So I cannot work
out how it is possible for "the bird that I saw earlier but it has now
grown a bit of white on its base of tail". Unless those feathers with
the white tips grow after the lower feathers have matured. This would
seem a bit odd but it is a possible explanation for those few birds that
show this feature. It surely is Pied Currawongs we are talking about not
Greys so we can forget that aspect. The feature is not that uncommon and
probably just some variability in the speed at which these feathers grow
or variability in the length of time during the growing of these
feathers from the point at which the switch for no pigment changes to
start pigment.
Phillip et al,
Is there a point at near maturity in birds where there is a shedding
of immature feathers? Sort of analogous to losing ones teeth at a
certain age as your adult teeth come through, at least in some
ways. If so, the immature dark feathers could be obscuring the white
adult feathers that have grown underneath. When the transitional
moult to adult-hood (if there is such a thing) occurs these white
feathers are revealed?
As I said, I don't know whether there is such a moult of immature
plumage, but it would explain the change in appearance with the white emerging?
Cheers.
Paul T.
Higgins, ACT
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