Predation risk and foraging behaviour: An experimental study of birds at feeders

Abstract

Influence of predation risk on the foraging behaviour of seven species of passerine birds was examined in London, Ontario (43°N, 81°W). Feeders containing black sunflower seeds were set up 1.7m, 2.7m, and 3.7m away from a dense row of cedar trees (Thuja sp.). The species and number of individuals at each feeder were recorded during 34 thirty-minute observation periods. Seed consumption during each observation period was also measured. Overall, there was a strong tendency for birds to feed close to cover. Variation in use of escape cover and foraging strategies, however, resulted in interspecific variation in feeding location. House Sparrows (Passer domesticus), White-crowned Sparrows (Zonotrichia leucophrys), Northern Cardinals (Cardinalis cardinalis), and Dark-eyed Juncos (Junco hyemalis) used feeders closer to cover more than those farther away. Conversely, House Finches (Carpodacus mexicanus) fed more frequently at feeders farther from cover. Black-capped Chickadees (Poecile atricapillus) and Red-breasted Nuthatches (Sitta canadensis) fed independently of feeder proximity to cover but these two species always carded food items to cover for consumption. When food became depleted in the feeders closest to cover, House Sparrows, House Finches, and Dark-eyed Juncos increased their use of the more distant feeders. Our results suggest that proximity to cover has a significant effect on foraging decisions of some species of birds.