. Ranges 
BREEDING  ~ 
= WINTER 
Fig. 17.-General North American distribution of the barn 
swallow. The outlined range may include large sections in which 
populations of the species are thin or even absent because of 
the terrain and paucity of suitable habitat. The barn swallow 
winters widely in South America, and also breeds in the Old 
World. 
porches, houses, and other buildings, and (2) under 
cement or metal bridges and culverts. There are 
no quantitative estimates on the relative use of the two 
settings for any area of the state. One barn in 
Johnson County had 41 swallow nests (Petersen 
1970), and we have seen bridges in the south with 
20 or more nests. 
The statewide censuses of 1957-1958 (Graber 
& Graber 1963) showed barn swallows foraging 
over a great variety of open field habitats, but favor- 
ing edge shrub areas (26 birds per 100 acres), 
alfalfa (13 per 100 acres), sweet clover (12 per 100 
acres), pastures (10 per 100 acres), and ungrazed 
grasslands (7 per 100 acres). Guth (1965, 1966, 
1967) conducted breeding bird censuses of an 
alfalfa-clover field in Tazewell County, and found 
densities of foraging barn swallows in different years 
of) 4) 7p eands 12a birdsm per 100 acres. Robertson 
(1941, 1942, 1944) found foraging densities of barn 
swallows over swampy prairie in Sangamon County 
to be about 3, 7, and 9 birds per 100 acres in 
different years. 
The barn swallow has undergone striking pop- 
18 
ulation changes through the years in Illinois. Ear! 
in this century the species was most abundant in th 
northern part of the state (Graber & Graber 1963) 
Ridgway (1915, and in Gault 1922) reported th 
in southern Illinois the barn swallow (as well 
the cliff swallow) had almost entirely disappeared 
a breeding bird. This scarcity was also shown | 
the censuses of 1907-1909, when the June popul 
tion for the whole southern third of the state d 
not exceed 20,000 birds. For the same area 
1957, we estimated the population to be abo 
500,000 birds, and it was even higher in 195320 
population also increased in central Illinois, fr 
about 100,000 in 1907-1909 to 300,000 in 195 
1958, but the northern Illinois numbers did 1 
change (about 150,000 in 1909 and in 1957-195! 
The remarkable recovery of the barn swallow 
southern Illinois was not duplicated by the ¢ 
swallow, and its populations remain very low in | 
south. Ridgway (1915) attributed the early 1! 
century decline of both species to interference fr 
a growing house sparrow population in Illin 
How and why the barn swallow overcame this pr 
lem when the cliff swallow could not is a myst 
though one factor may be the cliff swallow’s cove 
nest structure which is probably more attractive 
house sparrows than are the open nests of b 
swallows. There is an indication that house spar 
populations in rural habitats declined in south 
Illinois after 1900, following the human populal 
to urban areas (Graber & Graber 1963) . This we 
have helped to remove competition pressure f 
the barn swallow. It is also possible that la 
swallows made increased use of cement bridges” 
culverts for nesting. Futhermore, we have ni 
that isolated or recently abandoned farms in soutl 
Illinois have nesting barn swallows, but no, or | 
sparrows. Though we have found sparrows U 
barn swallow nests at colonies in all regions of 
nois, there is no recent evidence that sparrows 
tually displace barn swallows from active nests. 
Nesting Cycle 
Merrill (1947) recorded the same barn sw 
nest being used 7 consecutive years (with an 
remodeling) in Fayette County, but only Mussel 
(1939) has reported homing returns in Illinoi 
the basis of a banded bird, a female whict 
turned ‘“‘several years” to a barn in the Quincy 
Nesting activities may begin very soon after 
swallows arrive in the spring, as we have rect 
egg laying as early as April 15 in southern IJ 
and April 23 in central Illinois, but not before 
6 in the north (Fig. 18). Most of the ee 
duction comes between early May and mid 
and the egg-laying curve has several peaks (Fig. 
This suggests that two or more broods are Tt 
but though barn swallows have been reporte 
