Re: Cormorants, anhingas & soaked feathers

[don ohmes <d_ohmes@yahoo.com>]

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.

Conclusions-to-be-tested -- 
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 <zthemanvirus@hotmail.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
> considerable 
> disadvantage compared to their waterproof
> competitors.
> 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?
> 
> Brian
> 
>
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