1912 ' J GrosSj The Ydloir-billed Tropic bird. 53 



1909, saw on February 9 and 10 several groups of 2 or 3 individ- 

 uals each, which were flying in a direct course for the Bermudas. 

 This agrees with the supposed course of migration of the Tropic- 

 birds and illustrates the keen sense of direction and orientation 

 which they must possess. These birds would probably be ad- 

 mirable subjects for experimenting on orientation. 



When we arrived at the islands, June 17, 1910, and June 26, 

 1911, the birds were in the midst of their nesting activities. During 

 the early morning hours many of them could be seen in the vicinity 

 of their nesting sites gracefully circling and wheeling high above 

 the surface of the water, with their long graceful tail feathers 

 streaming out behind. As the birds flew back and forth over the 

 sound, their pure white breasts and underparts reflected the 

 bright emerald green of the water, in such a manner as to give their 

 plumage a distinctly greenish appearance. The effect thus pro- 

 duced under certain conditions of light is very deceiving even to an 

 experienced observer. 



The food of the Tropic-bird consists chiefly of marine animals, 

 which in the majority of cases are secured by diving. The birds 

 go on long foraging 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 June 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 speci- 

 mens was made up, for the greater part, of squids and fishes, 

 especially small minnows. In one of the stomachs there were a 

 few fragments of a crab and a sea urchin, as well as particles of 

 material which could not be identified. Two of the five kinds of 

 fishes found belonged to species of flying fish. (Exoccetus furcatus 

 and Exonautes exsiliens) which are common in the waters of 

 Bermuda. It would be interesting to know whether or not these 

 flying fish are captured while they are saihng above the surface 

 of the water. The food delivered to the young varies with the 

 age of the nestling, therefore is best considered in connection with 

 the account of the young birds. 



