Habitat-Specific Demography of Breeding Black-Throated Blue Warblers (Dendroica caerulescens): Implications for Population Dynamics

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The distribution of individuals among habitats and their relative success in those habitats can have important consequences for population dynamics. To examine these processes for a long-distance migratory bird species, we studied the population structure, age-specific reproductive output, and local survival of black-throated blue warblers (Dendroica caerulescens, Gmelin) in two breeding habitats differing in shrub density within northern hardwoods forests in New Hampshire, USA. 2. On forest plots with dense shrubs, warblers occurred at higher densities, and fledged significantly more young per capita per season than those occupying areas with lower shrub density. This differential productivity was due to higher reproductive output, mainly through double-brooding, of older (> 2 years of age) individuals, which were disproportionately more abundant in high shrub density sites. 3. Clutch initiation dates, clutch sizes, and predation rates at individual nests did not differ significantly between habitats. Mean body mass of nestlings on day 6 following hatching were higher on average on plots with high shrub density, but differences were not significant. 4. Annual return rates, as indices of local survival, did not differ between habitats for older males or for females. Yearling males, however, returned in subsequent years at a significantly lower rate to low shrub density plots, a result of either lower survival or, more likely, dispersal to more suitable habitat in their second year of breeding. 5. Parental age and habitat suitability interact in that older individuals, through their experience and/or dominance, acquire sites of higher quality, which results in higher reproductive output and probably higher survival. These differences between habitats in density, reproductive performance and local survival are consistent with an idealdespotic/preemptive distribution of individuals, and suggest that this population could be regulated by the availability, distribution, and extent of high and low quality breeding habitats.

Social information trumps vegetation structure in breeding-site selection by a migrant songbird

“…We chose fledgling presence as the most likely public information cue, instead of nestling condition and abundance, because unlike cavity nesters (Doligez et al 2002), nest failure rates are high in this species (approx. 0.50; Holmes et al 1996), so nestling number and condition would probably be poorly correlated with reproductive success. Both calls and songs used in our playbacks were recorded locally in the same year as the experimental treatments.…”

“…We chose black-throated blue warblers as our study species because their habitat requirements have been studied extensively (Holmes et al 1996;Rodenhouse et al 2003), they are specialized in their habitat use (Doran & Holmes 2005) and the structure of their mature hardwood forest habitat is relatively stable between years (Holmes et al 1996). Also, there is correlative evidence that this species aggregates, which suggests that individuals may use others as cues to locate suitable habitat (Betts et al 2006).…”

Matrix mediates avian movements in tropical forested landscapes: Inference from experimental translocations

“…The lower return probability of todies may be explained in part by a greater proportion of female todies (26.4%) translocated than female redstarts (15.7%), which may have been less site-faithful. The age of individuals or their pairing status (e.g., Greenwood and Harvey, 1982;Holmes et al, 1996) may also underlie why fewer todies returned -if we translocated juveniles and/or siblings acting as helpers on territories (this type of communal breeding has been documented for the congener T. mexicanus; Raffaele et al, 1998). The ultimate reason(s) todies failed to return to capture sites within the 3-month survey period is thus unknown -whether due to mortality during dispersal (i.e., predation), behavioral decisions to settle in new locations, and/or an inability to orient successfully to territories after displacement.…”

“…Female birds are typically more dispersive than males (e.g., Greenwood and Harvey, 1982). Birds inhabiting lower quality habitats may be less site-tenacious (e.g., Holmes et al, 1996), and individuals in reduced condition may be less prone to return to territories (e.g., Marra and Holmes, 2001) or less able to withstand physiological costs associated with translocation. Because homing abilities of our study species are unknown, we investigated the potential influence of sex, body condition, and territory habitat quality on return patterns.…”

Experimental food supplementation reveals habitat-dependent male reproductive investment in a migratory bird

“…Environmental effects on extrapair mating have traditionally been ascribed to aspects of the social environment often correlated with habitat quality [12 -15]. For example, black-throated blue warblers occur at higher breeding densities in higher quality habitat [46], and habitat quality tends to increase from low to high elevations at Hubbard Brook [24]. We designed our experiment to separate the effects of food availability on patterns in extrapair mating across the distribution of habitat quality.…”