Interpreting changing wader counts

Blog mixed flockWhen you count the number of Redshank on your local estuary and discover that there are fewer now than there were last year –  or five, or twenty years ago – what are the implications? Is this part of a national or international trend or has something changed within the estuary itself?

The first question to ask is, ‘what is happening elsewhere?’ and then to wonder about the ways in which numbers of birds in different sites might relate to each other. What actually happens to local counts when national counts go down – or go up, for that matter?

The UK Wetland Bird Survey (WeBS) data provide comprehensive and long-term monitoring of estuarine wader populations around our coastline. Thanks to volunteers who collect monthly counts each year, these data present an excellent opportunity to explore how bird distributions can change over time. A new paper by Verónica Méndez and colleagues from the University of East Anglia and British Trust for Ornithology uses counts of 19 species (18 waders plus Shelduck, an honorary wader) over a 26-year period to ask what happens to distribution and local abundance across our estuaries when overall population sizes go up or down.

Consequences of population change for local abundance and site occupancy of wintering waterbirds Verónica Méndez, Jennifer A. Gill, José A. Alves, Niall H. K. Burton & Richard G. Davies Diversity and Distributions. 2017;1–12. DOI: 10.1111/ddi.12653

The counters

Blog Counter 2A WeBS count can be a tough assignment for a volunteer birdwatcher. Being allocated to a stretch of an estuarine coastline and asked to visit it, whatever the weather, on a given weekend of every month, in every winter, is not the same as an invitation to go birdwatching in September to look for a Curlew Sandpiper.

The counts used in this paper are from the months of November through to February, when waders are largely settled for the winter and the weather can be less than clement. Many of the data-points for individual sites have been collected by the same person in all of the years analysed in the paper and every contribution is important.

WeBS70logo6a_smallWeBS is the successor of other, similar count schemes which are celebrating 70 years of continuous monitoring this year. It is organised by BTO, in partnership with RSPB and JNCC and in association with WWT. There are over 3000 registered WeBS volunteers, collecting data about the waterbirds that can be found on estuaries, in wetlands, on inland lakes, along river valleys and in local parks and villages.

Understanding change

Many populations of migratory birds are changing in number quite rapidly at present, but are these changes more likely to result in changes in occupancy (eg colonisation of or extinction from some sites) or changes in abundance within sites? Put simply, if extra waders arrive in the autumn, how do they distribute themselves across available sites? If fewer arrive, where will the gaps be found?

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The contrasting fortunes of Dunlin and Black-tailed Godwit over the period covered in the new paper

Over the period studied in the paper (between 1980-85 and 2002-07), populations of five species declined, with the greatest losses occurring in Purple Sandpiper and Shelduck (both declined by about 25%), while there were increases for four, the biggest of which were Avocet (+1690%), Golden Plover (+554%) and Black-tailed Godwit (+418%). No birdwatcher will be shocked by the figures for Avocet or Black-tailed Godwit, wintering numbers of which have shot up, but Golden Plover is more of a surprise and may be linked to a move from inland fields to estuaries.

When the size of a wintering population of waders declined, Verónica Méndez and her colleagues found that the main consequence was a reduction in numbers across all sites. Birds were likely to stay on a site even if local numbers were dwindling. This suggests high levels of site-fidelity by individual waders, which is something we know from ringing and tracking studies. If you’re still alive then just do the same again – there could be a better site with a higher number of conspecifics somewhere else but it would be risky to try to find that out.

 

Blog Avocets

Thirty years ago, few people can have expected that they would ever see such a large flock of Avocets on the Humber

If the size of a wintering population increased, generally numbers went up within all occupied sites. The exceptions tended to occur in species for which original numbers were very small, such as for Greenshank, or species for which the change in numbers has been rapid – as seen in Avocet and Black-tailed Godwit.

If adults don’t change their wintering sites then increases are presumably being driven by juveniles. Their settlement decisions may be influenced by the distribution of adults of the same species, resulting in increased local abundance, rather than colonisation of new sites. For the two rapidly-expanding species, Black-tailed Godwit and Avocet, there was colonisation of 25 and 15 new sites, respectively, between 1980-85 and 2002-07, with some indication of more similar increases in sites that were closer together, which may reflect local movements among groups of nearby sites.

Designating sites

Blog Blackwit

Juvenile waders may well settle in areas where there are already populations of wintering adults

One of the key conservation measures for waders across Europe is the Special Protection Area (SPA) network, a collection of sites that are designated because they hold internationally or nationally important numbers of species, measured as a percentage of the population. Designated sites need to maintain numbers of all the species that hit this threshold percentage. However, if a national or European population gets larger (for example because of high breeding success) but the number on a particular site does not grow (or grows more slowly), then the species might drop below the threshold for protection, even if the site is unchanged. Theoretically this could affect a site’s protected status for that species, although is unlikely to be a problem, as most sites are designated for many species.

