Population trends for waterbirds in the UK

This page hosts the Official Statistic ‘Population trends for waterbirds in the UK’ published on 22 May 2025, including data up to June 2024.

Official Statistics description
Scope of the statistics
Summary of results
Interpretation of results
Background and Methods
Confidence in results, quality assurance and caveats
Drivers of change
Involvement and contacts
Relation to other Official and National Statistics, and broader relevance
References

Official Statistics description

UK and country trends produced from the data from the Wetland Bird Survey (WeBS) and Goose and Swan Monitoring Programme (GSMP) are published annually as Official Statistics.

The point of first release for the headline Official Statistics on waterbird trends generated from these two monitoring schemes is JNCC’s website. The Statistics are also incorporated into the WeBS Annual Report titled Waterbirds in the UK; and further site-specific information can be accessed via WeBS Report Online.

WeBS is the principal scheme for monitoring the populations of the UK’s non-breeding waterbird populations, providing an important indicator of their status and of the health of wetlands. The monitoring scheme aims to assess the size of non-breeding waterbird populations, determine trends in numbers and distribution of wintering birds, and assess the importance of individual sites, in line with the requirements of international conservation conventions and directives. Data have been collected annually since 1947 for wildfowl, since 1969 for waders and since the 1980s or 1990s for other species. GSMP surveys contribute trends for six goose species/populations, where standard WeBS methodology is not adequate, for instance where the main roosts are located outside of the WeBS sites and the count needs to be carried out at a different time of the day.

WeBS is a partnership between the British Trust for Ornithology (BTO), Royal Society for the Protection of Birds (RSPB) and the Joint Nature Conservation Committee (JNCC), with fieldwork conducted by volunteers.

GSMP is a partnership between the British Trust for Ornithology (BTO), the Joint Nature Conservation Committee (JNCC) and NatureScot, with fieldwork conducted by volunteer and professional surveyors.

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Scope of the statistics

The statistics are presented as population trends for 52 species and populations of waterbirds wintering in the UK.

Annual indices and smoothed indices (a measure of population abundance) are calculated to generate 25-year trends and 10-year trends for these species in the UK and by constituent country.

These 2025 Statistics include data up to the end of the 2023/24 non-breeding season.

These headline waterbird trends are published as Official Statistics. Further detail on these and other species can be accessed via WeBS Report Online.

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Summary of results

Population trends are published as Official Statistics for 52 of the species and populations of waterbirds monitored in the UK by WeBS and GSMP. These represent the most numerous of the species monitored, with trends that are considered robust enough to meet the stringent quality criteria to be published as Official Statistics. These include 43 species of native waterbirds, of which four are goose species for which populations originating from separate parts of their breeding range can be distinguished and are monitored separately, resulting in 48 separate trends. In addition, the monitoring covers four non-native species – Canada Goose, Barnacle Goose (naturalised population), Egyptian Goose and Mandarin Duck – now established in the UK in large enough numbers to allow production of a robust trend.

Table 1 below presents the 25-year and 10-year trends for the 52 species and populations, and Table 2 presents the trends in England, Wales, Scotland and Northern Ireland. Unless specified, the interpretive text below refers to UK trends and indices. Country trends are discussed where they add to the narrative, and are clearly indicated.

Table 1. Population trends of non-breeding waterbirds in the UK

Species/population	25-year trend	10-year trend	Species/population	25-year trend	10-year trend
Dark-bellied Brent Goose	-11	-11	Scaup	-70	-52
Svalbard Light-b. Brent Goose	44	-4	Eider	-30	-20
Nearctic Light-b. Brent Goose	44	-5	Goldeneye	-54	-21
Canada Goose	70	30	Goosander	-23	-2
Naturalised Barnacle Goose	232	33	Red-breasted Merganser	-47	-25
Greenland Barnacle Goose	38	-17	Little Grebe	29	12
Svalbard Barnacle Goose	65	8	Great Crested Grebe	-23	-4
British/Irish Greylag Goose	170	26	Little Egret	764	58
Icelandic Greylag Goose	-24	-42	Cormorant	51	28
Pink-footed Goose	96	33	Moorhen	-19	-10
Greenland White-fronted Goose	-53	-6	Coot	-28	-20
European White-fronted Goose	-71	-30	Oystercatcher	-17	-1
Mute Swan	2	-4	Avocet	210	37
Bewick's Swan	-96	-89	Lapwing	-45	-13
Whooper Swan	191	20	Golden Plover	-26	-8
Egyptian Goose	562	100	Grey Plover	-31	-2
Shelduck	-25	4	Ringed Plover	-42	8
Mandarin Duck	147	31	Curlew	-38	-23
Shoveler	71	40	Bar-tailed Godwit	-30	-24
Gadwall	62	8	Black-tailed Godwit	138	18
Wigeon	-8	-5	Turnstone	-16	4
Mallard	-34	-18	Knot	7	-2
Pintail	-10	38	Sanderling	55	22
Teal	17	-1	Dunlin	-24	20
Pochard	-74	-40	Purple Sandpiper	-17	8
Tufted Duck	-18	-19	Redshank	-21	3

