U.S. Department of Agriculture: Animal and Plant Health Inspection Service
Date of this Version
2012
Citation
Northeastern Naturalist 19(3):527–532 (2012).
Abstract
Although crows cast pellets, there is little quantitative information on pellets from Corvus brachyrhynchos (American Crow), and none from C. ossifragus (Fish Crow). During a study of crow roost dispersal in Lancaster, PA, we collected samples of pellets from several locations. By mass, pellets consisted mostly of grit and other fi ne inorganic material, various seeds (principally Toxicodendron radicans [Poison Ivy] and Celtis occidentalis [Common Hackberry]), and vegetation remnants. Six pellets contained small-mammal bones. Because the Lancaster winter crow population included many Fish Crows, the source of the pellets was not certain. To clarify this, we compared the size of the Lancaster crow pellets to those produced by captive Fish Crows, and we provide the first quantitative description of pellets for either species. Our size comparisons suggest that >90% of the pellets in our sample from Lancaster were produced by American Crows.
Introduction
Pellet-casting has been reported within at least 18 orders of birds (Below 1979). Pellets usually contain indigestible parts of prey items, so pellet analysis is a standard means for studying avian food habits (Coleman and Fraser 1987, Errington 1932, Glading et al. 1943). Among passerines, Corvus spp. (crows) regularly produce pellets (Berrow et al. 1992, Dean and Milton 2000, Kurosawa et al. 2003).
Barrows and Schwarz (1895) described pellet production in Corvus brachyrhynchos Brehm (American Crow). They provided a sketch of a typical crow pellet, but included no measurements, nor did they characterize crow pellet contents except in a general way. We are aware of just two additional studies of crow pellets in the USA. Black (1941) collected 1214 pellets from 12 winter American Crow roosts in Illinois, but he combined all pellets from each site for analysis. Major food items identified by Black (1941) included corn, various common weed seeds, and small mammals (bones or teeth occurred in 178 pellets). He estimated that grit comprised 17.6% of the pellets, by volume. Platt (1956) collected 617 American Crow pellets year-round in south-central Kansas and examined them singly, although he quantified only the food items, “excluding sand and other extraneous material”, and he provided no measurements of pellet size. Field crops (wheat, sorghum, oats, sunflower, and corn) comprised 59% of the identifiable food residues, invertebrates comprised 26.5%, and mammal remains 2.6% (Platt 1956). Apparently, published information on pellets from Corvus ossifragus Wilson (Fish Crow) is lacking (McGowan 2001).