Blog post by Simon Wotton, Senior Conservation Scientist, RSPB Centre for Conservation Science.

The latest Wetland Bird Survey (WeBS) report, for 2016/17, has just been published. WeBS is the principal scheme for monitoring the populations of the UK's wintering waterbirds, providing an important indicator of the status of waterbird populations and the health of wetlands.

The report documents waterbird counts at nearly 3,000 wetlands across the UK, with counts primarily undertaken by over 2,000 volunteers.

Many of the sites monitored are of international importance and designated as Ramsar Sites and Special Protection Areas (SPAs), including the four principal WeBS sites over the past five years: The Wash, the Ribble Estuary, Morecambe Bay and Thames Estuary.

Pochard. Image by Ben Hall (rspb-images.com)

Seventy years of monitoring

This report marks the 70th anniversary of waterbird monitoring in the UK, starting in 1947 when a national scheme to count wildfowl in Britain was pioneered by the Wildfowl Inquiry Committee of the British Section, International Council for Bird Preservation.

The initial objectives of the scheme were to determine the status of wildfowl in Great Britain and to assess whether any long-term trends in numbers were occurring.

This followed concerns over possible population declines and the inability to assess with confidence the likely impact of an increasing number of developments upon wetlands.

In 1947/48 the survey was trialled at a limited number of waterbodies in the London and Birmingham areas, before the survey was extended to provide national coverage in the winter of 1951/52.

What's in the database?

Knot and dunlin in high tide roost. Image by Andy Hay (rspb-images.com)

The WeBS database contains data from over a million Core Counts stretching back to 1947/48, although there are still many forms from before 1966/67 to digitise.

Mining a data source as rich and historical as that of WeBS can help quantify differences in behaviour, such as which species tend to occur thinly and which aggregate together.

And it can prompt ecological questions, such as explaining the relationship between the number of waterbirds on a site and site size, that can then help improve waterbird population size and distribution estimates.

There are over 193 million counts of dunlin in the database – the highest number. While mallards are the species seen most frequently is mallard, on over 820,000 WeBS counts

What does the 2016/17 report show?

Male shoveler. Image by Andy Hay (rspb-images.com)

The report documents the changing fortunes of the UK's wintering waterbirds. Here are some highlights from this year’s report:

  • Bewick’s swans have declined by 77% over the past 25 years, with their peak index coming in 1990/91
  • The gadwall trend over the past 25 years is +144%, but is now showing signs of stabilising
  • Teals and shovelers continue to increase with record high indices, but mallards continue their decline with another record low
  • The downward trend in pochard shows no signs of abating, with yet another record low index value and a 25-year trend of -69%
  • Goldeneyes are also continuing to decline with a 25-year trend of -58%, and the lowest index value since 1979/80
  • Common scoter counts were very high at multiple coastal sites, resulting in a sharp increase in the index value to its highest ever level
  • Avocet and black-tailed godwit show strong 25-year increases, of 600% and 248% respectively, and both species reached record high index values in 2016/17
  • Oystercatcher, ringed plover, grey plover, knot, redshank and turnstone have negative 25-year trends of between -18% and -58%, but index values were higher in 2016/17 than 2015/16 for all these species
  • Curlew declines, however, seem to be continuing: the index value was the lowest since 1985/86

Detailed data on WeBS sites and species are available through the BTO WeBS interactive website. Or download a copy of the 2016/17 report

The survey is run by the British Trust for Ornithology (BTO), in a partnership between the BTO, the RSPB and the Joint Nature Conservation Committee (JNCC), in association with the Wildfowl & Wetlands Trust (WWT).

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