Trends are % changes of smoothed population index values for the 52 most abundant waterbirds and populations in the UK for which robust trends can be produced.

The 25-year smoothed trend refers to the 25-year period 1997/98 to 2022/23. The 10-year smoothed trend refers to the 10-year period 2012/13 to 2022/23. Note, it is customary to truncate the final year when reporting smoothed trends, so whilst data from 2023/24 have been used in creating the smoothed index values, the trend period assessed and reported is until 2022/23.

Trends use WeBS data except for Pink-footed Goose, Greenland White-fronted Goose, Icelandic Greylag Goose, Greenland Barnacle Goose and Svalbard Barnacle Goose, for which dedicated censuses are undertaken by GSMP. The Icelandic-breeding Goose census that contribute the data for Pink-footed Goose and Icelandic Greylag Goose, include birds residing in other countries at the time of the census, mostly birds still in Iceland in late autumn which come to the UK later in the winter.

Table 2. Population trends of non-breeding waterbirds in the constituent countries

Species/population	Scotland		Northern Ireland		England		Wales
	25-year trend	10-year trend	25-year trend	10-year trend	25-year trend	10-year trend	25-year trend	10-year trend
Dark-bellied Brent Goose	na	na	na	na	-10	-11	-54	-40
Svalbard Light-b. Brent Goose	391	11	na	na	40	-5	na	na
Nearctic Light-b. Brent Goose	1950	148	27	-10	3750	79	2733	67
Canada Goose	433	40	-43	-47	58	30	191	43
Naturalised Barnacle Goose	na	na	68	-10	237	30	9100	109
Greenland Barnacle Goose	38	-17	na	na	na	na	na	na
Svalbard Barnacle Goose	55	1	na	na	65	8	na	na
British/Irish Greylag Goose	na	na	na	na	160	24	40	43
Icelandic Greylag Goose	-24	-42	na	na	na	na	na	na
Pink-footed Goose	91	13	na	na	102	19	na	na
Greenland White-fronted Goose	-53	-6	na	na	na	na	na	-23
European White-fronted Goose	na	na	na	na	-77	-24	na	na
Mute Swan	-4	-10	-39	26	8	-5	26	-12
Bewick's Swan	na	na	-100	-100	-95	-87	-100	-100
Whooper Swan	26	-23	70	0	267	25	182	-13
Egyptian Goose	na	na	na	na	562	100	na	na
Shelduck	-20	-5	-15	-5	-25	8	-16	-3
Mandarin Duck	na	na	na	na	116	27	na	na
Shoveler	-47	0	-31	11	86	43	-13	-20
Gadwall	71	36	61	52	57	5	184	17
Wigeon	-15	3	-49	2	-6	-6	2	2
Mallard	-41	-12	-31	-18	-32	-20	-24	-1
Pintail	11	26	102	24	-17	34	-1	27
Teal	-2	4	51	14	19	-5	4	8
Pochard	-84	-53	-88	-66	-66	-30	-90	-63
Tufted Duck	-24	-24	-76	-39	6	-15	19	-14
Scaup	-56	-42	-82	-72	-90	-79	-84	-21
Eider	-37	-25	131	-1	-31	-2	-2	81
Goldeneye	-37	-9	-87	-57	-41	-20	-61	-40
Goosander	-12	-1	na	na	-32	-5	97	35
Red-breasted Merganser	-40	-13	-31	4	-53	-38	-62	-31
Little Grebe	91	37	14	58	22	3	44	10
Great Crested Grebe	-41	-8	-60	37	-11	-6	0	-12
Little Egret	na	1250	na	383	631	42	1243	92
Cormorant	-13	22	6	29	67	28	36	6
Moorhen	1	33	-26	12	-22	-16	-8	28
Coot	-55	-26	-45	25	-24	-22	-35	-15
Oystercatcher	-38	-17	-37	-21	-17	3	5	-5
Avocet	na	na	na	na	225	42	na	na
Lapwing	-67	-4	-69	-27	-42	-12	-21	-35
Golden Plover	-37	11	-70	-26	-14	-4	58	-23
Grey Plover	-68	-30	-73	-3	-30	-1	-40	-28
Ringed Plover	-28	9	-29	8	-47	-1	-16	13
Curlew	-42	-24	-46	-26	-36	-24	-34	-18
Bar-tailed Godwit	-47	-30	-42	-32	-26	-21	-34	-43
Black-tailed Godwit	386	229	550	38	132	19	150	-15
Turnstone	-32	-10	-27	-17	-10	9	35	33
Knot	-44	-22	-43	73	14	-2	-4	-50
Sanderling	125	20	1925	138	48	19	-2	-4
Dunlin	-22	52	-35	74	-21	19	-45	-11
Purple Sandpiper	8	-2	-57	20	-26	7	na	na
Redshank	-28	7	-33	7	-16	2	31	9

