Tasie 1. — Breeding populations of eastern kingbirds in various Illinois habitats. 
NE  ——EeEeEeEeEeEeEeEeEeEeEeEeEeEeEesseseeesse nnn | 
Habitat Acres aris a Years Bae meen Reference 
I 
Orchard 45 7 1907-1909 Strip South Graber & Graber 19 
78 4 1957-1958 South 
Shrub areas 32 9 1957-1958 Strip North Graber & Graber 19¢ 
50 8 Central 
129 1 South 
Late shrub 21 4 1966 Nest Vermilion (C) Karr 1968 
Swampy prairie 67 9 1941 Nest Sangamon (C) Robertson 1941 
64 B) 1942 Sangamon (C) Robertson 19424 
Pastureland 193 5 1909 Strip North Graber & Graber 19¢ 
442 3 1907-1909 Central 
882 2 South 
279 6 1957-1958 North 
172 2 Central 
Upland second growth hardwoods 56 4 1942 Nest Sangamon (C) Robertson 19426 
I 
2 All figures were converted to read birds per 100 acres (territorial males or nests 2) 
no referenes on intraspecific aggression or spacing of 
kingbirds. 
Nesting Cycle 
The Illinois literature is essentially devoid of 
information on the nesting cycle of the eastern kingbird, 
and we can add little. Egg laying begins as early as May 
12 in southern Illinois, and lasts at least through July 17 
in the north (Fig. 4). Bent (1942) gives May 2 as an egg 
date in Illinois, but we do not know the source or locality 
for this record. 
Data on 34 nests from the Illinois literature and our 
own field notes show clutch sizes for the kingbird as 
follows: 6 eggs — 9 percent, 5 eggs — 12 percent, 4 eggs 
— 41 percent, and 3 eggs — 38 percent. As most of these 
were nests without complete histories, the clutch data are 
crude. Better clutch data are needed particularly in view 
of the number of reports of nests with only one or two 
young. The implication is that this species has either low 
hatchability, or an unusually high loss of eggs or young 
even in successful nests. 
There have been no measurements of the incubation 
period in Illinois. Nestling life at one nest in central 
Illinois was 13 days (Finley 1917), but this may represent 
the short extreme, as, in general, flycatchers tend to 
remain in the nest as long as possible. Finley (1917) also 
studied feeding rates of nestlings. Between 4:15 a.m. and 
8:00 p.m. the adult birds made 168 trips to a nest with 
three young about 6 days old. Peak rates of feeding came 
at 6:00-7:00 a.m. and 5:00-6:00 p.m. and the lowest rate 
was at noon. The food of nestlings has not been recorded. 
We doubt Eaton’s (1878) statement that kingbirds raise 
two broods in northern Illinois, but there are insufficient 
data to settle the question. 
In view of the kingbird’s aggressive nature, it is 
surprising that the species is ever parasitized by cowbirds 
(Molothrus ater), but we know of two instances in which 
Illinois kingbird nests were parasitized. A nest collected 
on June 11, 1885 by Elmer Pierce near Meacham 
(DuPage County), Illinois contained two cowbird eggs. A 
8 
nest found July 7, 1967 near Havana (Mason Coi 
Illinois held one large cowbird, which probably fle 
successfully. 
Fall Migration 
The fall migration of kingbirds, as in the sprin; 
apparently never been witnessed in Illinois. Youngw 
(1950) observation of diurnal migration of kingbi 
Iowa is possibly indicative that the same kir 
migration occurs in Illinois. The migration that h 
starting early in the morning of August 28, lasted 5 
and involved loose flocks of from 40 to nearl} 
kingbirds flying southwest. Other large flights have 
seen in Iowa (Brown 1962). If such spect 
migrations occur in Illinois, why have they 
undetected? Another observation is indicative of 
migration of kingbirds in Illinois, for among hundr 
night migrants killed at a television tower in Sang 
County on the night of September 16-17, 1958 the 
a least one kingbird (Parmalee & Parmalee 1959). 
Just when the fall migration begins is also unk 
There is evidence of some movement of kingbii 
early as July (Nolan 1956). Our fall counts show v 
peaks in August and early September, but 
consistent from region to region (Fig. 4). It i 
impression that notable kingbird migrations often 
between August 20 and 25, and September 6 and | 
mid-September kingbirds have essentially disap} 
from Illinois. October records are probably excep 
even for the southern Illinois area (Anderson 1966 
the latest fall records known to us were those of 
seen October 17, 1906 by Alfred Gross (unpub 
notes) and one seen on October 16, 1971 (Kleen & 
1972a), both in west-central Illinois. 
The ratio of the spring to fall counts of kingbi 
Illinois does not account for any productivit 
northern and central Illinois the spring-fall rati 
almost exactly even, and in the south the ratio was 
four kingbirds in the spring to one in the fall. 
figures suggest that much of the fall migration ma’ 
