YELLOW-HEADED BLACKBIRD 103 



The behavior described above suggests promiscuity between the 

 sexes. He noted that there were many more females than males 

 engaged in nesting. No females were noticed that were not nesting, 

 but man} T males less brightly colored and with less perfect songs 

 were seen day after day half a mile or more away from the breeding 

 colonies. He inferred from this that females mature and are ready 

 to breed when 1 year old, but that the males require 2 years to mature, 

 and that the less brightly colored males, seen away from the breeding 

 colonies, were yearlings and would not breed until the following year. 



Ammann (MS.) says: "these young males, with their distinctive 

 plumage, were not welcome when they invaded the breeding grounds. 

 Wherever they went they were immediately driven away by the adult 

 males and thus became nomads by necessity. Breeding females did 

 not resent their intrusion, however; once a female was seen to take 

 a receptive position in front of a first-year male (thus evidently rec- 

 ognizing him as a male, in this plumage so similar to her own) to 

 which he did not respond." 



He gives a full account of the actual mating, as follows: "The 

 female stops in the midst of nest building and selects a more or less 

 solid stand low in the bulrush clump or on a mass of floating debris 

 and assumes the mating posture, at the same time giving the low, 

 soft mating call. If the male is anywhere in the vicinity, he responds 

 immediately; it seems almost incredible sometimes how far distant 

 he may be and yet hear this call. 



"He proceeds toward the female in one or more short, jerky flights — 

 thus causing the wings to beat very loudly, with bill pointing almost 

 straight up. Then he draws in his head, erects the feathers of breast 

 and back, droops his tail and approaches the female indirectly by 

 short hops through the rushes or over floating debris, sometimes com- 

 pleting a half circle before reaching her. Then he may strut, twist, 

 or turn in a foolish manner and rarely give vent to the buzzing song 

 before mounting. Meanwhile, the female remains in the mating pos- 

 ture — body tilted slightly forward, tail spread and pointing straight 

 up, bill raised high in the air. As the male comes closer, she watches 

 him attentively with open bill and alternately quivering wings, and 

 may repeat the mating call. She turns her head as he walks around 

 her, or he may stop directly in front of her and both remain motion- 

 less, except for the quivering of her wings, for 15 or 20 seconds. Then 

 the male mounts the female, placing first one foot on her back, then 

 the other; at the same time he flaps his wings vigorously high above 

 him and brings the bill close to his breast so that the neck is quite 

 arched; his tail is pressed down between the two central tail feathers 

 of the female, allowing the cloacae to come in contact. While the 



3S0928 — 57 8 



