10,000 
5,000 
eee NORTH : 
500 e e 
100 
50 
Ae CENTRAL 
BIRDS COUNTED PER DAY 
1,000 SOUTH 
1010 20 30 9 1I9 29 0 
JUN JUL AUG SEP 10) 
ROOSTS 
* * 
& * 
* x % )ROOSTS 
* 
% 
ROOST - _ 
* od % 
iy * u 
Thousands 
% ROOST * 
e 
ui ROOST 
% 
‘ 
4 
20 30 10 
Fig. 29.—Egg-laying and migration seasons of the purple martin in different areas of the state (see Fig. 1). Spring and fall g 
lines (1967-1970) show the highest daily count of each 2 days (left scale). Asterisk symbols represent counts made in other 
or by other observers. Shaded areas show the span of dates during which egg laying has been recorded. Dot symbols repr 
counts made on the western side of the state; lines without dots represent the eastern side. 
period was from “mid-May” to “early June.” Based on 
fledging and hatching dates (Widmann 1884, and 
Cooke 1888), egg laying at the St. Louis colonies ex- 
tended from about April 28 to June 25. In northern 
Illinois, egg laying has been recorded from May 5 to 
July 15 (Fig. 29), but the timing of peak production 
is unknown for any population in the state. 
At St. Louis, Widmann (1922) found the usual 
first clutch to be five eggs, with six eggs in only about 
20 percent of the nests, and four eggs the usual clutch 
32 
for renestings after failures. For northern and cel 
Illinois we have clutch records for only 12 nest: 
follows: 3 with six eggs, 6 with five eggs, 1 with | 
eggs, and 2 with three eggs. Far more data are ne 
on this phase of the cycle. Widmann (1922) repe 
a high incidence (20-25 percent) of “addled” | 
and in northern Illinois Gault (unpublished nc 
recorded an incidence of 17 percent between 
and 1914. 
We have found no published data on nesting 
