Seiurus Research Articles

Variation In Early-Successional Habitat Use Among Independent Juvenile Forest Breeding Birds

ABSTRACT Adults and juveniles of some forest breeding birds shift habitat use during the post breeding season from late to early successional forest. Juveniles of smaller passerine species are difficult to radio-track, and there is limited information on their habitat preferences, especially once they become older and independent. We determined if independent hatch-year birds captured in early-successional habitat remained there for extended periods, or if these habitats were only occupied infrequently during foraging activities. We determined habitat use for Ovenbirds (Seiurus aurocapilla), Worm-eating Warblers (Helmitheros vermivorum) and Red-eyed Vireos (Vireo olivaceus) during the independent post-fledging period in the Missouri Ozarks. We placed radio transmitters on 29 hatch-year birds captured in clearcuts and attempted to relocate them for 24 days in the summer of 2012. All three species had a greater relative probability of use of clearcut forest stands with small trees than older forests. Ovenbi...

Not all nesting guild members are alike: nest predators and conspecific abundance differentially influence nest survival in the ground-nesting Ovenbird (Seiurus aurocapilla) and Veery (Catharus fuscescens)

ABSTRACT At the nest guild level, nest predation is a major cause of failure for many passerines. Species differ in behaviors that influence nest predation risk, presenting a challenge to nest survival analyses at the nest guild level. At our study site in southeastern New York, previous findings have suggested rodent nest predator abundance strongly drives daily nest survival of the Veery (Catharus fuscescens), a ground or low shrub-nesting songbird. In cue playback experiments, the sympatric ground-nesting Ovenbird (Seiurus aurocapilla) shows a greater aversion to chipmunk vocalizations than Veeries. These behavioral differences suggest these two sympatric ground-nesters may be driven by different ecological mechanisms despite similarity in their nesting niche. We examined how nest predator abundance, regional songbird abundance, and timing of nest activity during the breeding season influence nest survival in two songbirds from the same nest guild by building competitive models for determining the extr...

Fledgling calls are a source of social information for conspecific, but not heterospecific, songbird territory selection

AbstractThe choice of breeding territory can strongly affect an individual's fitness. Individuals can use information obtained from social cues emitted by other organisms to assess territory quality when making settlement decisions. Social information sourced from cues indicating the current inhabitants' reproductive success (i.e., performance‐based cues) can be especially valuable as such cues may directly reveal territory quality. We tested social information use in a songbird system using experimental playbacks of Veery (Catharus fuscescens) fledgling calls (evidence of prior nest success) during the postbreeding season. We demonstrated that with year effects considered, Veeries used performance‐based social information available during the postbreeding season to select sites for territory establishment in the following year. During the first year of the study, Veeries occupied a greater proportion of plots with experimental broadcast of fledgling calls relative to control plots, whereas Ovenbirds (Seiurus aurocapilla), a coexisting heterospecific ground‐nesting species, did not. Fledgling call treatments did not have carryover effects that influenced Veery settlement decisions during the second year of the study. Ovenbird abundance varied with treatment combinations between years, but evidence indicating a carryover effect was limited. Our results indicate that postbreeding social information may vary among years for both conspecifics and heterospecifics, therefore highlighting the importance of considering year effects in studies on social information use.

Band-related Foot Loss Does Not Prevent Successful Return and Reproduction in the Ovenbird (Seiurus aurocapilla)

In spite of recent developments in tracking technology, leg bands are still the main marking method in songbird population studies. Yet, band-related injury rates and the effects of such injuries on survival and reproductive success have rarely been documented in songbirds. Over a 9-year period, we banded 525 male Ovenbirds using a numbered aluminum band and three celluloid color bands. Of these, 322 individuals returned to our study area in at least one of the subsequent years, including four males (1.2%) missing a foot. In all cases, foot loss occurred 2–3 years after banding, suggesting indirect effects of bands rather than injuries sustained at the time of capture or banding. Among returning individuals, 91 were recaptured and only one had noticeable leg injuries that did not result in foot loss. Three of the four males missing a foot were able to fledge young, one of which produced young during two successive breeding seasons. The fact that injured males could hold territories overlapping their previous one and produce young suggests that they could forage efficiently. Although leg injuries may carry a cost over the longer term, two of the four injured males were re-sighted in our study area the year following the first observation of foot loss. Our results, along with those of other studies, suggest that the benefits of bird banding greatly outweigh the costs associated with potential injuries, at least in this ground-foraging forest songbird.