This new paper shows that gains and losses tend to be fairly constant across all sites, making it unlikely that a site designation would be affected by national or European-scale changes. In only one species (Ringed Plover), have numbers declined so much in some sites that the total number of sites exceeding the threshold for that species has decreased.

Keep counting!

Blog Counter 1Habitat availability and site fidelity, along with species longevity, may explain the strong tendency for local population abundance to change much more than site occupancy, in our wintering waders. Given the statutory importance of maintaining waterbird populations in designated protected areas, it is important to continue local and national surveys that can identify changes in local abundance and relate these to large-scale processes.

Returning to the earlier question – When you count the number of Redshank on your local estuary and discover that there are fewer now than there were last year –  or five, or twenty years ago – what are the implications?

This new paper shows that it is unlikely that a local drop in a species’ numbers is caused by a redistribution of birds. Factors that might lie behind a local decline need to be investigated locally, if the trend is not replicated elsewhere. The authors could only reach this conclusion because they had 26 years of WeBS data from a range of sites at their disposal. Future generations of WeBS counters will hopefully continue to monitor the conditions of our estuaries, working together throughout the country to interpret local counts within a national framework.

Paper

Consequences of population change for local abundance and site occupancy of wintering waterbirds Verónica Méndez, Jennifer A. Gill, José A. Alves, Niall H. K. Burton & Richard G. Davies Diversity and Distributions. 2017;1–12. DOI: 10.1111/ddi.12653

Blog RINGOS


 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

 

 

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Do Iceland’s farmers care about wader conservation?

When working with Icelandic farmers to conserve internationally important wader populations, a shared understanding of beneficial practises may be more important than financial incentives.

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Species like Snipe, Redshank and Black-tailed Godwits have been squeezed out of lowland areas of countries such as the UK and the Netherlands by centuries of drainage, increasingly homogeneous landscapes and the introduction of quick-growing grassland monocultures. Adults have lost nesting sites, chicks have fewer feeding opportunities and pre-fledged youngsters fall victim to farm machinery. Do the same fates await waders in Iceland or might it be possible to work with farmers to leave space for birds?

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Pools, set within semi-natural lightly-grazed fields, are important

As part of her PhD at the University of Iceland, in collaboration with the Universities of East Anglia (UK) and Aveiro (Portugal), Lilja Jóhannesdóttir asked farmers what they think about having birds on their land, what their plans are for their farms, whether they might be willing to leave some pools and focus farming activities in areas less important for birds, and if farm subsidies might encourage them to be more proactive conservationists. The sometimes surprising results of this questionnaire have been published in Ecology & Society.

Reconciling biodiversity conservation and agricultural expansion in the subarctic environment of Iceland. Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill  and Tómas G. Gunnarsson. Ecology and Society 22(1):16.

The Waders of Iceland

tableIn a recent report prepared by AEWA (Agreement on the Conservation of African-Eurasian Migratory Waterbirds), in response to concerns about the effects of afforestation on Iceland’s waterbirds, Dave Pritchard & Colin Galbraith say “Iceland is second only to Russia in its importance as a breeding ground for migratory waterbirds in the AEWA region. It supports the most important breeding populations in Europe for six species of waders, and is the second most important country for three.”

Data in the table alongside have been extracted from Annex 4 of their report, which was discussed at the 12th Standing Committee of AEWA in Jan/Feb 2017. Iceland is home to c 75% of Europe’s breeding Whimbrel, over half of the area’s breeding Dunlin and perhaps half of its Golden Plover. The importance of Iceland has increased with the collapse of wader populations in other countries.

Waders on farmland

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Spring flock of Black-tailed Godwit feeding in a stubble field

Farmed landscapes in Iceland provide opportunities for waders. In the spring, newly-arrived flocks of Golden Plover spread out over hayfields, Black-tailed Godwits target the previous year’s barley stubbles and parties of feeding waders can be seen in sedge pools on farms. During the breeding season, the application of fertilisers, especially in areas where volcanic ash deposition is low, increases soil productivity and wader densities, as was shown in this blog about regional productivity. Come the autumn, hayfields attract flocks of birds fattening up for migration. Despite drainage of an estimated 55% to 75% of wetlands in Iceland in the last seventy years, the country is still a great place for waders.

