KIRTLAND'S WARBLER 419 



the female — who searched all parts of the chosen area, even the very 

 edge — usually in the lead. The male made a few long flights from 

 one side to the other of the territory, which was roughly circular, 

 measuring 195 yards from north to south and 212 yards from east 

 to west. A number of times (always in the immediate vicinity of 

 the female) the male performed what seemed to be a courtship or 

 display flight. This began at a height of 6 or 8 feet and was made 

 with rapidly beating wings. It was a slow, slightly descending flight, 

 usually carrying the bird directly over the female. 



The male sang steadily except on the infrequent occasions when 

 he participated, briefly, in the search along the ground for a nest site. 

 Several times he drove from his territory the males of three adjoin- 

 ing areas. Once this led to a melee of three birds — the intruding 

 male and both birds of the pair I was following — but the action was 

 so fast that I could not tell whether the female took any active part. 



Nesting. — The nests are usually very well concealed in the ground 

 cover, often completely arched over by vegetation, with entrance 

 from one side only. They are almost always placed within a few 

 feet (commonly within a few inches) of a jack-pine; occasionally, 

 though still among pines, they are in quite open situations. They are 

 always built directly on the ground and are usually made of dead 

 grass and other such fibrous vegetable materials. Sometimes they 

 are lined simply with finer grasses, but commonly with red sporo- 

 phyte stalks from moss or with white deer hair. They measure 40 

 to 45 millimeters inside depth and 48 to 55 millimeters inside diameter. 



The nest is constructed entirely by the female, but the male is always 

 nearby and seems to follow the work closely. As Axtell (1938) 

 observed, the approach of a female with nest material is "invariably 

 heralded by a resumption of song on the part of the male." Between 

 June 10 and 13, 1945, near Red Oak, Harold Mayfield and I watched 

 the entire building of a nest. The female (who had searched the 

 whole territory most of the day on June 8) began investigating the 

 site a half hour after sunrise. An hour later she brought what was 

 quite surely the first piece of nest material. Except for short periods 

 devoted to feeding, she worked hard through the remainder of the 

 day, obtaining most of the material at certain favored spots 50 to 

 YO feet from the site. She made 131 trips that day and 59 on the 

 following, thus completing the main structure of the nest. On the 

 third day she made 7 trips, and on the fourth day 6 trips, for the 

 lining (a total of 203 trips with nest material). The first warbler 

 egg was laid on the fifth day (June 14) about an hour after sunrise. 



Unless normal routine is disturbed by a cowbird, the eggs are laid 

 in the early part of the morning and on successive days. Incubation, 

 performed by the female alone, begins with the laying of the third 



