FOOD AND PREDATION RISK AS FACTORS RELATED TO FORAGING LOCATIONS OF NORTHERN FLICKERS

Abstract

Foraging site selection by birds may be related to foraging efficiency, food availability and abundance, and predation risk. We identified selectively used foraging habitat within home ranges of 29 adult radio-tagged Northern Flickers (Colaptes auratus) in British Columbia during the nestling period. We compared habitat characteristics of flicker foraging locations to randomly selected locations in their home range using discriminant function analysis. Foraging plots were located in grassland and were characterized by a lack of tall vegetation, a large percentage of bare ground, and a high density of small anthills. Foraging plots had five times more anthills than random plots. Foraging plots also were closer to trees and forest edges than random plots. The random plots had significantly more medium and tall vegetation than foraging plots, and litter (dead grass) was the most abundant type of cover. Mortality of adult flickers attributed to avian predation while foraging was 14% during 1999 and 3% during 2000. The sparse ground cover of foraging plots likely increased access to food, whereas foraging near trees likely decreased avian predation. The marked selectivity of foraging areas by flickers suggests that foraging ability could be negatively affected by land use practices that alter the structure of ground cover.