 29 March. Contact shane.wolsey@bto.org if you have any questions or would like to volunteer.

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GFA in Iceland

Graham (@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.

 

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From local warming to range expansion

blog adultOver the last century, Icelandic black-tailed godwits have increased 10-fold in numbers and their breeding range has expanded throughout lowland Iceland. Although changing climatic conditions seem likely to have enabled this process, what is the mechanism? How might warmer conditions have contributed to this growth? This blog is a summary of a paper by José Alves and colleagues in Ecology & Evolution.

Setting the scene

If scientists are going to try to predict species’ responses to future climatic conditions, they will need to understand the ecological, behavioural and historical factors that influence how change happens. In other words, what mechanisms can link changes in climate with changes in population size and distribution?

tableAppreciating how local climate effects can potentially scale up to population-level changes requires climate effects to be measured across a population. Iceland is a great place to study these processes as it has been getting warmer since at least 1845, as measured by one of the longest temperature time-series in the world. The country hosts internationally-important breeding populations of many migratory bird species, for which changing climatic conditions could have important implications, including Black-tailed Godwit. The data in the table alongside have been extracted from a report to AEWA that was discussed at the 12th Standing Committee in Jan/Feb 2017.

A booming population

godwit spread

Expanding breeding range in Iceland

In the early 1900s, Black-tailed Godwits were restricted to the southern lowlands of Iceland but, since then, birds have gradually colonised coastal lowland areas throughout the country, with larger areas closer to occupied sites being colonised first (as described in this WaderTales blog). The population now numbers over 50,000 individuals, which is likely to represent an approximately 10-fold increase over the last century.

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Newly hatched chicks, still in their nest-cup, well hidden in grass

Icelandic godwits are long-lived migratory shorebirds with a typical lifespan of between 15 and 20 years. They nest in lowland wetlands dominated by grasses or by dwarf birch and sedges. They hide their nests, which means that they require sufficiently tall vegetation to conceal the nest and an incubating adult. Both vegetation growth and the timing of emergence of invertebrate prey for wader chicks are strongly temperature-dependent, particularly at high latitudes, which means that the timing of nesting and the growth-rate of chicks are likely to be influenced by local temperatures.

blog colonisationOver eight years, during which temperatures in Iceland varied substantially, José Alves and colleagues were able to quantify the influence of temperature on laying dates and the duration of the pre-fledging period of Icelandic godwits, and the subsequent influence of hatching dates on recruitment of chicks to the wintering or subsequent breeding population. The authors then used these relationships to model how the timing of breeding and the annual recruitment of juveniles into the breeding population may have contributed to population growth and the successful colonisation of new (and now warmer) parts of Iceland.

Catch your godwits

blog cr chickBlack-tailed Godwits are very good at hiding their nests and chicks! These three quotes from the paper help us to appreciate the effort that goes into establishing some of the key facts that underpin the modelling at the heart of this paper:

  • “Every nest was visited regularly and successful nests were revisited at the estimated hatching date, in order to capture and mark chicks and adults with individual combinations of colour-rings.”
  • “For each family, one of the adults was captured using either a nest-trap or a hand-held net-gun.”
  • “In 2012 and 2013, 32 godwit families were tracked during chick rearing, from hatching to fledging (n = 18) or brood loss (n = 14).”

Away from the main study area, volunteer ringers, led by Pete Potts of Farlington Ringing Group, caught, measured and colour-ringed chicks, thereby providing an assessment of hatching dates of chicks in other parts of Iceland.

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The assessment of which chicks subsequently survived and recruited into the adult population relied heavily upon the observations of hundreds of birdwatchers, throughout Western Europe, who take the time and trouble to report sightings of colour-ringed birds. Examples of their dedication and links to other papers that rely upon their efforts can be found in Godwits and Godwiteers.

Major Findings

Effect of temperature on timing of breeding season events: In Icelandic godwits, mean laying dates were approximately 11 days earlier in the warmest of years than in the coldest (two-degrees Celsius lower). This earlier start to the breeding season is thought to be linked to faster vegetation growth in warmer springs. The lengths of the chick pre-fledging period varied by only about 3.6 days between the warmest and coldest years but this additional difference means that fledging can happen a fortnight earlier in the warmest of years. 

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blog juv flocksProbability of recruitment: Early-hatched chicks are more likely to survive and recruit into the adult population, and the 11-day advance in hatch dates in warm years equates to an increase in absolute recruitment probability of about 10%. The additional benefits of more rapid chick growth and fledging in warmer years probably further increases this differential. In cold years, when most nests are laid late, very few chicks are likely to recruit to the adult population. For example, in 2011, the coldest year recorded during the study, only about 16% of 118 ringed chicks recruited into the wintering population. Early-fledged chicks presumably have more time to improve body condition prior to migration, there is an increased probability of travelling in adult-dominated migratory flocks (see graphic from Gunnarsson 2006), and earlier departure for wintering areas may allow more time in which to find a favourable wintering location.

blog big chickRegional variation: Traditional breeding sites are warmer, and so nests are likely to be earlier and incubation shorter, which means that more of the chicks from these areas are likely to survive and recruit into the population. The range expansion in this system could therefore have been driven by increased productivity and dispersal from traditionally colonised areas, supplemented by increased productivity within newly colonised – and now warmer – areas. Given the high levels of natal philopatry in Black-tailed Godwits (WaderTales blog about philopatry), the authors suggest that improved breeding conditions, following colonisation of new areas, have fuelled local population increases and further range expansion.

Are these findings applicable to other species?

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Sightings of colour-ringed juveniles, such as this one in eastern England, helped to establish recruitment rates.

The authors of this paper have been studying a species breeding at the northern limit of its range, in a country that has been subject to rapid climate change and in which there are relatively large differences in temperatures over quite small distances. This provides an ideal gradient over which to study change. Also, and unusually, it was possible to measure recruitment of chicks from right across Iceland, because of the colour-ring reports from observers. This set of circumstances have combined to enable the team to show that warming trends have the potential to fuel substantial increases in recruitment throughout Iceland, and thus to have contributed to local population growth and expansion across the breeding range. They propose that the same factors may be harder to tease apart for other species, in different environments, but that advances in lay dates and increased recruitment associated with early hatching may be key processes that drive population and range changes in migratory systems.

Paper

Linking warming effects on phenology, demography and range expansion in a migratory bird population. José A. Alves, Tómas G. Gunnarsson, William J. Sutherland, Peter M. Potts & Jennifer A. Gill.

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Juveniles gather together in the late summer, prior to departure


GFA in Iceland

Graham (@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.