Detection heterogeneity and abundance estimation in populations of Golden-cheeked Warblers (<i>Setophaga chrysoparia</i>)

Warren, Christopher C.; Veech, Joseph A.; Weckerly, Floyd W.; O'Donnell, Lisa; Ott, James R.

doi:10.1525/auk.2013.13022

Cited by 20 publications

(39 citation statements)

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“…Obtaining unbiased and broadly applicable estimates of density and habitat associations of goldencheeked warblers, and songbirds in general, has been hampered by the difficulty in applying models to counts of breeding birds (Peak 2011;Hunt et al 2012;Warren et al 2013). Monitoring forest songbirds often requires counting primarily acoustic signals from individual territorial breeding males to estimate male density in an area (Brewster and Simons 2009;Hunt et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Landscape and local effects on occupancy and densities of an endangered wood-warbler in an urbanizing landscape

et al. 2015

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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.

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Section: Introductionmentioning

confidence: 99%

Landscape and local effects on occupancy and densities of an endangered wood-warbler in an urbanizing landscape

et al. 2015

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“…, Warren et al. ), we divided the abundance estimates by 113 ha to obtain the model‐based densities.…”

Section: Methodsmentioning

confidence: 99%

“…, Warren et al. ). Although we are unaware of studies comparing the dependent double‐observer method to actual density, Alldredge et al.…”

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Density influences accuracy of model-based estimates for a forest songbird

et al. 2015

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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 1.1–29.8 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.

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“…In particular, positive effects of male density on singing activity have been observed in several avian species (Laiolo & Tella 2007, Warren et al 2013). However, little is known about the effects of this parameter on the singing activity of the turtle dove.…”

Section: Introductionmentioning

confidence: 99%

Aspectos aplicados de la ecología de la tórtola común (Streptopelia Turtur L.) en un ambiente forestal mediterráneo

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Detection heterogeneity and abundance estimation in populations of Golden-cheeked Warblers (Setophaga chrysoparia)

Cited by 20 publications

References 65 publications

Landscape and local effects on occupancy and densities of an endangered wood-warbler in an urbanizing landscape

Landscape and local effects on occupancy and densities of an endangered wood-warbler in an urbanizing landscape

Density influences accuracy of model-based estimates for a forest songbird

Aspectos aplicados de la ecología de la tórtola común (Streptopelia Turtur L.) en un ambiente forestal mediterráneo

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