Mniotilta Research Articles

Strong differences in migratory connectivity patterns among species of Neotropical‐Nearctic migratory birds revealed by combining stable isotopes and abundance in a Bayesian assignment analysis

AbstractAimConservation planning for migratory species requires knowing how populations are connected throughout the annual cycle. We measured migratory connectivity for five migratory songbird species by combining stable‐hydrogen isotopes in feathers (δ2HF) with citizen science data on breeding range abundance.LocationCaribbean Basin and North America.TaxaNeotropical migratory birds: Mniotilta varia, Setophaga ruticilla, Seiurus aurocapilla, Setophaga americana, and Setophaga discolor.MethodsWe analyzed δ2HF in feathers grown on North American breeding grounds and sampled at 20 Caribbean Basin sites across most of the non‐breeding range of each species. We made Bayesian assignments to breeding origin by combining δ2HF values and North American Breeding Bird Survey abundance data. For each species, we used cluster analysis to group Caribbean sites into non‐breeding regions that shared birds with similar breeding ground assignment probabilities. We then mapped assignment probabilities for the non‐breeding regions of each species onto breeding ground δ2HF surfaces and estimated the strength of migratory connectivity.ResultsApart from some general similarities, the five species demonstrated different patterns of migratory connectivity. Species with larger non‐breeding ranges exhibited stronger migratory connectivity compared to those with smaller non‐breeding ranges. Despite geographical overlap, birds from each non‐breeding region had mostly unique breeding ground origins.Main conclusionsThe contrasting patterns of migratory connectivity shown by the five species suggest that geographic distribution during the non‐breeding period is a poor indicator of breeding ground origin. Our results indicate that full annual cycle conservation planning, which requires migratory connectivity information, should proceed on a species‐specific basis.

Social information affects prospecting, but not settlement, by Black‐and‐white Warblers (Mniotilta varia)

Birds use social as well as environmental cues to inform their habitat selection decisions. By manipulating social cues with song playbacks, biologists can influence where individuals search for breeding territories, which could be useful for conservation. Yet before we can predict how birds will respond to playback treatments, we must first understand how they integrate social cues with information about habitat quality at different stages in the habitat selection process. In this experiment, we examined whether vegetation structure and/or social cues affected Black‐and‐white Warbler Mniotilta varia abundance at three study areas that differed in habitat quality. We monitored Black‐and‐white Warbler habitat use across the breeding season, from the early prospecting period until after settlement decisions were made. During seasons without playback treatments, Black‐and‐white Warbler abundance was positively associated with levels of understorey vegetation cover. We then played Black‐and‐white Warbler songs daily for 5–6 weeks at selected survey sites at all study areas. We found that the model‐predicted abundance of Black‐and‐white Warblers was nearly three times greater at playback sites than at control sites during the prospecting period. During seasons with playbacks, understorey vegetation cover was no longer associated with Black‐and‐white Warbler abundance, indicating that individuals prioritized social information when searching for breeding territories. However, during the post‐settlement period, neither playbacks nor levels of understorey vegetation cover were associated with increased abundance, suggesting that playback treatments did not influence final breeding territory choice. We also found no difference in abundance between playback and control sites at a study area that represented low‐quality habitat, which suggests that playbacks should not induce maladaptive site selection.

Vertical sexual habitat segregation in a wintering migratory songbird

AbstractSexual habitat segregation during the wintering period is a widespread phenomenon and has important implications for the ecology and conservation of migratory birds. We studied Black-and-white Warblers (Mniotilta varia) wintering in second-growth scrub and old-growth mangrove forest in Jamaica to quantify sexual habitat segregation and explore whether patterns of habitat occupation have consequences on physical condition. We used this information along with a body size analysis and simulated territorial intrusions to assess whether behavioral dominance or habitat specialization was responsible for habitat segregation. Based on standardized capture data, we found that females were more abundant than males in both scrub and mangrove forests. Foraging observations, however, suggested vertical segregation within each habitat, with females foraging primarily near the ground and males in the mid-canopy and canopy, indicating that our sex ratio estimates may be biased. Using 2 measures of body condition, we show that males were in better body condition than females, regardless of habitat. We found that males were on average slightly larger than females, and home range analysis and simulated territorial intrusions indicated that males were more territorial than females. We argue that the observed vertical sexual habitat segregation is likely caused by behavioral dominance rather than habitat specialization. Winter body condition is known to carry over to affect migration timing, reproductive success, and annual survival in other songbirds, and therefore sexual habitat segregation may have important implications for year-round population dynamics in Black-and-white Warblers.

