Date: August 30, 2016
Birds that have to work harder
during breeding season will feel the effects of their exertions the following
year, according to research by Oxford University scientists.
A new study published in
the Journal of Animal Ecology found that migratory seabirds suffered
negative repercussions when they had to spend more time rearing chicks,
including decreased breeding success when they returned to the colony the
following spring.
The study artificially altered
the length of the chick-rearing period for pairs of Manx shearwaters, giving
new insights into the consequences for birds whose reproductive phase doesn't
go to plan. All parent pairs involved in the study cared for their foster
chicks until they were fully reared -- often at their own expense.
Lead author Dr Annette Fayet, of
the Oxford Navigation Group in the University of Oxford's Department of
Zoology, said: 'The results of this study provide evidence for carry-over
effects on the subsequent migratory, wintering and breeding behaviour of
birds.'
Carry-over effects are the
processes by which events in one breeding season may affect the outcome of the
subsequent season. But the exact nature of these effects, as well as whether
they affect other events in birds' annual cycles, such as migration and
wintering, has been unclear.
Dr Fayet said: 'Birds that had
their chick-rearing period extended in our study delayed the start of their
autumn migration and spent less time at the wintering grounds, and while they
were there they spent less time resting. When they returned to the colony the
following spring, they started breeding later, laid smaller eggs, reared
lighter chicks -- early, heavy chicks survive better -- and overall had a lower
breeding success.
'This suggests that the birds
were in poorer condition after working harder during the experimental breeding
season and shows the negative effects on both non-breeding and breeding
behaviour in the year following the experiment.'
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