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Incomplete detection during auditory point counts includes the component that individuals are present but silent (“availability”). If the probability of being ‘available’ is less than one and is not random with respect to time or space, population estimates that fail to address availability will be biased. I recorded minute-by-minute singing of 60 male Golden-cheeked Warblers (Setophaga chrysoparia) in 2010–2011 (133 surveys; 6517 min) to estimate availability, evaluate predictors, and provide survey guidance. The per-minute availability was 0.45 (95% confidence intervals [CI]: 0.37–0.54). The availability was higher for unpaired versus paired males (0.82 [0.64–0.92] versus 0.30 [0.20–0.42]) and when ≥1 conspecific was singing (0.61 [0.46–0.75] vs. 0.54 [0.39–0.68]). Availability declined across both day of year and hour of day. Aggregating to common survey lengths, the probability of ≥ 1 song per bin increased with duration but showed the same temporal declines: 3 min = 0.61 (0.52–0.70), 5 min = 0.72 (0.63–0.79), and 10 min = 0.83 (0.74–0.90). Temperature had a modest positive effect, clearest at the 10 min bins. Interaction terms among day, hour, and temperature were unsupported (all likelihood ratio tests p > 0.10). These findings indicate that availability is <1 and varies predictably with day and time, implying that point count protocols should standardize survey windows or model availability explicitly.

Population dynamics of migratory species are influenced by land use and climate patterns experienced across the full annual cycle. Identifying environmental factors influencing productivity, survival, and their relative contributions to abundance and population growth is critical for the recovery and management of at‐risk species in the face of continuing global change. The golden‐cheeked warbler (Setophaga chrysoparia) is an endangered passerine that breeds exclusively in the mixed Ashe juniper (Juniperus ashei)–oak (Quercus) woodlands of Central Texas, USA, and winters at high elevations in Central America. We evaluated the effects of precipitation, climate, and land cover on golden‐cheeked warbler productivity, adult male survival, and territory abundance using data from a long‐term monitoring site, the Balcones Canyonlands Preserve, in Austin, Texas. We jointly analyzed annual productivity, mark–recapture, and territory count data collected on 10 plots from 2011 to 2019 in an integrated population model. The number of young fledged per male territory was negatively related to percent urban land cover within 1 km of monitoring plots, and adult male survival was negatively related to a strong El Niño event. Estimates of population growth and abundance indicated a decline in abundance across our study period. We forecasted population viability 25 years into the future given increases in urban development and frequency of El Niño events. Quasi‐extinction probability increased from 0.17 under current urban land cover conditions and El Niño frequency to 0.41 under the scenario of a 10% increase in urban development around all plots and an increase in El Niño frequency. Productivity and adult survival were positively correlated with population growth, highlighting the need for conservation and management actions to maximize these vital rates on the breeding grounds and range‐wide.

Better knowledge of bird response to savanna and woodland restoration is needed to inform management of these communities. We related temporal and habitat variables to breeding demography and densities of the Eastern Wood-Pewee (Contopus virens) across a gradient of savanna, woodland, and forest. We determined nest success, clutch size, young fledged, and breeding densities and evaluated support for relationships with year, nest stage, date, nest height, tree cover, and percent forest in a 10-km radius. One hundred and twenty-eight of 310 nests (41.3%) fledged young. The most supported nest-survival model included nest stage and percent forest in the landscape. Daily nest survival was greater in the incubation than in the nestling stage and increased substantially with decreasing forest in the landscape. Four nests (1.3%) were parasitized by Brown-headed Cowbirds (Molothrus ater). Eastern WoodPewee density increased 83% over a range of 10–170% tree cover (percent tree stocking). Increased nest success with decreasing forest in the landscape indicates that Eastern Wood-Pewees are not highly susceptible to forest-fragmentation effects in the Missouri Ozarks, probably because they were not very susceptible to brood parasitism. The absence of any strong relationships between habitat measures and nest success, clutch size, or young fledged is in contrast to the large increase in density over the range of tree cover and is further evidence that variation in bird density does not always correspond to similar patterns in productivity.

