Dendroica Nigrescens Research Articles

Integrative phylogeography and ecological niche analysis reveal insight into the evolutionary history and taxonomy of the Black-throated Gray Warbler (Setophaga nigrescens)

Integrative phylogeography and ecological niche analysis reveal insight into the evolutionary history and taxonomy of the Black-throated Gray Warbler (Setophaga nigrescens)

A bird’s eye view of ecosystem conversion: Examining the resilience of piñon-juniper woodlands and their avian communities in the face of fire regime change

Climate change and land-use legacies have caused a shift in wildfires and post-fire growing conditions. These changes have strong potential to diminish the resilience of many ecosystems, with cascading effects and feedbacks across taxa. Piñon-juniper (PJ) woodlands are a diverse and widespread forest type in the western US and are home to many obligate and semi-obligate bird species. As such, this system is ideal for understanding wildfire resilience, or lack thereof, in terms of both vegetation and wildlife associations. This study evaluated post-fire vegetation structure and associated avian communities following three wildfires; one that burned one year prior to sampling (recent fire), and two that burned approximately 25 years previously (old fires). Vegetation characteristics and the habitat use of PJ-associated bird species were compared across severely burned patches, unburned refugia, and unburned sites outside of the burn perimeter. We expected wildfire to alter vegetation and bird usage for the first few years post-fire, which we observed in our recent burns. However, even 25-years post-fire, little recovery to PJ woodland had occurred and the associated bird communities had not returned, compared to unburned areas. No piñon regeneration was observed in any burned areas and no juniper regeneration in the recent fire. Piñon seedling densities in unburned sites and refugia averaged 80 ha−1 and 151 ha−1, respectively, while juniper seedling densities were 220 ha−1 in both habitat types. Habitat use for thirteen PJ-associated species were modeled, three of which (Woodhouse’s Scrub Jay, Ash-throated Flycatcher, and Virginia’s Warbler) used all habitats. Four species (American Robin, Gray Vireo, Black-throated Gray Warbler, and Gray Flycatcher) were essentially absent from the old burn habitat, reflecting species-specific need for mature piñon or juniper trees and/or greater canopy cover. Conversely, birds that were present in the old burn habitat (including Virginia’s Warbler, Blue-gray Gnatcatcher, Woodhouse’s Scrub-jay, Ash-throated Flycatcher, and Spotted Towhee) are typically associated with habitat edges, high shrub cover, or cavity nests. Altered vegetation structure and bird habitat use in burned areas 25 years post-fire are evidence for enduring conversion to non-forest vegetation types. However, unburned refugia embedded in burned areas maintain forest attributes and support obligate bird communities, supporting ecological function and biological diversity.

Geographic Variation in Type I Songs of Black-throated Gray Warblers

We studied songs of Black-throated Gray Warblers (Dendroica nigrescens) in a fragmented landscape in southwestern Oregon and northern California where each male sings a single Type I song consisting of two phrases. Fourteen variants of Type I songs were distributed in a complex geographic pattern across 19,400 km2 of the region. Variants differed in number of notes/syllables in the A-phrase (range 2–5), and the B-phrase differed in both the number and structure of syllables. Several variants occurred in well-defined areas and differed from neighboring songs; others overlapped adjacent variants or graded from one form to another across a narrow zone. Distinct variants could be identified, but the diversity of Type I songs and the pattern of distribution throughout the region does not describe a clear system of dialects. Geographic extent of the variants differed considerably; some occurred as small scattered populations occupying <250 km2 while the largest exceeded 3,000 km2. Variants in the most restricted area and having the most fragmented distribution had the least consistent structure among individuals both within local populations and across the range of the variant. Ridges >1,000–1,200 m in elevation served as effective barriers and separated sets of similar song variants. Fire also likely had a role in generation of variants as reflected by multiple variants occurring in areas lacking obvious geographic barriers.

