On Sun, 11 Apr 1999, Jill Dening wrote:
> A while back I started a thread of discussion about the flocking of
> Channel-billed Cuckoos (CBCU). People had seen flocks, but no one was able
> to say with any certainty whether the flocks comprised adults only,
> juveniles only, or if they were mixed.
>
> Now I have some solid information, which came from one Tim Siggs, of
> Mooloolah, which is a Sunshine Coast, Qld, hinterland township. Early on
> Feb 17, 1999, Tim saw a flock of 25 - 30 CBCU, feeding in a fruiting
> Moreton Bay Fig at his home. He estimated that there were half adults and
> half young in the flock. This gives weight to the notion that CBCU adults
> gather up the young before migration.
>
Jill:
I don't necessary disagree with you, but there is a simplier
explanation: since all CBCU (young and old) migrate north and probably
follow a similar route, they, as a consequence, eventually will form
flocks either while feeding or roosting. Conspecific attraction (perhaps
to the loud calls of the species)is all that is required to explain the
mixed-age flocks. There are a number of plausible interpretations why
CBCUs will go to the trouble to form flocks (increased feeding efficiency,
reduced harassment, learning, etc.). Just an idea.
Cheers, Jim
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