2,000 f * \ : 
e 
(Li e 
NORTH | \I 
e ® 
500 e \ e Os 
if | e \ * e ve 
* * ey of © |% * 
se EGG LAYING nae 
x Span of dates t 
50 * \ 
* < r) 
%& i / e-® 
20 30 9 I9 29 9 I9 10 20 a 9 19 29 9 19 2 
MAR APR MAY JUN AUG SEP OCT 
% %" Thousands" 
2,000 ot 
1,000 1968 
e 
e 
%* 
500 oe CENTRAL nr i 
\ 
e 
BIRDS COUNTED PER DAY 
SOUTH ° 
500 
100 EGG LAYING 
v4 Span of dates 
50 
ZO moO ©) Is 29 
MAR APR MAY JUN 
10 §620 30 19 
AUG SER OCT 
Fig. 24.-Egg-laying and migration seasons of the cliff swallow in different areas of the state (see Fig. 1). Spring and fall gt 
lines (1967-1970) show the highest daily count of each 2 days (left scale). Asterisk symbols represent counts made in other j 
or by other observers. Shaded areas show the span of dates during which egg laying has been recorded. Dot symbols repre 
counts made on the western side of the state; lines without dots represent the eastern side. 
Eifrig 1919; Ford, Sanborn, & Coursen 1934; Gault 
1922; and others) . 
Most observers blamed house sparrows, which 
usurped swallow nests, for the decline, and the evi- 
dence is strong in support of this view. The house 
sparrow was then well on its way toward colonizing 
the state, and its population was expanding rapidly 
(Barrows 1889). The competition was observed di- 
rectly. Loucks (1895) , for example, saw a large colony 
of cliff swallows completely displaced by house spar- 
26 
rows. Schafer (1920, 1921, 1922, 1932) has provi 
the best quantitative history of a colony, and its p’ 
lems with house sparrows. Before the house spat!’ 
colonization of the state, the Schafer’s barn in R 
Island County had about 200 cliff swallow nests ¢ 
year. After house sparrows arrived, the cliff swa. 
colony began to decline, and by 1913 the swal. 
were gone. That year Schafer began a sparrow — 
trol program. He protected the swallows and 
stroyed house sparrows. One pair of swallows retu) 
