114 Trans. Acad. Sci. of St. Louts 
ruptedly, produced a veritable gamut of ecological conditions 
during spring and summer which proved suitable to a long 
series of birds. Since the flora, here otherwise undisturbed, was 
modified with the advance of season, it follows that the ecological 
categories of the open field were modified likewise and were 
followed, as a consequence, by a change of population wherein 
the Prairie Horned Lark figured conspicuously. 
Because opportunity was presented thus so ideally to make 
close comparisons between Lark and its open field congeners, 
this treatise will not be complete’ without so comparing. The 
Lark began to nest in March with flora at its minimum and 
suitable breeding territory extensive, and continued to nest 
into July when flora was at its maximum and suitable areas 
greatly reduced. Such a change closed some territories com- 
pletely and greatly modified others. But what was unsuitable 
for Larks proved highly acceptable to others and it is this suc- 
cession that interests us here. This succession was both seasonal 
and, in June, geographical. For instance, a region might satisfy, 
with its seasonal conditions, the Lark in March and April, the 
Vesper Sparrow in May and the Dicksissal in June. Such con- 
ditions were frequently presented at Evanston. Likewise, at @ 
single period in June, the same sequence would be presented by 
walking from an old sanded hazard to a neighboring weed patch. 
In addition to ecology of habitat the dates of arrival, seasons 
of song and other characteristics of interest are given and 
reference made back in each case to the Prairie Horned Lark, 
our main thesis. This material can be presented best by con- 
sidering the species separately. 
Bartramia longicauda. Upland Plover. Notes of this bird 
were heard on the main subdivision June 17, 1925. In 1926 
they were first heard in April 21, and almost daily thereafter 
until May 8, when a peculiar interval occurred with no records. 
They were noted again on May 30 and with one or two excep- 
tions were seen or heard daily until July 22, the last visit to 
the area. 
On April 26 that most astounding weird and mournful wail 
(song), of the Plover was first heard and frequently from that 
time to July 12. 
On June 18 a nest with three eggs was found in the timothy 
