http://www.guardian.co.uk/uk_news/story/0,,1569265,00.html
Birds with smaller brains less likely to survive
Alok Jha, science correspondent
Wednesday September 14, 2005
The Guardian
Being bird-brained is far worse than the jokes might have suggested.
Never mind that birds have never been one of the most intelligent
animals, research shows that the smaller a bird's brain, the more
likely the species is to die out in the wild.
British farmland bird populations have been declining for 50 years and
the accepted explanation is the intensification of agriculture. Based
on the fact that some species have survived better than others,
researchers looked for specific characteristics that influenced
survival rates.
Using data gathered by the British Trust for Ornithology between 1968
and 1995, they found that, as well as habitat loss through increased
agriculture, there were basic biological reasons influencing survival.
"There does seem to be a positive advantage to these birds in being
smart," said Tim Blackburn, an ecologist at the University of
Birmingham. "The size of the brain influences the probability that
these farmland birds are declining."
The population of great tits, for example, increased on farmland by
around 75%, and the number of magpies went up by 80%. However, the grey
partridge population fell by 75% and the lapwing by 40%. The relative
sizes of the brains in the former are bigger than those in the latter.
The brain has a variety of functions, but there are parts that
scientists think are the sites of higher-level function. In mammals,
the higher functions are concentrated in the cortex and the frontal
lobe. In birds, the equivalent is an area of the brain called the
telencephalon.
"When you release a bird in an environment it is not naturally
distributed in, you'd expect that anything that could be more
behaviourally flexible might be able to take advantage of their
environment," said Dr Blackburn. "We think a similar thing may be going
on here: these brighter species have more opportunity to be flexible
and adapt to changing situations."
The results are published today in the Proceedings of the Royal Society
B: Biological Sciences. "I just really didn't think that we would find
these kinds of relationships," said Dr Blackburn. "It's not only that
it was a brain size effect, it's when you break the brain down into
these bits. The fact that it was the telencephalon that clearly came
out in our models, I was amazed."
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