A study of the great tit - Parus major - population
in Wytham Woods, near Oxford in the UK, has shown that the
birds are now laying their eggs, on average, two weeks earlier
than half a century ago.
The change in their behaviour enables them to make the most
of seasonal food - a bonanza of caterpillars that now also
occurs around two weeks earlier due to warmer spring temperatures.
"We found that, in this great tit population, female
birds are able to adapt their behaviour from year to year,
to respond to changing environmental conditions" - said
Professor Ben Sheldon, of the Edward Grey Institute in Oxford’s
Department of Zoology and lead author of a report of the research
in this week’s Science.
"In this case, they have been able to keep track with
the changes that have happened over recent decades, showing
that population responses to climate change can be driven
by the adaptability of individuals rather than genetic changes."
Oxford scientists have been studying the Wytham Woods great
tits for more than 60 years. While the data they collected
from nearly 10,000 breeding reports shows an overall trend
of birds laying eggs earlier in response to warmer spring
temperatures, there is surprisingly little variation between
individual females as their behaviour closely follows the
‘early bird’ trend.
Professor Sheldon commented - "While our study shows
how important it is to be able to adjust behaviour from year
to year, the lack of variation between individuals in their
response to climate change is surprising and contrasts with
a recent study of Dutch great tits - which found a much greater
variation in flexibility between individual birds.
"Little is known about the basis of this sort of behavioural
adaptability and why it can vary within species. More work
is also needed to discover whether the close matching of the
changing environment found by the birds in our study is, indeed,
unusual."
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