This research examined how song is used to transmit information on individual identity in American redstarts (Setophaga ruticilla). Specifically, it attempted to determine whether American redstarts (1) discriminate between neighbors and strangers on the basis of their respective songs, and (2) recognize individuals by their distinctive voice characteristics. I tested the latter by exposing subjects to identical song types sung by different birds. Each subject's behavior was evaluated according to a variety of response variables. In all trials, for all response variables, subjects responded highly but equally to each of the songs played. A post-hoc analysis revealed that the order in which treatment songs were presented affected the birds' responses. For four of five response variables, subjects successfully distinguished between the songs of neighbors and strangers when played the fourth song in the trial. Thus, it would appear that in redstarts this type of discrimination may be observed only after an initial song-exposure period.

No description available.

The occurrence of three reproductive tactics in a population of American redstarts was estimated: extra-pair fertilization, egg-dumping, and male polyterritoriality. Using DNA fingerprinting we show that none of 108 nestlings samples were the result of egg dumping. In contrast, 40% of nestlings were the result of extra-pair fertilizations. Males sired a greater proportion of their broods as they aged. In addition, promiscuous females were never fertilized by males that were younger than their social mates. Whether the poor reproductive performance of younger males was caused by female preference for older males or by intra-sexual competition was not determined. In any case, females would have benefited by mating with older males, if the traits that allowed the survival of the father were inherited by the females' offspring. Only three of 80 males attracted two females through polyterritoriality. One male fledged two broods: he sired both nestlings from his first brood, but none of the four nestlings from his second brood. We concluded that male redstarts can improve their reproductive success by trying to obtain extra-pair copulations, but less so by establishing a second territory.

No description available.

Differences in patterns of species richness and taxonomic composition across continents are well documented. However, less is known about how these patterns originate from the fundamental processes that contribute to the assembly of continental biotas: speciation, extinction, immigration, and emigration. To truly decipher how these processes operate at a continental scale, it is crucial to understand how Earth-history events and environmental change shaped the biogeographical history of the taxa occurring in a region. The Pleistocene glacial cycles have been hypothesized to be a significant geological event which affected the Earth’s biota over the past three million years. During this period, multiple cycles, in which ice sheets covered a large portion of the Northern Hemisphere, have been hypothesized to facilitate allopatry and ecological differentiation. The central goal of this dissertation is to understand the assembly of continental biotas by integrating the role of Earth’s geological and environmental history and recent (late Quaternary) changes in distributions. Here, I studied the North American wood-warblers, which are passerine birds belonging to the family Parulidae. In the first chapter of this dissertation, I examined the extent to which recent diversification is underestimated by ignoring recently diverged taxa. To do so, I evaluated the effect of taxonomic delimitation on the inferred temporal patterns of diversification of wood-warblers in the genus Setophaga. My results show that species-level taxonomic delimitation in ecological and evolutionary studies is crucially important but is often ignored. Evaluating the effect of taxonomic delimitation in the genus Setophaga is particularly relevant because it has been widely cited as an ideal example of niche saturation, and previous studies suggested that lineages in this particular radiation exhibited an asymptotic accumulation of diversity through time. In this chapter, however, I demonstrate that this pattern was likely a consequence of the ways in which taxonomic diversity was sampled. In the second chapter, I examined how biotic and abiotic factors limit the distribution of species of the genus Oreothlypis at a continental scale. For most of the taxa examined, climatic- and biotic-based areas of suitability were equivalent, and therefore the relative importance of these factors could not be disentangled. However, in some cases, biotic variables limited the distribution in areas climatically suitable, and vice versa. The results of this chapter highlight the importance of considering potential effects of biotic interactions in the study of climate-driven range shifts. This paper is also an important methodological contribution to the general field of ecological niche modeling (ENM) by integrating climatic and palynological data to empirically estimate both abiotically and biotically suitable areas which that has only been done theoretically so far. In the third chapter, I integrated phylogenetic data, biotic and climatic ENMs, and reconstructions of environments during the LGM to test how cycles of fragmentation, differentiation, and expansion during the Pleistocene shaped the biogeographical patterns of the genus Oreothlypis in North America. Based on a time-calibrated phylogeny I identified two groups of taxa that diversified during the last million years and therefore were potentially affected by glacial cycles. My analyses suggest that there were rapid switches in the environmental conditions in which species of the genus occur and that glacial cycles resulted in dramatic range shifts from glacial maxima to interglacials. Distribution patterns during the LGM suggest that divergence in areas isolated by glaciers presumably contributed to the geographical structuring of Oreothlypis, as well as to their taxonomic and ecological diversity in the present. In summary, this work illustrates how wood-warblers are an ideal model system for examining the large-scale history of the North America biota and environment, particularly over the Pleistocene. They are highly diverse, have endemics in virtually all of North America's areas of endemism and ecosystems, and many of these patterns are repeated within and across clades. Furthermore, distributional patterns in warblers show high congruence with those of other organisms; thus inferences made about the history of this group likely have implications for understanding the biotic history of North America in general. In addition, many warblers have narrow ecological preferences in that they occupy forest environments with specific tree compositions. As a consequence, ecological models of their distributions, integrated with the North American pollen record of forest change, provide a new perspective on ecosystem change during glacial cycles, and its impact on the origin and maintenance of biodiversity in the continent.

