U. S. NATIONAL MUSEUM BULLETIN 211 



respective singing posts which were in separate cattail patches about 

 20 feet apart. For 3 or 4 minutes they kept close to each other, 

 walking back and forth along the boundary with fluffed feathers and 

 arched necks. In turn, they made short flights, getting scarcely more 

 than a foot above the ground and moving, altogether, only 3 or 4 

 feet. Once one went as far as 10 feet. In these flights the wings 

 were flapped violently, but the bird moved slowly, and the body was 

 held with the bill pointing upward 80° above the horizontal. Finally, 

 each bird returned to its own singing post, having had no actual 

 combat." 



On another occasion he noticed severe fighting for about 30 seconds, 

 one holding the other down and pecking at it. Referring to the ter- 

 ritorial behavior, he says in part: 



Judging from continued watching at this pond through the greater parts of 

 2 nesting seasons, territory for these yellow-headed blackbirds was a definitely 

 recognized area for males only. Moreover, this area was a remarkably small 

 one, when the size of the birds is considered. Each male established itself in 

 1 small patch of cattails or a portion of a patch. * * * 



From the first establishment of the territories one of the chief concerns of 

 each male was to keep other male yellow-headed blackbirds off his area. The 

 enmity seemed aroused in inverse proportion to familiarity with the trespassing 

 individual. When 2 males owned portions of the same cattail patch, they were 

 much more tolerant of each other than of males from another part of the pond. 

 Newly arrived, strange males arouse a quicker response than ones already settled 

 in the same pond. * * * 



Besides their vigorous defense against intrusion by other male yellow-headed 

 blackbirds the males were especially active in driving red-winged blackbirds from 

 their territories. The pursuit, however, was usually a short one. In observed 

 instances male red-wings were pursued for only about 30 feet, or just to the 

 limits of the yellow-head territory. If, in leaving, a red-wing crossed the terri- 

 tory of a second yellow-head, the latter would take up the chase and the first 

 jrellow-head would turn back. 



Of the actual mating, he says: 



Males were noticed flying to females especially when the latter uttered a cer- 

 tain type of screeching note. Sometimes these notes were given on the pursuit 

 flight. The notes along with the posturing of the female seemed to be the signal 

 that the female was near the mating stage. 



Mating of yellow-headed blackbirds was noticed in late afternoon on May 26, 

 1932. In territory III a female flew to the top of a currant bush where it pos- 

 tured, and then male III flew there from the cattail patch and they copulated. 

 The union lasted about 2 seconds during which the male flapped his wings rapidly. 

 After perching a few inches away for a short time, the whole procedure was 

 repeated until it had taken place 9 times in quick succession. Then the male 

 flew back to the cattails where it perched on a dead stem and shook its plumage. 

 The female may have been the same one noted earlier in territory II. Posturing, 

 with bill and tail pointed upward, had been noticed there, but male II had made 

 no response. The circumstances seemed to indicate that male III was the oDly 

 one ready for mating, and the female hunted it out. 