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.

Offshore surprises: new at-sea bird records for Suriname (2013\u20132015)

Bird observations were collected from various types of survey vessels in Suriname’s territorial waters between 2013 and 2015. Dedicated, effort-related surveys were carried out from geophysical seismic survey vessels within an area located 80–110 km offshore (in 2013) and 165–290 km (in 2015). Opportunistic observations were recorded during fisheries surveys on a shrimp trawler operating along the 30 m depth contour, approximately 40–60 km offshore (in 2014). In total, 10 bird (sub-)species were observed during these surveys that previously were not recorded for Suriname, including Manx Shearwater Puffinus puffinus, Ruff Calidris pugnax, South Polar Skua Stercorarius maccormicki, Long-tailed Jaeger Stercorarius longicaudus, Sandwich Tern Thalasseus sandvicensis (ssp. acuflavidus), Roseate Tern Sterna dougallii, Bridled Tern Onychoprion anaethetus, Black Noddy Anous minutus, Scarlet Tanager Piranga olivacea and Black-and-white Warbler Mniotilta varia. In addition, Lesser Black-backed Gull Larus fuscus and Bulwer’s Petrel Bulweria bulwerii were photographed for the first time in Suriname. A Sooty Shearwater Ardenna grisea was recorded just outside the Exclusive Economic Zone (EEZ), and therefore does not count as a new country record. This paper contributes to a better understanding of the avifauna frequenting the waters off Suriname, which historically has been poorly studied. Most of the species reported here are migratory. The timing of our sightings therefore also helps in a better understanding of their at-sea distribution and migration patterns.

Connecting the dots: Stopover strategies of an intercontinental migratory songbird in the context of the annual cycle.

The phases of the annual cycle for migratory species are inextricably linked. Yet, less than five percent of ecological studies examine seasonal interactions. In this study, we utilized stable hydrogen isotopes to geographically link individual black‐and‐white warblers (Mniotilta varia) captured during spring migration with breeding destinations to understand a migrant's stopover strategy in the context of other phases of the annual cycle. We found that stopover strategy is not only a function of a bird's current energetic state, but also the distance remaining to breeding destination and a bird's time‐schedule, which has previously been linked to habitat conditions experienced in the preceding phase of the annual cycle. Birds in close proximity to their breeding destination accumulate additional energy reserves prior to arrival on the breeding grounds, as reflected by higher migratory condition upon arrival, higher refueling rates measured via blood plasma metabolites, and longer stopover durations compared to birds migrating to breeding destinations farther from the stopover site. However, late birds near their breeding destination were more likely to depart on the day of arrival (i.e., transients), and among birds that stopped over at the site, the average duration of stopover was almost half the time of early conspecifics, suggesting late birds are trying to catch‐up with the overall time‐schedule of migration for optimal arrival time on the breeding grounds. In contrast, birds with long distances remaining to breeding destinations were more likely to depart on the day of arrival and primarily used stopover to rest before quickly resuming migration, adopting similar strategies regardless of a bird's time‐schedule. Our study demonstrates that migrants adjust their en route strategies in relation to their time‐schedule and distance remaining to their breeding destination, highlighting that strategies of migration should be examined in the context of other phases of the annual cycle.