Short‐term responses of birds to prescribed fire in fire‐suppressed forests of California

AbstractPrescribed fire is one tool for restoring fire‐suppressed forests, but application of fire during spring coincides with breeding and arrival of migrant birds. We examined effects of low‐severity prescribed fires on counts of birds in a managed forest in the Sierra Nevada of California immediately, 1 year, and 3–6 years after fire was applied in spring. Of 26 species analyzed, counts of 3 species increased after fire (Pacific‐slope flycatcher [Empidonax difficilis], brown creeper [Certhia americana], and American robin [Turdus migratorius]), and 6 species decreased after fire (Anna's hummingbird [Calypte anna], Hutton's vireo [Vireo huttoni], warbling vireo [Vireo gilvus], golden‐crowned kinglet [Regulus satrapa], Nashville warbler [Vermivora ruficapilla], hermit warbler [Dendroica occidentalis]). Black‐throated gray warbler (Dendroica nigrescens) increased in the first year following fire but decreased 3–6 years after fire. When grouped into guilds, habitat association and foraging guild best explained responses to fire, with the greatest changes occurring for oak‐associated species (negative), riparian‐associated species (positive), aerial foragers (positive), and bark foragers (positive). Lastly, when we compared our counts to those collected during the 1910s, changes were consistent with those predicted from fire suppression and species' affinity for burned forests, suggesting that results from contemporary fire studies should be interpreted within an ecological context that includes effects of fire suppression. We found that low‐severity prescribed fires applied in spring served to drive the bird community towards pre‐suppression conditions. © 2011 The Wildlife Society.

RESPONSE OF BIRDS TO THINNING YOUNG DOUGLAS‐FIR FORESTS

Silvicultural practices, such as thinning, are increasingly performed both for commodity production and to help achieve biodiversity goals and promote ecological restoration. However, relatively little research has examined effects of thinning conifer forests on vertebrates. We experimentally manipulated stands using a randomized block design to evaluate influences of two thinning intensities on populations of diurnal breeding birds in western Oregon. We conducted point counts of birds seven times each year in 1994 (prior to treatment) and from 1995 through 2000 (subsequent to treatment). We analyzed data using multiple linear regression and information‐theoretic approaches to model selection. Of the 22 species for which we had sufficient data for analysis, detections of nine species decreased and eight species increased in thinned stands relative to controls, and there was no strong evidence that thinning influenced numbers of five species. Of the 17 species that responded to thinning, the magnitude of response of eight species varied with thinning intensity; for each of these species, response was greatest in the more heavily thinned stands. Although no species was extirpated from stands following thinning, detections of Hutton's Vireos (Vireo huttoni), Golden‐crowned Kinglets (Regulus satrapa), Brown Creepers (Certhia americana), Black‐throated Gray Warblers (Dendroica nigrescens), and Varied Thrushes (Ixoreus naevius) decreased to less than half of the detections in controls in one or more treatment types, suggesting thinning significantly reduces their numbers. In contrast, American Robins (Turdus migratorius), Townsend's Solitaires (Myadestes townsendi), and Hammond's Flycatchers (Empidonax hammondii) were rare or absent in controls but regularly present in thinned stands, and detections of Western Tanagers (Piranga ludoviciana), Evening Grosbeaks (Coccothraustes vespertinus), and Hairy Woodpeckers (Picoides villosus) increased by threefold or more in thinned stands relative to controls. Only Pacific‐slope Flycatchers (Empidonax difficilis), Warbling Vireos (Vireo gilvus), and Western Tanagers showed strong evidence of temporal trends in response. For these species, differences between numbers in controls and treated stands became more extreme through time. Our findings suggest that thinning densely stocked conifer stands in landscapes dominated by younger stands enhances habitat suitability for several species of birds, but that some unthinned patches and stands should be retained to provide refugia for species that are impacted by thinning.

Breeding Bird Response to Riparian Buffer Width in Managed Pacific Northwest Douglas-Fir Forests

