Yellow-bellies probably occur throughout Illinois in 
migration, but the variation in populations from place to 
place is not known. 
Though we did not often hear yellow-bellied 
flycatchers sing, we did hear them in all regions of the 
state, including the extreme south. The song was a softly 
uttered “too-reet” or “too-weeet,” with only slight 
emphasis on the rising second syllable. More often fom 
yellow-bellies, we heard a call — “che-bunk” — similar to 
a single song phrase of the least flycatcher (Robbins et al. 
1966). 
The relatively large number of yellow-bellied 
flycatchers we identified in the south, versus central and 
northern Illinois, may indicate that we were confusing 
yellow-bellies with Acadians, a species particularly 
numerous in the south. However we do not believe this to 
be the case, because most of our identifications were 
based on calls. Yellow-bellied flycatchers were 
particularly vocal in the spring of 1970 when we were in 
southwestern Illinois, and the relatively high counts in the 
south may have been annual variation rather than 
regional variation. 
The spring migration of the yellow-bellied flycatcher 
regularly extends into June even in the south (June 6), 
and at least as late as June 12 in the north (Ferry 1908). 
The yellow-bellied flycatcher does not nest in Illinois 
(Fig. 26), and a specimen found dead near Palatine, 
Illinois on June 24, 1948 (Ford 1956) should be 
considered an abnormally late migrant. 
Fall Migration 
As do other species of Empidonax, yellow-bellied 
flycatchers begin their fall migration relatively early. 
Specimens have been found in northern Illinois, which is 
not more than 200 miles south of the southern edge of the 
breeding range, as early as July 29 and 30 (Brodkorb 
1928, Bush 1920). They are of fairly regular occurrence 
in their migration through Illinois from early August 
(Ford et al. 1934, Brodkorb 1927) through September, 
with at least a few lingering into October even in northern 
Illinois (as late as October 12, Ford 1956). The earliest 
fall record known to us for central Illinois is August 23, 
and for the south it is August 25 (George 1968), but 
earlier August records will probably be recorded for both 
regions in view of the number of earlier records for the 
north (Ford et al. 1934, Clark & Nice 1950, Brodkorb & 
Stevenson 1934, Coursen 1947). George (1968) has 
records for the species in southern Illinois between 
August 25 and October 1 (Fig. 26). 
As explained in the introductory paragraphs of this 
report, the fall counts of Empidonax flycatchers are even 
more problematical than the spring counts, partly 
because there is relatively little identifying vocalization by 
the birds in fall. Thus our fall counts of identified 
Empidonax are low (Fig. 27), and they probably do not 
accurately reflect the actual migration patterns. Our few 
fall observations suggest that the peak fall migration of 
the yellow-bellied flycatcher comes in late August and 
30 
early September (Fig. 27), but the tower-kill dat; 
indicate strong migration even in late September. 
At least 15 specimens of yellow-bellied flycatcher 
have been picked up from kills of night migrants a 
central Illinois television towers, on dates fron 
September 2 through October 7. During the one night 6 
September 26-27, 1972, five yellow-bellies were killed a 
towers between Monticello and Springfield, Illinoi 
(David Bohlen and James Seets, personal communica 
tions). 
Because Empidonax flycatchers can be identified i 
the hand, netting operations seem to offer a bette 
method than direct field observation for the study of th 
migrations of these small flycatchers. In the Davenpor 
Iowa area between August 20 and September 25, 197 
Petersen (1971) banded 22 yellow-bellied flycatcher 
about half of his spring catch (41 birds) for this species j 
1968 (Peterson 19686). For such netting studies to t 
useful for comparisons of spring and fall or othe 
populations, however, it is important to have continuoi 
daily coverage. 
Food Habits 
One yellow-bellied flycatcher specimen examined | 
Forbes (18826) had eaten beetles, which comprised ha 
of the stomach contents, and also Lepidoptera adults ar 
caterpillars. 
ACADIAN FLYCATCHER 
(Empidonax virescens) 
(Fig. 28 and 29) 
Spring Migration 
The Acadian flycatcher regularly arrives about t 
third week of April in southern Illinois, the last of Ap 
in central Illinois, and the second week of May 
northern Illinois. The earliest recorded arrival dates < 
April 22 in the south, April 28 in central Illinois (Strau 
1917), and May 6 in northern Illinois (Gault 1901). T 
peak of the Acadian’s spring migration appears to occ 
about May 18 in the south, May 24 in central Illinois, a 
May 26-28 in the north (Fig. 30). 
In the southern part of the state more Acadi 
flycatchers were counted in the spring on the western s! 
of the state than on the east, in a ratio of about 3 (west) 
1 (east). The difference probably reflects an act 
difference in the amount of lowland forest in the t 
areas censused. 
Distribution 
The Acadian flycatcher is a bird of the eastern Uni 
States (Fig. 29). Acadians may nest in every county 
Illinois, but as yet the distribution is poorly known (1 
31). The species is common in southern and cent 
[linois in suitable habitat, but is rather rare in the nor 
The limit of its fairly common occurrence to the no 
seems to be the Illinois River. Excellent lowland fores! 
