Official statistic on seabird breeding population changes

Summary of results

The results presented in Tables 1–4 show that, in 2024, the number of significant declines for seabird species where sufficient data are available, both at a UK and country level, largely outnumber those showing a significant increase.

For the UK, abundance change figures for a total of 17 breeding seabird species could be estimated (Table 1), and a range of species showed significant declines in abundance over both the long-term (1986–2024) and 24-year (2000–2024) periods. Significant declines were apparent for Fulmar, Shag, Lesser Black-backed Gull (natural nesters only), Herring Gull (natural nesters only), Kittiwake, Sandwich Tern and Common Tern over both periods, while the decline for Arctic Skua was significant across the long-term period but not the 24-year period. Razorbill was the only species to show a significant increase (across the long-term time period only).

In England, abundance change figures could be produced for nine species (Table 2), and of these only Common Tern showed a significant change, with a decline in abundance over both the long-term (1986–2024) and 24-year (2000–2024) periods.

In Scotland, abundance change could be estimated for 13 species (Table 3), with many showing a similar pattern of decline to the UK, although there were some differences in the species affected and the extent of the effects. Significant decreases were shown for Fulmar, Shag, Herring Gull (natural nesters only), Great Black-backed Gull, Kittiwake, and Common Tern across both the long-term (1986–2024) and 24-year (2000–2024) periods. There were significant declines for Arctic Skua and Little Tern across the long-term period, but not for the 24-year period. No significant increases were identified.

In Wales, abundance change figures could be produced for eight species (Table 4). Razorbill showed significant increases over both time periods, whilst Great Black-backed Gull increased significantly over the long-term period (1986–2024) but not over the 24-year period (2000–2024). Kittiwake abundance declined significantly over both periods.

Changes in productivity estimates between 2023 and 2024 varied greatly between species and regions (Tables 1–4). Notable results included Sandwich Tern productivity estimates increasing across the UK, England and Scotland, whereas Shag productivity estimates declined in the UK, Scotland and Wales. Arctic Skua had a particularly poor year for productivity in 2024, with an estimate of only 0.03 chicks/fledged per pair in Scotland.

Possible drivers of change for the observed results are described in Section 4.1.

UK: Abundance and productivity changes for 22 species

• In the UK, Razorbill was the only breeding seabird species to show a significant long‑term (1986–2024) increase in abundance (+110%) (Table 1).
• Eight species declined significantly in abundance over the same period, with the steepest declines observed in Arctic Skua (−93%), Lesser Black‑backed Gull (natural nesters, −72%) and Shag (−71%) populations.
• Over the 24‑year period (2000–2024), no species increased significantly. The strongest significant declines were observed in Lesser Black‑backed Gull (natural nesters, −81%), Shag (−65%) and Common Tern (–60%) populations.
• From 2023 to 2024, the largest increases in productivity estimates (chicks fledged per pair) were recorded for Black‑headed Gull (0.30 to 0.72), Sandwich Tern (0.17 to 0.58) and Great Black‑backed Gull (1.04 to 1.24).
• Over the same period, the largest decreases in productivity estimates were observed for Arctic Skua (0.58 to 0.03), Shag (1.31 to 0.93) and Little Tern (0.61 to 0.25).

England: Abundance and productivity changes for 10 species

• In England, the only seabird species to show a significant change in breeding abundance was Common Tern, which declined by 47% and 51% over the long‑term (1986–2024) and 24‑year (2000–2024) periods, respectively (Table 2).
• From 2023 to 2024, the largest increases in productivity estimates (chicks fledged per pair) were recorded for Sandwich Tern (0.20 to 0.77) and Arctic Tern (0.19 to 0.41).
• Over the same period, the largest decreases in productivity estimates were observed for Common Tern (0.90 to 0.38) and Little Tern (0.76 to 0.26).

Scotland: Abundance and productivity changes for 18 species

• In Scotland, no breeding seabird species showed a significant long‑term (1986–2024) increase in abundance (Table 3).
• Over the same period, eight species declined significantly, with the steepest long‑term declines observed in Arctic Skua (−93%), Little Tern (−75%), and Common Tern (−73%) populations.
• Over the 24‑year period (2000–2024) the pattern is similar, with no significant increases and the strongest significant declines in Common Tern (−67%), Shag (−62%) and Great Black-backed Gull (–57%) populations.
• From 2023 to 2024, the largest increases in productivity estimates (chicks fledged per pair) were recorded for Great Black‑backed Gull (1.00 to 1.23), Sandwich Tern (0.11 to 0.26), and Puffin (0.48 to 0.58).
• Over the same period, the largest decreases in productivity estimates were observed for Arctic Skua (0.58 to 0.03), Shag (1.26 to 0.83), and Great Skua (0.44 to 0.17).

