Simon Wotton digests the most recent BTO publication.
The 41st Wetland Bird Survey (WeBS) report, for 2022/2023, has just been published, which also includes results for the Goose and Swan Monitoring Programme (GSMP). WeBS aims to assess the size of non-breeding waterbird populations, determine trends in numbers and distribution, and assess the importance of individual sites for waterbirds. The GSMP monitors the abundance and breeding success of the UK’s native geese and migratory swans during the non-breeding season.
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 survey is run by the British Trust for Ornithology (BTO), in a partnership between the BTO, the Joint Nature Conservation Committee (JNCC) and RSPB, with fieldwork conducted by volunteers. GSMP is a partnership, run by and jointly funded by BTO, JNCC and NatureScot, with fieldwork conducted by both volunteer and professional surveyors.
The 2022/23 report focuses particularly on populations of waterbirds that breed to the northeast of the UK: from Norway, including the Svalbard archipelago, to the Russian Taimyr peninsular. The majority of our migratory wintering waterbirds travel wholly or partially from this region, mixing here with UK and Iceland/Greenland breeders. Situated as we are on the western edge of the wintering range for some of these populations, in Britain and Ireland we have often been first to experience changes in migratory behaviour.
(C) RSPB Images
2022/23 summary
The 2022/23 report documents waterbird counts at 3,325 sites across the UK, surveyed by 3,801 WeBS counters.
Many of the sites monitored under WeBS are of international importance and designated as Ramsar Sites and Special Protection Areas, including the five principal WeBS sites over the past five years: The Wash, Ribble Estuary, Morecambe Bay, Dee Estuary and Thames Estuary. In 2022/23, the number of sites with a five-year average in excess of 100,000 birds remained at nine, and a further 40 sites had a five-year average in excess of 20,000 birds.
It was the coldest December since 2010, although overall, the winter was slightly milder and drier than average. December and January core counts coincided with freezing weather, resulting in the two highest average ice cover on sites recorded since February 2012. The conditions were frozen in many sites throughout the UK in both months, but with December being slightly the more extensive; in both months a fifth of WeBS count sectors had ice cover of 90% or more and over two fifths had ice cover of at least 5%. The winter was rather dry, particularly February, although there were some high river flows and flooding from rainfall between the December and January counts in some parts of the country.
UK waterbird numbers in winter can be influenced by continental conditions, particularly around the Baltic. European air temperatures for the winter were on average milder than normal, except for cold conditions in December in northern Europe. The Baltic ice season was mild in terms of ice extent, and the maximum sea ice extent was reached later than normal, in mid-March.
The overall trends show the Icelandic Greylag Geese, Greenland White-fronted Goose and Greenland Barnacle Geese continue to decline. Greenland Barnacle Geese were notably affected by HPAI in 2022/23, which will have contributed to the lowest index since 2004/05. Following a long-term increase and continuing positive 10-year trend, Pink-footed Goose has been declining since the record highs in 2015/16, and Svalbard Barnacle Geese are showing a similar pattern, although in 2022/23 both increased slightly, compared with the previous year.
Compared to 2021/22, dabbling ducks showed an increase in index values in 2022/23, with a record high for Shoveler, the highest value since 2011/12 for Gadwall (25-year trend +70%) and highest since 2006/07 for Pintail (25-year trend -18%). The diving ducks all show declining trends over both 10- and 25-year time periods. The latest index for Tufted Duck (10- year trend -15%) was the lowest since 1985/86 and Red-breasted Merganser (10-year trend -24%) had its lowest index value since 1983/84. Non-Shetland Eider (10-year trend -26%) and Pochard (10-year trend -42%) both had record low index values for 2022/23.
Increases continued for Avocet (10-year trend +33%) and Black-tailed Godwit (10-year trend -19%) both of which recorded their highest ever index values in 2022/23. Trends for Knot are stable, after the latest index value fell slightly compared with the previous year. Increases in index values for 2022/23 helped stabilise the 10-year trends for Ringed Plover, Dunlin, Purple Sandpiper and Redshank, all of which showed negative 10-year trends in 2021/22. However, the 25-year trends for these species are all still showing declines of between -15% and -46%. Curlew (10-year trend -20%), also continues its decline, with its lowest index value for 41 years. In the past 25 years, Grey Plover has declined throughout the UK: by 70% in Scotland, 71% in Northern Ireland, 47% in Wales and 35% in England. In recent years the index is most stable in England and Northern Ireland, but declines continue in Scotland and Wales. This Arctic-breeding species is one of many with evidence of short-stopping towards the east.
Detailed data on WeBS sites and species are available through the BTO WeBS interactive website (BTO WeBS Reports). A copy of the 2022/23 report can be downloaded from waterbirds in the uk webs 202223.pdf (bto.org)
For more information contact Simon Wotton, Senior Conservation Scientist, or Lydia Tague, Science Communications Executive, or follow us on Twitter @RSPBScience #WeBS #wetlandbirds.