Chris Corben asked;
> If Little Terns can have pale bill
> tips and paler dorsal surfaces than most, then that won't help distinction
> from Fairy Terns. Could I be seeing hybrids? My inclination is to think
not,
> because the birds with pale bill tips or pale backs looked otherwise like
> typical Littles. I think it's more likely that at least some Littles
> progress from dark tipped yellow bills through a stage where the black tip
> is lost while the rest of the bill is largely yellow, then darken up all
> over. Furthermore, I think it's quite likely that the paler upperparts
could
> be a result of fading. It's interesting that the juvenal showed paler
> upperparts also. Any comments?
Many Little Terns which breed in Victoria have only a microscopic amount
of black on the bill tip even in full breeding plumage and some appear to
have none. See e.g. ABW 17:(7) 346-348. So they don't have any black to
lose. There were several examples in the Tern colony at Marlo in January
(about 200 least terns of which c. 12 were Fairies) where variation in
amount of black on the lores added to ID problems. There may have been some
hybrids there too. I photographed one. I noted there again, that the Little
Tern nests were very spread out, many metres apart, whereas the Fairies were
in a discrete, compact colony. Best ID characters are still those we learnt
in the 60's. Fairies are bigger, bulkier, shorter legged (especially tibia),
heavier billed, and have less black in primaries. Typically, they're paler,
less grey above, but even when together, in some, the distinction can be
slight. Is it our older, less discriminating eyes, or has there been some
gene flow?
Mike Carter
30 Canadian Bay Road
Mt Eliza Vic 3930
03 9787 7136
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