^^^ioif^^] Strong, HaUts of the Herring Gull. 197 



paid no attention to the fresh supply I left. They were very restless 

 and they were almost constantly flying about their quarters, often 

 rising to the top of the enclosure, the most unusual feature of their 

 activities. They went to the swimming tank which appears in 

 Plate XX, frequently, though one of them prevented the others from 

 spending much time on the water by driving them away. The 

 gulls alighted frequently on the edge of the tank as shown in 

 Plate XX, and they often remained there two or three minutes 

 except when the belligerent gull drove the others away. 



I have never seen so much activity by these birds as at that time 

 except possibly on two or three other occasions which were also at 

 the time of gull migrations. Unfortunately, it has not been practi- 

 cable for me to watch the birds carefully during periods when mi- 

 grations occur. The performances just described suggested to me 

 the possible existence of a migration impulse as the cause. This 

 suspicion is strengthened by the observations of others on the 

 behavior of other captive wild birds at migration times, but it must 

 be admitted that my notes on these performances of my gulls have 

 only suggestive value. 



Summary.^ 



1. The Herring Gull is gregarious in habit, but it is also quarrel- 

 some. Some of the fights are undoubtedly the consequence of 

 invasions upon nesting precincts as stated by H^rrick, but many are 

 probably due to simple belligerency. This bird is often a great cow- 

 ard and may be routed by smaller birds, the crow for instance. The 

 fights between adults have always been harmless, in my experience. 

 Herring Gulls will fight fiercely for food when very hungry. 



2. Herrick's conclusion that the frequent killing of the young by 

 adults is the consequence of the instinct to guard a nesting precinct 

 probably holds true in many cases. There is, however, some evi- 

 dence that this is not always the explanation. Juvenals sometimes 

 attack younger birds just as savagely as the adults do and in the 

 same manner. 



3. Other birds often nest safely even on a small island densely 

 populated by breeding gulls. 



' This section Is not complete. It includes principally the more important 

 conclusions of this paper. 