Area requirements and landscape‐level factors influencing shrubland birds

ABSTRACTDeclines in populations of birds that breed in disturbance‐dependent early‐successional forest have largely been ascribed to habitat loss. Clearcutting is an efficient and effective means for creating early‐successional vegetation; however, negative public perceptions of clearcutting and the small parcel size typical of private forested land in much of the eastern United States make this practice impractical in many situations. Group selection harvests, where groups of adjacent trees are removed from a mature forest matrix, may be more acceptable to the public and could provide habitat for shrubland birds. Although some shrubland bird species that occupy clearcuts are scarce or absent from smaller patches created by group selection, some of these smaller patches support shrubland species of conservation concern. The specific factors affecting shrubland bird occupancy of these smaller patches, such as habitat structure, patch area, and landscape context, are poorly understood. We sampled birds in forest openings ranging 0.02–1.29 ha to identify species‐specific minimum‐area habitat requirements and other factors affecting shrubland birds. We modeled bird occurrence in relation to microhabitat‐, patch‐, and landscape‐level variables using occupancy models. The minimum‐area requirements for black‐and‐white warblers (Mniotilta varia), common yellowthroats (Geothlypis trichas), chestnut‐sided warblers (Setophaga pensylvanica), eastern towhees (Pipilo erythrophthalmus), and gray catbirds (Dumetella carolinensis) were ≤0.23 ha, whereas indigo buntings (Passerina cyanea) and prairie warblers (S. discolor) required openings of 0.56 ha and 1.11 ha, respectively. Notably, prairie warblers were more likely to occur in openings closer to large patches of habitat such as powerline corridors, even if those openings were small in size. We concluded that, despite their inability to support the entire suite of shrubland species, small forest openings can provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics. © 2017 The Wildlife Society.

Prolonged Interspecific Care of Two Sibling Golden-winged Warblers (Vermivora chrysoptera) by a Black-and-white Warbler (Mniotilta varia)

ABSTRACT We observed a fledgling abandonment and adoption event that subsequently led to an extended period of interspecific parental care between a male Black-and-white Warbler (Mniotilta varia) and two radio-tagged fledgling Golden-winged Warbler (Vermivora chrysoptera) siblings. Both fledglings were initially accompanied by their maternal Golden-winged Warbler until 5 and 9 days after fledging. At this time, a male Black-and-white Warbler began feeding both fledglings, and maternal care ceased. In the 23 days we monitored the fledglings between onset of interspecific feeding and independence, the male Black-and-white Warbler was observed with at least one of the fledglings on 20 of those occasions. Furthermore, the Black-and-white Warbler was seen feeding at least one of the fledglings on 16 of those visits. We photographed several feeding events. The Black-and-white Warbler remained with the fledglings until they successfully reached independence 28 days post-fledging.

Multi-scale responses of breeding birds to experimental forest management in Indiana, USA

Forest managers frequently must balance timber production and wildlife conservation goals when choosing management approaches. We studied the response of the breeding bird community to silvicultural treatments at multiple spatial scales over a 10-year period in 60–90year old oak-hickory forests of Indiana, USA. We conducted point count surveys in a 3603-ha study area both before (n=3years) and after (n=6years) application of silvicultural treatments. Bird responses were analyzed at two spatial scales: management units and individual harvests. At the multi-stand management unit scale, treatments were even-aged management, uneven-aged management, and a no-harvest control. We also analyzed the responses of birds at the spatial scale of individual timber harvests (clearcuts, patch cuts, shelterwood harvests, and single-tree selection). Multi-species N-mixture models were used to estimate bird species density and richness at both spatial scales. At the management unit scale, 4 species increased in density following even-aged management (relative to the control), while 1 species (Red-eyed Vireo [Vireo olivaceus]) declined. A larger number of species responded both positively (n=9) and negatively (n=3) to uneven-aged management. Overall richness was significantly greater in the even- and uneven-aged treatments than in the control. At the harvest scale, only the clearcuts and patch cuts resulted in changes in the density of any species, but a larger number of species were impacted and effect sizes were generally larger in these harvests than at the management unit scale. In the clearcuts, 13 species increased in density relative to the no-harvest control, while 5 species declined. A larger number of species were impacted by patch cut harvests (18 species increasing and 6 decreasing). Overall richness was greatest in the clearcut harvests. At both scales, species that increased were generally those associated with early successional habitat, including the Eastern Towhee (Pipilo erythrophthalmus) and Indigo Bunting (Passerina cyanea), while species that declined were typically associated with mature forest habitat (e.g., Red-eyed Vireo [Vireo olivaceus] and Ovenbird [Seiurus aurocapilla]). Harvesting appeared to benefit several species of conservation concern in Indiana, including the Cerulean Warbler (Setophaga cerulea) and Black-and-white Warbler (Mniotilta varia). Both management treatments appear to be good options for simultaneously conserving bird species diversity (particularly of early-successional specialist species) while meeting other forest management goals. However, the impact of the next phases of the shelterwood harvests remains to be evaluated.

