Aspects of Behavioral Ecology of Red-Headed and Red-Bellied Woodpeckers

Abstract

Habitat utilization of red-headed and red-bellied woodpeckers was compared. Since these species are sympatric over much of their range, an examination was made of their segregation and overlap in vertical distribution, and a temporal and spatial analysis was made of their foraging behavior, nesting habits and aggression patterns. Greatest niche segregation was found during the breeding seascn, particularly in choice of nest site and territory use. During the nonbreeding season, interspecific aggression between the two species increased as they overlapped more in various spatial and behavioral parameters. INTRODUCTION Red-headed woodpeckers (Melanerpes erythrocephalus) and redbellied woodpeckers (Centurus carolinus) are structurally and taxonomically similar species, and exist sympatrically over much of the eastern United States. This study was undertaken to compare the activities of these species and, specifically, to study the spatial, temporal and behavioral segregation that permits their coexistence. An analysis of habitat utilization was undertaken to enumerate environmental factors and more importantly, to quantify their relative importance or degree of utilization. Similar studies of patterns of habitat utilization, particularly in terms of foraging strategies, have been made in recent years by Hartley (1953), Gibb (1954), MacArthur (1958), Root (1967), Morse (1967, 1968), Sturman (1968), Jackson (1970) and Willson (1970). Temporal segregation of the two species was studied by constructing time budgets for each morph-red-heads, male red-bellies and female red-bellies-and investigating how partitioning of time into various behavior patterns was modified by diurnal and seasonal environmental changes. Orians (1961), Verbeek (1964), Verner (1965 ), Smith (1968), and Schartz and Zimmerman (1971) have discussed the importance of maintaining an efficient time budget in terms of reproduction and survival for several species. METHODS AND STUDY AREAS Methods.-In order to observe seasonal changes in the behavioral ecology of red-headed and red-bellied woodpeckers, this study was conducted during an entire year; however, the seasonal fluctuation of local woodpecker populations necessitated changing woods each season and decreased the reliability of seasonal comparisons. Data were continuously recorded in the field, using a time base provided by a portable, electronic metronome that was set to emit tones through an 1 Current address: 200 North Smith Road, Bloomington, Indiana 47401.