The difference between the nests of straw^{106} and those of sticks^{107} were so marked that it seems probable their makers regularly selected sites on the ground or in the trees respectively. Or, assuming that the same individuals might build a stick nest in the bushes one year and a straw nest on the ground the next, we have an unusual variation in the character of the nest of the same species. In the case of the Fish Hawks of Plumb Island the birds evinced an appreciation of the protection afforded them by the owner of the island by often placing their nests on the ground. Photographs of these nests, however, made by Dr. C. S. Allen, show that the birds employed as much material when nesting on the ground as when nesting in trees, the eggs on the ground being surrounded by a useless mass of large sticks. Certain of the birds, therefore, in response to new conditions, had chosen new nesting sites, but had not as yet made corresponding changes in the character of their nests. When the nest is completed, as we have seen, from one to three eggs are laid. The period of incubation is probably about four weeks, and a careful listener may detect the presence of a hatching egg by the choking bark which the young Pelican begins to utter as soon as he has made an opening in the shell which holds him. When he has finally freed himself and appears in the world, he is about as unattractive a bit of bird life as can well be conceived.^{106} His dark, purple skin is perfectly naked, he is blind, and when he is deprived of shade provided by the brooding parent, he twists restlessly about in the nest, uttering the same choking bark with which he first greeted the light. Even at this early age he displays one of the strong characteristics of the immature Pelican—a pugnacious disposition. Almost before his eyes are open he bites at his nest mates for apparently no other reason than that they come within reach of his bill. Soon his eyes open and within a few days a wonderful change begins to take place in his appearance.^{107} Little bunches of white down sprout all over his body, and, growing rapidly, transform the ugly, purple-black nestling into a snowy creature clad in softest down. [Illustration: 107. Young Pelican in tree nest, showing first appearance of white down.] At the same time he has been growing much stronger; he is able to sit up,^{108} his fighting abilities have greatly increased, and his voice, after passing through a rasping _k-r-r-r-ing_ stage, has become a high, piercing cry very closely resembling the scream of a child in extreme pain. Young Pelicans uttering this call chiefly made up the chorus one could hear all day and at intervals during the night on Pelican Island.