Trends are % changes of smoothed population index values for the most abundant waterbirds in the UK constituent countries for which robust trends can be produced; note that numbers in some countries may be small. na = inadequate data or species not present in that country

Geese and Swans

Having peaked in 2011/12, the trends suggest an apparent decline of the Icelandic population of Greylag Goose, with the latest index the lowest since 1967/68. However, this trend needs to be treated with caution due to the increase in the British/Irish population into areas traditionally used by Icelandic birds in winter, which is making an accurate estimate increasingly more difficult. Research into this is ongoing. Numbers of Pink-footed Goose which also breeds in Iceland continue to increase with a 10-year trend of +33%. Greenland population of White-fronted Goose continues to decline. Having been affected by HPAI outbreaks in 2021/22 and 2022/23, Svalbard Barnacle Geese appear to be recovering strongly, to the extent that the population index in England is the highest on record. Greenland Barnacle Goose was impacted by HPAI in 2022/23 and 2023/24, resulting in a sizeable drop in the population.

British/Irish Greylag Goose and the non-native Canada Goose and Egyptian Goose continue the notable long-term increase in their populations, with 10-year trends of +26%, +30% and +100% respectively, each attaining record high indices. While the population trend for the naturalised Barnacle Goose is still increasing (10-year trend of +33%), there was a sudden drop in the index between 2022/23 and 2023/24, making the 2023/24 index the lowest since 2012/13.

The three Brent Goose populations all have negative 10-year UK trends of between -11% and -4%. Out of these, the Nearctic Light-bellied Brent Goose has contrasting trajectories in Great Britain and in Northern Ireland. While the trend is strongly positive with record high indices in England, Scotland and Wales, recent declines in Northern Ireland have resulted in the lowest index there since 2004/05. The vast majority of the Nearctic population winters in Northern Ireland, which is why the UK trend is negative despite an increase in GB.

The index value for Bewick Swan, with its wintering range now practically restricted to England and with a 10-year trend of -89%, is similar to recent years, while Whooper Swans continue to increase, particularly in England. Following a relatively stable period (25-year trend of +2%), the Mute Swan population index fell to the lowest value since 1996/97.

Ducks

The mixed fortunes of dabbling duck species continued in 2023/24. Shoveler continues to increase with UK 25- and 10-year trends of +71% and +40% respectively, and a record high index in England. Gadwall continued to increase across the UK (25-year trend of +62%) and attained a record high index in Northern Ireland. Teal and Wigeon numbers have been relatively stable. Shelduck has also been fairly stable, apart from in Scotland where recent decline has resulted in the lowest index since 1988/89. Mallard continues to decline with a record low index in England and Northern Ireland.

Diving duck declines continued with many species showing marked declines in both 25- and 10-year trends. Eider recorded yet another record low and UK 10-year trend of -20%. There were large declines also for Tufted Duck (10-year trend of -19%), Goldeneye (10-year trend of -21%) and Scaup (10-year trend of -52%), with Scaup having its lowest index since 1989/90. The UK 10-year trend for Pochard is -40%, with record lows in Wales and Scotland.

Both sawbill species, Goosander and Red-breasted Merganser, have declined with 25-year trends of -23% and -47% respectively, which is reflected in all country-level trends except for a strong increase of Goosander in Wales (25-year trend of +97%). Red-breasted Merganser has declined to its lowest index since 1975/76. In the short-term, Goosander continues to increase in Wales, while in England and Scotland the short-term trend is described as stable.

