HISTORICAL AND EXPERIMENTAL STUDY OF HOMING. 37 



FEEDING INSTINCTS. 



The noddy and sooty live almost exclusively upon minnows during the 

 breeding-season. During the remainder of the year nothing is known of their 

 diet. But since captive birds learn to eat cut fish with the greatest difficulty, 

 we judge that their food, even during the winter months, is live minnows. 

 The minnows are obtained in the following way: when large fish begin to 

 prey upon the schools of minnows, the minnows, in their efforts to escape, 

 spring out of the water; the birds, always hovering over the surface of the 

 water, flock to these places and catch the minnows just as they leave the water. 

 The following note was made on one of our trips around the island : 



June 15, 1910: Watched birds feeding about 2 miles out. The group comprised about 50 

 birds, mostly noddies. Some sooties were present and 6 least terns. The noddies hovered 

 about 12 inches over the water, following the school of minnows. They make a rattling 

 noise, all the while, audible 200 feet away. The noise made by any individual bird gets 

 stronger as the fish is sighted. The noddy steps on the water often, sometimes strikes it 

 with the breast, not in diving movements, but in those of pursuit. Never folds the wings 

 and sits in the water.* The sooty behaves in a very similar manner, except that I saw one 

 bird apparently diving for a fish; it certainly partially submerged its body. The least 

 tern fishes in a characteristic way: It hovers about 6 to 10 feet above the water. The 

 moment the fish is sighted, it folds its wings in a V shape, and shoots vertically downward, 

 striking the water head first and going under. It does not always swallow the fish, but 

 comes up with it in its beak. No resting on water, even with least tern; dives in an 

 incredibly short time; comes up and is ready to strike again. 



It is obvious that the tern, in order to obtain food on long trips, must be 

 constantly in an environment both where large schools of minnows abound 

 and where schools of large fish are constantly attacking these minnows. 

 Furthermore, the minnow must be of a type which will spring out from the 

 water in its efforts to escape. These peculiar conditions can be found in May 

 (the one month when homing can be conducted) probably only in tropical and 

 juxtatropical waters. This fact probably will always make a flight from New 

 York, e. g., impossible. On the other hand, the line from Bird Key to Gal- 

 veston (Galveston being more nearly in the latitude of Bird Key) probably 

 offers favorable feeding conditions throughout its length. 



In regard to the distance from Bird Key covered by birds in their daily 

 search for food, our 1910, 1912, and 1913 observations abundantly confirm our 

 early (1907) observation that this distance rarely exceeds 17 to 18 miles. It 

 may be said in passing that these birds are practically unknown both in Key 

 West and in Galveston. Furthermore, in the many trips which we have made 

 between Key West and New York we have never noted these birds north of 

 Key West; hence we must conclude that Bird Key (plus 17 to 18 miles) is the 

 northern limit of migration for both noddy and -sooty. t 



*In the 1907 paper we had never seen noddies and sooties swimming in the water. In 1910 

 we saw one noddy fly into the water, fold its wings, and begin swimming like a duck. About 10 

 other noddies joined this one. This is the only occasion upon which we have ever witnessed 

 swimming movements. We have never seen the sooty in the water, except when accident has 

 overtaken it. 



fThey are reported sporadically along the eastern coast of North America. Such birds in all 

 probability have been blown northward by heavy winds. This occurs rather frequently in the 

 migrating period. 