Robust models of wildlife population size, spatial distribution, and habitat relationships are needed to more effectively monitor endangered species and prioritize habitat conservation efforts. Remotely sensed data such as airborne laser altimetry (LiDAR) and digital color infrared (CIR) aerial photography combined with well‐designed field studies can help fill these information voids. We used point count‐based distance sampling survey data and LiDAR‐fused CIR aerial photography to model density of the Golden‐cheeked Warbler (Setophaga chrysoparia), an endangered songbird, on the 10 000‐ha Balcones Canyonlands National Wildlife Refuge (BCNWR). We developed a novel set of candidate models to explain Golden‐cheeked Warbler detection probability and density using habitat covariates characterizing vegetation structure, composition, and complexity as well as habitat fragmentation, topography, and human infrastructure. We had the most model support for covariates calculated using focal means representing a 3.2 ha territory size (100 m radius) vs. 1.8 and 7.0 ha territory sizes. Detection probability decreased with canopy cover and increased with topographic roughness. Golden‐cheeked Warbler density increased with canopy cover, was highest at a 7:3 ratio of Ashe juniper (Juniperus ashei) to broadleaf tree canopy cover, and decreased with global solar radiation. Predicted warbler densities using 3 min point counts were similar to six estimates from independently collected warbler territory mapping on BCNWR with a mean difference of 6% and a Root Mean Squared Error of 1.88 males/40 ha. The total population size for BCNWR was estimated at 884 Golden‐cheeked Warbler males (95% CI 662, 1206) and predicted densities across the refuge ranged from 0.0 to 0.50 male warblers per ha. On the basis of observed habitat relationships, we defined high quality habitat as having at least 60% canopy cover with Ashe juniper comprising 50–90% of the canopy. We estimated 48% of the area at BCNWR managed for Golden‐cheeked Warblers was in high quality habitat conditions and identified patches within the lower habitat quality areas (14% of warbler management areas) that had the greatest potential to become high quality habitat with management. Our approach combined robust wildlife surveys with highly scalable remotely sensed data to examine habitat relationships, estimate population size, and identify existing areas of high quality habitat. This method can be applied to other species of conservation interest and can be used with multiple years of remotely sensed data to assess changes in habitat at local to regional scales.

Woodhouse's scrub-jay (Aphelocoma woodhouseii texana) is a relatively understudied subspecies inhabiting juniper scrub and woodland in central Texas. We estimated density and examined habitat associations at the eastern edge of their breeding range. Scrub-jays were strongly associated with intermediate proportions of juniper land cover at a 100-m scale and showed lower density in areas of greater mixed oak-juniper woodland and greater urban land cover at a 1-km scale.

Midwestern savannas and woodlands were once dominant transitional communities but are now considered endangered. Savanna and woodland habitat is being restored and managed throughout the central and east-central portions of the United States, but few studies have investigated the effects of management on songbird nest survival. We monitored songbird nests in managed savanna and woodland sites in southern Missouri from 2009 to 2011 to estimate nest survival and to predict the relationships between nest survival and temporal, vegetation structure, and nest site variables. Daily nest survival was generally higher for the four canopy-nesting species, Acadian flycatcher (Empidonax virescens), blue-gray gnatcatcher (Polioptila caerulea), Eastern wood-pewee (Contopus virens), and summer tanager (Piranga rubra) (0.96-0.98), than the four shrub-nesting species, field sparrow (Spizella pusilla), indigo bunting (Passerina cyanea), prairie warbler (Setophaga discolor), and yellow-breasted chat (Icteria virens) (0.92-0.95), for which we estimated survival rates. In general vegetation structure around the nest had little influence on nest survival, except for canopy cover, which occurred in the top model set for four species. Nest survival of yellow-breasted chats was much higher in areas of lower canopy cover, whereas nest survival of Eastern wood-pewees was moderately lower and indigo buntings and summer tanagers peaked at low and intermediate levels of canopy cover, respectively. Therefore, savanna and woodland management, which tends to open the tree canopy, may benefit some bird species in this forested landscape, particularly those associated with low to intermediate canopy cover.