We examined the relative importance of riparian vs. upland habitats to breeding birds by comparing species abundance, richness, and similarity of bird communities in managed Douglas-fir forests in western Washington State, USA. We also examined whether forested buffer strips along second- and third-order streams effectively maintain the pre-logging riparian breeding bird community by comparing species abundance, richness, and turnover among three treatments: (1) unharvested controls; (2) sites that were clear-cut, leaving a narrow (∼14 m) forested buffer on both sides of the stream; and (3) sites that were clear-cut, leaving a wide (∼31 m) forested buffer along both sides of the stream. Deciduous trees, berry-producing shrubs, and other deciduous shrubs less common in adjacent upland forest characterized streamside zones. Despite different vegetation features, riparian and upland habitats did not differ in any measures of bird species richness and composition. No species or species group was more abundant in the upland. Neotropical migrants, resident species, and species associated with deciduous trees and shrubs in forested habitats were more abundant in riparian habitats than in adjacent uplands. Total bird abundance and abundance of four species (American Robin [Turdus migratorius], Pacific-slope Flycatcher [Empidonax difficilis], Black-throated Gray Warbler [Dendroica nigrescens], and Winter Wren [Troglodytes troglodytes]) were higher in riparian habitats. Abundance of these riparian associates was correlated with percent cover of berry-producing shrubs and the number of deciduous trees in the canopy. We found that the number of breeding bird species on sites with narrow buffers increased from slightly fewer than controls before harvest to an average of 10 more species than controls after harvest, a change reflected in an average 20% increase in species turnover on narrow-buffer sites relative to controls. Total bird abundance did not differ between treatments and controls. Resident species, those species associated with shrubs in forested habitats and conifer trees, declined on both buffer treatments. Species associated with upland and riparian forests (Black-throated Gray Warbler, Golden-crowned Kinglet [Regulus satrapa], and Brown Creeper [Certhia americana]) decreased in abundance on riparian buffer treatments relative to controls, whereas species associated with open, shrubby habitats (Dark-eyed Junco [Junco hyemalis], Cedar Waxwing [Bombycilla cedrorum], and Song Sparrow [Melospiza melodia]) increased in abundance on one or both riparian buffer treatments. High species turnover on narrow-buffer treatments indicated that buffers <14 m on each side of the stream did not maintain the pre-logging bird community. There was little difference in species turnover or species richness between the wide-buffer treatment and the control, indicating that a 30-m buffer on both sides of second-order and third-order streams maintains most of the pre-logging bird community in the first two years postharvest. The Black-throated Gray Warbler was the only riparian associate to decline on both the narrow- and wide-buffer treatments; its abundance was positively correlated with buffer width, and a buffer ≥45 m wide on each side of second- and third-order streams was needed to support populations at densities found on unharvested controls. To maintain the entire breeding bird community associated with forested riparian habitats in the coastal Northwest, we recommend a minimum buffer of 45 m along both sides of second- and third-order streams. Habitat features such as deciduous trees (Alnus rubra and Acer macrophyllum) and berry-producing shrubs (especially Rubus spectabilis) appear to be important and should be maintained within forested riparian buffer strips. This study documents short-term effects of riparian treatments on the breeding bird community, which may take several years to respond to habitat manipulations. Thus, we recommend continued monitoring to assess long-term effects of buffer width reduction.

Habitat Preferences of Pinyon-Juniper Specialists Near the Limit of Their Geographic Range

Abstract We investigated habitat preferences for five pinyon-juniper specialists during the 1998 and 1999 breeding seasons in Utah juniper (Juniperus osteosperma) woodlands of southwestern Wyoming. We compared avian use and availability of vegetation features using univariate and multivariate analysis to detect selection for vegetative features of pinyon-juniper specialists near the northeastern range boundary of pinyon-juniper habitat on the Colorado Plateau. Gray Flycatchers (Empidonax wrightii), Juniper Titmice (Baeolophus griseus), and Bewick's Wrens (Thryomanes bewickii) preferred woodlands with high overstory juniper cover. The Juniper Titmouse was associated with senescent trees, Blue-gray Gnatcatcher (Polioptila caerulea) with rock outcrops and shrubs in the family Rosaceae, and Black-throated Gray Warbler (Dendroica nigrescens) with pinyon pine (Pinus edulis). We suggest the geographic distribution of four of five pinyon-juniper specialists is limited by the occurrence of pinyon pine in semiarid woodlands on the northeastern Colorado Plateau. The geographic limit for Blue-gray Gnatcatchers in this region may correspond to the presence of mountain mahogany in the woodland understory. The conservation of pinyon-juniper specialists in southwestern Wyoming will benefit from the maintenance of successional processes, particularly those that perpetuate mature woodlands with a pinyon pine component.

