Migrating birds such as swallows and house martins are increasingly reluctant to leave the UK and return to Africa, apparently taking advantage of longer and warmer summers in Europe, new research has found.
They may even be nesting more often.
The study in the international science journal, Global Change Biology, says migrant birds that arrive at their breeding grounds early in spring might be expected to depart early in autumn too, as soon as their chicks have fledged. But in consecutive seasons that didn't happen.
The research used daily observations of migrant birds from the remote Fair Isle Bird Observatory, between Orkney and Shetland , to measure how spring and autumn migration timing has changed over 60 years.
Dr Will Miles, of the Fair Isle Migration Project says, “Environmental conditions are changing rapidly at a global scale. In response to these changes, the seasonal life-cycles of plants and animals are shifting too, often in dramatic and unexpected ways.
"It’s too early to know for sure exactly why bird migrations now last so much longer in spring and autumn, but it’s possible that conditions in Europe and Africa have gradually become more favourable for long-distance migration, and the birds are now under less pressure to migrate quickly within a short time window."
He said that for example on Fair Isle, Swallows and House Martins were migrating up to a fortnight later than they did a few decades ago. Willow Warblers used to migrate within a five week period in spring but now this species is seen on migration for up to 10 weeks.
"Some species appear to be staying in Europe for longer in the summer and may breed several times, and that is an advantage for the birds,” he said.
He added this latest test analyses demonstrated that long-term changes in migration timing can be more complex than widely assumed.
The Fair Isle Migration Project is a scientific collaboration between the Fair Isle Bird Observatory Trust and the University of Aberdeen.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules here