Pine Warbler Research Articles

Pine Warbler (Setophaga pinus Wilson): new record for the state of Durango, Mexico

The Pine Warbler (Setophaga pinus) inhabits eastern North America, where it breeds in the northern USA and Canada, and winters in southeastern USA. In Mexico, the species is considered an irregular winter migrant in the states of Nuevo Leon and Tamaulipas. We report the first record of the Pine Warbler for the state of Durango, in the protected area of the Cañon de Fernandez State Park, municipality of Lerdo. On 8 January 2023 at 11:42 h, a Pine Warbler was observed perched on a cypress tree (Taxodium huegelii), located on the banks of the Nazas River. The bird was on a branch approximately two meters above the ground. This record expands the species’ winter distribution in Mexico. Observations like this are essential for confirming movements of species in time and space during migration, and for documenting changes in the distribution of migratory species.

Nevada Bird Records Committee Report for 2019–2020

In 2019 and 2020, the Nevada Bird Records Committee reviewed 79 reports from the period 4 November 1955 to 23 October 2020. Seventy of them were endorsed. It added three species to the state checklist, the Field Sparrow (Spizella pusilla), Mexican Duck (Anas diazi), and Pine Warbler (Setophaga pinus). Two of those (the Field Sparrow and Pine Warbler) were added to the review list. The Mexican Duck was elevated from subspecies to species status, and it, along with six other species, were removed from the review list. We also continued reviewing records that precede the committee’s establishment in 1994.

Effects of pine-oak woodland restoration on breeding bird densities in the Ozark-Ouachita Interior Highlands

Restoration is underway to restore lost or degraded remnants of savanna and woodland in the Midwestern United States in the hopes of restoring floristic and wildlife diversity. Information is needed on the effects of pine savanna-woodland restoration on bird abundance to inform management decisions. We conducted point-count surveys for 19 bird species across the gradient of savanna, woodland, and forest in restored and non-restored areas throughout the Ozark-Ouachita Highlands in parts of Missouri, Arkansas, and Oklahoma during the 2013–2015 breeding seasons. We estimated densities of 16 species using distance sampling to account for detection probability, and we determined relationships of bird abundance with management and vegetation variables by evaluating support for a priori models. Densities of early-successional and generalist species were positively related, and interior-forest species negatively related, to restoration. Densities of Brown-headed Nuthatch (Sitta pusilla), Eastern Towhee (Pipilo erythrophthalmus), Eastern Wood-Pewee (Contopus virens), Pine Warbler (Setophaga pinus), Prairie Warbler (Setophaga discolor), Red-headed Woodpecker (Melanerpes erythrocephalus), White-eyed Vireo (Vireo griseus), and Yellow-breasted Chat (Icteria virens) were positively related to prescribed fire activity. Blue-winged Warbler (Vermivora cyanoptera), Kentucky Warbler (Geothlypis formosa), and Yellow-breasted Chat densities were positively related to tree thinning. Many species had higher densities in areas with less canopy cover, tree density, and forest cover. Acadian Flycatcher (Empidonax virescens), Black-and-white Warbler (Mniotilta varia), Ovenbird (Seiurus aurocapilla), Wood Thrush (Hylocichla mustelina), and Worm-eating Warbler (Helmitheros vermivorum) were negatively related to one or more aspects of restoration treatment and generally preferred areas with greater tree density and canopy cover. Summer Tanagers (Piranga rubra) were abundant but density was not strongly related to management or vegetation variables. Restoration provided breeding habitat for disturbance-dependent species and woodland generalists, many of which are species of conservation concern, but canopy cover generally remained too great for species that require more open savanna.