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.

Behavioral development and habitat structure affect postfledging movements of songbirds

ABSTRACTPostfledging survival of neotropical migrant songbirds has been linked to seasonal and annual changes in the environment and to individual condition. Understanding what influences variation in postfledging movements may provide insight into the differential value of habitat across life‐history stages. We conducted a radio‐telemetry study of postfledging ovenbirds (Seiurus aurocapilla; n = 45) and Acadian flycatchers (Empidonax virescens; n = 62) in mature‐forest fragments from 2012 to 2015 in Missouri, USA. We documented variability in behavior and space use and used generalized linear mixed models to evaluate the relationship of postfledging movement rates to individuals’ condition, temporal variables, and local habitat variables. We found effects of age and season on movement distances for both study species. Additionally, daily movements of fledgling ovenbirds were negatively related to understory foliage density, a characteristic previously linked to increased survival. Habitat features are useful in predicting the postfledging movements of ovenbirds. By including behavioral development (age) and season in movement models, we were able to isolate and detect habitat effects on movement of ovenbirds and Acadian flycatchers. We suggest researchers use models of daily movement to further strengthen resource quality hypotheses generated by habitat selection and survival studies. © 2016 The Wildlife Society.

Contrasting patterns of nest survival and postfledging survival in Ovenbirds and Acadian Flycatchers in Missouri forest fragments

ABSTRACT We can improve our ability to assess population viability and forecast population growth under different scenarios by understanding factors that limit population parameters in each stage of the annual cycle. Postfledging mortality rates may be as variable as nest survival across regions and fragmentation gradients, although factors that negatively impact nest survival may affect postfledging individuals in different ways. We examined nest and postfledging survival of Ovenbirds (Seiurus aurocapilla) and Acadian Flycatchers (Empidonax virescens) in mature forest fragments in central Missouri. We used an information-theoretic approach to determine support for effects of factors intrinsic to the individual or nest site, temporal factors, local vegetation characteristics, and distance to edge on survival in both stages. We also examined the effect of incorporating the resulting survival estimates on population growth. In both species, survival increased from nest to postfledging stages (Ovenbirds: 0.2...

Changes in breeding bird abundance and species composition over a 20 year chronosequence following shelterwood harvests in oak-hardwood forests

Birds play an integral ecological, functional, and cultural role in New England forests and timber harvesting is known to affect their diversity and abundance. While much is known about bird communities immediately following a harvest (one to about three years), less is known about how communities shift through stand development. This study examines breeding-bird species diversity and composition in the 22years following shelterwood harvest of second-growth oak-hardwood forests in southern New England. We documented bird species richness, Shannon diversity, abundance, and evenness in 28 regenerating shelterwood harvests and compared them with eight mature forest stands. Early-successional regenerating stands (<12years since harvest) had higher bird abundance than regenerating stands 13–22years old and mature stands (80–100years old). Species richness and Shannon diversity were greater in regenerating shelterwoods compared to mature stands. Within the regenerating shelterwoods, species richness, Shannon diversity, and total bird abundance generally decreased with time since harvest. Species community composition differed between stands <12years old and older regenerating and mature stands. Abundances of forest dwelling, ground-nesting species increased steadily with time since harvest, while early-successional, shrub-nesting species decreased with time since harvest. Specifically, we observed higher abundances of shrub-nesting species such as chestnut-sided warbler (Setophaga pensylvanica) and indigo bunting (Passerina cyanea) in early stand-initiation (0–7years). Ground-nesting birds, such as ovenbirds (Seiurus aurocapilla), are present and abundant as early as 13years following a harvest and are not obligate to closed-canopied forest conditions. Indeed, abundances of species considered ‘late-successional’ were as high in early stem exclusion (13–22years) as in mature stands and were present in moderate numbers in stands considered late initiation (8–12years). Contrastingly, we found many early-successional species confined to stand initiation (<13years). In summary, bird communities in shelterwood harvests are highly dynamic in the 22years following harvesting and our understanding cannot be distilled to a single diversity number such as species richness. Our findings convey that bird abundance, richness, diversity and species composition change following a harvest, suggesting that natural resource managers in New England hoping to promote diverse and abundant bird populations should create forests composed of mosaics of differently aged managed stands, and mature forest reserves.

