Territorial Movements of Black-throated Blue Warblers in a Landscape Fragmented by Forestry

—Many forest bird species show inhibition to entering open areas, including crossing habitat gaps. We examined the responses of Blackthroated Blue Warblers (Dendroica caerulescens) to conspecific song playback within forest, at clearcutforest ecotones, and across logging roads to assess movements of this Neotropical migrant into open areas. Males responded readily to song playbacks in all areas, and moved significantly farther into clearcuts than they did within intact forest (40.4 2.9 m and 17.1 1.2 m, respectively). Their singing, aggressive trilling, and alarm-calling rates were highest in response to playback from clearcuts, intermediate during road-crossings, and lowest within forest. Males moved farthest into the oldest regenerating clearcuts ( 15 years old), indicating that vegetation structure also influences their movement into open areas. Second-year males were more responsive than older males, moving farther to reach speakers in all areas, and showing a nonsignificant trend of moving farther into clearcuts. We found that extensive movements into open areas occur in response to simulated territorial intrusion, indicating that small-scale habitat fragmentation by forestry may not disrupt territorial movements of that species. Understanding the abilities of animals to move among habitat types is critical to understanding dispersal and habitat selection, particularly in areas where habitat is not contiguous (Fahrig andMerriam 1994, Wiens 1996). Some studies of forest birds report inhibition of individuals moving into open areas (Sieving et al. 1996, Desrochers and Hannon 1997, Rail et al. 1997, Grubb and Doherty 1999, St. Clair et al. 1999). Clearly, forest songbirds are physically capable of moving into unforested habitats (e.g. Kilgo et al. 1999); therefore, movement inhibition is likely to be behaviorally based (Lynch and Whigham 1984). Most interest in behavioral barriers to movement focuses on its potential to disrupt dispersal (e.g. Villard and Taylor 1994). It is also important to understand how a bird moves in fragmented habitat within the breeding season because it could affect habitat selection, fledgling foraging patterns, and prospecting for future breeding sites (Rail et al. 1997, Reed et al. 1999). Those effects become important to population persistence as forests become increasingly 1 E-mail: [email protected] fragmented, and might be key to the observed declines of some Neotropical migrant species (Askins et al. 1990, Lynch and Whigham 1984). We are particularly interested in understanding the effects of industrial forestry practices on bird populations because they create a habitat mosaic (Hagan and Boone 1997). Considering the territorial requirements of breeding forest birds (Robbins et al. 1989, Wenny et al. 1993), including the potential for increased inhibition of movement during the breeding season (Bentley and Catterall 1997, St. Clair et al. 1998), it is of interest to determine whether forest birds incorporate clearcuts and logging roads into their