Revision of the status of bird species occurring or reported in Colombia 2018

Chilean Flamingo Phoenicopterus chilensis, an Antshrike Thamnophilus sp., Yellow-crowned Elaenia Myiopagis flavivertex and Red-crested Finch Coryphospingus cucullatus are each newly added to the Colombian bird checklist, based on photographic records. Ochraceous Wren Troglodytes ochraceus is added based on a sonogram of an archived sound recording. Red-tailed Tropicbird Phaethon rubricauda, Juan Fernandez Petrel Pterodroma externa, White-chinned Petrel Procellaria aequinoctialis, Tahiti Petrel Pseudobulweria rostrate, Gould's Petrel Pterodroma leucoptera and Lincoln's Sparrow Melospiza lincolnii are each added as unconfirmed based on sight records. Following new publications and a revision, several species are removed from Colombia's checklist: South American Tern Sterna hirundinacea, Christmas Shearwater Puffinus navitatis, White-bellied Storm-Petrel Fregetta grallaria, Bluish-fronted Jacamar Galbula cyanescens, Black-necked Araçari Pteroglossus aracari, Undulated Antshrike Frederickena unduliger, Chestnut-shouldered Antwren Euchrepomis humeralis, Painted Tody-Flycatcher Todirostrum pictum, Roraiman Flycatcher Myiophobus roraimae, Couch's Kingbird Tyrannus couchii and Dotted Tanager Tangara varia. New photographic records allow White-throated Kingbird Tyrannus albogularis and Pacific Parrotlet Forpus coelestis to be promoted from unconfirmed to confirmed status. Short-tailed Field Tyrant Muscigralla brevicauda is returned to confirmed status based on a specimen and further supported by new photographic records presented here. We publish sonograms of archived sound recordings so as to promote Buffthroated Tody-Tyrant Hemitriccus rufigularis and Foothill Schiffornis Schiffornis aenea to confirmed status. Imperial Snipe Gallinago imperialis and Beautiful Treerunner Margarornis bellulus are now known from field observations as well as historical "Bogotá" specimens. Following status revisions, various species are downgraded to unconfirmed status, namely: Galapagos Penguin Spheniscus mendiculus, Little Woodstar Chaetocercus bombus, Black Nunbird Monasa atra, Graychested Greenlet Hylophilus semicinereus, Guianan Gnatcatcher Polioptila guianensis, Pirre Chlorospingus Chlorospingus inornatus, Pine Warbler Setophaga pinus and Palm Warbler Setophaga palmarum (the latter being confirmed on San Andrés and Providencia only, with photographs presented here). We present details of an overlooked specimen record for Colombia and new photographic records of Cape May Warbler Setophaga tigrina and Crimson-breasted Finch Rhodospingus cruentus as well as photographic records of White-bellied Spinetail Mazaria propinqua, Ecuadorian Tyrannulet Phylloscartes gualaquizae and Pink-footed Shearwater Ardenna creatopus, all of which we retain as confirmed species. We present new information on the status of the Mallard Anas platyrhynchos and Feral Pigeon Columba livia as breeding and introduced species. Common Quail Coturnix coturnix is a newly recorded escaped species that lacks evidence of establishment. Island Canary Serinus canaria and Zebra Finch Taeniopygia guttata are now confirmed escapees, due to photographic records. Splits are accepted of Rufescent Antshrike Thamnistes rufescens and Choco Screech-Owl Megascops centralis, with Bogota Sunangel Heliangelus zusii and Colombian Screech-Owl Megascops colombianus no longer recognized as valid species. Several amendments to genus and species names, English names and linear order are made, following recent publications. The Colombian checklist changes to 1,934 species (excluding escapees). Methods for categorizing records and the assessment of the status of species for a national checklist are discussed, in terms of the kinds of records (sight records, photographs, sound recordings, telemetry, specimens, etc), escaped or introduced species and taxonomy. We discuss all identified differences between our list and another recently published checklist of Colombia's birds

English

Abstract. Surface mining transforms landscapes and ecosystem functions through the removal of vegetation and soil. Losses of vegetation correlate with declines, displacement, and transformations of songbird communities. Mine reclamation is a legislative requirement that can influence wildlife communities. The purpose of this study was to examine the avian community responses to mine reclamation practices and, as a proxy, assess the potential benefits and limitations of current reclamation approaches. Avian point counts were carried out at 202 plots on mined and surrounding non-mined areas throughout the Shale Hills Region of Alabama. These mines were reclaimed across a 26 year time-frame and using a variety of reclamation techniques. Six of the thirty-six bird species observed in high enough densities for detailed analysis showed differences of interest between reclaimed and random non-mined sites. Two species showed negative density responses: Carolina Chickadees (Poecile carolinensis), Hooded Warblers (Setophaga citrina). Conversely, densities of Field Sparrows (Spizella pusilla), Gray Catbirds (Dumetella carolinensis), Pine Warblers (Setophaga pinus), and Prairie Warblers (Setophaga discolor) responded positively to mine reclamation. We found that most mine reclamation in the Shale Hills Region of Alabama tended to shift habitat towards open canopy, edge, and grassland habitats. Though our study area tended to have fairly open forest structures (average basal areas around 13 m 2 /ha and average canopy closures around 50%), species that responded negatively were often associated with older sites with more closed canopies. Reclamation techniques should incorporate diverse canopy vegetation and thick mid-story cover to promote more complex vertical forest structure.

Songbird Responses to Land Preservation Within Southern New England Cluster Subdivisions

Cluster subdivisions were designed to protect open space in response to rapid rates of conventional development. One of the proclaimed benefits of preserving open space within cluster subdivisions is the provision of habitat for native wildlife, but this has rarely been evaluated. This study examined songbird response to the amount of land protected within cluster subdivisions in Rhode Island (USA). We selected 11 sites along a gradient based on the relative amount of land protected within a site (% land under a conservation easement; %CE). We used nonparametric multivariate statistics to compare songbird communities between protected and developed areas within subdivisions and regression analyses to relate bird abundance and community metrics to %CE. Songbird communities differed significantly between protected and developed areas within cluster subdivisions. Songbird richness and diversity both peaked between 73-74 %CE, while densities of forest interior and human intolerant species increased with increasing %CE. Ovenbird, Veery, and Pine Warbler most typified high %CE sites and were found most often in protected areas far from development edges. This study demonstrates that cluster subdivisions need to preserve approximately 70-75% of the original undeveloped parcel of land in order to maximize songbird diversity. A higher percentage should be preserved in large contiguous blocks to further benefit forest interior species. This suggests that proposed regulations that require Rhode Island subdivisions to protect at least 50% of a parcel’s buildable land may not be adequate to enhance bird diversity or preserve species that depend on large contiguous blocks of forest interior habitat.

Use and characteristics of two singing modes in Pine Warblers

Abstract North American wood-warblers (Parulidae) are well known for exhibiting two distinct singing modes: first category song, in which a single song type is sung repeatedly, usually before dawn, and second category song, in which several song types are sung in irregular sequence. Studies suggest that first category song types have higher performance characteristics and that second category song types are shared preferentially among territorial neighbors. Here we present the first formal description of two-category singing in the Pine Warbler (Setophaga pinus). Similar to other species in the genus Setophaga, Pine Warblers produce second category song before dawn and first category song primarily during daylight hours. First category songs also had significantly higher trill rates, suggesting that they are more challenging to perform. Unlike many congeners, however, Pine Warblers regularly alternate between first and second category singing throughout the day, and first category song types often appear ...

