84 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). 




N Ege Inc. CY.inN. CYout N. Mig. 
Fic. 16. DIAGRAM OF ANY GIVEN REPRODUCTIVE CycLH—A-B, interrupted by fear or 
accident at term 4, and a new cycle, A1B1, 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 may be summarized as follows: 
Abandoned empty nests, from which young have been PEMTEU. 2. 6 4% 64 
Abandoned nests with addled ges sc sca te ees Seeger ets Te 8 
Nesta with chicks outeile...mga fewer se eee oe 5 
Nests with newly hatched chicks or pipped eggS .---+++++++e++4ss 1 
Nests with fresh or slightly incubated CG@S «1... sere eee eee eees 5 
New nests, begun or completed 1 hws ix panne Preteen gh aie eee Ay 
Total ou ece see ew vv erase npmeecemiiee angtee ms este eka o aaa 100 
