The Skomer Island Blog: 2018 whole island count totals

Saturday 21 July 2018

2018 whole island count totals

After having double checked this years whole island seabird counts we can now reveal some interim totals and begin to talk about trends. Generally 2018 was a protracted and poorly synchronised breeding season with some birds starting breeding on time and others up to a week late. Unsurprisingly (for Skomer anyway), Puffin and Razorbill numbers are up and some of the gulls, notably Kittiwakes, are down. A slight surprise was that Fulmar numbers have fallen by 14% since the last count was conducted in 2016. The number of Fulmar breeding sites had dropped below 500 in 2011 and 2012 but numbers steadily rose again between 2013 and 2016 (see graph).

Species and count units	Totals (year of count)	% Change from previous count (years)
Fulmar (AOS)	578 (2018)	-14.37 (2016-2018)
Manx Shearwater (pairs)	316,000 (2011)	+9.0 per annum (1998-2011)
Storm Petrel (AOS)	220 (2016)	Stable (2003/4-2016)
Shag (AON)	6 (2018)	+20 (2017-2018)
Lesser Black-backed Gull (AON)	4,935 (2017)	-28.85 (2016-2017)
Herring Gull (AON)	365 (2018)	+22.90 (2017-2018)
Great Black-backed Gull (AON)	120 (2018)	No change (2017-2018)
Kittiwake (AON)	1,236 (2018)	-7.49 (2017-2018)
Guillemot (IND)	24,788 (2017)	+4.39 (2015-2017)
Razorbill (IND)	7,529 (2018)	+3.85 (2016-2018)
Puffin (IND)	30,895 (2018)	+22.47 (2017-2018)

AOS = Apparently Occupied Site (or ‘pairs’ e.g. a fulmar occupying a crevice, as they don’t build proper nests)
AON = Apparently Occupied Nest (or ‘pairs’ e.g. a fully built gull nest capable of holding eggs)
IND = Individuals

Fulmar population trends show a sharp increase in the late twentieth century followed by a decline thereafter. The population had begun to stabilise and even increase but numbers have dropped by 14% since 2016 (the last time there was a whole island count)

Puffin numbers continue to increase

Due to the increasingly large number of birds to count, a decision was made in 2016 to rotate counts of Guillemots with those of Fulmars and Razorbills. So in one year Guillemots will be counted and Fulmars and Razorbills not, then the following year Fulmars and Razorbills are counted and Guillemots not, and so on. This reduces the work load and potentially increases accuracy but does not allow for fine scale inter annual variation in numbers to be picked up quickly. We do, however, conduct annual plot counts of Fulmars, Guillemots and Razorbills, which are thought to be representative of the whole island.

The gargantuan task of censusing the whole island population of Manx Shearwaters was undertaken this year, however, the data takes a long time to analyse and results will not be available for a while, so the figure in the table above is from the previous whole island census, undertaken in 2011. Lesser Black-backed Gull numbers also take a while to analyse so are unavailable for 2018 just yet. Guillemots were not counted in 2018 so the most up to date count is from 2017.

Field work for other studies, such as productivity monitoring and adult survival, are drawing to a close for the year now and as soon as all this data is put together the 2018 seabird report will go online. Last years full report is available here.