Waders

Avocet, Black-tailed Godwit and Sanderling are the only common wintering wader species with clear long-term increases in the UK. Avocet and Black-tailed Godwit reached their highest indices on record and 10-year trends of +37% and +18% respectively. The Sanderling index is the highest since 1994/95 in Wales, and attained its highest index on record in Northern Ireland.

The continued decline of Curlew (25-year trend of -38%, 10-year trend of -23%) marks its lowest index since 1980/81. Bar-tailed Godwit, Lapwing and Golden Plover continue to decline, although there are signs of recovery for Golden Plover in Scotland (10-year trend of +11%).

A number of wader species with negative 25-year trends have stabilised or increased in recent years, including Ringed Plover (10-year trend of +8%), Grey Plover (10-year trend of -2%), Dunlin (10-year trend of +20%), Purple Sandpiper (10-year trend of +8%), Redshank (10-year trend of +3%) and Turnstone (10-year trend of +4%).

Oystercatcher has a stable trend overall and in England and Wales, but it continues to decline in Scotland and Northern Ireland. The Knot population trend is regionally variable, with a relatively stable overall trend (25-year trend of +7%, 10-year trend of -2%) masking long- and short-term declines in Scotland and Wales, and a strong short-term increase in Northern Ireland (10-year trend of +73%).

Other waterbirds

Little Egret range expansion and, with it, population growth continues (10-year trend of +58%), with record high indices yet again in all four countries. In contrast, Moorhen (10-year trend of -10%) and Coot (10-year trend of -20%) had record low index values in 2023/24.

Notable population changes

The four non-native species continue to increase in numbers and expand in range in the UK, and as a result show some of the largest population increases in both 25-year and 10-year trends: Canada Goose 70% and 30%, naturalised Barnacle Goose 232% and 33%, Egyptian Goose 562% and 100%, Mandarin Duck 147% and 31%.

Largest UK population changes for the native species were:

25-year increases: Little Egret 764%, Avocet 210%, Whooper Swan 191%, British/Irish Greylag goose 170%, Black-tailed Godwit 138% and Pink-footed Goose 96%.
10-year increases: Little Egret 58%, Shoveler 40%, Pintail 38% and Pink-footed Goose 33%.
25-year declines: Bewick’s Swan -96%, Pochard -74%, European White-fronted Goose -71%, Scaup -70%, Goldeneye -54% Greenland White-fronted Goose -53%, Red-breasted Merganser -47% and Lapwing -45%
10-year declines: Bewick’s Swan -89%, Scaup -52%, Icelandic Greylag Goose -42%, Pochard -40% and European White-fronted Goose -30%.

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Interpretation of results

WeBS reporting, including data from GSMP, provides, in one place, information that can be used to understand the status and trends of key populations of waterbirds, thereby contributing to international reporting commitments, to national-level policy and management, and to scientific research.

The UK is an important wintering area for waterbirds due to its climate, large number of estuarine feeding grounds, and position on bird migration routes. As a result, an internationally important proportion of the world population of many waterbird species or subspecies occur in the UK, including Greenland White-fronted Goose, Pink-footed Goose, Bewick’s Swan, Whooper Swan, Knot, Dunlin and Black-tailed Godwit. Out of the 48 native species and populations featured in this publication, 33 reach internationally important numbers even on individual sites. Overall wintering waterbird numbers regularly exceed 20,000 birds on 46 sites; nine of which – The Wash, Ribble Estuary, Morecambe Bay, Dee estuary, North Norfolk Coast, Thames Estuary, Humber Estuary, Solway Estuary, and Breydon Water & Berney Marshes – exceed 100,000 birds.

It is important to note that many waterbirds are migratory, and so population changes and drivers of change are best considered across the whole flyway, not just in a UK context. Winter temperatures in Europe were on average milder than normal in 2023/24, following the pattern of recent years. Such mild conditions are known to affect waterbird migration patterns with short-stopping on migration contributing to the declines in the long-term trends for species such as Bewick’s Swan, Scaup and Coot, and could be contributing to increases in Black-tailed Godwit numbers as some juveniles winter in the UK instead of travelling to the Iberian peninsula. Short-staying and phenological change in migration timing can also affect index values, as the index is an average over several winter months.