Dietary opportunism, resource partitioning, and consumption of coffee berry borers by five species of migratory wood warblers (Parulidae) wintering in Jamaican shade coffee plantations

Diets reflect important ecological interactions, but are challenging to quantify for foliage-gleaning birds. We used regurgitated stomach samples from five primarily insectivorous species of long-distance migrant warblers (Parulidae) wintering in two moderate-elevation shade coffee farms in Jamaica to assess both foraging opportunism and prey resource partitioning. Our results, based primarily on 6120 prey items in 80 stomach samples collected during a one-week period in March 2000, confirm opportunism. The diets of all five warblers, including American Redstarts (Setophaga ruticilla), Black-and-White Warblers (Mniotilta varia), Black-throated Blue Warblers (S. caerulescens), Northern Parulas (S. americana), and Prairie Warblers (S. discolor), overlapped strongly based on consumption of the same prey types, even many of the same prey species (4 of 10 interspecific overlaps >0.9, range = 0.74–0.97). Moreover, all five species fed on similarly small, often patchily distributed prey, including coffee berry borers (Hypothenemus hampei; Coleoptera, Curculionidae). Nonetheless, permutational multivariate analysis of variance also revealed that the diets of these species differed significantly, primarily with respect to prey mobility (winged vs. sessile); American Redstarts fed on the most mobile prey, and Northern Parulas on the least mobile prey and a relatively restricted set of prey taxa compared to the other four species of warblers. Overall, our results suggest both dietary opportunism consistent with a migratory life-history, and interspecific resource partitioning consistent with differences in morphology and foraging behavior during a food-limited season. Having provided evidence of the three necessary conditions, namely intraspecific competition, resource limitation, and interspecific overlap in resource use, the results of our study, in combination with those of other studies, also provide evidence of interspecific competition among wintering migrant insectivores. We thus argue that diffuse interspecific exploitative food competition may be more important than previously recognized. Las dietas reflejan importantes interacciones ecológicas, pero son difíciles de cuantificar para las aves que depredan los artrópodos en el follaje. Para evaluar el forraje oportunista y la repartición de recursos, se utilizaron muestras regurgitadas del estómago de cinco especies, los cuales fueron reinitas (Parulidae) principalmente insectívoros y migrantes de larga distancia invernados en dos fincas de café de sombra en elevación moderada en Jamaica. Nuestros resultados, basados principalmente en 6120 presas de 80 muestras regurgitadas durante un período de una semana en marzo de 2000, confirman el comportamiento de forraje oportunista. Las dietas de las cinco reinitas (incluyendo Setophaga ruticilla, Mniotilta varia, S. caerulescens, S. americana, y S. discolor) se solapaban especialmente basada en el consumo de los mismos tipos de presas, además, consumieron muchas de las mismas especies de presa (4 de 10 interespecífica se superpone >0.9, rango = 0.74–0.97). Por otra parte, las cinco especies se alimentaban de presas igualmente pequeña, a menudo distribuidos irregularmente, incluyendo los perforadores de la baya del café (Hypothenemus hampei, Coleoptera, Curculionidae). Sin embargo, el análisis de varianza multivariado con permutaciones también reveló que la dieta de estas especies difieren significativamente, sobre todo en relación con la movilidad de la presa (alada contra sésiles); S. ruticilla se alimentaron de las presas más móviles, y S. americana se alimentaron de la presas menos móviles y un conjunto relativamente limitado de taxones de presas en relación con las otras cuatro especies de reinitas. En general, nuestros resultados sugieren tanto que la dieta oportunista es consistente con un ciclo vital migratorio, y la repartición de recursos interespecífica es consistente con las diferencias en la morfología y el comportamiento de forrajeo durante una temporada limitada de alimentos. Haber proporcionado pruebas de las tres condiciones necesarias, a saber, la competencia intraespecífica, la limitación de los recursos, y la superposición interespecífica en el uso de los recursos, los resultados de nuestro estudio, en combinación con las pruebas de otros estudios, también proporcionan evidencia de la competencia interespecífica entre migrantes invernantes insectívoros. Por tanto, argumentamos que la competencia interespecífica por explotación de presa puede ser más importante que se había reconocido.

