NESTS AND NEST-BUILDING IN BIRDS 169 



beginning of a second, to the desertion of backward young in 

 favor of those which have left the nest, or of the entire brood 

 when the maternal impulses are swamped by the rising migratory 

 instinct, by a recrudescence at the close of the season, of a cycle 

 which is never finished, as well as to a great variety of eccentric 

 behavior. Whenever a " stitch is dropped," as when the annual 

 cycle is broken by fear or accident, they must usually go back 

 in order to pick up the thread ; in other words, a new cycle is 

 begun, and commonly by building a new nest on a new site. 

 Whenever the old nest is chosen as a site for the new, and this 

 may repeatedly happen, we have in some cases a remarkable pro- 

 duction indeed, — a storied or compound nest. Whenever fear 

 is simply repressed by the brooding impulse, or through other 

 conditions, a loss of eggs is very often repeatedly made good 

 by the production of more, checked only at last it would seem 

 by the capacity of the ovary, and the physical resources of the 

 individual. Some species normally repeat the breeding cycle 

 more than once during the season. 



In all the higher animals the store of nervous energy is ex- 

 pended mainly for three prime purposes, for getting food, defence 

 from enemies, and in reproducing their kind. It is during the 

 breeding period of birds in particular, that emotion is keyed to 

 the highest point, when every power is likely to be taxed to the 

 uttermost, and the cup of nervous energy drained even to the 

 dregs. Individual struggle is then complicated by the presence 

 of offspring, which may call into play at one time or another 

 ev^ery sharpened power, strategy, or device, with which nature 

 has equipped them to fight their hardest battles, for a strong 

 and useful weapon, — fear and retreat, — is often for a time so 

 dulled that self-sacrifice, however needless, is frequently 

 demanded. 



The more brilliant coloring, the joyous or ecstatic song, the 

 keener instincts as seen in the greater caution, alertness, or pug- 

 nacity, displayed at one time or another in this cycle of events, 

 and after a period of recuperation, all bear witness to the inten- 

 sity of emotion, which in all the higher exponents of their class, 

 characterize the climax of reproduction. It is a sane and safe 

 conclusion that no mental powers with which this race is endowed 

 are ever wholly v.ithdrawn from the most critical period of 

 their lives. This is whv the round of dailv life at other times 



