Seabird 2000
Northern Gannet Morus
bassanus
Maps and Figures
The following was adapted from original text by Sarah
Wanless and Mike P. Harris in
Seabird Populations of Britain and Ireland (with
permission from A&C Black, London).
The Northern Gannet is the largest seabird in the North
Atlantic. Gannets often perform dramatic plunge dives from high in
the sky to catch fish up to depths of 20m and can stay submerged
for over half a minute. They also feed from the surface on small
shoaling fish like sandeels and on discards from fishing vessels,
where their large size helps them out compete most other scavenging
species. The Northern Gannet is endemic to the North Atlantic and
most breed in Britain and Ireland. There are 21 gannetries around
the British Isles, with most being on remote offshore islands and
stacks, and two on mainland cliffs. Some colonies have been
occupied for centuries and are large and conspicuous. The largest
is in St Kilda (Western Isles).
There is a long tradition of counting Northern Gannets and the
world population has been censused several times since the early
1900s, revealing a remarkably consistent increase of 2.0% per
annum. While many of the smaller gannetries are surveyed annually,
the larger colonies on remote offshore islands can only be censused
by aerial survey which is a formidable undertaking. A complete
census was carried out in 1994/5 and therefore full coverage of the
species was not a top priority for Seabird 2000. However, counts
were made of 14 of the 21 colonies in Britain and Ireland that
together had held 26% of the population 1994-95. The size of those
colonies not surveyed by Seabird 2000 was estimated by
extrapolating the 1994/95 counts to 1999 using colony-specific
trends between 1984-85 and 1994-95.