Long‐term changes in spatial distribution of birds responding to a group‐selection timber harvest

AbstractWe investigated the spatial response of 20 bird species to a group‐selection timber harvest within a 40‐ha forest stand over a 20‐year period (5 yr preharvest and 15 yr postharvest). To characterize the spatial response of each species, we examined trends in 3 metrics: proportion of harvest‐created canopy‐gap area that occurred within the area used by a species in each year, average distance to the nearest gap of all observations of a species in a year, and distribution of distances between observations and gaps for each species in each year. Eight species (eastern wood‐pewee [Contopus virens], winter wren [Troglodytes troglodytes], hermit thrush [Catharus guttatus], Nashville warbler [Vermivora ruficapilla], black‐and‐white warbler [Mniotilta varia], pine warbler [Dendroica pinus], common yellowthroat [Geothlypis trichas], and white‐throated sparrow [Zonotrichia albicollis]) responded positively to the timber harvest (i.e., the proportion of gaps in their area of use increased, the distance from gaps decreased, and their use of gaps and edges [0–25 m from gaps] increased). In contrast, veeries (Catharus fuscescens), black‐throated green warblers (Dendroica virens), and ovenbirds (Seiurus aurocapillus) avoided gaps and edges. Changes in spatial distributions were generally short‐lived; by 15 years postharvest the use of the harvested areas by nearly all species had approached preharvest levels. The spatial response of birds to group‐selection timber harvesting indicates that there are unlikely to be serious long‐term effects of the harvest on forest bird populations. However, there may be more subtle, short‐term effects, such as crowding of mature‐forest bird species into surrounding forest, which merit further study. © 2012 The Wildlife Society.

Width of riparian buffer and structure of adjacent plantations influence occupancy of conservation priority birds

Conservation of biodiversity on forest landscapes dominated by plantations has become an increasingly important topic, and opportunities to maintain or enhance biodiversity within these forests need to be recognized and applied. Riparian buffers of mature forest retained along streams in managed forest landscapes offer an opportunity to enhance biodiversity across these landscapes. However, influence of buffer width and structure of adjacent plantations on habitat use by birds is not well understood. We modeled probability of occupancy, while accounting for variable detection probabilities, for 16 bird species of regional conservation importance in the Ouachita Mountains of Arkansas, USA. We examined occurrence of breeding birds in streamside management zone (SMZ) buffers embedded in three structural classes of pine plantation: young open-canopy, closed-canopy, and older thinned plantations. Our occupancy models included a positive association with SMZ width for nine bird species associated with mature forests. Models for three early successional species (prairie warbler [Dendroica discolor], white-eyed vireo [Vireo griseus], and northern bobwhite [Colinus virginianus]) included a negative association with SMZ width. Occupancy models for Acadian flycatcher (Empidonax virescens), summer tanager (Piranga rubra), pine warbler (Dendroica pinus), prairie warbler, and northern bobwhite also included structural condition of adjacent plantations, but most species did not appear affected by condition of surrounding plantations. We found diverse responses among species to width of retained SMZs and structure of adjacent plantations; some species apparently benefitted from SMZs >100 m wide, while others benefitted from narrow buffers. Furthermore, most species traditionally associated with mature forests were common in narrow SMZs, regardless of width. Thus, optimal width of SMZs relative to avian conservation depends on the species of greatest conservation interest.

Change in avian abundance predicted from regional forest inventory data

An inability to predict population response to future habitat projections is a shortcoming in bird conservation planning. We sought to predict avian response to projections of future forest conditions that were developed from nationwide forest surveys within the Forest Inventory and Analysis (FIA) program. To accomplish this, we evaluated the historical relationship between silvicolous bird populations and FIA-derived forest conditions within 25 ecoregions that comprise the southeastern United States. We aggregated forest area by forest ownership, forest type, and tree size-class categories in county-based ecoregions for 5 time periods spanning 1963–2008. We assessed the relationship of forest data with contemporaneous indices of abundance for 24 silvicolous bird species that were obtained from Breeding Bird Surveys. Relationships between bird abundance and forest inventory data for 18 species were deemed sufficient as predictive models. We used these empirically derived relationships between regional forest conditions and bird populations to predict relative changes in abundance of these species within ecoregions that are anticipated to coincide with projected changes in forest variables through 2040. Predicted abundances of these 18 species are expected to remain relatively stable in over a quarter (27%) of the ecoregions. However, change in forest area and redistribution of forest types will likely result in changed abundance of some species within many ecosystems. For example, abundances of 11 species, including pine warbler ( Dendroica pinus), brown-headed nuthatch ( Sitta pusilla), and chuck-wills-widow ( Caprimulgus carolinensis), are projected to increase within more ecoregions than ecoregions where they will decrease. For 6 other species, such as blue-winged warbler ( Vermivora pinus), Carolina wren ( Thryothorus ludovicianus), and indigo bunting ( Passerina cyanea), we projected abundances will decrease within more ecoregions than ecoregions where they will increase.