HABITAT PREFERENCES OF PINYON-JUNIPER SPECIALISTS NEAR THE LIMIT OF THEIR GEOGRAPHIC RANGE1

Abstract We investigated habitat preferences for five pinyon-juniper specialists during the 1998 and 1999 breeding seasons in Utah juniper (Juniperus osteosperma) woodlands of southwestern Wyoming. We compared avian use and availability of vegetation features using univariate and multivariate analysis to detect selection for vegetative features of pinyon-juniper specialists near the northeastern range boundary of pinyon-juniper habitat on the Colorado Plateau. Gray Flycatchers (Empidonax wrightii), Juniper Titmice (Baeolophus griseus), and Bewick's Wrens (Thryomanes bewickii) preferred woodlands with high overstory juniper cover. The Juniper Titmouse was associated with senescent trees, Blue-gray Gnatcatcher (Polioptila caerulea) with rock outcrops and shrubs in the family Rosaceae, and Black-throated Gray Warbler (Dendroica nigrescens) with pinyon pine (Pinus edulis). We suggest the geographic distribution of four of five pinyon-juniper specialists is limited by the occurrence of pinyon pine in semiarid ...

A New Hybrid Warbler (Dendroica Nigrescens × D. Occidentalis) and Diagnosis of Similar D. Townsendi × D. Occidentalis Recombinants

Abstract We use 13 color characters to describe the first known Dendroica nigrescens × D. occidentalis hybrid. Because this specimen was collected in the southeastern Cascade Mountains of Washington during the breeding season, D. townsendi, D. occidentalis, and D. nigrescens are the only plausible parents for a hybrid male falling within the black-throated clade of Dendroica warblers. Multiple character states in the hybrid refute the alternative parental combinations, townsendi × occidentalis and townsendi × nigrescens. Two characteristics of this hybrid suggested further tests of the parentage of 38 problematic hybrids that were treated previously as townsendi × occidentalis recombinants by assumption only. These hybrids lack yellow on their breast, the only character that refutes a nigrescens × occidentalis parentage. The new hybrid is intermediate between nigrescens and occidentalis in the color of its posterior face and its anterior crown; thus, we scored these new characters in the 38 problematic hybrids. None of these 38 specimens was intermediate or white in either of these regions, and there was no correlation between having tinges of white in these regions and the extent of flank streaking. These results fail to support nigrescens in the parentage of these 38 specimens; furthermore, none of the problematic hybrids carried a nigrescens mitochondrial DNA haplotype. Thus, we conclude that all are unusual recombinants of townsendi × occidentalis hybridization, rather than nigrescens × occidentalis hybrids.

A NEW HYBRID WARBLER (DENDROICA NIGRESCENS × D. OCCIDENTALIS) AND DIAGNOSIS OF SIMILAR D. TOWNSENDI × D. OCCIDENTALIS RECOMBINANTS

Abstract We use 13 color characters to describe the first known Dendroica nigrescens × D. occidentalis hybrid. Because this specimen was collected in the southeastern Cascade Mountains of Washington during the breeding season, D. townsendi, D. occidentalis, and D. nigrescens are the only plausible parents for a hybrid male falling within the black-throated clade of Dendroica warblers. Multiple character states in the hybrid refute the alternative parental combinations, townsendi × occidentalis and townsendi × nigrescens. Two characteristics of this hybrid suggested further tests of the parentage of 38 problematic hybrids that were treated previously as townsendi × occidentalis recombinants by assumption only. These hybrids lack yellow on their breast, the only character that refutes a nigrescens × occidentalis parentage. The new hybrid is intermediate between nigrescens and occidentalis in the color of its posterior face and its anterior crown; thus, we scored these new characters in the 38 problematic hy...

