Puffin numbers on the remote Farne Islands are “stable”, despite early results of a survey which prompted fears they could be struggling.
The National Trust said rangers conducting the survey last May had thought initial low numbers on the outlying islands of the 28-island archipelago were due to the harsh winter and a decline in readily available food.
There were fears the initial results in the five-yearly study would be replicated across the islands, which are situated off the coast of Northumberland, spelling bad news for the threatened seabird.
But it now seems the lower numbers on the outer islands are the result of the thriving grey seal population, causing puffin burrows to be inadvertently crushed and leading more birds to nest on the inner isles, the Trust said.
Final results from the 2018 survey, which involved checking a proportion of burrows on eight of the islands, reveal there are around 44,000 pairs, up 9% on the last count conducted in 2013.
Numbers of the seabird, which is listed as globally vulnerable to extinction amid declining populations, have risen on the islands in the past 25 years, the National Trust said.
Some 37,710 pairs were recorded in 1993 and the population peaked at 55,674 pairs in 2003, but that was followed by a sudden crash in 2008 when numbers fell by a third before slowly recovering.
National Trust ranger, Thomas Hendry said: “When we started the count in the outer group of islands we were very anxious that numbers were down, especially as we know puffins are struggling for survival across the globe.
“After further investigations on the inner group of islands, numbers seemed to be much more positive.
“This could be due to the islands being more sheltered, providing an ideal habitat for the puffins to successfully breed and raise their young.
“Another factor for the lower bird numbers on the outer islands could be the success of our grey seal population. ”
He said the seal pup numbers had grown from 1,704 to 2,602 in the last five years.
“A rather unfortunate consequence of this growth is the seals are competing with puffins for areas to raise their young.
“Although the two species are in residence and breed at different times of year, the weight of the seals could be crushing the puffin burrows and eroding surrounding vegetation.”
Dr Chris Redfern, emeritus professor at Newcastle University, who helped to verify said the count suggests “population of puffins on the Farne Islands overall is at least stable at the moment”.
“However, there are indications of some re-distribution of puffins between different islands so we need to be vigilant to ensure that all islands remain in tip-top condition for this seabird to breed successfully in the future.”
But he said the results suggested the seas off the Northumberland coast could still support good numbers of breeding seabirds and indicate the colonies were not showing the declines seen in populations further north.