As previously reported, avian influenza was recorded causing major mortality in the winters of 2021/22 and 2022/23 among a number of waterbird species. The Svalbard Barnacle Goose on the Solway Estuary suffered badly in both years, and in 2022/23 the Greenland Barnacle Goose also suffered significant mortality which continued into 2023/24. A study by Ross et al. (2024) on returning Solway geese in 2022/23 suggested partial immunity to avian influenza, possibly due to previous exposure. The strong recovery of the Svalbard Barnacle Goose population in 2023/24 may be mediated by such immunity or be the result of density-dependent change in breeding success, but it is too early to comment on Greenland Barnacle Goose. More research is needed to understand the dynamics at play.

WeBS data provide necessary information on the status and trends of individual species as required by international agreements such as the Agreement on the Conservation of African Eurasian Migratory Waterbirds (AEWA). Assessment of migratory bird populations is important at a flyway scale, and January WeBS data are supplied to Wetlands International for inclusion in the International Waterbird Census. Summaries are used in waterbird population estimates, and in AEWA Conservation Status reports which inform the triennial update of AEWA species listings, which most recently occurred at the 8th meeting of the parties to the Agreement in 2021. This Agreement has legal consequences for the UK, including the requirement that hunting of globally threatened species such as Pochard is sustainable. Data from WeBS was also used in the 6th UK National Report to the Convention on Biological Diversity. At a country level, the data help countries in the UK to report on, implement or deliver country biodiversity strategies and biodiversity indicators. In addition, the data are widely used in local site management.

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Background and Methods

Wintering waterfowl have been surveyed since 1947. The first national counts were carried out in the winter of 1951/52 and included 500 sites. Today, over 220 waterbird (wildfowl, waders, rails, divers, grebes, cormorants and herons) species, races or populations are recorded every year by the Wetland Bird Survey (WeBS), and trends are produced for the most numerous 110 of these.

The Goose and Swan Monitoring Programme (GSMP) monitors the abundance and breeding success of the UK’s native geese and migratory swans during the non-breeding season. GSMP data are used to produce trends for Icelandic Greylag Goose, Pink-footed Goose, Svalbard Barnacle Goose, Greenland Barnacle Goose, Taiga Bean Goose and Greenland White-fronted Goose.

The objectives of waterbird monitoring are to assess the size of non-breeding waterbird populations, trends in their numbers and distribution, and the importance of individual sites for waterbirds.

The annual WeBS and GSMP report Waterbirds in the UK presents syntheses of the data, and provides a single, comprehensive source of information on waterbird status and distribution in the UK.

Data collection and method overview

The wintering waterbird statistics are comprised of data from two survey components: WeBS core counts and GSMP goose counts.

WeBS core counts: Monthly counts (year-round, but with an emphasis on winter months) of all waterbirds are carried out on coastal and inland wetland sites. The WeBS waterbird counts are made using a so-called “look-see” method (Bibby et al. 2000) where the observer, familiar with the species involved, surveys the whole pre-defined area, and records the numbers of each species of waterbird present. The counts include all waterbird species, including non-natives and escapes, but recording of gulls is optional. Smaller sites are counted as one unit, while larger sites are divided into sectors with sector counts pooled to give the site totals. The same sites and sectors are revisited each survey. Counters are encouraged to do the WeBS counts on pre-determined weekends each month, although weather conditions and counter availability can result in different days being chosen. Synchronising the sector counts within a site is particularly important. Coastal sites are counted at high tide, with a small number at other states of the tide because of site-specific practical considerations.

GSMP goose counts: A number of native goose populations, mostly migratory, are surveyed by the Goose and Swan Monitoring Programme. Co-ordinated counts are carried out, usually timed to coincide with each species’ peak populations on sites of known concentrations of birds. Goose count data are used to produce the trends for Icelandic Greylag Goose, Pink-footed Goose, Svalbard Barnacle Goose, Greenland Barnacle Goose, Taiga Bean Goose and Greenland White-fronted Goose.

Sample site selection

WeBS Core Counts: WeBS core counts are carried out on pre-determined coastal and inland sites across the UK. This site network is designed to cover the majority of sites where large aggregations of waterbirds are regularly found. Sites include all wetland habitats used by waterbirds – freshwater lakes, ponds, reservoirs, gravel pits, rivers, canals, freshwater marshes as well as open coast and estuaries. The latter habitat provides the majority of data for all the species that tend to congregate in key estuaries over the winter. Sites that are not being counted are advertised to WeBS counters on a vacant sites map, from which new and existing counters can select a site of their choice. The counters are encouraged to choose sites where obtaining data is particularly important, including on SSSIs and SPAs where wintering waterbirds are a feature.

