62 



HOMING AND RELATED ACTIVITIES OF BIRDS. 



recognizing their nests seem worth recording as exemplifying the extremely 

 complicated habit-systems which wild animals may develop under a normal 

 environment, and, also, as showing that, whatever the mechanism of distant 

 orientation may be, proximate orientation is readily explainable in terms of 

 visual and kinesthetic habits. 



I wish to express my indebtedness to Professor Watson for much helpful 

 suggestion and cooperation in the work, and to Dr. Alfred G. Mayer, of the 

 Carnegie Institution of Washington, for his kindness in placing the facilities 

 of the Marine Biological Laboratory at my disposal. 



Plate 7, figs. 1 and 2, show roughly the character of the nesting areas of 

 the sooties and noddies. Detailed descriptions of the nests and eggs have been 

 given by previous writers, and the following biicf notes are included only for 

 the sake of a clearer presentation of the cxj^erimental control of orientation. 



The nest of the sooty consists usually of a shallow depression in the sand, of 

 about the depth and diameter of a large saucer. The birds hollow it out by a 

 sort of wallowing movement, turning around and around and pushing the sand 

 away with their breasts. In this depression a single egg is laid. Rarely two 

 eggs are found in a single nest, but whether both are laid by a single l)ird, or one 



Fig. 2. — Diagram of Bird Key. Buildin)j;s in black at the left. The chief nest- 

 ing areas .ire represented tiy stippling. Solid arrows represent direction of 

 prevailing winds. Dotted lines show chief paths followed by birds in ap- 

 proaching the island. 



is stolen from a neighboring nest, is uncertain. In 1913 the greater number of 

 sooty nests were made on the western end of the island. Their position and 

 relative number are indicated by the stip])ling in figure 2. The nests of the 

 noddies are loose masses of sticks piled among the branches of the low shrubs 

 which cover the greater part of the island. They are frequently lined with bits 

 of coral and shells, and, like the nests f)f the sooties, rarelj' contain more than 

 a single egg. 



The key upon which the nests are built is roughly triangular, about ')0() yards 

 in length and half as broad. Its principal features are shown in figure 2. 

 Its greatest elevation is not more than (5 feet. The key was formerly over- 

 grown thickly with bay cedars, but the greater number of these were killed 

 by the hurricane of IfllO and only a few living cedars remain, for the most part 



