6 BULLETIN" 621, U. S, DEPARTMENT OP AGRICULTURE. 



THE ROOSTING HABITS 



While crows, even in the nesting season, are more or less clannish, 

 their gregarious habit is most highly developed during the colder 

 months. Soon after the nesting season one may expect to see evi- 

 dences of it, but in the latitude of Washington, D. C, roosts are not 

 well established until the end of September. xVt this time their 

 migratory habits have brought together in a comparatively small 

 area the bulk of the crow population of North America, so that the 

 area lying between the thirty-seventh and forty-second parallels of 

 latitude — that is, from Connecticut to Virginia — and extending west- 

 ward from the Atlantic coast to beyond the Mississippi Eiver har- 

 bors these birds in extremely large numbers. Their roosts are occu- 

 pied with considerable fluctuation in population until the advent of 

 milder weather in March, when the numbers rapidly decrease. 



A variety of situations, differing widely in the character of vege- 

 tation, are acceptable as sites for crow roosts. Pine and other ever- 

 greens are most frequently chosen, though records of crows passing 

 the night in groves of deciduous trees, as oaks and maples, are com- 

 mon. A large roost in Crawford County, Ivans., was in a heavy 

 stand of catalpa. That crows roost among such low vegetation as 

 reeds or tall grass has been noted, while in some cases even in severe 

 weather the birds have been known to gather on the ground in open 

 fields or on exposed sand bars. 



Many attempts have been made to estimate the number of- birds 

 which gather at some of these roosts, but the daily fluctuation, caused 

 by changes in weather and by birds stopping at some local roost 

 when they have been overtaken by darkness, makes the computing 

 of their number difficult and. in large measure, unsatisfactory. The 

 wide variation of the estimates made by several observers at the 

 same roost readily shows the uncertainty of results. Furthermore, 

 the impression made upon a person not very familiar with the sight 

 of the gathering thousands is quite likely to be an exaggerated one. 



A roost at Arlington, Va., was supposed to contain at the height 

 of its occupancy from 150,000 to 200,000 birds. These figures have 

 been averaged from the records of a number of observers and may 

 be regarded as reliable. The " Arbutus " roost, near Baltimore, 

 contained in 1888, according to the account of Mr. C. L. Edwards, 2 

 a population of more than 200,000. The St. Louis roosts, about 1886, 

 contained from 70,000 to 90,000 crows. One at Peru, Nebr., at the 

 same time had 100,000 to 200,000. Other roosts numbering approxi- 

 mately 200,000 birds were recorded about the same year in New 



1 More fully treated by the author in Winter Crow Roosts : Yearbook for 1915, U. S. 

 Dept. Agr., pp. 83-100 (Sep. 659), 1916. 



2 Edwards, C L., Amer. Journ. Psychol. I, No. 3, p. 454, May, 18S8. 



