Skip to content

Britain’s Wintering Common Gull Estimate Fell About 26% in Two Decades

Common gull in winter plumage on water
Conservation · Population & status

Great Britain’s wintering common gull (Larus canus) population was estimated at about 516,000 birds in the 2023/24–2024/25 Winter Gull Survey, usually rounded to 520,000. The comparable estimate from 2003/04–2005/06 was about 696,000, making the new point estimate 25.9% lower.

The survey was the first comprehensive British winter gull assessment in roughly two decades. Because it estimates birds at places that were not all counted in both survey periods, the report also used a second method to test change within sectors surveyed in both periods.

Roost counts were used to estimate birds beyond the best-known sites

Observers counted gulls as they gathered to roost, usually around dusk. Large known inland and coastal roosts were treated as key sites, while additional inland and coastal areas were sampled using a stratified design. The sampled sites were then used to estimate birds roosting away from the major known concentrations.

The resulting figure of 515,834 common gulls is therefore a population estimate rather than a direct count of exactly that many birds. The report gives substantial uncertainty around the precise total, so it is normally reported as about 520,000.

Two comparisons both indicated a substantial decline

Comparing the full population estimates gives a 25.9% decline between the two survey periods. A separate paired analysis restricted the comparison to survey sectors covered in both periods and estimated a decline of about 19% across Great Britain.

The two values are not contradictory. The full-estimate comparison uses all available data in each survey period, including sites that were not covered both times. The paired analysis asks how counts changed within the same set of repeatedly surveyed sectors. Both approaches therefore point to a substantial decline, but they measure change in slightly different ways.

England showed the clearest country-level decline

The paired-sector analysis found a clear overall decline in England. Scotland and Wales did not show clear overall changes in the same analysis, although their full population point estimates differed from the earlier survey.

This distinction matters because country-level point estimates can shift when survey coverage and the distribution of birds differ between periods. The repeatedly surveyed sectors provide the more direct like-for-like comparison of local change.

The report does not identify one cause

The authors discuss several possible contributors to changes in wintering gull numbers, including highly pathogenic avian influenza, changes in agriculture and land use, climate, waste management, reduced fisheries discards and changes elsewhere along the migration flyway. The survey itself does not distinguish among these explanations.

The lower population estimate also changes how nationally important roosts are identified. One per cent of the updated Great Britain estimate is about 5,200 common gulls, so a winter roost holding at least that number can meet the updated national-importance threshold.

Sources and image credit

  1. Caulfield, E. B., Clarke, J. A., Burton, N. H. K., Boersch-Supan, P. H., Frost, T. M., Balmer, D. E., & Woodward, I. D. (2026). Winter gulls in the United Kingdom: Results from the 2023/24–2024/25 Winter Gull (Roost) Survey (BTO Research Report 807). British Trust for Ornithology.Primary research report. Great Britain common gull estimate 515,834 (95% CI 438,175–604,179), down 25.9% from 2003/04–2005/06; country estimates and paired trend models are also reported.
  2. British Trust for Ornithology. (2026, May 18). Gulls all at sea as UK populations take a dive.Official BTO news release announcing the new Winter Gull Survey results.

Image: Alexis Lours / Wikimedia Commons — common gull (Larus canus) in Parc Georges-Valbon, Saint-Denis, Île-de-France, France, 17 February 2024; representative species image; cropped to 16:9 · CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/ · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Population & status

SPECIES IN THIS STORY

Species in this story

Common Gull Larus canus Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.