>I suspect that, firstly, deep-diving seabirds have exceptional eyesight
>that enables them to see in remarkably low light levels. Nocturnal
>alcids like Cassin's Auklets (not really a deep diver) are able to
>navigate quite well on extremely dark, moonless nights, finding their
>burrows with ease when humans are groping around unable to see more than
>their hand in front of their face. Even surface-feeding nocturnal
>seabirds such as storm-petrels are able to fly incredibly zig-zaggy
>flights on very dark nights, suggesting they, too, see in very low light
>levels. Do these birds have extremely high density of light recepters in
>their eyes to pick up images in low light?
>
>Since all these seabirds are quite vocal, they may not need to click
>bills to echo-locate as you suggest. Could they also just vocalize
>underwater? Sounds like an experiment to be done with captive birds,
>like at the Seattle Aquarium.


Difficult questions to answer but certainly very interesting to entertain.
It would seem to me that one potential way to answer this question of
echolocation would be to examine the auditory organs and their respective
functions of the seabirds in question.
In order for organisms to echolocate, there must be a few key features that
need to be present in the ear and functioning... something about detecting
interaural time differences, amplitudes....if the appropriate conditions
were right (in terms of having the right hardware) then it would be worth
conducting experiments.

cheers,

Don Cecile
dcecile at cln.etc.bc.ca