Nesting Cycle 
Ridgway (1918, 1923) reported that mockingbirds 
could be heard singing throughout the winter in Rich- 
land County, even when the temperature was near zero. 
In Pope County we have noticed relatively little singing 
in winter, but a definite increase in song just before mid- 
March, a more pronounced increase in mid-April, and in 
fall a resurgence of song in early October. Though the 
mocker’s talents are well known, little has been recorded 
about the vocalizations in Illinois. At Aledo, Greer 
(1919) heard a mocker mime 22 species of birds in an 
hour. The alarm note that we heard most often around 
nests was a sharp, staccato, crackling sound, similar in 
character to notes uttered in agitation by both catbirds 
and thrashers. Freeman (1950) has described the mock- 
ingbird’s curious habit of periodically jumping 3 feet or 
so in the air from a perch, then landing at the same spot 
again. We have also seen mockers “wing-flashing,”’ but 
have no data on the seasonal periodicity or function of 
either of these performances. 
The nesting season of the mockingbird in southern 
Illinois lasts at least from March 24 (our earliest record 0 
nest-building) to September 1 (our latest record of youn; 
fledged). Further study will probably show the season t 
be longer at both extremes, but most of the nesting surel 
falls in this period (Fig. 2). On our study area in 1967 
most of the egg production occurred between April 8 anc 
June 20 (Fig. 2), a much longer season than that of thy 
thrasher in the same area. The egg-laying curve for thy 
mockingbird has several peaks, and the species may bi 
double brooded, but there was a high incidence of nes 
failures (see below), and banding studies are essentia 
to learn the number of broods reared. The few nestin; 
records available for central Illinois indicate the duration 
of the nesting season there to be from at least May 1 t 
August 23. 
Data from a number of nests in southern Illinois shoy 
that one nesting cycle may take 33-36 days. Nest-buildin; 
at one early nest required 7 days; laying, to the onset o 
incubation, took 3 days; and incubation time was |) 
Fig. 6. — Mockingbird nest (not in situ) with eggs, about life size. The eggs, usually 3 or 4, are often pale green or greenis 
blue, blotched with reddish brown. These two eggs were chosen to show pigment varation. 
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