Threshold Responses of Forest Birds to Landscape Changes around Exurban Development

Marcela Suarez-Rubio,Peter Leimgruber,Todd Lookingbill,Scott Wilson,Justin G Boyles

doi:10.1371/journal.pone.0067593

Abstract

Low-density residential development (i.e., exurban development) is often embedded within a matrix of protected areas and natural amenities, raising concern about its ecological consequences. Forest-dependent species are particularly susceptible to human settlement even at low housing densities typical of exurban areas. However, few studies have examined the response of forest birds to this increasingly common form of land conversion. The aim of this study was to assess whether, how, and at what scale forest birds respond to changes in habitat due to exurban growth. We evaluated changes in habitat composition (amount) and configuration (arrangement) for forest and forest-edge species around North America Breeding Bird Survey (BBS) stops between 1986 and 2009. We used Threshold Indicator Taxa Analysis to detect change points in species occurrence at two spatial extents (400-m and 1-km radius buffer). Our results show that exurban development reduced forest cover and increased habitat fragmentation around BBS stops. Forest birds responded nonlinearly to most measures of habitat loss and fragmentation at both the local and landscape extents. However, the strength and even direction of the response changed with the extent for several of the metrics. The majority of forest birds’ responses could be predicted by their habitat preferences indicating that management practices in exurban areas might target the maintenance of forested habitats, for example through easements or more focused management for birds within existing or new protected areas.

Highlights

The expansion of human settlement along the urban-rural fringe has received considerable global attention in recent decades [1,2,3,4,5]
In the Mid-Atlantic region of the United States, the dispersed, isolated housing units typical of exurban areas are embedded within a forest matrix, often close to protected areas [7] and natural amenities [8,9]
We focused on 11 forest-nesting passerine species whose habitat preferences included forest –Ovenbird (Seiurus aurocapilla), Redeyed Vireo (Vireo olivaceus), American Redstart (Setophaga ruticilla), Wood Thrush (Hylocichla mustelina), Scarlet Tanager (Piranga olivacea), Eastern Wood-Pewee (Contopus virens), Eastern Phoebe (Sayornis phoebe); and forest-edge –Eastern Towhee (Pipilo erythrophthalmus), Gray Catbird (Dumetella carolinensis), Northern Cardinal (Cardinalis cardinalis), and Indigo Bunting (Passerina cyanea) [52]

Summary

Introduction

The expansion of human settlement along the urban-rural fringe has received considerable global attention in recent decades [1,2,3,4,5]. In the United States, conversion of privately owned rural lands into low-density residential development (i.e., exurban development) has increased five- to sevenfold between 1950 and 2000 [6]. Humans generally remove natural habitats by building settlements, which can serve to fragment the landscape [12,13,14]. Both habitat loss and fragmentation modify the spatial pattern of remnant habitats, creating smaller and isolated fragments, compromising habitat quality and quantity. Possible reasons for long-term reductions of forest-bird species in these environments include predation [19], brood parasitism [20], and competition with human-adapted species [21]. Forest birds have been shown to be susceptible to human settlement even at housing densities as low as 0.095 house/ha [22,23,24,25,26,27]

Objectives

Methods

Results

Conclusion