Nomenclatural History and a New Name for the Blue-winged Warbler (Aves: Parulidae)

Abstract Linnaeus (1766) proposed Certhia pinus based on two different entities, the Blue-winged Warbler (Vermivora pinus) and the Pine Warbler (Dendroica pinus). The confusion was noted by Wilson (1808–1814) who restricted Latham's (1790) Sylvia pinus, based on C. pinus, to the Pine Warbler (in 1811) and proposed, as a new species (in 1810), S. solitaria, for the Blue-winged Warbler. Wilson's effective lectotypification, long ignored, following which Bonaparte (1824) unequivocally restricted C. pinus to the Pine Warbler, has resulted in misapplication of C. pinus. The correct name of the Pine Warbler should be Dendroica pinus (Linnaeus) and not D. pinus (Wilson) as in modern lists. Wilson's Sylvia solitaria is unfortunately preoccupied by Sylvia solitaria Lewin 1808 ( = Origma solitaria, the Rockwarbler of Australia). A new scientific name is provided here for the Blue-winged Warbler because no other is available.

Songbird response to experimental retention harvesting in red pine ( Pinus resinosa) forests

Traditional harvesting practices frequently result in simplification of the structure and composition within managed forest stands in comparison to their natural counterparts. In particular, loss of heterogeneity within stands may pose a problem for maintaining biodiversity in perpetuity. In this study, we survey breeding bird diversity and abundance in response to different spatial harvesting patterns in mature red pine forests located on the Chippewa National Forest of northern Minnesota, USA. Treatments are designed to increase structural complexity over time and include three overstory manipulations (dispersed retention, aggregate retention with small gaps, and aggregate retention with large gaps), one understory manipulation (brush removal), and controls (no harvesting, and/or no brush removal). In 2003, the first breeding season following the harvest, we found little difference in bird community composition between control and treatment stands. In 2005, the third breeding season following harvest, avian abundance, richness, and diversity were all greater within treatments. Species associated with edge, shrub, and early successional habitats generally show positive response to treatments (e.g. Chestnut-sided Warbler [ Dendroica pensylvanica], Mourning Warbler [ Oporornis philadelphia], Chipping Sparrow [ Spizella passerine]), as do some species associated with mature forest (e.g., Pine Warbler [ Dendroica pinus], Rose-breasted Grosbeak [ Pheucticus ludovicianus]). Ovenbirds ( Seiurus aurocapilla) and Black-throated Green Warblers ( Dendroica virens) were more abundant in control stands. There are, as of yet, no discernable differences in avian community composition among the three overstory treatments or between the single understory treatment and the understory control, but differences are expected as the treatments diversify due to understory development. While overstory retention harvests provide habitat for a diverse and abundant bird community, the temporal divergence in avian community composition that we observed between treatment and control stands reveals the importance of uncut, mature red pine forest as a component of a biodiverse landscape.

