PRAIRIE HORNED LARK 345 



ever, were on a tract of ground that was largely fall wheat, partly 

 fall rye, and the remainder devoted to experimental vegetable gar- 

 dens. The growth of the wheal forced the larks from its surface 

 by late May. The gardens and portions of the fall rye area that 

 were turned under as green manure remained suitable throughout. 

 Clean vegetable gardens will always present a considerable amount 

 of bare soil, and the prairie horned lark is usually able to occupy 

 such gardens until late in June. 



A breeding territory was delimited by a male lark on February 7, 

 1926, at Evanston, 111. From his selected territory he could not be 

 driven. This territory was about 100 yards square. Late March 

 snows disrupted all territories, and it was not learned whether the 

 original sites were ultimately resumed or whether the same territory 

 was maintained through more than one nesting. The pressure of 

 vegetation in late May and June greatly modified the territories at 

 Evanston and caused, eventually, the abandonment of most of those 

 on tlie erstwhile golf course. 



At Ithaca, N. Y,, a male lark was forced to mark territory for the 

 first time on March 13, 1927, though it had undoubtedly been estab- 

 lished some time before this. Territories voluntarily marked were 

 somewhat larger than those indicated when the birds were forcibly 

 driven about. The regions of a breeding territory most frequently 

 occupied were those boundaries that joined the territories of a 

 neighboring lark. 



The territores at Ithaca were much larger than those at Evanston, 

 possibly because fewer larks attempted to occupy them. At Evanston 

 they were seldom over 100 yards square, whereas at Ithaca they ran 

 out to lengths of 300 yards and widths of 200 yards, in March and 

 April. In general all suitable territory was occupied at Ithaca and 

 most boundaries were established by the margins of unsuitable areas, 

 though a large amount of suitable territory, extending beyond, was 

 used only in part by the bird. Boundaries between males were 

 often definitely established on ground that had no natural marker 

 whatsoever. 



The territory history of three pairs of larks was followed from 

 March to June at Ithaca. One influence only modified the territories, 

 namely, the growth of vegetation. One territory, completely on fall 

 wheat, was abandoned by the close of the second nesting in May. 

 Another territory, in part on fall wheat and in part on the gardens, 

 was gradually reduced to the gardens, from an area once 300 by 200 

 yards to an ultimate area about 100 by 50 yards. A third territory, 

 almost entirely on the gardens, suffered no major reduction. But the 

 owner of this third territory, which abutted that of the second, gave 

 no ground to the latter. 



