Taken 2011 July 29 from off the southwestern end of Ciboux Island
GPS 46°22.810'N 60°22.624'W
Six bald¹ eagles are clearly visible in this photo. They abound on the Bird Islands, but most are to be found skulking in caves like this one on Ciboux Island. Note that no eagle nests are present here—as the largest nests constructed by any bird, they’d be immediately obvious were they present. As this Wikipedia article tells us (footnote numbers omitted):
The Bald Eagle's diet is opportunistic and varied, but most feed mainly on fish. […] Locally, eagles may rely largely on carrion, especially in winter, and they will scavenge carcasses up to the size of whales, though it seems that carcasses of ungulates and large fish are preferred. They also may sometimes feed on subsistence scavenged or stolen from campsites and picnics, as well as garbage dumps. Mammalian prey includes rabbits, hares, raccoons, muskrats, beavers, and deer fawns. Preferred avian prey includes grebes, alcids [puffins], ducks, gulls, coots, egrets, and geese. Most live prey are quite a bit smaller than the eagle, but predatory attacks on larger birds such as swans have been recorded. Reptiles, amphibians and crustaceans (especially crabs) are preyed on when available.
Given that they prey both on fish and on other birds, they would certainly have rich hunting grounds here on the Bird Islands! But why are they hiding in caves? Our tour guide told us that they are (understandably) very much unloved by the birds on which they prey and, should an eagle come into view, they are immediately set upon by the gulls protecting their nests and young (and themselves). Now the gulls on these islands are good sized birds in their own right, though not so large as the eagles, and they are as abundant as the eagles. So any eagle that hopes to dine on another bird is in for a fight! Hence, they sit in the caves where the other birds cannot swoop down and attack them, biding their time for an opportunity to strike.
¹ Bald eagles are not bald, but have heads covered in white feathers. In this usage, the word bald retains its Middle English sense of marked or streaked with white.↩