Long‐Term Effects of Group‐Selection Timber Harvesting on Abundance of Forest Birds

Relatively few studies have examined the ecological effects of group-selection timber harvesting, and nearly all have been short-term and have lacked experimental manipulations that allow pre- and posttreatment comparisons. We have been documenting the effects of a group-selection timber harvest on bird abundance in a Maine forest for 24 years (preharvest, 1983-1987; postharvest, 1988-2006). Here we characterized the trends in bird abundance over the first 20 years of the study in the managed and control halves of the 40-ha study area. Species responses to the group-selection harvest were idiosyncratic, but in general the mature-forest bird community was retained and species dependent on early successional habitat temporarily (</=8 years) benefited. The Eastern Wood-Pewee (Contopus virens), Winter Wren (Troglodytes troglodytes), Pine Warbler (Dendroica pinus), and White-throated Sparrow (Zonotrichia albicollis) increased in abundance in the managed half of the study area following timber harvest, whereas the Veery (Catharus fuscescens) decreased. The Black-and-White Warbler (Mniotilta varia), Nashville Warbler (Vermivora ruficapilla), and Common Yellowthroat (Geothlypis trichas) responded positively to harvesting, as indicated by decreases in abundance in the control area and more protracted declines or stable abundances in the managed area. This study constitutes the longest experimental investigation to date of the effects of a group-selection harvest on birds and thus provides important information on the strength, direction, and duration of temporal changes in bird populations following forest management.

Effects of the Sustainable Forestry Initiative on the Quality, Abundance, and Configuration of Wildlife Habitats

We analyzed the effects of landscape measures within the Sustainable Forestry Initiative (SFI) program on the suitability, abundance and spatial pattern of vertebrate habitats based on modeling and simulation of landscape and stand structure in a forested watershed in East Texas. Eight vertebrate species representing guilds established according to breeding and foraging requirements were selected: American beaver (Castor canadensis), American woodcock (Scolopax minor), pine warbler (Dendroicapinus), downy woodpecker (Picoides pubescens), barred owl (Strix varia), wild turkey (Meleagris gallopavo silvestris), fox squirrel (Sciurus niger) and gray squirrel (Sciurus carolinensis). Habitat suitability of the landscape in general increased with the implementation of SFI measures and habitat conditions were more diverse and even. Fragmentation and establishment of narrow and elongated habitat areas in a network configuration were the main consequences of the implementation of SFI measures in terms of habitat spatial structure. These changes were usually not limiting for the species analyzed. Mature pine and hardwood stands were absent from the simulated landscapes limiting the habitat for species like downy woodpecker or barred owl. Most of the species considered in this work benefited particularly from the implementation of streamside management zones (SMZs).

One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species Distributions

Abstract: Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre‐Euro‐American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid‐1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black‐throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public‐land survey records represented historical habitat conditions, and a combination of forest inventory and national land‐cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black‐throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long‐term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority.

Assessment of Sustainability in Intensively Managed Forested Landscapes: A Case Study in Eastern Texas

Abstract We developed a methodology to analyze the effects of management practices on landscape structure and function to be used in the assessment of sustainability in intensively managed forest landscapes. It is based on modeling and simulation of landscape and stand structure as well as biological and physical processes. The methodology includes a landscape structure model and several forest stand-level models to simulate the dynamics of landscapes and stands as a function of management rules. It also includes habitat models to evaluate landscape quality and spatial characteristics of vertebrate habitat, and a hydrologic model to simulate water and sediment yield at the subarea and watershed levels. The application of this methodology to the Sustainable Forestry Initiative (SFI) program in eastern Texas indicated that this is an effective way to evaluate effects of sustainable forestry programs on landscape structure and processes. During simulation years, the habitat of pine warbler, the species used as an example to illustrate the methodology, became apparently fragmented under the SFI scenario. This fragmentation was caused mainly by narrow, forested streamside management zones dissecting pine stands and should have little negative influence on the pine warbler habitat. Sediment yield at the landscape level decreased by the implementation of SFI measures, particularly by the reduction of channel degradation. FOR. SCI. 51(4):321–333.

