Cuckoo years: good and bad

[Michael <>]

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.