We suspect, Stephen, that you are pushing your argument for a causal
connection between breeding and moult further than it wants to go. For
brevity, we take you up on three points only.
First, what is "intensive breeding"? We have never heard of it. Birds are
either breeding or they are not; there wouldn't seem to be much room for
qualification.
Secondly, your assertion, repeated several times, that breeding leads to "a
lot of" feather wear. Feather wear happens because of the combined effects
of feather age, sunlight, and abrasion. Fully grown feathers are "dead"
keratin and can do nothing but decay. Prolonged exposure to sunlight might
hasten the process. If birds moult after breeding, it will generally be
because they have tatty old feathers. The fact that they have just bred is
irrelevant - the poor dears must fly.
Indeed, there are quite a few species that don't have amazingly worn
primaries after breeding. This brings us to our third point; there are
exceptions to the rule that moult happens soon after breeding. They
include:
- 50+ species of wader that breed in the northern hemisphere and migrate
to Australia with eight to nine month old wings before moulting;
- many holarctic passerines that migrate south before moulting (e.g.
Sand and House Martin; Barn Swallow; Rufous Bush-robin; Grasshopper,
Savi's, Aquatic, and Marsh Warblers; Eurasian, Basra, and Great
Reed-warblers; Icterine, Olivaceous, Booted, and Olive-tree Warblers;
Whitethroat; Garden, Subalpine, Bonelli's, and Wood Warblers; Spotted
Flycatcher; Isabelline, Red-backed, Lesser Grey, and Woodchat Shrikes);
- the many ducks that migrate to special moulting grounds after breeding
that this that this has been given its own special term, "moult-migration";
- some (at least) Australian Reed Warblers migrate north before
moulting;
- Rufous Fantails that go north before moulting unlike the closely
related Grey Fantails which moult first;
- the Yellow-tufted and Fuscous Honeyeaters mentioned by Danny in an
earlier posting.
We suspect that the list of exceptions would be pretty large if we worked
hard at it. So, explanations please. It is insufficient to say, "... one
ocasionally comes across a species that hasn't read the rule book"!
Ken and Annie Rogers
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