Conservation and management plans often rely on indicators such as species occupancy or density to define habitat quality, ignoring factors that influence reproductive success, and potentially limiting conservation achievements. We examined relationships between predicted density and nest survival with environmental features at multiple spatial scales for the golden-cheeked warbler (Setophaga chrysoparia) in a large preserve within an urbanizing landscape. Larger-scale features of the forest and landscape composition best predicted density, whereas small-scale vegetation features best predicted nest success. Predicted warbler density was more influenced by vegetation structure at the forest (100-m) and landscape (1-km) scales than at the plot (5–11.3-m) scale. Predicted warbler density increased with greater woodland cover (100-m), average canopy height (100-m), and mixed woodland cover (1-km). Average predicted density derived from distance sampling models fit to count data across 1,506 points surveyed during 2011–2014 was 0.21 males/ha (95% CI = 0.20–0.22). Nest survival (n = 610 nests) was strongly correlated with vegetation and terrain characteristics at the plot scale. Period nest survival decreased 28% and increased 36% and 21% across the range of slope, woody understory, and juniper basal area, respectively. Daily nest survival averaged 0.97 (0.96–0.98) but declined throughout the breeding season and varied annually (2011–2015). We recommend management for a high percentage of closed-canopy, tall mixed juniper (Juniperus ashei)-oak (Quercus spp.) woodland at the forest and landscape scales to support high densities of warblers. We also recommend protecting upland woodlands with a well-developed woody understory and greater basal area of junipers because these characteristics were associated with greater nest success.

Knowledge of demographics is important in conservation planning for endangered species. We monitored the endangered Golden-cheeked Warbler (Setophaga chrysoparia) at a large, discontinuous preserve in an urbanizing landscape in central Texas, USA, to estimate survival and productivity. We estimated adult male survival using a spatial Cormack-Jolly-Seber model that separated emigration from mortality by incorporating location data from resightings. Annual male survival varied from 0.45 to 0.67 from 2010 to 2015 (posterior mean ± SD = 0.57 ± 0.06). Sixty-seven percent of resighted males moved <100 m among years, but a large minority of males moved far enough across years that dispersal should be accounted for in future survival analyses. Mean predicted seasonal productivity varied from 2.32 to 3.18 fledglings territory−1 from 2011 to 2015 (mean ± SD = 2.46 ± 0.51). Seasonal productivity was best predicted by the proportion of total woodland land cover in a 1 km radius around the annual median location, total edge density in a 1 km radius, and the standard deviation of canopy height in a 100 m radius. Seasonal productivity peaked at high proportions of total woodland cover, and decreased with increasing edge and canopy height standard deviation. Annual trends for survival and productivity were similar; that is, survival and productivity were above or below average in the same years, which could have important implications for population stability. Our estimated demographic rates are within the range of those reported from the best long-term data, from Fort Hood, Texas, and support the need for large patches of nonfragmented, mature woodlands to provide high-quality breeding habitat for this species.

CONTEXT: Golden-cheeked warblers (Setophaga chrysoparia), an endangered wood-warbler, breed exclusively in woodlands co-dominated by Ashe juniper (Juniperus ashei) in central Texas. Their breeding range is becoming increasingly urbanized and habitat loss and fragmentation are a main threat to the species’ viability. OBJECTIVES: We investigated the effects of remotely sensed local habitat and landscape attributes on point occupancy and density of warblers in an urban preserve and produced a spatially explicit density map for the preserve using model-supported relationships. METHODS: We conducted 1507 point-count surveys during spring 2011–2014 across Balcones Canyonlands Preserve (BCP) to evaluate warbler habitat associations and predict density of males. We used hierarchical Bayesian models to estimate multiple components of detection probability and evaluate covariate effects on detection probability, point occupancy, and density. RESULTS: Point occupancy was positively related to landscape forest cover and local canopy cover; mean occupancy was 0.83. Density was influenced more by local than landscape factors. Density increased with greater amounts of juniper and mixed forest and decreased with more open edge. There was a weak negative relationship between density and landscape urban land cover. CONCLUSIONS: Landscape composition and habitat structure were important determinants of warbler occupancy and density, and the large intact patches of juniper and mixed forest on BCP (>2100 ha) supported a high density of warblers. Increasing urbanization and fragmentation in the surrounding landscape will likely result in lower breeding density due to loss of juniper and mixed forest and increasing urban land cover and edge.

