8 4 THE POPULAR SCIENCE MONTHLY 



abruptly ended at term 3 or 4, as a result of fear, through discovery or 

 disturbance of the nest, and a new series is promptly begun at 3. This 

 is the simplest type of disturbance which we can record (Fig. 16). 



CYmN. CYoutN. 



Fig. 16. Diagram of any given Reproductive Cycle — A-B, interrupted by fear or 

 accident at term 4, and a new cycle, A 1 /} 1 , begun at term 3. 



The old nest may be torn down by the little builders, and its materials 

 used again, but this does not commonly happen. Since fear is rapidly 

 depressed, with the rise of the brooding instinct, beginning at term 5, 

 interruptions are less liable to occur after this point is reached, but 

 wherever the thread is dropped, it is usually picked up again at stage 3. 



Of far greater interest is the fact that a new cycle may be begun 

 at the very close of the breeding season, when it seldom goes far, and 

 is bound to fail for lack of time. Probably no stronger witness to 

 the instinctive basis of the behavior of birds could be found than this 

 recrudescence of the reproductive activities at a time when most must 

 answer the fatal summons of the migratory impulse. It is typically 

 illustrated by the great herring gulls, which toward the close of their 

 usual cycle in mid-July begin to build new nests, and will even lay eggs 

 in them, though all are eventually abandoned. It would not be sur- 

 prising to find that many young were also left to their fate, but my 

 observations have never extended late enough to determine this defi- 

 nitely. At the Great Duck Islands, Maine, where these facts were 

 gathered, the birds arrive early in March, and depart about September 

 1, according to the warden and lighthouse keeper, Captain Stanley, 

 who has found that the first eggs are laid about the middle of May, 

 while the first young begin to appear the second week in June. 



In a census of one hundred nests of this gull taken on the island 

 July 17, 1902, at the close of the breeding season, some interesting 

 facts were brought out, which mav be summarized as follows : 



Abandoned empty nests, from which young have been reared 64 



Abandoned nests with addled eggs 8 



Nests with chicks outside 5 



Nests with newly hatched chicks or pipped eggs 1 



Nests with fresh or slightly incubated eggs 5 



New nests, begun or completed 17 



Total 100 