GSMP goose counts: Since wintering geese tend to concentrate at specific locations, both on and off wetland sites, GSMP goose counts are carried out on sites with known concentrations of geese with the aim to arrive at as complete a count for the species or population as possible.

Data submission

The primary method for capturing waterbird data from both schemes is through an online capture system by surveyors themselves or by surveyor co-ordinators, although some data are submitted to BTO via paper forms or spreadsheets to be added to the dataset.

Data validation and verification

The online database is programmed to automatically carry out validation and verification processes of the inputted data. It attaches standardised species nomenclature to the data, and carries out automated data integrity checks that ensure that all mandatory information is captured with valid date and time information and accurate geographic location information. Any particularly unusual counts are flagged, checked by the Local Organisers or National Organisers and confirmed with the counters if necessary.

Data analysis

WeBS core counts provide the information used in assessing population trends for most species wintering in the UK. Annual and monthly indices are produced for each species. There are occasions when counters miss one or two months during the season, and so an imputing process is used to derive these missing counts and to make the data comparable from one year to the next. Counts can also be marked incomplete by counters where the count is considered to be a minimum estimate due to visibility, disturbance or inaccessibility of some of the count area, meaning it is possible some birds were missed. At complex sites containing multiple count sectors, some of which may not have been visited, completeness for the entire site is calculated on a species-by-species basis using historical data of bird distribution within the site. The Underhill Index (Underhill and Prys-Jones 1994) was specifically developed to analyse the waterbird population counts to produce a time series of index values for each species or subpopulation. This method includes a calculation to estimate counts for missing and incomplete site-month combinations, based on counts in other months and all sites, hence making counts comparable across years.

Monthly indices reveal the patterns of seasonality for the species concerned. The annual index values are calculated from the average of counts carried out between November and March for waders (for which high numbers of passage birds need to be separated from wintering birds) and between September and March for other species. The index for the resident British/Irish Greylag Goose is based on data from April to September in order to separate them from the migratory Icelandic Greylag Geese in parts of their range where the two populations overlap. These are then fed into General Additive Models (GAMs) to produce smoothed indices and trends which are especially useful when assessing changes through time.

The 25-year and 10-year population trends are calculated by comparing the smoothed index value for the last but one year in the data series and the 25 and 10 years previous to that year. It is customary to truncate the final year when reporting smoothed trends, so whilst data from 2023/24 have been used in creating the smoothed index values, the trend period assessed and reported is until 2022/23.

Index values for 2020/21 are not available due to data limitations related to COVID-19 restrictions (Frost & Calbrade 2022).

More information on the survey protocols, analysis and results can be found on the scheme websites for Wetland Bird Survey and Goose and Swan Monitoring Programme.

Technical details of the WeBS method are set out in a separate document available on the BTO website.

Value of citizen science approach

Over 3,900 WeBS volunteer counters contributed to the survey in 2023/24, making around 44,500 count visits to almost 5,900 sectors on over 3,400 sites (mostly estuaries and large still waters). GSMP surveys cover around 100 further sites. This ‘citizen science’ approach, with an estimated value of over £2.5 million per year (using a day rate of £150 a day for the majority of volunteers and £350 a day for ‘Local Organisers’), enables very broad simultaneous sampling coverage that would not be possible using professional surveyors only, and it provides an opportunity for volunteers to engage with nature in an active outdoor interest as they take part in a national conservation/monitoring project.

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Confidence in results, quality assurance and caveats

WeBS volunteers follow standardised, peer-reviewed methods, and the submitted data undergo a combination of automated and manual validation and verification processes. These measures ensure that results derived from these data are scientifically robust. Trends are based on changes in smoothed population indices and are produced using Generalised Additive Models – this reduces the risk that short-term fluctuations obscure long-term trends. Missing values are accounted for using the Underhill indexing method (Underhill & Prys-Jones 1994). Although the statistical significance of trends is not currently assessed, the statistical approaches used to generate and compare indices are routinely used in peer-reviewed publications.

Trends are only published as Official Statistics where they are considered statistically robust, and where the long-term trends in index values can be used to assess changes in overall wintering numbers with confidence. There are many reasons why this may not be the case, including low numbers present in the winter months and a species being either cryptic or secretive, resulting in low detection rates. Differential coverage of different habitats is a recognised potential bias, especially for those species where a substantial proportion of wintering birds occur away from the monitored sites (e.g. on farmland or on the open coast), or use the sites at times of the day when they are unlikely to be encountered by WeBS counters. Recording of gull and tern species is optional to WeBS counters, and so the data for them are considered incomplete. While only those trends considered scientifically robust are published as Official Statistics, all trends are available via WeBS Report Online.

