12 BULLETIN" 113, UNITED STATES NATIONAL MUSEUM. 



contributed the following notes on one of its spectacular perform- 

 ances : 



On several occasions I have seen the " gull chaser " turn a complete back 

 somersault in the air to make a dive upon some piece of food on the water which 

 the sweeping gale had caused it to overrun. Often, too, it thus makes its 

 piratical raids upon some luckless hag, which, almost too late, it finds in 

 possession of a morsel which it deems too dainty to be wasted on a mere 

 squealing shearwater. And ?o it rises against the breeze, turns itself upside 

 down and. with wings half closed, darts at its victim from above like a lance. 

 But the hag stands to his guns ; a squealing, choking remonstrance, a mighty 

 gulp, and if the jaeger has luclc he may capture a small fragment of the spoil. 



Mr. Rich says that the usual " call is a sharp ' which-yew,' also 

 a squealfy whistle, and occasionally a squealing note like the ' week- 

 week ' of the herring gull." Doctor Nelson (1887) ssljs that it " has a 

 low, harsh, chattering cry when feeding with its companions." 



Its behavior toward other species, which has been partially shown 

 above, is not above criticism; its motto seems to be that might makes 

 right; it therefore uses some discretion in the choice of victims for 

 persecution. The terns and the kitti wakes are the ones most regu- 

 larly abused, the ring-billed and the herring gulls are less frequently 

 persecuted, and it seldom ventures to attack the glaucous or the 

 great black-backed gulls. Size and strength do not always bring 

 courage, and the pomarine jaeger seems to be lacking in the latter 

 quality. Doctor Nelson (1887) writes: 



They are clumsy and cowardly as compared with their smaller relatives. 

 When one of this species chances to cross the path of the smaller species, the 

 latter almost invariably gives chase and beats its clumsy antagonist off the 

 field by repeatedly darting down from above. This attack embarrasses the 

 large bird, so that it flinches and dives and often alights and watches an 

 opportunity to escape from its nimble assailant. One that was driven to 

 alight in the river thrust its head under water at every swoop of its assailant 

 and exhibited the most ludicrous terror. When on the wing they usually ward 

 off an attack from one side by a half-closed wing, and if above, both wings are 

 raised, forming an arched shield above the back. 



Fall. — ^The fall migration of the jaegers is governed largely by 

 the food supply, which depends on the movements of the fish on 

 which the gulls, terns, and shearAvaters feed. On the New England 

 coast we usually look for the jaegers in August, especially where the 

 bluefish or mackerel are running in schools and driving the small 

 fry to the surface. During seasons when these fish are scarce the 

 jaegers and shearwaters are absent, perhaps following other schools 

 of fish far out at sea. And when the bluefish and mackerel move off 

 the coast in the fall the jaegers disappear with them. They are 

 seldom seen on our coasts in winter. We do not know very much 

 about their winter range and habits, but they probably spend this 

 season roaming at large over the open ocean wherever they can find 

 a chance to ply their trade as pelagic pirates. 



