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Re: Cormorants, anhingas & soaked feathers
Knowing very little about comorants/anhingas--
1. The default hypothesis is that
flight-ability-immediately-post-dive, and thermal
insulation "in-dive" are not a significant advantages
for these birds.
2. A sub-hypothesis is that predation risk is NOT such
that flight is a necessary escape mechanism.
Predation-- Body size protects them from aerial
predators, water protects them from terrestrial
predators, and aquatic predators are only a factor
during resource aquisition (i.e., diving).
Thermal relations-- Body size and water temps are such
that insulation is not a significant selection
pressure in their habitat range.
--- Brian Lauret <email@example.com> wrote:
> As we all know (I presume), cormorants and anhingas
> lack water-repellent
> plumage. That is, diving means they'll get soaked to
> the skin and will have
> to dry their feathers afterwards.
> The latter thing takes time while the succes of the
> dive isn't even assured.
> In my logic, this puts cormorants and anhingas at a
> disadvantage compared to their waterproof
> The diving itself doesn't seem like the reason for
> the strange strategy
> employed by these birds. After all,
> loons,grebes,auks and mergansers all
> dive succesfully with their waterrepellent plumage.
> So I wonder, what could be the use of getting soaked
> to the skin and having
> to dry up, what makes it such a succesful strategy
> and why could it have
> evolved in the first place (or: why didn't
> waterproof plumage evolve in
> cormorants and anhingas?
> Nooit ongewenste berichten ontvangen: gebruik MSN