Over the past few decades, Skomer Island off the south coast of Wales has witnessed a remarkable resurgence in its guillemot population. Before 1930, Skomer was home to over 100,000 common guillemots. But by the end of the second world war, this number had plummeted by about 95% and continued to decline for the next few decades. This population decline was probably caused by chronic oil pollution during the second world war and several major oil tanker incidents in the subsequent years

However, counts conducted by the Wildlife Trust of South and West Wales show that Skomer’s guillemot population has consistently grown at an annual rate of about 5% since the 1980s. In 1972, there were around 2,000 guillemots breeding on Skomer. Fast forward to 2023 and that number has skyrocketed to around 30,000.

Oil pollution has declined, but it has been superseded by the even more insidious and far-reaching effects of climate change. Together with persistent overfishing and the recent emergence of avian flu, climate change has further contributed to the increasing fragility of seabird populations.

The guillemot population has been the subject of a long-term study conducted by Prof Tim Birkhead and colleagues over past 50 years. One of our most striking results is that the timing of guillemot breeding has advanced by more than two weeks on average since the 1970s. The cause of this advance, which has also been noted in many bird species on land, is probably climate change.

The researchers believe the early breeding season might be linked to the seasonal availability of their fish prey. There is increasing evidence that warmer seas are having a marked effect on both the distribution and abundance of marine fish in the UK.

To read the full article in The Conversation click here