Potential effects of Brown-headed Cowbirds (Molothrus ater) on host postfledging dispersal and survival

ABSTRACT Nest parasitism by Brown-headed Cowbirds (Molothrus ater) negatively affects nest production and nest success of the majority of their hosts. However, it is unclear what effects cowbird fledglings have on host broods during the postfledging period. We monitored 65 nests of Ovenbirds (Seiurus aurocapilla) from 2012–2014 in central Missouri, 49% of which were parasitized by Brown-headed Cowbirds. We used radio-telemetry to track daily movements, survival, and parental care for 13 Ovenbird fledglings from parasitized nests that fledged cowbirds and 21 Ovenbird fledglings from non-parasitized nests. Clutch size and nest productivity were lower in parasitized nests, but mean nestling mass at fledging and total brood size (host and parasite young) did not differ between parasitized and non-parasitized nests. All mortalities occurred within the first 10 days after fledging. Estimated postfledging cumulative survival and observed adult care were similar between parasitism groups. There was no difference ...

Avian occupancy response to oak woodland and savanna restoration

ABSTRACTOak (Quercusspp.) woodlands and savannas throughout the Mid‐South, USA have become closed‐canopy forests through succession in the absence of fire, contributing to declines in disturbance‐dependent avian species. Restoration could ameliorate these trends, but effects of such management practices on avian communities of the Mid‐South are poorly understood. We implemented an experiment on the Cumberland Plateau, Tennessee with treatments involving fall (Oct) or spring (Mar) fire with woodland (14 m2/ha) or savanna (7 m2/ha) residual basal area and unmanaged control stands (20 ha each). We conducted fixed‐radius point counts 3 times annually (2010–2012) and analyzed trends in naïve occupancy for 41 species. For 20 species with adequate data (10 early‐, 10 late‐successional), we performed multiple‐season, robust‐design occupancy modeling and accounted for detection bias. We then used mixed‐model polynomial regression to define relationships between occupancy and measures of live and dead basal area, midstory density, and herbaceous groundcover. Restoration substantially altered forest structural characteristics but did not affect the occupancy of most late‐successional species. In contrast, the presence of early‐successional species increased as live basal area decreased and herbaceous groundcover increased. Only 3 of 41 species (hooded warbler [Setophaga citrina], ovenbird [Seiurus aurocapilla], and worm‐eating warbler [Helmitheros vermivorum]) exhibited reduced occupancy as woodland and savanna conditions were approached. The presence of all other species, including 13 regionally and 2 continentally declining, remained constant or increased as restoration progressed. Woodland conditions of 10 m2/ha live basal area and 20% herbaceous groundcover maximized occupancy of early‐successional species with little consequences for late‐successional species. Proceeding further toward savanna conditions negatively affected species associated with lower strata of mature‐forests but further increased the presence of some early‐successional species. Midstory density and dead basal area were poor predictors of occupancy and thus may be necessary but not sufficient in promoting early‐successional species. Our results suggest implementing oak woodland and savanna management in the Mid‐South could benefit disturbance‐dependent birds of high conservation priority with minimal negative impacts on the presence of late‐successional species. © 2016 The Wildlife Society.

Assessment of Error Rates in Acoustic Monitoring with the R package monitoR

Detecting population-scale reactions to climate change and land-use change may require monitoring many sites for many years, a process that is suited for an automated system. We developed and tested monitoR, an R package for long-term, multi-taxa acoustic monitoring programs. We tested monitoR with two northeastern songbird species: black-throated green warbler (Setophaga virens) and ovenbird (Seiurus aurocapilla). We compared detection results from monitoR in 52 10-minute surveys recorded at 10 sites in Vermont and New York, USA to a subset of songs identified by a human that were of a single song type and had visually identifiable spectrograms (e.g. a signal:noise ratio of at least 10 dB: 166 out of 439 total songs for black-throated green warbler, 502 out of 990 total songs for ovenbird). monitoR’s automated detection process uses a ‘score cutoff’, which is the minimum match needed for an unknown event to be considered a detection and results in a true positive, true negative, false positive or false negative detection. At the chosen score cut-offs, monitoR correctly identified presence for black-throated green warbler and ovenbird in 64% and 72% of the 52 surveys using binary point matching, respectively, and 73% and 72% of the 52 surveys using spectrogram cross-correlation, respectively. Of individual songs, 72% of black-throated green warbler songs and 62% of ovenbird songs were identified by binary point matching. Spectrogram cross-correlation identified 83% of black-throated green warbler songs and 66% of ovenbird songs. False positive rates were for song event detection.

