Black Guillemot - Cepphus grylle

Black guillemot (Cepphus grylle), also know as 'Tystie', are an auk smaller in size than common guillemot (Uria aalge). Adult breeding plumage consists of an all black body with white oval-shaped upperwing patches, a black bill, and red feet (fig. 1 ) (Svensson et al, 2020). Black guillemots typically nest among coastal rock crevices and boulders, usually low to ground, in lone pairs or loose colonies. Their diet consists largely of butterfish and sandeels. Black guillemot typically live to around 11 years old, breeding at 4 years (Harris et al, 2024).

Population & Distribution:
Black guillemot are an uncommon local resident species along the East Coast. Around 3-10% of the global black guillemot breeding population is hosted by Britain and Ireland, with 86% of this population found in Scotland (fig. 2) (Burnell et al, 2023; Harris et al, 2024). 
Black guillemot have been recorded at a small number of nesting sites along the East Grampian coast (fig. 3), particularly Muchalls and Newtonhill (North East Scotland Bird Report). 

Conservation Status:
Blackguillemot are a Green listed species, with their breeding range considered stable oer the last 50 years (Stanbury et al, 2024). 

Factors Impacting Black Guillemot: 
Climate change is impacting distribution and abundance of prey species for black guillemot due to rising sea temperatures. Studies show that black guillemots are laying eggs earlier in the year, and there is a mismatch between the chick rearing period and the peak availability of prey species (Greenwood, 2007). Increasing frequency of extreme weather events and rising sea levels is also impacting seabird breeding success. Modelling suggests that the geographic range of black guillemot will shrink due to climate change, and that by 2100 only Shetland, Orkney, and the northern edges of mainland Scotland will hold breeding colonies. Black guillemot will likely disappear as a breeding species from the East Grampian Coast altogether by the end of the 21st century(Daunt & Mitchell, 2013).

Black guillemots are considered at low risk for collision with wind turbines,, but the presence of offshore wind farms likely displaces them during foraging trips (Furness et al, 2013). No mortality from Highly Pathogenic Avian Influenza (HPAI) was reported in black guillemot as of November 2022 (Tremlett et al, 2024).

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