Michael, you raise an excellent question to which no one probably has an
answer.

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

Since


>
>The assumption is that deep-diving seabirds use eyesight alone in prey
>location.
>
>But does anyone know whether they use echolocation in finding prey? Would
>they be sensitive to turbulence caused by swimming fish? Has it ever been
>shown that they use (bill-) click-ranging for determining distance to a prey
>fish, as do dolphins?
>
>>From that, might they be sensitive to the extremely low cycles of
>infrasound? To the extent they may abandon an area?