Demographic response of a neotropical migrant songbird to forest management and climate change scenarios

Demographic models for species sensitive to human activities that are still relatively common are of particular interest to compare the relative influence of human land use and climate on population trends. Yet, data limitations often restrict our ability to interpret the numerical response of species to habitat alteration and climatic change adds to this challenge. In this study, we used habitat-specific demographic information from an individually-marked population of Ovenbird (Seiurus aurocapilla) and a forest timber supply model to project population trends over an 80-year horizon. We modelled changes in Ovenbird abundance, productivity, and population growth rate as a function of harvesting scenarios (no harvest, forestry-as-usual, and increased [10% or 20%] harvesting intensity) and projected impacts of climate change (0%, 10%, and 50% reductions in population size over the 80-year period), as well as contrasting assumptions about population dynamics (i.e. open vs. closed population). Among the many effects of climate change, it has been hypothesized that reductions in annual snow cover will occur, causing deeper and more frequent frost penetration into the soil and, in turn, a reduction in invertebrate (food) abundance during the following breeding season. Our models suggest that the study area currently is a demographic sink (λ=0.920) for Ovenbirds, although some habitat types still act as demographic sources. Over the first 7years, a large decline in abundance of territorial males (∼25%) is projected, unless population levels are maintained through immigration. Interestingly, when we allowed for immigration from outside the study area, population growth rate remained <1 because a larger proportion of the population occupied habitat types acting as sinks. Over an 80-year period, the climate change scenarios we simulated were more likely to have negative impacts (5–49%) than forestry activities, whether we applied the current management plan or more intensive harvesting scenarios. To our knowledge, this study used some of the most detailed habitat-specific demographic information available for a North American forest songbird to model the relative influence of land use, climate, and population dynamics on population trends. Future studies should examine the possibility of synergistic effects between harvesting and climate change, to model their influence on Ovenbird or other species foraging on litter invertebrates.

Density‐dependent home‐range size revealed by spatially explicit capture–recapture

The size of animal home ranges often varies inversely with population density among populations of a species. This fact has implications for population monitoring using spatially explicit capture–recapture (SECR) models, in which both the scale of home‐range movements σ and population densityDusually appear as parameters, and both may vary among populations. It will often be appropriate to model a structural relationship between population‐specific values of these parameters, rather than to assume independence. We suggest re‐parameterizing the SECR model usingkp= σp√Dp, wherekprelates to the degree of overlap between home ranges and the subscriptpdistinguishes populations. We observe thatkpis often nearly constant for populations spanning a range of densities. This justifies fitting a model in which the separatekpare replaced by the single parameterkand σpis a density‐dependent derived parameter. Continuous density‐dependent spatial variation in σ may also be modelled, using a scaled non‐Euclidean distance between detectors and the locations of animals. We illustrate these methods with data from automatic photography of tigersPanthera tigrisacross India, in which the variation is among populations, from mist‐netting of ovenbirdsSeiurus aurocapillain Maryland, USA, in which the variation is within a single population over time, and from live‐trapping of brushtail possumsTrichosurus vulpeculain New Zealand, modelling spatial variation within one population.Possible applications and limitations of the methods are discussed. A model in whichkpis constant, while density varies, provides a parsimonious null model for SECR. The parameterkof the null model is a concise summary of the empirical relationship between home‐range size and density that is useful in comparative studies. We expect deviations from this model, particularly the dependence ofkpon covariates, to be biologically interesting.

Miniaturized GPS Tags Identify Non-breeding Territories of a Small Breeding Migratory Songbird.