The amount of intensively-farmed land in Iceland is increasing, to some extent driven by rapid recent increases in the number of tourists, who consume milk products and meat. This can be seen in the ongoing development of hayfields, to feed cattle, and barley production, for pig-feed. There is concern that these developments will impact upon wader numbers, through the reduction in the amount of semi-natural habitat, especially in the lowlands, loss of pools and reduced landscape heterogeneity. On top of these changes, warmer temperatures allow earlier cuts of silage which increases the risk of killing wader chicks that nest within these fields.

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More and more semi-natural land is being lost to grass monocultures

Lilja Jóhannesdóttir’s PhD is focused on how birds use the gradient of habitats that comprise farmland in lowland Iceland – from more intensively farmed fields through to lightly-grazed, semi-natural habitats. The paper that forms the focus of this blog looks at farmers’ attitudes to the birds that share Iceland’s farms and their plans for the future. It then attempts to reveal the willingness and capacity of landowners to engage with conservation management practises.

The questionnaire

To understand the views of Icelandic farmers toward bird conservation, given the current potential for agricultural expansion, Lilja interviewed 62 farmers across Iceland, using a structured questionnaire. Some of the key findings are:

  • Over 60% of farmers are likely or very likely to increase their area of cultivated land
  • Over 90% of farmers think it is important or very important to have rich birdlife on their estates
  • About 60% would consider modifying grazing regimes to help birds
  • More than 80% would be unlikely or highly unlikely to consider changing the timing of harvesting operations.
  • More than 80% would be happy to consider keeping pools intact
  • Information on conservation needs are more likely to change attitudes than financial incentives

The information collected in the questionnaires was analysed by region and by the age of the interviewee but no strong patterns emerged. Older farmers seem to appreciate birdlife more than their younger colleagues but are no more likely to change their behaviours to support conservation objectives. The detailed figures are reported in the paper.

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Creating new hayfield to produce cattle-food is at the expense of areas of semi-natural land

The majority of the Icelandic farmers who took part in the survey plan to expand their agricultural land in the next five years, and this is likely to be driven further by increasing demands for farming products. This implies that conversion of semi-natural land into farmland is likely to greatly increase in the near future, with potentially severe and widespread impacts on the internationally important bird populations that currently breed in these areas. Such expansion could put Iceland on a similar trajectory to many other countries that have experienced substantial biodiversity declines on the back of agricultural intensification and expansion. On the positive side, Icelandic farmers like wildlife and the results suggest that if they are better informed about the consequences of their actions they might well try to modify plans in ways that reduce negative impacts. The possibility of financial incentives to off-set potential losses did not seem to influence farmers’ views, but the authors suggest that this might be because there is no tradition for farmers to receive subsidies for conservation action.

b-horsesA clear finding of the study is that farmers are unlikely to change the timing of agricultural operations in order to help birds. Perhaps this is unsurprising in a country with a very short growing season and where periods of settled weather are rare. With relatively few consecutive dry days, opportunities to mow and turn silage or hay crops just have to be taken. The timing of farming operations, such as harvesting/mowing, can be crucial for breeding waders because they can result in the destruction of nests, chicks, and adults during the breeding season. For example, advances in timing of mowing of hayfields in the Netherlands has meant that this now coincides more frequently with wader nesting and chick rearing, causing unsuccessful breeding attempts and leading to lower recruitment. There is more about the Dutch experience in this Ibis paper.

If Icelandic farmers are unlikely to delay operations, perhaps other strategies, such as mowing fields from the centre – as used in the Outer Hebrides to reduce Corncrake losses – might be more acceptable to farmers who are so constrained by the weather? Read more about the Corncrake issue here. 

The Future

b-whimbrelAs a signatory to international agreements on the conservation of birds and wetlands (Ramsar Convention, Bern Convention, Convention on Biological Diversity and African-Eurasian Waterbird Agreement), the Icelandic government is required to take action to protect the internationally important bird populations breeding in the country. Given that there is no strong tradition of using planning laws or centralised agricultural policy to influence farmers’ decisions, working with individual farmers might be the best way to deliver conservation objectives.

Farmers’ views on the importance of having rich birdlife on their land and their willingness to participate in bird conservation provide a potential platform to work with landowners to design conservation management strategies – and to do this before further substantial changes in the extent of agriculture take place in this subarctic landscape. With three-quarters of Europe’s breeding Whimbrel and about half of the Golden Plover and Dunlin dependent upon decisions made in Iceland, there is a lot at stake.

Reconciling biodiversity conservation and agricultural expansion in the subarctic environment of Iceland. Lilja Jóhannesdóttir, José A. Alves, Jennifer A. Gill  and Tómas G. Gunnarsson. Ecology and Society 22(1):16.

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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

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