BREWER'S BLACKBIRD 305 



mounts the wing quivering ceases and the female's body becomes 

 rigid. 



The male elevated tail display is similar to the female general- 

 ized display in body appearance, wing action, and tail cocking, but 

 with the tail somewhat spread and the wings possibly held out a 

 bit wider. This is accompanied by the series utterances chug-chug- 

 chug (see p. 325). It is possible that this display may function as an 

 invitation to the female or an indication of the male's receptive 

 state. It is never addressed to another male and has no significance 

 as a threat. 



The head-up display is used regularly by males, rarely by females. 

 With the bill pointing nearly vertical the body is drawn upward with- 

 out ruffing the feathers. In its fullest development the bird has a 

 slim, drawn-out appearance. This display is held for an appreciable 

 length of time, unlike the momentary ruff-out, and there is no ac- 

 companying call. It functions as a threat. 



All these displays except the pre-coitional ones have been observed 

 in more or less rudimentary form in the flock during the non-breeding 

 season. The threat displays (ruff-out and head-up) are used in disputes 

 over food and in other aggressive situations at all times of year. 



Activities that I have termed "pairing behavior" are as follows: 



Pairs walking together segregate from the flock and forage to- 

 gether, usually keeping within a few feet of each other. 



Pairs, either isolated or in the flock, perch on wires or on the tips of 

 pine boughs; if on the wires the distance between male and female is 

 quite regularly about 18 inches. There they indulge in mutual dis- 

 play, exchanging the ruff-out, with squeee and schl-r-r-r-up notes. 

 They may keep this up for several minutes. It usually ends by their 

 flying off together, the female usually taking flight first and the male 

 immediately following; sometimes the takeoff is nearly simultaneous. 



When perched on the wires the male may hop at, or dart toward, the 

 female. This action, the dart, is often preceded by the female assum- 

 ing the generalized display, or it may cause her to assume it; or the 

 female may respond with the ruff-out. 



Frequently, in response to the dart, the female may fly off, the male 

 in close pursuit, in a more or less circular flight. In this action, the 

 chase, a third bird or even a second pair, often joins. 



At the river-mouth colony, Phase 1 usually begins toward the end 

 of January or in February, when a change from winter behavior can 

 be detected. Instead of spending a large part of the day in long forag- 

 ing expeditions away from the colony area, the flock remains longer in 

 the vicinity of the colony. Pairs sort themselves out ; a pair may perch, 

 isolated, on the wires or on the tips of pine limbs and engage in mutual 

 display, then fly to the ground to forage together. Other pairs may 



