138 Trans. Acad. Sci. of St. Louis 
will be noted below. During these periods nests may be located 
by a systematic search that involves first, driving the male about 
until the female is noted (she will flush from the nest and the 
male will go to her), then a patient watch of the female will, 
after a variable length of time, disclose the nest. When young 
are being fed the male will, at times, disclose the nest much more 
quickly than the female, for he assists in feeding and has nest- 
concealing instincts that are very poorly developed. Though the 
nest of the Prairie Horned Lark is never concealed from above, 
it fits its semi-barren environment so closely that a promiscuous 
search over a breeding territory is nearly always tiresome and 
unavailing. An incubating or brooding Lark, as will be dis- 
eussed below, often remains close to her nest when the day is 
chilly or in the very early morning or toward evening. Nests 
ean be found under these cireumstances by a systematic search 
of likely habitats and so flushing the bird from the nest. 
5. Nest building. No evidence of the use of a natural depres- 
sion was noted either at Evanston or at Ithaca, all were dug by 
the female. According to Sutton (1927) and observations which 
the writer has made of O. a. strigata in western Oregon, this 
excavation is dug with both beak and feet. The nest is con- 
structed, usually, at the edge or partially under a grass tuft 
or clod which, in the case of the Prairie Horned Lark, lies most 
frequently on the west, northwest or north (see Tables 3, 4, 7 
and 8) possibly because the cold and violent winds, of the early 
nesting season, come from this region. The body of the nest 
consists of coarser stems and leaves with a finer lining within. 
The time spent in nest construction varies from two to four days. 
6. Seasonal variations in nest structure. The evidence shows 
that any seasonal variation in nest structure is due to variations 
in available material and has nothing to do with variations in 
*‘necessity’’ or ‘‘onerous duties’. 
7. ‘‘Paving’’. The majority of the nests of the Prairie Horned 
Lark showed a variable amount of clods, pebbles or similar items, 
Jaid about the margin usually on the side away from the protec- 
tive tuft or clod. These so-called ‘‘pavings’’, were, again, always 
composed of the material most easily obtained regardless of the 
permanency of such. It is suggested that the purpose of ‘‘pav- 
ings’, if there is a purpose, arises from the method of nest 
