The National Trust has said it will closely monitor numbers and that several factors could be behind the decline.
A survey of puffins on the internationally important Farne Islands has shown a drop in numbers of almost a quarter.
The National Trust which looks after the islands off the Northumberland coast said the long-term trend needed to be monitored and cautioned against interpreting it as a sudden population decline.
The number of breeding pairs recorded in the survey fell from 50,103 in 2024 to 38,500 this year, a drop of 23%.
Ben McCarthy, head of nature conservation at the National Trust said: “Counting puffins is a notoriously complex task.
“There is no single perfect method, and annual variations in survey conditions, puffin behaviour, and environmental factors all influence the count.
“While the decline in numbers is concerning, it’s important to view this year’s results within the broader context of global puffin trends.”
National Trust experts said the bird flu outbreak in 2022 and 2023 did not affect the puffin population as badly as other species.
But factors which may have affected their numbers include extreme weather such as Storm Arwen, soil erosion and the expanding grey seal colony.
Rangers will put measures in place to deter seals from disturbing the puffin burrows during the birds’ breeding season.
Sophia Jackson, Farne Islands area ranger, said: “We know puffins are facing challenges globally, from climate change to shifting food sources.
“What we’re seeing on the Farnes is part of a much bigger picture.
“This year’s census doesn’t necessarily mean puffins are disappearing overnight – but it does reinforce the need for consistent, long-term data.”
The Farnes attract around 200,000 seabirds every nesting season and the survey has revealed encouraging trends in other species.
The National Trust said the Northern Fulmar numbers were up from 106 pairs last year to 235 and Common Eiders are up 50%.
The numbers of Greater Black-backed Gull, Herring Gull, European Shags and Razorbills were also up.
Arctic Terns, another species for which the Farnes are known, increased by over 26% on 2024 figures, from 410 to 519 nesting pairs, which was welcomed as they face increasing pressure from climate change and food availability.
The 28 Farne Islands, some of which are submerged with the tides, stand one-and-a-half miles out to sea and are an internationally recognised haven for wildlife.
