INOIS BIRDS: Turdidae 
a 
HIS IS THE SECOND of a series of papers in- 
tended to summarize the available data on the birds 
inois. The introduction to the entire work was present- 
1 the first paper, entitled Illinois Birds: Mimidae 
ber et al. 1970), and the policies and procedures for 
eries were outlined therein. This paper deals with the 
hes, and here we need mention only a few problems of 
pretation not encountered in the family covered by the 
rT paper. 
ur censuses from 1967 to 1970 inclusive were made 
ly in nonurban habitats, i.e., they represent the coun- 
le away from towns. Thus, our summer counts for the 
, which shows a strong preference for human residen- 
reas, are unrealistically low. 
| discussing the robin we are also confronted with the 
em of large aggregations of birds. Our censuses of the 
tion for each species are intended to show the num- 
f birds in their diurnal or foraging distribution among 
habitats in the study areas we selected (Fig. 1). We 
interested in the quantitative relationship between 
nt and breeding populations. We avoided censusing 
vicinity of roosts where birds from hundreds of 
= miles may be aggregated in a small area. At certain 
is, robins do form massive roosts, and counts made in 
reas could be expected to differ greatly from our daily 
es. Robins are also greatly aggregated during their 
il migrations, and in graphing our counts of migrants 
+) we have sometimes shown two counts for a given 
ne representing the foraging distribution of the popu- 
and the other the number of birds in active migra- 
"hus, for example, our maximum count of robins for 
1 in southern Illinois was only about 400 birds seen 
the day, but during the late afternoon migration 
1,600 birds flew over in 1 hour. 
ough we tend to be conservative about nomenclatur- 
iges, we believe that Dilger’s (1956) reclassification 
ocichla much better represents the relationships of 
rthern thrushes, and have, therefore, included the 
thrush, Swainson’s thrush, gray-cheeked thrush, 
ry under the genus Catharus. 
the preparation of this paper, we received help from 
ersons. We want especially to acknowledge W. Ear] 
y of the National Museum of Canada, for examining 
of our Swainson’s thrushes and advising on taxon- 
roblems in this species, and Donald F. Hoffmeister 
University of Illinois Natural History Museum for 
Paper is published by authority of the State of Illinois, IRS Ch. 127, Par. 
's a contribution from the Section of Wildlife Research of the Illinois Nat- 
ry Survey. Dr. Richard R. Graber is a Wildlife Specialist at the Survey. 
V. Graber is a Research Assistant Professor of Animal Science at the Uni. 
Illinois. The late Miss Ethelyn Kirk served as Technical Assistant in the 
Wildlife Research at the Survey. 
Richard R. Graber, Jean W. Graber, and Ethelyn L. Kirk 
the use of the University collections. We wish to emphasize 
our gratitude also to the staffs of the State Museum at 
Springfield, and the Chicago Museum of Natural History 
Bird Department. 
We owe a special debt to Laurence C. Binford of the 
California Academy of Sciences, who has loaned us his 
notes on Illinois specimens in the University of Michigan 
Museum of Zoology and Kansas University Museum of 
Natural History, plus other notes on Illinois Birds. 
To the list of persons who have made contributions of 
field data on a number of species we need to add the names 
of Dale E. Birkenholz of Illinois State University, Lawr- 
ence G. Balch of Chicago, Mrs. William Carroll, Jr., of 
Woodstock, Peter Dring of Willow Springs, Everard C. 
Hall of Chicago Heights, William R. Hawkins, formerly of 
Carbondale, Marilyn Campbell of the Vermilion County 
Conservation District, and Natalia Belting of the Universi- 
ty of Illinois. For valuable information on one or more spe- 
cies of thrushes, we are grateful to Don Varner of Morri- 
sonville, Paul Heye of Southeast Missouri State College, 
Robert Russell of Wilmette, Charles Clark of Des Plaines, 
Alfred Reuss and Karl Bartel of Blue Island, Lee Johnson 
and Jack Armstrong of Rockford, Mrs. Harry A. Shaw of 
Sterling, and Elton Fawks of Moline. Elton Fawks also 
loaned us the notes of John J. Schafer who lived at Port 
Byron, Illinois, and published many notes on the birds of 
that area. 
We should also mention our colleagues and associates 
of the Natural History Survey for help with many phases of 
the project. 
Finally, we should point out that much of what is 
known about the bluebird in Ilinois represents the work of 
one man, the renowned Illinois naturalist, T. E. Mussel- 
man. We have depended greatly on his published works for 
our account of that species. 
ROBIN (Turdus migratorius) 
(Fig. 2 and 3) 
Spring Migration 
Though one may see robins at any season in Illinois, 
there are clearly defined migrations in spring and fall (Fig. 
4). There is little in the literature to indicate whether the 
migration is diurnal, nocturnal, or both. Cooke & Wid- 
mann (1883) recorded one instance of nocturnal migration. 
We have seen robins migrating in late afternoon (4:15— 
6:15 pm CST) in March and April, but whether these 
flights were sustained into the night, we do not know. We 
have also observed definite diurnal migrations of robins 
throughout the morning hours, though more often in fall 