Habitat fragmentation and isolation can result in decreased occupancy and reproductive success within songbirds, particularly for species inhabiting urban environments where suitable habitat may be limited. The golden-cheeked warbler (Setophaga chrysoparia) is a federally endangered songbird that inhabits oak-juniper (Quercus spp.- Juniperus spp.) across central Texas. Past research on this warbler has indicated decreased patch occupancy near urban areas and negative reproductive effects associated with decreased distance to edge and decreased canopy cover. A rural study indicated warblers occupy patches ≥3 ha, and warblers in patches ≥20 ha are more likely to successfully fledge young. There are no thresholds yet identified for this warbler within urban environments, where effects of habitat fragmentation on reproductive success are more pronounced than within rural environments. I monitored patch occupancy, territory establishment, pairing success, and fledging success of warblers in an urban environment. I determined minimum patch-size thresholds for productivity measurements, and also monitored effects on productivity from canopy cover, woodland composition, distance to and size of the nearest habitat patch, and distance to the nearest habitat patch >100 ha. I compared my results to those from a similar study conducted in a rural system. I compared territory size and territory density between an urban and rural system. Warblers occupied 24% (n = 63) patches surveyed; the smallest patch occupied was 3.5 ha. The smallest patch with an established territory was 10.7 ha, and 10% (n = 63) of habitat patches had at least one established territory. Warblers successfully fledged young in 3 patches, the smallest of which was 26.5 ha. I found patch-size was predictive for territory establishment and pairing success with warblers requiring 13 ha (95% CI: 10.0 – 16.8 ha) and 19 ha (95% CI: 15.7 – 22.6 ha) habitat patches, respectively. I found a minimum threshold of approximately 66% canopy cover (95% CI: 65.2 – 66.4%) required for patch occupancy, and found no warblers established a territory in a habitat patch >25 m from the next nearest patch. I found higher minimum thresholds within an urban system for territory establishment and pairing success than those seen within a rural system. I suggest preserving warbler habitat patches >22 ha that are in close proximity to other habitat patches. This will help to enhance warbler habitat within urban areas and maintain reproductively viable habitat patches, while not halting development completely.

No description available.

As shrubland bird populations decline, there is a critical need to understand the effects of habitat management. I studied a population of color-banded prairie warblers (Setophaga discolor) between 2008-2011 in a shifting mosaic landscape within a Massachusetts inland, pitch pine-scrub oak barren consisting of persistent, newly created, succeeding, and disturbed habitats. I present data showing that the abundance and population structure at this site appears to be a function of colonization of newly created habitat by second-year birds, which are likely excluded from mature early-successional habitat by site-faithful older birds. Breeding season fecundity did not differ significantly between newly-created and mature habitats. Birds displaced by mowing or fire dispersed to nearby suitable habitat the following year, had relatively similar reproductive success, and did not negatively affect pairing or reproductive success in adjacent areas. My findings are novel and show that the effects of shrubland management on shrubland birds are beneficial in the short- and long-term. I also examined prairie warbler nest-site selection and nest survival in relation to plant leafing phenology and other factors. Prairie warblers selected distinct nest sites and certain attributes of these selected sites increased nest survival; thus I conclude that nest-site selection is adaptive. Plant leafing phenology influenced nest-site selection and nest survival in this system; its effects on birds should be considered as a potential mechanism by which bird communities can be affected by global climate change.

The Cerulean Warbler (Setophaga cerulea) is a mature forest obligate and one of the fastest declining songbird species in the United States. This decline may be related to a lack of disturbance within contemporary forests; however, the consequences of disturbance on the species have not been rigorously evaluated. Thus, we assessed multiple responses by Cerulean Warblers to a range of experimental forest disturbances across the core of their breeding range in the Appalachian Mountains. We quantified individual and population responses to these manipulations, and assessed the potential consequences of disturbance on the sexual signaling system. Male ceruleans were strongly attracted to intermediate and heavy disturbances at the stand scale. Despite attraction to disturbed habitats, nest success declined in these conditions, particularly in the highly productive Cumberland Mountains of northern Tennessee. Taken together, these opposing responses suggest that anthropogenically-disturbed forests may act as local ecological traps, but the impact of these local traps on the global population is dependent on several unestimated parameters. At a finer scale, selection for habitat features varied spatially. Males consistently selected for territories near canopy gaps and on productive slopes, but they displayed inconsistent territory selection in regards to tree diameter, basal area, overstory canopy cover, and canopy height. Females were more consistent in their selection of features within territories, selecting nest patches with large, well-spaced trees near disturbances. Floristically, female ceruleans consistently selected for sugar maples (Acer saccharum), white oaks (Quercus alba), and cucumber magnolias (Magnolia acuminata) as nest trees and they selected against red maples (A. rubrum) and red oaks (Q. rubra). Disturbances had little effect on male age structure, but males that occupied disturbed forest habitat were in better condition than those in undisturbed habitat. Parental behavior differed among disturbances, with birds in more highly disturbed habitats provisioning their young at greater rates, but bringing smaller food loads, potentially helping to explain the decrease in nest survival in disturbances. Finally, we found that male ceruleans displayed various plumage ornaments that signaled individual quality. However, the relationship between breast band width and body mass was contingent on habitat, and only existed in intermediate disturbances.