Joyce:
As a general comment these results are very interesting, but not totally
unexpected because it has been know for at least 10 years that different
areas of the avian brain will increase and decrease in size on a seasonal
basis. For example, the vocal centers of some songbirds, e.g. Canaries,
will change in size in response to exposure to seasonal change in hormones
levels. There are also known sex (and species) differences in the size of
the hippocampus of birds that cache food. It would seem that size of
different modules in an avian brain remain as small as possible until
there is a need -- then to accommodate extra memory, or
perhaps added processing power brain size increases usually in response to
hormones (perhaps decreasing brain mass is a way to reduce weight during
the off season). In the present case (I have not read the article), the
presence of responsive (???) females has probably stimulated the male's
endocrine system in some fashion or the other for the purpose of storing
memory of social interactions, perhaps? Is this possible?
What part of the forebrain was affected - the forebrain of birds do not
much resemble the forebrain of mammals? Vocal areas? It is also known
that many birds learn to sing and mimic sounds better in rich social
environments (e.g. presence of females in winter flocks of cowbirds
drammatically affects the vocal behaviour of young male Brown-headed
Cowbirds) as oppose to impoverished environments.
Thanks for bring the article to our attentions. I look forward to reading
it.
Dr. Wm. James Davis
e-mail
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