An indicator system to assess ecological integrity of managed forests

Ecological integrity of managed forests includes the ability of an ecosystem to support a community of organisms with a similar species composition and functional organization as found in nearby natural systems. We developed an indicator system for ecological integrity based on simulated natural disturbance and indicator species to test if forest condition and habitat in managed forests are similar to that found or expected in natural systems. We then applied the method in an area of the boreal forest (Ontario, Canada) where the objective of Ontario's strategic forest management planning approach is, in part, to conserve ecological integrity through the emulation of the natural disturbance process. Forest condition controls the supply of habitat to support the diversity of native organisms, and historically in boreal forests the natural disturbance process drove forest condition. We selected indicators of forest condition (landscape pattern and compositional mosaic) and habitat function (occupancy rates for a broad range of forest birds), and applied our assessment system to test whether indicators of forest condition and habitat function reflect outcomes expected if natural disturbance processes were successfully emulated. We collected occupancy data in natural and managed forest disturbance types using autonomous acoustic recorders, applied occupancy/detection modeling to estimate corrected occupancy rates (ψ), and then tested for differences in ψ between disturbance types. Some indicators of forest condition were within the range expected under natural disturbance, but we found relatively less old conifer, more young deciduous and greater edge density in managed forests relative to forests of natural disturbance origin. Most species (11 of 14) occurred with equal ψ in habitat originating from the two disturbance types. Brown creeper (Certhia americana), bay-breasted warbler (Mniotilta varia) and red-eyed vireo (Vireo olivaceus) differed between disturbance types. Brown creeper uses older conifer and occurred at lower rates in managed forest, while red-eyed vireo uses a range of deciduous forest ages, and occurred at higher rates in managed forest. Differences in quantity and/or quality of specific habitat types likely explain the responses. The results suggest what directional changes in the forest pattern and compositional mosaic would improve ecological similarity with natural systems, but also indicate what further research is required. We believe this approach to assessing ecological integrity can be adapted to study the effectiveness of conservation management strategies in other systems, and will contribute to adaptive management approaches and evidence-based policy development.

Daytime sleeping behavior observed in a Black-and-white Warbler during spring stopover

AbstractNocturnally migrating birds experience loss of sleep during the migratory period especially when undertaking long, non-stop flights. We report a field observation of daytime sleeping behavior in a Black-andwhite Warbler (Mniotilta varia) during spring migration. It is likely that this individual was compensating from sleep loss experienced during a trans-Gulf of Mexico flight. Only a few observations of daytime sleeping behavior have been reported in free-living migrants and all have been associated with long-distance flights in relation to ecological barriers.

