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I think Terrill raises an interesting possibility here . Most of us have at
some time observed birds with varying degrees of leucistic ( help, how do you
spell that word ??) white or pale patches. All references I have to
it say that it is a lack of pigment, but I see little explanation of what
might cause it. Might it in fact be an effect caused by pollution ? Or is there
some more natural explanation for this loss of pigment, like a lack of something
in diet etc.
I can recall quite frequent white patches on Blackbirds in ( polluted ?) UK
[and where the people are very white], but what about
the Blackbirds occurring on Lord Howe Is. etc. ? Surely the air there has
to be a lot cleaner , or might it be some ground pollution at work? Or might the
Blackbirds there just be descendants of others with the "complaint" introduced
years ago?
Tony.
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