Golden-cheeked Warblers (Setophaga chrysoparia) are endangered songbirds that breed exclusively in the Ashe juniper (Juniperus ashei) and oak (Quercus spp.) woodlands of central Texas. Despite being the focus of numerous studies, we still know little about the size of the range-wide breeding population and how density varies across the spectrum of juniper co-dominated woodlands. Models that have been tested and shown to be accurate are needed to help develop management and conservation guidelines. We evaluated the accuracy and bias of density estimates from binomial mixture models, the dependent double-observer method, and distance sampling by comparing them to actual densities determined by intensive territory monitoring on plots in the Balcones Canyonlands Preserve, Austin, Texas. We found that the binomial mixture models consistently overestimated density by 1.1–3.2 times (actual density = 0.07–0.46 males/ha), and the other two models overestimated by 1.129.8 times at low density and underestimated by 0.5–0.9 times at high density plots (actual density = 0.01–0.46 males/ha). The magnitude of error for all models was greatest at sites with few or no birds (<0.15 males/ha), with model performance improving as actual density increased. These non-linear relationships indicate a lack of sensitivity with respect to true changes in density. Until systematic evaluation demonstrates that models such as those we tested provide accurate and unbiased density estimates for a given species over space and time, we recommend additional field tests to validate model-based estimates. Continued model validation and refinement of point-count methods are needed until accurate estimates are obtained across the density spectrum for Golden-cheeked Warblers and other songbird species. Setophaga chrysoparia es una especie de ave paseriforme amenazada, que se reproduce exclusivamente en bosques de Juniperus ashei y Quercus spp. en la región central de Texas. A pesar de ser el foco de numerosos estudios, aun conocemos poco acerca del tamano de las poblaciones a lo largo de su raneo y sobre como varia la densidad a través del espectro de bosques co-dominados por Juniperus ashei. Los modelos que han sido evaluados y que han mostrado que son precisos, son necesarios para desarrollar estrategias de manejo y conservation de la especie. Evaluamos la precisión y el sesgo de los estimativos de densidad a partir de modelos mixtos binomiales, el método dependiente de doble observador y muestreo distancia, comparándolos con densidades determinadas que los modelos mixtos binomiales consistentemente sobrestimaron la densidad entre 1.1 y 3.2 veces (densidad real = 0.07–0.46 machos/ha) y que los otros dos modelos sobreestimaron la densidad entre 1.1 y 29.8 veces a densidades bajas y subestimaron entre 0.5 y 0.9 veces en las parcelas con densidad alta (densidad real = 0.01–0.46 machos/ha). La magnitud del error para todos los modelos fue mayor en sitios donde encontramos pocas o ningun ave (<0.15 machos/ha), incrementando el rendimiento del modelo a medida que la densidad real incrementaba. Estas relaciones no lineales indican una falta de sensibilidad relacionada con cambios reaies en la densidad. Solo hasta que una evaluatión sistemâtica demuestre que los modelos, similares a los que evaluamos en este estudio, provean estimativos precisos y no sesgados de densidad para una especie determinada a través del tiempo y del espacio, recomendamos que se realicen pruebas adicionales en el campo con el fin de validar los estimadores basados en modelos. La continuación de la validación de los modelos y el refinamiento de los métodos de puntos de conteo serân necesarios hasta que se obtengan estimadores precisos a lo largo del espectro de densidades para Setophaga chrysoparia y otras especies de aves paseriformes.