Effects of Hardwood Reduction on Winter Birds in Northwest Florida Longleaf Pine Sandhill Forests

Abstract Reversing decades of fire exclusion by hardwood midstory reduction is now used to recover populations of the federally endangered Red-cockaded Woodpecker (Picoides borealis) in longleaf pine (Pinus palustris) forest ecosystems. The effects of Red-cockaded Woodpecker management on winter birds in longleaf pine sandhill forests are largely unknown. Examining habitat use of winter migrants, some of which are declining, may influence the selection of habitat management techniques used for Red-cockaded Woodpeckers to benefit overwintering migrants. During the winters (December–February) of 1997–1998 and 1998–1999, we tested experimentally the effects of hardwood reduction treatments applied in 1995 on winter birds at Eglin Air Force Base in fire-excluded northwest Florida longleaf pine sandhills. Treatments were (1) prescribed spring burning, (2) herbicide application, (3) mechanical felling and girdling, and (4) a control where decades of fire exclusion was maintained. We also sampled winter bird flocks in frequently burned, nonexperimental reference plots to measure management success. Hardwood reduction techniques had no effect on flock species richness, which averaged 7.9 and 7.2, respectively, during 1997–1998 and 1998–1999. Larger flocks in felling and girdling and in herbicide plots were primarily due to significantly higher numbers of overwintering Chipping Sparrows (Spizella passerina), as well as resident Red-cockaded Woodpeckers and an influx of temperate migrant Pine Warblers (Dendroica pinus). In contrast, flocks in control plots were smaller (flock size and species composition in spring burn plots were intermediate) and composed of hardwood-associated species, such as Tufted Titmouse (Baeolophus bicolor) and Carolina Chickadee (Poecile carolinensis). The relative uses of longleaf pines and hardwoods by Red-cockaded Woodpeckers, Pine Warblers, and Brown-headed Nuthatches (Sitta pusilla) during both winters best explained that winter birds present in herbicide, felling and girdling, and reference plots were more likely to forage on the same tree species and substrates than birds in spring-burned plots, and least likely to forage on the same species and substrates as birds in the control plots. Those differences corresponded to the following increasing order of hardwood stem mortality among treatments: control, spring burn (41%), felling and girdling (62%), and herbicide (92%). Repeated burning is recommended to restore the reference foraging condition because it was eight times less expensive than other techniques, which favored mostly Chipping Sparrows.

Effects of Hardwood Reduction on Winter Birds in Northwest Florida Longleaf Pine Sandhill Forests

Reversing decades of fire exclusion by hardwood midstory reduction is now used to recover populations of the federally endangered Red-cockaded Woodpecker (Picoides borealis) in longleaf pine (Pinus palustris) forest ecosystems. The effects of Red-cockaded Woodpecker management on winter birds in longleaf pine sandhill forests are largely unknown. Examining habitat use of winter migrants, some of which are declining, may influence the selection of habitat management techniques used for Red-cockaded Woodpeckers to benefit overwintering migrants. During the winters (December–February) of 1997–1998 and 1998–1999, we tested experimentally the effects of hardwood reduction treatments applied in 1995 on winter birds at Eglin Air Force Base in fire-excluded northwest Florida longleaf pine sandhills. Treatments were (1) prescribed spring burning, (2) herbicide application, (3) mechanical felling and girdling, and (4) a control where decades of fire exclusion was maintained. We also sampled winter bird flocks in frequently burned, nonexperimental reference plots to measure management success. Hardwood reduction techniques had no effect on flock species richness, which averaged 7.9 and 7.2, respectively, during 1997–1998 and 1998–1999. Larger flocks in felling and girdling and in herbicide plots were primarily due to significantly higher numbers of overwintering Chipping Sparrows (Spizella passerina), as well as resident Red-cockaded Woodpeckers and an influx of temperate migrant Pine Warblers (Dendroica pinus). In contrast, flocks in control plots were smaller (flock size and species composition in spring burn plots were intermediate) and composed of hardwood-associated species, such as Tufted Titmouse (Baeolophus bicolor) and Carolina Chickadee (Poecile carolinensis). The relative uses of longleaf pines and hardwoods by Red-cockaded Woodpeckers, Pine Warblers, and Brown-headed Nuthatches (Sitta pusilla) during both winters best explained that winter birds present in herbicide, felling and girdling, and reference plots were more likely to forage on the same tree species and substrates than birds in spring-burned plots, and least likely to forage on the same species and substrates as birds in the control plots. Those differences corresponded to the following increasing order of hardwood stem mortality among treatments: control, spring burn (41%), felling and girdling (62%), and herbicide (92%). Repeated burning is recommended to restore the reference foraging condition because it was eight times less expensive than other techniques, which favored mostly Chipping Sparrows.

