Over three-quarters of seabird species breeding in Ireland have increased, with only two species declining, according to a census just published.
The “Seabirds Count” census shows that Ireland is particularly important for species such as Roseate Tern and European Storm-petrel as 94% and 73% of the total populations breed here.
Roseate Tern, European Storm-petrel and Razorbill are some of the 17 species which have increased over the last 20 years, it says while the Kittiwake and Puffin are in decline.
It says that increasing populations of some seabird species are linked to effective conservation management measures, such as tern-wardening projects.
Seabirds Count, which has been released as a book by wildlife publishers Lynx Edicions, is said to be the most comprehensive seabird census produced to date.
It provides population estimates for the 25 regularly breeding species of Britain, Ireland, Isle of Man and the Channel Islands.
The survey took place between 2015 and 2021 and was led by the Joint Nature Conservation Committee (UK) with over 20 steering group partners.
BirdWatch Ireland and the National Parks and Wildlife Service were the key partners in Ireland.
It has found that seabirds are “doing well in Ireland with 17 species increasing and only two declining”.
“A similar pattern prevails in Northern Ireland, with four species declining and nine increasing,”it says.
“ This is in contrast to census results across the entire UK and Ireland, which show that 11 of the 21 seabird species, where there is confidence in their trends, have declined since the last census in 1998-2002,” it says.
It notes that results differ significantly by region or country, with “ encouraging trends” in Ireland for species such as the Black-headed Gull and the Arctic Tern.
At the overall census level, the Arctic Tern breeding population is in decline (35%), but the population is considered stable across the island of Ireland.
The Black-headed Gull, which breeds on inland wetlands as well as the coast, has suffered an overall decline of 26%, but this is in contrast with an analysis of Irish data, which shows increases (Ireland 84%; NI 23%, all-island 40%), it says.
Overall, Black-legged Kittiwake has declined by 42% since the last census, but the population in Northern Ireland “bucks this trend” and shows an increase of 33%, it says.
“Further south in Ireland, the population of Kittiwake is in decline (36%),” it says.
“Little appears to have changed in the colonies where they breed, so these declines are driven by changes in the marine ecosystem upon which they depend,” it suggests.
“Other main drivers for declining populations vary between species and even location, however, there are some prevalent themes,” it says.
These include predation by American mink, which may have been released onto or swum to seabird colony islands, and brown rats, which may have stowed away on boats.
“Climate change is another important factor. Adverse weather conditions are causing nest sites to be swept away and making foraging conditions more difficult,”it says.
“ Increased water temperatures reduce the availability of important food such as small fish, for example, sand eels and sprats, which leads to seabird parents not finding enough food,” it notes.
“This could be exacerbated by fish stock depletion by commercial fisheries, meaning that there is not enough food to go around during the important breeding season,” it says.
