Common Guillemot - Uria aalge

Guillemot (Uria aalge) are one of the most abundant seabirds in the UK. They have a dark brown head and upperparts with white underparts, and a slim pointed bill (fig. 1). There is a 'bridled' variety of guillemot wth a white eye stripe - these are more common to the north of the UK (fig. 2) (Svensson, 2020). Guillemot breed in large colonies on cliffs, laying their egg onto the bare rock. Their diet is largely comprised of  sandeel, clupeids (such as herring and sprat) and gadoids (such as cod and haddock). Guillemots will typically live to around 23 years old, breeding at around 5 years (Harris et al, 2024).

Population & Distribution:
Around 8% of the global breeding population of common guillemots can be found in Britain and Ireland, with 56% of this population in Scotland (Burnell et al, 2023, Harris et al, 2024). Between 1998-02 and 2015-21 the guillemot population declined by 11% across the UK and by 31% in Scotland specifically (Harris et al, 2024), although there is regional variation with numbers in Northern Ireland, Wales, and England increasing.

Guillemot breed on the cliffs all along the east coast (fig. 3), with Bullers of Buchan to Collieston and Fowlsheugh being key sites with high numbers. NatureScot have monitored a small variable population at Forvie National Nature Reserve, with this population growing from 15-17 individuals in 2006-2008 to a peak of 61 in 2016. In 2022, 26 individuals were recorded (fig. 4). RSPB Fowlsheugh is a stronghold for the species along the east coast, with over 80,000 individuals counted in 2023 (fig. 5) (North East Scotland - Bird Report).

Conservation Status:
Guillemot are an Amber listed species (Stanbury et al, 2024).

Factors Impacting Guillemot:
There are a number of factors which have an impact on guillemot, such as avian flu, coastal development, and fishing pressures.
In 2023, a Highly Pathogenic Avian Influenze (HPAI) Seabird Survey Project found that of the 52% of UK guillemot population surveyed, there was a 6% decrease in the overall guillemot population between 2015-2021 (Seabird Census period) and 2023 (Harris et al, 2024). So, HPAI has had some impact on guillemots but it is not a major threat on its own.

Coastal development such as offshore wind farms can have a strong displacement effect on guillemot, with avoidance behaviours exhibited in the presence of turbines (Peschko et al, 2020).

In 2021, dead guillemots were reported washing up along the coast. Initially believed to be HPAI, analysis showed these birds had all died of starvation. It is unknown what caused this, with an algal bloom offshore detected (North East Scotland - Bird Report, 2023). However climate change and rising sea temperatures is influencing the distribution and abundance of guillemot prey and could be impacting survival.

Guillemot are vulnerable to fishing gear entanglement, from longline fisheries, to midwater trawling, to gillnets in shallow water.

Conservation Efforts:
In April 2024 a sandeel fishing ban came into effect in English and Scottish areas of the North Sea, in an effort to conserve seabird species such as guillemot (RSPB, 2024). It is hoped that this will offer a lifeline for struggling seabirds to increase survival and boost populations.

Mitigation measures for seabird bycatch are being looked into, to address the issues of guillemots and other seabirds becoming entangled in fishing gear.

Report any sightings to BirdTrack, or NESBReC via the link below.