GSMP aims at a complete population count of those geese where the species or population wholly or nearly wholly winters in the UK. As a result of the later timing of migration, the population count of Icelandic Greylag Goose includes individuals still residing in other countries at the time of the census. Including these birds in the count ensures a more complete population estimate and maintains comparability of the census data across the full time series.

There are slight differences in how the count data were processed for some of the goose species, which is reflected in the country trends for Pink-footed Goose in particular. These datasets are being scrutinised further with a view to making adjustments in future years where necessary to improve consistency.

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Drivers of change

Changes in bird populations can be caused by a wide range of drivers, including climate/weather, breeding ground conditions, direct human-induced pressures such as habitat loss, human disturbance, and activities impacting water quality, and by conservation interventions such as protection afforded by the UK’s Special Protection Area network.

Climate/weather

Climate/weather impacts birds as it can affect food availability (e.g. frozen ground affects invertebrate availability), energy expenditure and survival rates. Climate/weather also influences migration routes and the timing of migration. Although species respond differently, the changing patterns of winter climate are contributing to changes in the timing and extent of migration by many species of waterbird, as birds move to milder areas to avoid freezing conditions. Analysis of this is best carried out within the context of longer-term species’ trends at the flyway level, and to this end, WeBS collaborates with other national monitoring schemes through the International Waterbird Census to provide such international contexts and encourage such analyses. The flyway population trends were published in 2021 in the latest Conservation Status Report of the African-European Waterbird Agreement (AEWA). An updated report with revised trends is expected to be published in late 2025.

Breeding ground conditions

Most waterbirds that we see in the UK in the winter months are migratory, returning to the Arctic and Boreal zones (Greenland, Iceland, high arctic Canada, Scandinavia, Russia) to breed in the summer. Population levels are influenced by breeding success which is influenced by conditions in their breeding grounds. Key factors influencing breeding ground conditions include climate/weather and predator-prey relations.

Direct human induced pressures

Other possible human-induced reasons for waterbird declines include changes in wetland management, deterioration in water quality, abstraction and drought causing falling water tables, and non-native predators such as Mink. A paper published in 2017 listed intensive agriculture, forestry, increases in generalist predator populations and climate change as possible factors negatively affecting the curlew during the breeding season (Franks et al. 2017), as can disturbance or loss of habitat that reduces the carrying capacity of the estuarine wintering habitat impact the over-wintering population (Woodward et al. 2021).

A potential site-specific pressure is coastal human disturbance; a recent study by Whittingham et al. (2019) found that offshore refuges appear to benefit Turnstone. Habitat loss in the form of loss of intertidal mudflats to land claim and other forms of erosion (Foster et al. 2013) and from impacts of the invasive plant species Spartina anglica (Borges et al. 2021), can also be factors. An example of site-specific pressure is development at busy estuaries, such as Southampton Water.

Conservation Interventions

The key UK sites – protected under various legislative measures – play a critical role in supporting waterbird populations under changing environmental conditions, and operate as a functional ecological network at national and international scales. The UK’s Special Protection Area network holds over one-third of the total UK over-wintering waterbird populations. Recent research by Gaget et al. (2021) suggests that conservation policy aimed at waterbirds and their habitats can help waterbird communities respond to climate warming.

Conservation action such as habitat management carried out on protected sites (as well as in other situations), has played a role in tempering population declines, or restoring or increasing some species population levels (Wauchope et al. 2022). For instance, the Pochard is notable in having less severe declines in SPAs, which may be due to site management in these areas (Caulfield et al. 2025).

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Involvement and contacts

These statistics were produced by the Wetland Bird Survey partnership, with BTO having primary responsibility for producing the statistics.

Quality Assurance was carried out by BTO, JNCC, RSPB and NatureScot. Additional information on quality assurance and WeBS methods is provided in the Methods section.

The population trends are published as a JNCC Official Statistic. If you have any queries, please contact us.

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Relation to other Official and National Statistics, and broader relevance

These statistics form part of a suite of statistics produced through partnership monitoring schemes as part of JNCC’s terrestrial evidence programme.

The statistic feeds into the National Statistics Compendium – UK Biodiversity Indicators – and country-level indicators (e.g. for Scotland and for England).

