The Shag is very much a coastal bird, breeding exclusively around our rocky shores during the summer months and not moving very far during the winter.
It’s long thin bill, peaked forehead and small yellow gape set it apart from its close cousin the Cormorant. Shags can be seen in large feeding flocks, sometimes numbering in the hundreds, when birds at the back of the group will take off and fly to the front, the whole flock moving in this way as they catch the small fish that make up their diet.
Shags nest in loose colonies and there have been several studies of these – ringing data show that this is quite a long-lived species.
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A black, reptilian-looking bird swims by low to the water - but is it a Cormorant or a Shag? Cormorants are more familiar and wide-spread, although Shags are more numerous. Let us help you to separate these two similar-looking species of water bird.
Listen to example recordings of the main vocalisations of Shag, provided by xeno-canto contributors.
Call
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The Shag is found almost exclusively in marine habitats where it is restricted to inshore waters. It is found around much of the coast of the UK where cliffs are available but is largely absent from south and east England where there is no suitable nesting habitat. Data from censuses indicate that numbers increased by around 21% between 1969–70 and 1985–88 but dropped by around 27% between 1985–88 and Seabird 2000 (1998–2002). Results from the more recent Seabird Count (2015–2021) are not yet available, but data from annual monitoring suggest that there has been a further decline since Seabird 2000 and hence the population is believed to be well below the level in 1969–70 (JNCC 2022).
Shags are recorded around much of the coast of Britain & Ireland in winter, with the highest densities in northern and western Scotland and western Ireland. Breeding colonies are found on many northern and western coastlines with suitable cliffs.
Britain and Ireland Breeding Distribution 2008-2011. More from the Atlas Mapstore.
Britain and Ireland Winter Distribution 2008-2011. More from the Atlas Mapstore.
Marked population declines have not yet resulted in significant range loss: there has been only a 9% range contraction in Britain & Ireland since the 1968–72 Breeding Atlas.
Britain and Ireland Breeding Distribution Change 1968–72 to 2008–11. More from the Atlas Mapstore.
Britain and Ireland Winter Distribution Change 1981–84 to 2007–11 More from the Atlas Mapstore.
Change in occupied 10-km squares in the UK
% change in range in breeding season (1968–72 to 2008–11)
Shags are recorded throughout the year at suitable coastal locations.
Weekly occurrence patterns (shaded cells) and reporting rates (vertical bars) based on BirdTrack data. Reporting rates give the likelihood of encountering the species each week.
Movement
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
The increase in the reported population between 1969–70 and 1985–88 may partly reflect better coverage of colonies which are difficult to access, but increased legal protection and reduced persecution may also have contributed (JNCC 2022). The annual monitoring data indicate that mass mortality during prolonged periods of severe weather in some winters strongly affects breeding abundance (Harris & Wanless 1996), and increased frequency of such events due to climate change may potentially be driving population declines. Analysis of year-round diet between 1985 and 2014 suggests that reductions in sandeel abundance have also resulted in diet changes throughout the year and hence changes in sandeel abundance (and abundance of other prey species) could potentially also have an impact on the population through survival (Howells et al. 2018).
Links to more information from ConservationEvidence.com
SHAG. 
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