Stand-level bird response to experimental forest management in the Missouri Ozarks

Long-term landscape-scale experiments allow for the detection of effects of silviculture on bird abundance. Manipulative studies allow for strong inference on effects and confirmation of patterns from observational studies. We estimated bird-territory density within forest stands (2.89–62 ha) for 19 years of the Missouri Ozark Forest Ecosystem Project (MOFEP), a 100-year experiment designed to study the effects of even-age and uneven-age management on wildlife. We spot-mapped territories of 15 species in 228 stands for 5 years before treatment and 14 years after treatment to assess the effects of stand-level silvicultural treatments (clearcut, select cut, thin, and no-harvest) applied within even-age, uneven-age, or no-harvest (control) management sites and year on avian territory density. We used 2 a priori contrasts to compare pre-treatment bird densities with densities during early (3–5 yr) and late (12–14 yr) post-treatment periods. The interaction of silvicultural treatment and year had significant effects on the densities of all 15 species. Densities of hooded warbler (Setophaga citrina), indigo bunting (Passerina cyanea), prairie warbler (Setophaga discolor), and yellow-breasted chat (Icteria virens) increased significantly 3–5 years post-treatment with the greatest changes in clearcuts, but densities 12–14 years post-treatment did not differ from pre-treatment densities. Densities of Acadian flycatcher (Empidonax virescens), wood thrush (Hylocichla mustelina), and especially ovenbird (Seiurus aurocapilla) had significant decreases in clearcut stands after treatment and lesser decreases in select cut or thin stands post-treatment. Densities of black-and-white warbler (Mniotilta varia), eastern wood-pewee (Contopus virens), and Kentucky warbler (Geothlypis formosa) increased in clearcut, thin, and select cut stands, but these increases were short-lived and sporadic by year after treatment. Densities of Acadian flycatcher and ovenbird remained lower in clearcut stands than no-harvest stands 13 years post-treatment. The results of this manipulative experiment were mostly consistent with our predictions of bird response to common silvicultural treatments in these forests. Managers can use these species-specific responses to silvicultural treatment to guide management decisions for target species or to balance management practices in a landscape to meet the needs of multiple species. © 2014 The Wildlife Society.

Black-and-white Warbler (Mniotilta varia)

Black-and-white Warbler (Mniotilta varia)

Coccidia in passerines from the Nevado de Toluca National Park, Mexico.

In this study, we found unsporulated coccidia oocysts in passerines from the Nevado de Toluca National Park, Mexico. We captured birds and took samples of their droppings during three field visits. We examined a total of 72 fecal samples and found unsporulated coccidia oocysts in 10 samples from five passerine species: Atlapetes pileatus (3), Cardelina ruber (1), Mniotilta varia (1), Oreothlypis celata (2) and Regulus calendula (3). This appears to be the first recorded study of unsporulated coccidia oocysts in passerine species from Mexico.

Comparative Occupancy and Habitat Associations of Black-and-White (Mniotilta varia) and Golden-Cheeked Warblers (Setophaga crysoparia) in the Juniper-Oak Woodlands of Central Texas

Abstract The golden-cheeked warbler (Setophaga chrysoparia) and the black-and-white warbler (Mniotilta varia) breed in the deciduous/evergreen woodlands of central Texas. The golden-cheeked warbler is endemic, while for the geographically widespread, black-and-white warbler, these woodlands represent the southwestern terminus of the breeding range. To estimate relative abundance and to compare habitat associations, we estimated occupancy, corrected for probability of detection, for both species using replicated point-count surveys of 36 survey stations at each of six sites within the Balcones Canyonlands Preserve Travis Co. TX. Model selection using an a priori, set of candidate models suggested that the probability of detection differed among warbler species and study sites and both species were influenced by time of season, time of day, and habitat characteristics of the survey station—slope and canopy cover. Naive occupancy estimates suggested that occupancy of black-and-white warblers was much lower t...

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.

