346 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



Though most of the feeding was done on the nesting territories, a 

 neutral feeding territory was discovered, and others were indicated 

 because, now and then, the larks would go off on purposeful flights 

 entirely out of their areas. 



The female would mark the same territory as that marked by 

 the male, and if anything she was more closely restricted to it than 

 the male. She selected the nest site with little or no regard to the 

 center of the area. 



The literature contains four February records of nests and many 

 records of March nests in many States, and two or three records of 

 nests in July. I have records of nests from about March 21 to 

 July 12, in 1926, at Evanston, 111. ; from about March 11 to June 28, 

 in 1927, at Ithaca, N. Y. 



It is suggested that such a strange phenomenon as that of a 

 passerine bird nesting in March in eastern United States cannot 

 be easily explained. The bird has too long a nesting season to 

 explain it on the conditions that might exist in early spring alone; 

 and then, in the range where the prairie horned lark was studied, 

 nests are frequently destroyed by inclement weather and many young 

 die of starvation at this season. Since this bird demands barren 

 conditions, and not verdure, for a nest site, the conditions are suit- 

 able very early, and it is suggested that an early-nesting physiological 

 cycle may have been acquired in a more propitious climate and 

 subsequently carried north and east. It is further noted that O. a. 

 actia of California nests in March where conditions are quite ideal. 



With one exception all of the 14 observed nests of March and 

 April were not begun until the mean temperature rose above 40° 

 F. for two or more days in succession. The exception was the ini- 

 tiation of a nest on the first day that the temperature rose above a 

 mean of 40° F. Once weather conditions suitable for the initiation 

 of nesting activities prevailed, no subsequent weather, no matter 

 how severe, except deep snow only, would inhibit these activities. 

 Even birds that had nested in March and whose nests were destroyed 

 by late March and early April snows, would not renest until weather 

 conditions were as given, though this necessitated a delay of nearly 

 three weeks in two cases at Ithaca, N. Y. That this was a delay 

 caused by the weather is easily demonstrated by the fact that an 

 exceptional case, as noted above, began renesting on a single suitable 

 day, but two other larks waited two weeks longer for renesting or 

 until weather again was suitable and for a longer period. It is 

 known that two of these birds, and probably all, had former nests. 



On the basis of this known weather control it was possible to 

 calculate the frequency, over a period of years, with which nestings 

 would occur in March, by a study of weather summaries for the 



