http://news.bbc.co.uk/2/hi/science/nature/5130538.stm
Long-haul birds 'returning early'
By Catherine Owen
Sunday, 2 July 2006, 15:06 GMT 16:06 UK
Birds that migrate long distances have adapted to the world's changing
climate in unexpected ways, a study shows.
As the planet warms, and spring arrives earlier in Europe, birds are
being forced to change their migration patterns.
It had been thought that birds travelling long distances from Africa to
Europe would be unable to adapt.
But a study in Science suggests they have evolved in response to
climate change and are returning earlier.
The need for migratory birds to time their arrival at breeding grounds
with plentiful food supplies is a known evolutionary pressure.
Scientists had assumed that birds travelling short distances would be
better able to adapt - and arrive earlier for spring - because of
similar climate conditions in their nearby winter grounds.
But researchers in Europe decided to test this theory, using long-term
banding and observational data from Scandinavia and Italy dating back
to 1980.
The study revealed that long-distance fliers have adjusted their
migration habits to arrive earlier in northern Europe in time for the
start of spring.
This suggests a more permanent change in migratory behaviour due to
climate change than previously thought.
'Surprising' response
Study-co-author Nils Christian Stenseth, from the University of Oslo in
Norway, said migration in the species studied was thought to be a
biological response triggered by day length, and not climate
variations, in breeding grounds.
"Long-migrating birds arrive at least as early as short-migrating
birds," he told the BBC News website.
"The trigger is probably related to the length of day, or the
photoperiod.
"Birds typically respond to the right photoperiod for bringing up as
good offspring as possible."
The birds begin to reproduce at just one year of age and so have the
potential for a rapid genetic response to recent environmental events.
They are showing a "surprising and interesting evolutionary response to
climate change", he added.
The research is the latest in a string of studies looking at the
widespread effects of climate change on birds.
Dr Paul Donald, senior research biologist at the Royal Society for the
Protection of Birds, UK, said populations of long-distance migrants
breeding in the UK and across Europe were showing worrying declines.
"This study highlights the potential role climate change is playing,"
he said. "However, we must not ignore other potential factors affecting
their fortunes here in the UK or on their wintering grounds in Africa."
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