LIFE HISTORIES OF NORTH AMERICAN PETRELS AND PELICANS. 185 



the region of the head and rump." The distinguishing features of 

 this phimage are well illustrated in the photograph reproduced in 

 the accompanying plate. Just how long this plumage is w^orn does 

 not seem to be known, but probably the adult plumage is acquired 

 before the end of the first year. Of the molts and plumages of the 

 adult I have been unable to learn anything. 



Food. — Regarding the food and feeding habits of the yellow-billed 

 tropic bird, Doctor Gross (1912) writes: 



The food of the tropic-hird consists chiefly of marine nninials, wliich in the 

 majority of cases are secured by diving. The birds go on long foi*aging flights, 

 wandering, according to some observers, as far as 50 miles from land. On our 

 return trip to New York in 1910 a lone individual was seen which was estimated 

 to be 150 miles distant from Bermuda, and on .Tune 25, 1911, I saw two of these 

 birds which were 200 miles from land. These are probably extreme cases, but 

 they serve to illustrate the unusually long excursions which the tropic-birds 

 may make in their search for prey. 



The food contained in the gullets and stomachs of 5 adult specimens was 

 made up, for the greater part, of squids and^ fishes, especially small minnows. 

 In one of the stomachs tliere were a few fragments of a crab and a sea urchin, 

 as well as particles of material which coidd not be identified. Two of the five 

 kinds of fishes found belonged to a species of flying fish {Erocoetus furcatus and 

 Exonmitcs exilictis) which are eonnnon in the waters of Bermuda. It would 

 be interesting to know whether or not these flying fish are captured while they 

 are sailing above the surface of the water. 



The adult birds are most active during the early morning hours; it is only 

 occasionally that they can be seen feeding during the middle of the day, the 

 heat at that time being, perhaps, great enough to account for the diminution in 

 tlieir numbers. 



The numbers remained practically constant until about S..30 a. m., when there 

 was a uniform but rapid decrease, and by 11.00 a. m. there was only an occasional 

 tropic^bird to be seen fiying about. The birds were again active during the few 

 hours before sunset, but the numbers at this time never equaled those of the 

 morning hours. 



The diving of the tropic-bird is remarkable in that the plunge is usually made 

 from a height of 50 feet or more above the surface of the water. The bird, after 

 sighting its prey, poises a second or two in midair by rapidly vibrating the wings, 

 meanwhile maintaining a gaze on its victim. It then turns quickly at right 

 angles and, with wings fioldif^d, darts through the air with the swiftness and 

 precision of an arrow. Frequently this downward plunge takes the form of a 

 spiral descent. It is uncertain whether this spiral course is the result of a 

 voluntary act or not. 



Behavior. — The flight of the tropic-bird has been likened to that 

 of a large tern or a pigeon ; it is entirely unlike any of the other 

 Steganopodes in all of its movements and seems to belong in a class 

 by itself; its flight is swift and graceful, accomplished by rapid wing 

 strokes. It is decidedly an aerial species and its feet have become 

 weak and abortive by disuse. Doctor Gross (1912) says of it: 



The birds neve** walk upright, but the body is shoved along in a cumliersome 

 manner by their diminutive legs. The wings are often brought into service 



