of all the avian world, and have the habit of soaring with extended wings for hours at a time. The males have an inflatable air-sack under the throat which can be distended at will into a great red pensile bag, resembling both in color and size the red toy balloons in which 
Fig. 15. Young of Shearwater showing Protective Coloration.children delight. These birds are probably the most inveterate thieves and pirates of all the feathered tribe, robbing other birds of their fish, and even making them disgorge for the benefit of their persecutors. They lay a single white egg, and young in all stages of development were numerous. When the rookery was disturbed the incubating birds, both male and female, reluctantly left their eggs or young, in some instances carefully depositing a fish beside the young before leaving. Afterward, greatly to our surprise, they would swoop down, actually grazing our faces with their wings, and deftly seize a nestling by the head and make off with it, circling around high in air, finally dropping it to the ground, where it was eventually devoured. We could not
determine whether the parents actually destroyed their own young or not, but it is probable that this revolting form of cannibalism must be added to the other crimes charged to their account.
