Fig. 6.—Distribution of recoy- 
of robins banded in Illinois. 
-and shaded areas indicate the 
d of recoveries from five band- 
ations. 
ROBIN 
band recoveries 
ed that 99 percent of the state’s winter robin popula- 
vas in the southern region (Graber & Graber 1963). 
ome winters (note especially 1955-1956, 1964-1965 
g. 8) large numbers of robins appear even in northern 
entral Illinois. In such high years hundreds or even 
sands of robins may be seen per day incentral and 
ern Illinois (Fawks 1967, Musselman 196309 ink 
Mayfield 1951, and Rice 1946). Various explana- 
have been offered for these high populations, and 
are some data to support the following hypotheses: 
nusually high productivity in the preceding breeding 
n, productivity that increased population pressure 
where in the eastern United States; (2) exceptionally 
winter food reserves in the north; and (3) exceptional- 
ly northward migration, reflecting an unusually mild 
r (Robbins 1956, and Nolan 1956). 
00ke (1885) believed that bottomland forest was the 
S primary winter habitat (note also the winter distri- 
1, Fig. 7), but there are few population measurements 
ble for any habitat. Between 1927 and 1970, Ken- 
and his students reported populations in forest edge 
ntral Illinois ranging from none in most years 
eigh 1948) to eight birds per mile of edge (Kendeigh 
St 1958). In southern Illinois, Shawetal. (1961, 
© BANDING STATIONS 
@ NOV. -- FEB 
4 MAR. -- APR. 
O MAY -- AUG. 
WY SEP -- ocr. 
ay 
300 400 MILES 
* aioe = ae = PR greet « "1 as) 
1965) recorded populations in a shrubby field ranging from 
none (1961) to 13 robins per 100 acres (1965). 
Food Habits 
Forbes’ (1903) studies were based almost entirely on 
specimens from central and northern Illinois. In the spring 
robins fed almost exclusively on animal matter (Fig): 
The items most frequently mentioned in the literature are 
earthworms and larvae of March flies, especially Bibio al- 
bipennis (LeBaron 1853-1854, Thomas 1920, Rice 1946, 
and T'womey 1945). Forbes’ studies showed the Bibio lar- 
vae to be important, but did not show the expected preval- 
ence of earthworms (Fig. 9). He related the low tally of 
worms to their quick digestibility. Cutworms (Noctuidae), 
and even the egg masses of tussock moths (Liparidae) are 
prominent in the diet (Hulsberg 1917-1918, and Schantz 
1933), as are ground beetles (Carabidae) and wireworms 
(Elateridae) later in the spring. At a Tazewell County or- 
chard that was heavily infested with canker worms 
(Geometridae), Forbes (1883) found that robins increased 
their intake of the pest, but kept many other items of their 
usual diet. Cleveland (1923) found robins feeding 17-year 
cicadas to their young. 
