Yes
all fine. I suspect several 'catchment
areas' for the local Little
Corellas, e.g. large numbers around Erindale would seem unlikely to be
the same ones as Michael describes. As for Regarding competition between the 2 species, due to body size they
have different cavity requirements. Very likely there will be separation but I wouldn't
think a big amount. Hollows don't come in two sizes but all sorts of random
forms. Some will be favoured by just one species but for such adaptable species
there is surely a big overlap too, very likely the overlap is bigger
between Galah & Little
Corella.
Another point in passing, these are likely to be very long lived
birds. Quite possibly some of the Sulphur-crested Cockatoos now being recorded
were already alive and breeding when the GBS started in 1981. So trends on
breeding etc (especially declines) could take a long time to
show.
Philip
Con,
your morning flock of Little Corellas may have come from
the ANU roost where actually both species roost together (I think Leo Berzin
provided to the chat line some figures on totals for both species from a mid
winter count, last year)). Of course, we do not know the size of the
'catchment area' for this population coming to roost at the ANU. To judge by the
L. Corellas I see crossing Lyneham in the morning (often in various directions),
they may well travel some distance to their day-feeding grounds.
Regarding competition between the 2 species, due to body
size they have different cavity requirements. The smaller L. Corella
may have better chance of finding a suitable hollow (or may find a hollow in
younger trees) than an SCrCockatoo may be able. The L. Corella may then be more
likely to be in competition with the Galah, as was already mentioned in another
message.
Also many thanks to Martin B for the various graphs,
including the latest set. Great that Martin can draw from the full spectrum of
GBS data, and hence can give a most comprehensive picture.
Michael Lenz