Ticks (Acari: Ixodidae) and spirochetes (spirochaetaceae: spirochaetales) recovered from birds on a Georgia Barrier Island.

From September 1997 through July 1999, 300 individuals and 46 species of birds were mist-netted and screened for ticks and spirochetes on St. Catherine's Island, Liberty County, GA. Seventy-six (25%) of the birds were parasitized by a meal intensity of 4.6 ticks. Seasonally, more birds were infested with ticks during the summer (50% in 1998, 34% in 1999) than in spring (15% in 1998, 11% in 1999) or fall (21% in 1997, 20% in 1998), mainly because of severe infestations on some birds by immature stages of the lone star tick, Amblyomma americanum (L.), during this season. Eight species ofticks were recovered from 14 species of birds during this study: A. americanum (74 nymphs, 168 larvae); the blacklegged tick, Ixodes scapularis Say (11 nymphs, 28 larvae), the Gulf Coast tick, Amblyomma maculatum Koch (two nymphs, 29 larvae); Ixodes minor Neumann (16 larvae); the rabbit tick. Haemaphysalis leporispalustris (Packard) (one nymph, 14 larvae); the bird tick Ixodes brunneus Koch (two larvae); the American dog tick, Dermacentor variabilis (Say) (one nymph); and Ixodes affinis Neumann (one larva). The Carolina wren was parasitized by more species of ticks (seven) than any other bird species, followed by the northern cardinal (five), white-throated sparrow (four) and painted bunting (three). Spirochetes were isolated in BSK II medium from one tick (a nymphal A. americanum) and from skin biopsies of 12 (4%) of the individual birds (three downy woodpeckers, three northern waterthrushes, two Carolina wrens, one American redstart, one pine warbler, one Swainson's thrush, and one white-eyed vireo) all in fall 1997. This concentrated phenology of spirochete isolations might reflect periodic amplification or recrudescence of spirochetes in reservoir avian hosts.

An experimental test of dietary enzyme modulation in pine warblers Dendroica pinus.

Modulation of gut function is important in an ecological and evolutionary context because it likely determines what food items an animal can and cannot eat. We examined how diet affects activity of digestive enzymes in an omnivorous bird, the pine warbler (Dendroica pinus). Pine warblers were fed insect-based, fruit-based, and seed-based diets for approximately 54 d. We then measured activity of amylase, maltase, sucrase, aminopeptidase-N, trypsin, chymotrypsin, carboxypeptidase A, carboxypeptidase B, pancreatic lipase, and carboxyl ester lipase. We predicted that carbohydrase activities would be highest in birds fed the diet highest in carbohydrates (fruit based), protease activities would be highest in those fed the diet highest in protein (insect based), and lipase activities would be highest in those fed the diets highest in lipid (insect based and seed based). Also, we predicted that pine warblers would exhibit greater dietary modulation of enzyme activity than reported for a less omnivorous congener, the yellow-rumped warbler (Dendroica coronata). All predictions were upheld, supporting the hypothesis that pine warblers modulate the activity of digestive enzymes in proportion to demand from substrates in the diet.