Food abundance does not determine bird use of early‐successional habitat

Abstract

Abstract. Few attempts have been made to experimentally address the extent to which temporal or spatial variation in food availability influences avian habitat use. We used an experimental approach to investigate whether bird use differed between treated (arthropods reduced through insecticide application) and control (untreated) forest canopy gaps within a bottomland hardwood forest in the Upper Coastal Plain of South Carolina, USA. Gaps were two-to three-year-old group selection timber harvest openings of three sizes (0.13, 0.26, and 0.50 ha). Our study was conducted during four bird use periods (spring migration, breeding, post-breeding, and fall migration) in 2002 and 2003. Arthropods were reduced in treated gaps by 68% in 2002 and 73% in 2003. We used mist-netting captures and foraging attack rates to assess the influence of arthropod abundance on avian habitat use. Evidence that birds responded to arthropod abundance was limited and inconsistent. In 2002, we generally captured more birds in treated gaps of the smallest size (0.13 ha) and fewer birds in treated gaps of the larger sizes. In 2003, we recorded few differences in the number of captures in treated and control gaps. Foraging attack rates generally were lower in treated than in control gaps, indicating that birds were able to adapt to the reduced food availability and remain in treated gaps. We conclude that arthropod abundance was not a proximate factor controlling whether forest birds used our gaps. The abundance of food resources may not be as important in determining avian habitat selection as previous research has indicated, at least for passerines in temperate subtropical regions.

Perennial Agroenergy Feedstocks as En Route Habitat for Spring Migratory Birds

“…For example, habitat heterogeneity is commonly associated with species richness of fall migrants in forested systems [e.g., 18,19,[42][43][44], and may be particularly important in attracting species with a range of habitat structural preferences to grasslands during fall when within-field heterogeneity is relatively low (fall0 0.35, SD00.18; spring01.0, SD00.53) [this study, and 15 with comparable methodology]. Though seasonal changes in habitat use at the species and community level have been noted in temperate forested systems [42,[45][46][47], they have not been explicitly linked to variation in microhabitat structure.…”

Avian Use of Perennial Biomass Feedstocks as Post-Breeding and Migratory Stopover Habitat

“…The most important within-patch factor explaining variation in avian richness, species density and abundance in both switchgrass and prairie patches was microhabitat heterogeneity (MHET, Table 3, Figure 1b). Avian richness and abundance during the fall migratory period commonly exhibits a strong positive relationship with habitat structural complexity in forested habitats [15], [16], [21], [22], [23], though some studies have reported only weak relationships [17], [24]. This inconsistent relationship might result from the cumulative effects of variable species-specific responses to habitat structure [25].…”

“…Yet, recent experimental evidence suggests that arthropod abundance is not a proximate factor in habitat selection during migration [23]. Because birds are flexible in both their foraging behavior and the foods they select [31], [32], behavioral plasticity can allow migrants to effectively exploit unfamiliar and unpredictable habitats during migration [25].…”

Arthropod Communities Associated with Habitats Occupied by Breeding Swainson's Warblers

“…Even though experimental evidence from bottomland hardwood forests has suggested that abundance of food resources is not a proximate cue for habitat use (Champlin et al 2009), food still may be a limiting factor. Indeed, increased food abundance is associated with decreased territory size for other ground-foraging warblers (Smith and Shugart 1987).…”