Invasions of non-native earthworms related to population declines of ground-nesting songbirds across a regional extent in northern hardwood forests of North America

Non-native invasive earthworms (Lumbricus spp.) substantially change previously earthworm-free hardwood forests of North America by consuming the leaf litter layer, reducing cover and richness of herbaceous plants, and increasing dominance of sedges and grasses. These changes have been associated with reduced density of Ovenbirds (Seiurus aurocapilla) and Hermit Thrushes (Catharus guttatus) in 10–20 ha forest stands, and with reduced Ovenbird nesting success. Whether earthworms reduce songbird populations across a regional extent is unclear. We investigated relationships among Lumbricus, vegetation structure, landscape patterns of forest cover, and density of four ground-nesting songbird species at points scattered across the Chequamegon-Nicolet (Wisconsin) and Chippewa (Minnesota) National Forests, USA. In both national forests, Ovenbird density was significantly lower at invaded points than Lumbricus-free points, but only in sugar maple (Acer saccharum) and sugar maple/basswood (Tilia americana) (hereafter, maple-basswood) woodlands. Density of the Hermit Thrush, Black-and-white Warbler (Mniotilta varia), and Veery (Catharus fuscescens) did not differ in relation to Lumbricus. In maple-basswood forests, Lumbricus biomass was the best predictor of Ovenbird density, with greater biomass associated with reduced density. Vegetation structure and landscape pattern variables received weak support as density predictors. Across all forest types, Ovenbird density was most strongly related to forest cover within 500 and 1,000 m radii. Our results suggest that earthworm invasions may pose a regional threat to Ovenbirds within maple-basswood forests of the U.S. northern Midwest.

Observaciones de Aves Raras en España, 2009

Summary. Report on rare birds in Spain 2009. This is the 26th annual report of the Spanish rarities committee (Comite de Rarezas de SEO/BirdLife). This report includes 291 records on the presence of 84 rare bird taxa, with an acceptance rate of 75%. The report contains nine additions to the Spanish Bird List: Pacific Loon Gavia pacifica, white-backed vulture Gyps africanus, African purple swamphen Porphyrio porphyrio of the race madagascarensis, hudsonian whimbrel Numenius phaeopus of the race hudsonicus, bridled tern Onychoprion anaethetus, belted kingfisher Megaceryle alcyon, Naumann's thrush Turdus naumanni and black-and-white warbler Mniotilta varia. Having agreed acceptance criteria, the first accepted records of Caspian gull Larus cachinnans registered since 2005 are also included in this report. Second records for Spain of hooded merganser Mergus cucullatus, white wagtail Motacilla alba of the race subpersonata, house bunting Emberiza sahari and of a petrel assigned to the species pair Zino's/Fea's...

Fire severity has mixed benefits to breeding bird species in the southern Appalachians

Fire is frequently applied as a management tool on both public and private lands. However, in some ecosystems there is little information about bird species’ responses to these fire programs. In 2004 we measured habitat characteristics and conducted point counts in 12 burned sites and four unburned sites in the Chattahoochee National Forest of northern Georgia. Burns were categorized by severity (low, medium, or high) and time since fire (1–2 or 3–6 years). The basal area of snags, shrub stem density and percent canopy cover were similar among all treatments except high severity. Otherwise, fire severity had limited impacts on measured habitat characteristics. Following fires the densities of early-succession species such as eastern towhee ( Pipilo erythropthalmus) and indigo bunting ( Passerina cyanea) were greatest in areas of higher fire severity. A ground-nesting species (ovenbird [ Seiurus aurocapilla]) was less abundant in burned sites and the density of a shrub nesting species, the hooded warbler ( Setophaga citrine) was greatest in areas that received low severity fires. Scarlet tanager ( Piranga olivacea), tufted titmouse ( Baeolophus bicolor), red-eyed vireo ( Vireo olivaceus), black-throated green warbler ( Setophaga virens), and black-and-white warbler ( Mniotilta varia) had similar densities among all burn severities and showed no relationships with time since fire. Low and medium severity fires provided few benefits for most bird species. When conditions allow for their application, severe fires may be considered as a useful and historically appropriate management tool for some high-priority bird species in the southern Appalachian Mountains.