27 September 2016
Migrating birds such as swallows
and house martins are increasingly reluctant to leave the UK and return to
Africa, a study on Shetland's Fair Isle has suggested.
The research, published in the
science journal Global Change Biology, indicated some were arriving earlier and
others were leaving later.
The study used daily observations
of birds from Fair Isle Bird Observatory.
The aim was to measure changes over
the past 60 years.
Dr Will Miles, of the Fair Isle
Bird Observatory, said: "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.
"For example, on Fair Isle,
swallows and house martins are 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.
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