Temporal Variation in Resource Use by Black-Throated Gray Warblers

We studied foraging behavior and habitat use of male and female Black-throated Gray Warblers (Dendroica nigrescens) to quantify the effects of temporal variation on interpretations of avian resource use. Overall, both sexes primarily foraged by gleaning in single-leaf pinyon pine (Pinus monophyla); however, within-season and between-year variation in behavior and habitat use were found for both sexes. Warblers increased use of shrubs from May to mid-June, and decreased use of shrubs and increased use of pinyon pine from mid-June through August, during each year. Use of sagebrush (Artemisia tridentata) and Utah juniper (Juniper osteosperma) varied between years. Sex differences were found in proportional use of foraging maneuvers. Within-season shifts in plant species and habitat use corresponded to changes in arthropod numbers on the plant species used by the warblers, but between-year shifts in behavior did not correspond as closely with changes in arthropod numbers. Temporal variation in microhabitat use resulted from shifts within seasons in the plant species used for foraging, which was associated with temporal changes in food abundance. Our results also demonstrate the importance of considering the effects of temporal scale in studies of bird-resource interactions.

Effects of stream size on bird community structure in coastal temperate forests of the Pacific Northwest, U.S.A.

Abstract. Vegetation and spring breeding bird populations associated with riparian forests on high and low order rivers of the Olympic peninsula, Washington (USA), were censussed in 1990 and 1991. The objectives were to (1) provide a baseline description of bird communities associated with unmanaged riparian forests, (2) determine whether there is a difference between bird communities along large and small rivers, and (3) identify what biophysical aspects of the fluvial corridor are most important in determining bird community structure. The approach was to link riparian bird community structure to river order and discuss relationships to vegetation, geomorphology and associated hydrologic disturbance regimes.Large rivers tended to have more deciduous vegetation than small rivers (P = 0.07). Deciduous vegetation and patch types appeared to be linked to river size through stream valley shape and disturbance history. Bird species richness and abundance were significantly higher (P&lt;0.05) on larger rivers (67–140 m width) than on small rivers (12–21 m width) and were positively correlated with the percentage of deciduous trees present at a site. The data suggest that migrant birds, such as the black‐throated grey warbler (Dendroica nigrescens) and warbling vireo (Vireo gilvus), require large tracts of contiguous hardwoods for successful breeding. Additionally, birds such as the Hammond's flycatcher (Empidonax hammondii) and hairy woodpecker (Picoides villosus) appear to depend on the juxtaposition of hardwoods and conifers during the breeding season. We conclude that bird communities on large rivers differ from those on small rivers and that these differences occur predictably with stream order.

Morphological and Vocal Variation in the Black-Throated Gray Warbler in the Pacific Northwest

Morphological and Vocal Variation in the Black-Throated Gray Warbler in the Pacific Northwest

Black-Throated Gray Warbler - A Saskatchewan First

Black-Throated Gray Warbler - A Saskatchewan First

Nesting Black-Throated Gray Warblers, Dendroica nigrescens, East of the Rocky Mountains

Nesting Black-Throated Gray Warblers, Dendroica nigrescens, East of the Rocky Mountains

Black-Throated Gray Warbler at Miami, Florida

Black-Throated Gray Warbler at Miami, Florida

Black-Throated Gray Warbler on the Coast of South Carolina

Black-Throated Gray Warbler on the Coast of South Carolina

Black-Throated Gray Warbler in Massachusetts

Black-Throated Gray Warbler in Massachusetts

Two Oregon Warblers

D URING the warm days of May when the mystery of life seems suddenly unveiled in a miraculous manner, I often frequent a woody retreat above the old mill dam on Fulton creek. A clump of firs and maples overhang where the limpid water whirls gurgling among the gray rocks. Star flowers gleam from the darker places of shade, white anemones are scattered among grass blades and ferns, and Linna~an bells overhang the moss-covered logs. This is the haunt of the black-throated gray warbler. a Just below the brow of the hill half a mile above the creek, a little spring bubbles out of an alder copse. Instead of trickling down the hillside like an ordinary streamlet, the water scatters and seeps into the spongy soil. This forms a wet place an acre or so in extent over which has grown a rich growth of swamp grass. This is the yellow-throat'sb home. I call it the Witch's Garden. I have a great admiration for the little feathered individual dressed in gray because his extreme shyness is a good indication of his finer nature. But there is a fascination about lying in the shade of the tall fir and listening to the fanciful call of yellow-throat. You may hear him and his mate almost any time of the day calling Witch-et-y! Witch-et-y ! Yes, you may hear him but seldom see him.

Notes on the Black-Throated Gray Warbler

Notes on the Black-Throated Gray Warbler