At 01:51 PM 3/09/97 +1000, Michael wrote:
>Horsfield's Bronze-cuckoos arrived here in SE Melbourne in the last week
>of August and seem to be staying. They were "everywhere" in 1994 but in
>1995 I collated only 3 records and in 1996 a mere one, and that an
>immature in February).
>
>Why are there good and bad cuckoo years when our population of small
>birds (potential nest hosts) does not seem to vary much ? You would
>think one bad year would mean fewer cuckoos next year and a continuing
>decline.
>
>Are the good and bad years localised ? Ie. do the cuckoos do well one
>year in one place and then (like a farmer rotating crops) deliberately
>go elsewhere the next ?
>
>The answer is probably RTFM, as they say on Usenet, but I'd be
>interested in references.
>
>Thanks. Mike.
>
>
This is an interesting question. One explanation I have heard for
Horsfield's BC is that it prefers the southern arid zone and concentrates
there in good years years but in very dry years (when the host species would
be breeding less) moves further south into more coastal areas. It does seem
to hold for south-western Australia, where we get some birds every year in
both arid and wetter areas, but in some years there are rather more than
others in the wetter areas.
Could this also be an explanation for variations in south-eastern Australia?
Cheers,
Allan
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Allan Burbidge http://cygnus.uwa.edu.au/~austecol/birds.html
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Snail PO Box 312, Wanneroo, Western Australia 6065
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