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UK Common Murre Index Was 40% Above 1986 Level, While Scotland Was 29% Below

Common guillemots on the Isle of May, Scotland
Conservation · Population & status

The Seabird Monitoring Programme report published on 19 March 2026 shows a marked regional contrast in the long-term abundance index for common murres, or common guillemots (Uria aalge). In 2024, the UK index was 40% above its 1986 baseline, while the Scottish index was 29% below the 1986 level.

The difference is also visible over the medium term. Relative to 2000, the 2024 UK index was 18% higher, whereas the Scottish index was 38% lower. The report lists 810,645 common murres across 70 Scottish colonies, compared with 1,265,888 birds across 105 monitored colonies in the UK as a whole. Scotland therefore accounted for a large share of the breeding birds represented in the monitoring data, so the national and Scottish trajectories are not independent pictures of two separate populations.

Breeding productivity was more similar across regions

Breeding productivity told a less contrasting story. In 2024, productivity was estimated at 0.51 chicks fledged per breeding pair for the UK and 0.55 for Scotland. Their long-term productivity patterns have also tracked one another closely because many of the monitored colonies are Scottish.

Abundance indices are not complete population censuses

The abundance indices are not equivalent to complete population censuses and should be interpreted with care. Colony coverage varied substantially among recent years, and some recent indices were disproportionately influenced by smaller colonies; coverage improved in 2023 and 2024. The separate Seabirds Count census showed a more modest overall decline since Seabird 2000, with decreases concentrated in the north and increases farther south. This illustrates why an annual monitoring index and a full census should not be treated as the same measure.

Sources and image credit

  1. Harris, S. J., Baker, H., Balmer, D. E., Bolton, M., Burton, N. H. K., Clarke, J. A. E., Dunn, T. E., Evans, T. J., Hereward, H. F. R., Humphreys, E. M., Langlois Lopez, S., Money, S., Taylor, E. A., & O'Hanlon, N. J. (2026). Seabird Population Trends and Causes of Change: 1986–2024. British Trust for Ornithology.Primary 2026 annual monitoring report published 19 March 2026. The Common Guillemot species account gives a 2024 long-term abundance index 40% above the 1986 baseline for the UK and 29% below for Scotland, and cautions that varying colony coverage affects confidence in recent annual indices.

Image: marsupium photography / Magnus Hagdorn — common guillemots (Uria aalge) on the Isle of May, Scotland, photographed 11 May 2014; Wikimedia Commons / Flickr; cropped to 16:9; representative Scottish colony image · CC BY-SA 2.0 · Source

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