Wales: Abundance and productivity changes for 8 species

• In Wales, significant long‑term (1986–2024) increases in abundance were observed in Razorbill (+256%) and Great Black-backed Gull (+170%) populations (Table 4).
• Over the same period, a significant decline was observed in the Kittiwake (−56%) population.
• Over the 24‑year period (2000–2024), Razorbill abundance increased significantly (+141%) and the only significant decline was in the Kittiwake population (-53%).
• From 2023 to 2024, the largest increase in productivity estimates (chicks fledged per pair) was recorded for Herring Gull (0.55 to 0.81).
• Over the same period, the only decrease in productivity estimates was observed for Shag (1.63 to 1.59)

Drivers of change

• From 2021 onwards, High Pathogenicity Avian Influenza (HPAI) caused major mortality and rapid population decline in several UK seabird species, most notably Great Skua and Gannet (Tremlett et al. 2024). Although HPAI outbreaks were less prevalent in 2024, they may continue to affect survival and productivity in future years.
• Climate‑related changes, including warming seas, have caused shifts in the distribution, timing and availability of key prey species, leading to reduced foraging efficiency and breeding success in many seabird species. More frequent extreme weather events, also linked to climate change, such as winter storms and prolonged wet periods during the breeding season, can reduce overwinter adult survival, cause nest failures and increase chick mortality.
• Pressures from non‑native predators, such as rats and American Mink, or in some cases from native predators, can lead to the loss of eggs, chicks and adults.
• Fisheries interactions, including seabird bycatch in gillnets and on longlines, can reduce adult survival, while reductions in fishery discards have affected the food supply for species that scavenge from fishing boats. Reduced access to discards may force birds to forage further or switch to lower‑quality prey, potentially reducing adult condition and breeding success.
• Human disturbance, including recreational activity near colonies and egg collection, can reduce breeding success in sensitive species, particularly among terns and gulls.
• Renewable energy infrastructure, especially offshore wind farms, may displace some species from preferred foraging areas, increasing energetic costs, or create collision risks for species that fly at rotor height.
• Habitat change, including erosion, vegetation change and loss of suitable nesting areas, may limit breeding opportunities for species such as Little Tern and Mediterranean Gull.

For a detailed review of UK breeding seabird population drivers of change, see Seabirds Count: A census of breeding seabirds in Britain and Ireland (2015–2021) (Burnell et al. 2023).

Confidence in results and caveats

• SMP surveys and analytical approaches follow standardised peer-reviewed methods to ensure results are comparable between survey sites and over time. All data undergo a combination of automated and manual validation and verification. See Walsh et al. (1995), JNCC (2014) and Harris et al. (2026) for full details.
• Valid abundance and productivity figures require sufficient spatial and temporal coverage, and species with challenging survey requirements (e.g. burrow‑nesters, nocturnal or remote breeders) are often under-represented. Results for these groups have lower confidence or cannot be produced, for example where fewer than the required proportion of colonies are monitored (see Section 5 for criteria), leading to gaps in some species and regions.
• Abundance index graphs showing 95% confidence intervals are presented in the SMP annual report (Harris et al. 2026) and on the BTO Bird Trends Explorer.
• Results for species with sparse datasets carry wider confidence intervals and should be interpreted cautiously.
• Assessment of the significance of abundance changes considers whether the confidence intervals of the estimate for 2024 overlap the index values for 1986 (long-term change) or 2000 (24-year change). These assessments reflect the relative level of sampling effort in the relevant years.
• Imputation is used to estimate missing annual counts, with uncertainty quantified through bootstrapping (see Section 5). Confidence intervals only reflect uncertainty in the imputation of missing data. They do not reflect uncertainty in abundance counts and, therefore, the overall uncertainty in the population estimates, so caution should be applied when interpreting the significance of reported population change figures. Due to sparse datasets for several species, especially at a country level, there is a high risk of false negatives when assessing the significance of population changes.
• The indices used to assess population change are unsmoothed and therefore percentage changes could be influenced by extreme annual estimates.
• Productivity estimates rely on Generalised Linear Mixed Models, but the absence of confidence intervals for productivity values limits the ability to assess statistical uncertainty in annual estimates.
• COVID‑19‑related disruptions in 2020 and low sample sizes in some later years created gaps in productivity and abundance data, meaning estimates for these years are either interpolated or excluded from model fitting.
• Some species’ datasets are dominated by a small number of long‑running study sites, particularly in Scotland, which improves consistency but may reduce the representativeness of UK‑wide figures where regional differences exist.
• Changes in monitoring effort during national census years or periods of targeted surveying can temporarily increase coverage, but these peaks may create inconsistencies when compared with typical annual effort.
• For several gull species, inland or urban colonies are not well covered because of survey difficulty, meaning reported abundance change figures reflect only natural or coastal nesters and should not be assumed to represent entire populations. Natural nesters are defined as breeding on moors, cliffs, marshes, beaches and other areas of natural or semi-natural habitat, whilst coastal nesters are defined as colonies located within 5 km of the mean high water mark.
• A 2024 review of the SMP sampling strategy (O’Hanlon et al. 2024) found that some abundance and productivity trends were imprecise, absent, or geographically limited. Its recommendations included expanding monitoring in under-represented regions and inland areas, covering more species and colony sizes and revising trend analysis methods. Measures to implement these improvements are planned but will take time to complete.