The Behavior of Noddy and Sooty Terns. 193 



the birds have been going there year after year. The terns arrive at approxi- 

 mately the same time eacli year (during the last week in April), live there 

 until toward the first of September, and then begin their southern migration. 



FOOD AND FEEDING HABITS OF THE TERNS. 



In a locality where marine forms are so abundant as in this favored 

 Gulf region, the terns collect their food with little difficulty. They feed upon 

 small fish of different kinds, which are present in great abundance.^ I have 

 searched in the literature for statements concerning the methods utilized by 

 these terns in catching their fish, but I was nowhere able to find any state- 

 ments of value concerning this. I made a careful study of the water habits 

 of these birds. To my great surprise, I found that the birds never swim nor 

 dive. As a matter of fact, they never touch the water except when drink- 

 ing or bathing. The bird drinks the sea-water as it skims the surface of the 

 water with open beak. Bathing they perform in much the same way, never 

 coming to a stop in the water nor completely immersing the body ; usually 

 the breast and head are the only parts dipped into the water. 



The birds fish by following schools of minnows which are being attacked 

 by larger fish. The minnow, in its efforts to escape, jumps out of the 

 water and skims the surface for a short distance. The terns pick off these 

 minnows as they hop up above and over the surface of the water. The rapid- 

 ity and accuracy of visual-motor adjustment in this reaction is wonderful. 



The birds feed singly or in groups, usually in groups. The group may 

 be composed of both noddies and sooties and may contain sometimes as many 

 as 50 to 100 individuals. All during the day groups of noddies and sooties 

 may be seen at work. As the minnows cease to jump above the surface of 

 the water, the group disbands and scatters in every direction. An instant 

 later, as an attack is made upon the minnows in some other locality, the 

 birds immediately rush there and renew their feeding. Whether there is a 

 true following instinct at hand in this reaction can not be stated, but when 

 one considers that such an instinct is probably present in the sunning reac- 

 tion (which will be described presently) one feels justified in assuming that 

 the act of feeding in groups is likewise a sign of gregariousness. 



In view of my experiments upon the function of distant orientation in 

 these birds, it became very necessary to ascertain when the birds leave the 

 island, how far they go, and when they return. Taking up these questions in 

 order, I suggest the following probable answers : Both species of birds leave 

 the island at early daybreak. In order to observe this more accurately, I 

 rowed out from the island at 3 o'clock in the morning to a distance of 1.5 

 knots. No birds were seen on their way to feed until daylight began to 

 appear. From that time they appeared in ever-increasing numbers — noddies 



'Examination of the stomach contents of both young noddies and sooties showed 

 the presence of representatives of the two families of fish Casangidae and Clupeidae. 

 14 



