The ecological and evolutionary ramifications of habitat selection for the population dynamics of Prothonotary Warblers (Protonotaria citrea) were examined by evaluating specific factors affecting choice of habitat by the warblers, and testing the predictions of habitat selection theories proposed by Fretwell and Lucas (1970). Seven study plots were established along the Tennessee River in west—central Tennessee between 1987 and 1989. Each plot consisted of 80 nest boxes in a 20 column $\times$ 4 row grid, with one row placed along shoreline over standing water (flooded habitat), and three parallel rows placed inland at 35—m intervals (dry habitat). Flooded and dry habitats differed in vegetative structure and species composition, and flooded habitat contained more natural nest sites, higher arthropod abundances, and fewer species competing for nest sites than did dry habitats. Warblers settled preferentially in flooded habitat, where breeding density was higher than in dry habitat. When predation effects were excluded, birds in flooded habitat fledged more young per nest and made more nesting attempts than did birds in dry areas. With predation included, no significant differences in breeding success in the two habitats were found. Distribution of breeding warblers across wet and dry habitats followed the “ideal dominance” model of Fretwell and Lucas (1970), with older and larger males excluding younger and smaller ones from flooded areas. Territoriality in Prothonotary Warblers apparently serves to limit breeding density and to maximize breeding success within preferred habitat.

Ecological indicators for long‐term monitoring programs are needed to detect and assess changing environmental conditions. We developed and tested community‐level environmental indicators for monitoring forest bird populations and associated habitat. We surveyed 197 sampling plots in loblolly–shortleaf pine forests, spanning an area from Georgia to Virginia ( U.S.A.) and representing a gradient in levels of anthropogenic disturbance. Ninety of these plots were randomly selected from a sampling grid, permitting quantitative assessment of cumulative distribution functions for bird community and habitat parameters. Species were independently classified into habitat assemblages indicating birds typical of disturbed habitat (e.g., shrubland, forest edge) and undisturbed habitat (mature forest). Relative abundances of these assemblages were used to form a bird community index—similar to the index of biotic integrity applied to aquatic systems—showing the effects of habitat disturbance on forest bird communities. Bird communities on the majority of the sample area (52–75%, 90% confidence interval) were dominated by disturbance‐tolerant species. Sites dominated by mature‐forest species were comparatively uncommon. Habitat assemblages appeared to be particularly useful tools for environmental monitoring; individual species abundance was positively correlated with assemblage species richness, and assemblage members showed consistent responses to variations in disturbance level. To a lesser extent, component species of nesting guilds showed this pattern of cohesive responses, but those of foraging guilds did not. We also developed a habitat index based on habitat variables that predicted bird community index values. Habitat and bird community indices were strongly correlated in an independent validation dataset, suggesting that the habitat index can provide a reliable predictor of bird community status. The two indices may be used in combination, with the bird community index providing a direct measure of the status of the bird community and the habitat index providing a basis on which to separate changes in the bird community into local habitat effects versus other factors (e.g., landscape level effects, changes on wintering grounds).

1999. Bird communities of natural and modified habitats in Panama. Ecography 22; 292-304.Only a small proportion of land can realistically be protected as nature reserves and thus conservation efforts also must focus on the ecological value of agroecosystems and developed areas surrounding nature reserves. In this study, avian communities were surveyed in 11 habitat types in central Panama, across a gradient from extensive forest to intensive agricultural land uses, to examine patterns of species richness and abundance and community composition. Wooded habitats, including extensive and fragmented forests, shade coffee plantations, and residential areas supported the most species and individuals. Nearctic-Neotropical migratory species were most numerous in lowland forest fragments, shade coffee, and residential areas. Introduced Pinu.s carihhea and sugar cane plantations supported the fewest species compared to all other habitats. Cattle pastures left fallow for less than two years supported more than twice as many total species as actively grazed pastures, such that species richness in fallow pastures was similar to that found in wooded habitats. Community similarities were relatively low among all habitat types (none exceeding the observed b5% similarity between extensive and fragmented lowland forests), but communities in shade coffee and residential areas were 43% and 54' M> similar to lowland forest fragments, respectively. Fallow pastures and residential areas shared 60% of their species. Bird communities in shade coffee and residential areas were characterized by higher proportions of frugivorous and nectarivorous species than in native forests. These same guilds also were better represented in fallow than in grazed pastures. Raptors and piscivorous species were most prevalent in cattle pastures and riee fields. These results, though based upon only species richness and abundance, demonstrate that many human-altered habitats have potential ecological value for birds, and conservation efforts in tropical areas should focus greater attention on enhancement of agricultural and developed lands as wildlife habitat. To understand the true conservation value of these modified lands will require examination not only of numbers but also of the types of species supported by these habitats, their reproductive output and survival rates.