Data from WeBS are used in scientific research and to inform conservation action.

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References

Bibby, C.J., Burgess, N.D., Hill, D.A. and Mustoe, S. (2000). Bird Census Techniques. Second Edition. Academic Press, London.

Borges, F.O., Santos, C.P., Paula, J.R., Mateos-Naranjo, E., Redondo-Gomez, S., Adams, J.B., Caçador, I., Fonseca, V.F., Reis-Santos, P., Duarte, B. and Rosa, R. (2021). Invasion and extirpation potential of native and invasive Spartina species under climate change. Frontiers in Marine Science, 8, p.696333.

Caulfield, E.B., Feather, A., Smith, J.A., Frost, T.M. & Woodward, I.D. (2025). Wetland Bird Survey Alerts 2021/2022: Changes in numbers of wintering waterbirds in the Constituent Countries of the United Kingdom, Special Protection Areas (SPAs), Sites of Special Scientific Interest (SSSIs) and Areas of Special Scientific interest (ASSIs). BTO Research Report 786. BTO, Thetford. www.bto.org/webs-reporting-alerts.

Foster, N.M., Hudson, M.D., Bray, S. & Nicholls, R.J. (2013). Intertidal mudflat and saltmarsh conservation and sustainable use in the UK: A review. Journal of Environmental Management, 126, 96–104.

Franks, S.E., Douglas, D.J.T., Gillings, S. & Pearce-Higgins, J.W. (2017). Environmental correlates of breeding abundance and population change of Eurasian Curlew Numenius arquata in Britain. Bird Study 64, 393–409.

Frost, T.M. & Calbrade, N.A. (eds). (2022). Wetland Bird Survey News 2020/21 Special Edition. BTO, RSPB and JNCC. British Trust for Ornithology, Thetford.

Gaget E. & Frost T. et al. (2021). Protected area characteristics that help waterbirds respond to climate warming. Conservation Biology doi: 10.1111/cobi.13877.

Ross, C.S., Byrne, A.M.P., Mahmood, S., Thomas, S., Reid, S., Freath, L., Griffin, L.R., Falchieri, M., Holmes, P., Goldsmith, N., Shaw, J.M., MacGugan, A., Aegerter, J., Hansen, R., Brown, I.H. & Banyard, A.C. (2024). Genetic Analysis of H5N1 High-Pathogenicity Avian Influenza Virus following a Mass Mortality Event in Wild Geese on the Solway Firth. Pathogens 13(1), 83; https://doi.org/10.3390/pathogens13010083.

Underhill, L.G. & Prŷs-Jones, R. (1994). Index numbers for waterbird populations. I. Review and methodology. Journal of Applied Ecology, 31, 463–480.

Wauchope, H.S., Jones, J.P.G., Geldmann, J. et al. (2022). Protected areas have a mixed impact on waterbirds, but management helps. Nature 605:103–107. https://doi.org/10.1038/s41586-022-04617-0.

Whittingham, M.J., McKenzie, A.J., Francksen, R.M., Feige, D., Cadwallender, T., Grainger, M., Fazaa, N., Rhymer, C., Wilkinson, C., Lloyd, P., Smurthwaite, B., Percival, S.M., Morris-Hale, T., Rawcliffe, C., Dewson, C., Woods, S., Stewart, G.B., Oughton, E. (2019). Offshore refuges support higher densities and show slower population declines of wintering Ruddy Turnstones Arenaria interpres. Bird Study 66:431-440.

Woodward, I. D., Austin, G. E., Boersch-Supan, P. H., Thaxter, C. B., & Burton, N. H. K. (2021). Assessing drivers of winter abundance change in Eurasian Curlews Numenius arquata in England and Wales. Bird Study, 68(3): 289–301. https://doi.org/10.1080/00063657.2022.2049205.

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Published: Thursday, May 22, 2025.

Population trends for waterbirds in the UK

Contents

Official Statistics description

Scope of the statistics

Summary of results

Geese and Swans

Ducks

Waders

Other waterbirds

Notable population changes

Interpretation of results

Background and Methods

Data collection and method overview

Sample site selection

Data submission

Data validation and verification

Data analysis

Value of citizen science approach

Confidence in results, quality assurance and caveats

Drivers of change

Climate/weather

Breeding ground conditions

Direct human induced pressures

Conservation Interventions

Involvement and contacts

Relation to other Official and National Statistics, and broader relevance

References