For the first time, we use a small archival global positioning system (GPS) tag to identify and characterize non-breeding territories, quantify migratory connectivity, and identify population boundaries of Ovenbirds (Seiurus aurocapilla), a small migratory songbird, captured at two widely separated breeding locations. We recovered 15 (31%) GPS tags with data and located the non-breeding territories of breeding Ovenbirds from Maryland and New Hampshire, USA (0.50 ± 0.15 ha, mean ± SE). All non-breeding territories had similar environmental attributes despite being distributed across parts of Florida, Cuba and Hispaniola. New Hampshire and Maryland breeding populations had non-overlapping non-breeding population boundaries that encompassed 114,803 and 169,233 km2, respectively. Archival GPS tags provided unprecedented pinpoint locations and associated environmental information of tropical non-breeding territories. This technology is an important step forward in understanding seasonal interactions and ultimately population dynamics of populations throughout the annual cycle.

Does Exurban Housing Development Affect the Physiological Condition of Forest-Breeding Songbirds? A Case Study of Ovenbirds (Seiurus aurocapillus) in the Largest Protected Area in the Contiguous United States.

Exurban development (low-density development in rural areas) can significantly alter wildlife community composition, but it is largely unknown whether it also affects wildlife at the individual level. We investigated individual-level impacts of exurban development in New York State's Adirondack Park by comparing the physiological condition of 62 male ovenbirds (Seiurus aurocapillus) breeding in forests with low-density housing development with those in contiguous forests. We used hematocrit (HCT) volume and plasma triglyceride (TRIG) levels to compare energetic condition, plasma uric acid (UA) and total plasma protein (TPP) levels to compare diet quality, and heterophil∶lymphocyte ratios (H∶L) to compare chronic stress. HCT was the only parameter to differ, with birds near houses exhibiting lower values. The comparable TRIG, UA, and TPP that we found between treatment types suggest that ovenbird food quality and availability are unaffected by exurban development in our study area. Similar H∶L suggests that homeowner activities do not significantly change chronic stressors faced by breeding male ovenbirds. We also found no difference in body mass, body size, or age ratio to indicate that habitats in either treatment type were in higher demand or more difficult to acquire. Although our results suggest that exurban development does not reduce habitat quality for male ovenbirds in a way that affects their condition, we caution that it may still ultimately reduce fitness by attracting synanthropic predators. Further work is needed to better understand the impacts of exurban development on wildlife at all levels and provide science-based information needed to meet conservation challenges in rapidly developing exurban areas.

Migratory connectivity of a Neotropical migratory songbird revealed by archival light-level geolocators.

Understanding migratory connectivity is critical for interpreting population dynamics, seasonal interactions, and for the implementation of conservation strategies of migratory species. We evaluated the migratory connectivity of a Neotropical migratory songbird, the Ovenbird (Seiurus aurocapilla) using archival light-level geolocators deployed at two breeding and four nonbreeding locations while incorporating Ovenbird abundance as prior information using Bayes' Rule. We also included band recoveries submitted to the United States Geological Survey's Bird Banding Laboratory to assess connectivity of areas where geolocators were not deployed. We created a probabilistic map of origin for each capture site and mapped spring migration routes between nonbreeding and breeding locations. We found a complete separation of eastern and western populations of Ovenbirds throughout the annual cycle. Breeding Ovenbirds from western Canada spent the nonbreeding season throughout Central America and migrated through central North America during spring migration. Birds breeding in the northeastern United States were distributed throughout the central Greater Antilles in the Caribbean and migrated through eastern North America during spring migration. Fall migration routes were not included because the timing of migration coincided with fall equinox when latitudinal estimates are unreliable. However, longitudinal estimates suggest no overlap between eastern and western populations during fall migration. Ovenbirds with geolocators attached in Jamaica bred in the northeastern United States with the highest posterior probability of origin found in Massachusetts, while Ovenbirds captured in Florida and Puerto Rico bred primarily in the mid-Atlantic. Incorporating Ovenbird abundance as a prior into geolocator estimates decreased the area of origin by 90.37% ± 1.05% (mean ± SE) for the breeding season and 62.30% ± 1.69% for the nonbreeding season, compared to geolocator estimates alone. Ovenbirds exhibited strong migratory connectivity between breeding and nonbreeding season, which has important implications for various aspects of the ecology, evolution, and conservation.

