cance of any of these predators is unknown. Lyon (1922) 
noted particularly heavy predation on robin nests by grac- 
kles in 1922, when nearly all observed nests failed. 
Finley (1912) and Davis (1 969) have described the 
growth and development of nestlings. 
Taste 2.—Plants and structures used by robins as nest sites 
in Illinois (mainly nonurban areas). 
Percent of Total Nests 
North Central 
Nest Site (228 Nests) (84 Nests) 
Man-made structures (shed, house porch, etc.) 16 12 
Osage orange (Maclura pomifera) 10 24 
Apple and crabapple (Malus sp.) 8 10 
Elm (Ulmus americana, U. pumila, and sp.) 7 10 
Oak (Quercus velutina, Q. borealis, 
macrocarpa, and sp.) 8 4 
Pine (Pinus strobus, P. sylvestris, 
P. nigra, and sp.) I 4 
Mulberry (Morus sp.) 9 1 
Box-elder (Acer negundo) 4 6 
Other maples (Acer spp-) 3 6 
Cedar (Juniperus virginiana, J. chinensis, 
and sp.) 5 2 
Cherry, Plum, etc. (Prunus serotina, 
and spp.) 2D 4 
Hawthorn (Crataegus spp-) s) J 
Spruce (Picea sp.) 2 2 
Hackberry (Celtis occidentalis) 2 1 
Willow (Salix spp-) l 2 
Honey locust (Gleditsta triacanthos) 3 
Lilac (Syringa vulgaris) 3 ; as 
Honeysuckle (Lonicera spp.) as 2 
Birch (Betula nigra, and sp.) 2 oft 
Rose (Rosa multiflora, and sp.) 1 1 
Sycamore (Platanus occidentalis) 2 
Pear (Pyrus communis) ae 1 
Ash (Fraxinus sp.) 1 
Grape (Vitis sp.) 1 Bue 
Catalpa (Catalpa sp.) “Be 1 
Tree of heaven (Ailanthus altissima) Ns 1 
Magnolia (Magnolia sp.) ss 1 
Pignut hickory (Carya glabra) ar . 
Golden bell (Forsythia sp.) ats 
Virginia creeper 
(Parthenocissus quinquefolia) + 
Black locust (Robinia pseudoacacia) + 
4 Plus symbols (+) = less than one. 
Fall Migration 
In early September most robins in central Illinois are 
still in molt, and we have seen young still largely in juvenal 
plumage as late as mid-October. 
Smith (1941) reported that young robins were in full 
migration in northern Illinois by July 21. We have seen 
robins flocking in early July wherever there were good food 
supplies, but whether there is any real migration this early 
we do not know. Robins banded in Illinois have appeared 
in the Gulf States at least as early as October 8 (Louisiana) 
and October 20 (Mississippi). Our censuses show marked 
10 
day-to-day population changes in July and August in | 
tral and northern Illinois, but very little change in sout| 
Illinois until September (Fig. 4). We have not witne 
active migrations of robins in any part of the state 1 
September, but Robert D. Crompton (personal comm: 
cation) has seen diurnal southward migration as ear! 
August 11 in Mason County. The most massive migrat 
we have seen occurred in October in northern and ce 
Illinois near major waterways. Though all of the fall r) 
migrations we have seen were oriented either near s 
(180°) or west of south, the recoveries of banded birds s 
great dispersal (Fig. 6). We have seen more morning | 
rations of robins in the fall, and more evening flights i1 
spring. The robin is a rare casualty at television tov 
We have found only one specimen (on October 6, | 
among thousands of night migrants (of other spe: 
picked up at towers in central Illinois. _ 
Highest fall populations occurred in September 
October in central and northern Illinois, and in Oct 
and November in the south (Fig. 4). Fall counts of ~ 
were three to four times higher in east-central Illinois 
in the west. 
In the north we saw about four robins in the 
(August-October, inclusive) to one in the spring (M 
and April). In the central sections, both east and wes 
saw only about 1.5 in the fall to one in the spring. I 
south the ratio was, inexplicably, reversed: three in s| 
(February through April) to one in fall 
ust-November, inclusive). These data represent 
“rounded” robins, and not birds in active migration. 
A notable ecological change occurs in the robin bet 
spring, when most birds are found foraging in open ¢ 
land, and fall and winter when the population freq 
woody habitats much more. 
Roosting 
We have no records of Illinois robin roosts that 
approach the dimensions of those found in eastern: 
souri, where as many as 3% million birds have bee 
ported (Petersen 1965, and Widmann 1895). James ( 
studied local roosts in Champaign County, and roosts 
also been recorded in Cook County (Back 1934-193: 
Bailey 1932), and in Fulton County where the popu 
peaked at 22,500 birds on October 23. Roosting ags 
tions occur inspring from March into May, andi 
summer and fall from July through October (James 1 
Large winter roosts should be looked for especia 
southern Illinois. | 
Winter Records 
Robins have been found in winter throughout n 
the state (Fig. 7), but generally only in small nul 
north of the southern zone (Fig. 8), and the bulk of th 
ern robin population winters south of latitude 35° 
i.e., south of Illinois (Speirs 1953). Though there a! 
cember and January records for the Chicago area in. 
3 of the past 40 years (1930-1969), our statewide ce 