Benefits of aggregate green tree retention to boreal forest birds

We evaluated the function of aggregate tree retention as mature habitat in a harvested matrix for boreal forest birds in a boreal mixedwood. We compared insular and peninsular residual patches ranging from 0.51ha to 4.32ha with plots in dispersed retention and intact forest to evaluate their usefulness to forest birds as habitat in a harvested matrix. We found that forest bird communities were significantly different in all three treatments and that bird communities in patches were an intermediate condition between intact forest and dispersed retention harvest. We observed 12 predominantly forest species, including Brown Creeper (Certhia americana), Ovenbird (Seiurus aurocapilla), Yellow-bellied Sapsucker (Sphyrapicus varius), and Black-throated Blue Warbler (Setophaga caerulescens), in patches at abundance levels between dispersed retention and intact forest plots. For these species, it appears that patches offer an important habitat in a harvested matrix but at lower abundance than in intact forest. Of the 12 predominantly forest species found in patches, 8 had confirmed breeding. Our results suggest that aggregate retention patches provide breeding quality habitat to a large group of forest species; however, the patches are not equivalent to intact forest suggesting that intact forest should be maintained in landscapes.

Comparison of autonomous and manual recording methods for discrimination of individually distinctive Ovenbird songs

Many animals produce individually distinctive vocalizations with increased outputs during the breeding season. Many animals, including birds, can recognize other individuals based on the distinctive features of their songs and researchers can use bioacoustics tools to discriminate among individuals. Typically, bioacoustics analyses use recordings made with highly directional microphones that are free of background noise and spectral overlap. However, recent technological advances in automated recording have made it possible to record remotely and cover larger areas simultaneously. We tested whether spectrogram cross-correlation can be used to discriminate among songs of 19 individual Ovenbirds (Seiurus aurocapillus). We used two microphone types: directional (Sennheiser MKH-70) and omnidirectional (SMX-II) microphones. Because birds may vary in their distance from the SMX-II microphones, songs were selected as either high-quality (close to the recorder) or low-quality (further away from the recorder). We found that all recording types could be used to discriminate the songs of individual male Ovenbirds from other males in the population. Discrimination among directional recordings was significantly better than among omnidirectional recordings, and high-quality recordings could be used to discriminate among individuals significantly better than low-quality recordings. Taken together, our results suggest that automated omnidirectional recording could be valuable for future behavioural research allowing individuals to be followed over an entire breeding season. In addition, acoustic surveys of communities could provide information about abundance as well as presence and/or absence of species.

ENSO, nest predation risk, food abundance, and male status fail to explain annual variations in the apparent survival rate of a migratory songbird.

Adult mortality can be a major driver of population decline in species whose productivity is relatively low. Yet, little is known about the factors influencing adult survival rates in migratory bird species, nor do we know much about the longer-term effects of habitat disturbance on the fitness of individuals. The Ovenbird (Seiurus aurocapilla) is one of the vertebrate species most sensitive to forest management, yet it is still common and widespread. We monitored the fate of 330 colour-banded Ovenbird males in four pairs of 25-ha plots during 9 successive breeding seasons. One plot of each pair was treated through selection harvesting (30–40% basal area removed) during the first winter. We tested the following hypotheses: (1) higher physiological costs in harvested plots as a result of lower food abundance will reduce apparent survival rate (ASR) relative to controls; (2) lower ASR following years with low nest survival and higher probability of renesting; (3) fluctuations in ASR reflecting El Niño Southern Oscillation (ENSO); and (4) higher ASR in returning males than in recruits (unbanded immigrants) owing to greater site familiarity in the former. We tested the relative importance of these hypotheses, or combinations thereof, by generating 23 models explaining variation in ASR. The year-dependent model received the most support, showing a 41% decrease in ASR from 2007 to 2014. The important year-to-year variation we observed in ASR (Σwi = 0.99) was not explained by variation in nest predation risk nor by ENSO. There was also little evidence for an effect of selection harvesting on ASR of Ovenbird males, despite a slight reduction in lifespan relative to males from control plots (2.7 vs 2.9 years). An avenue worth exploring to explain this intriguing pattern would be to determine whether conditions at migratory stopover sites or in the wintering area of our focal population have gradually worsened over the past decade.

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.