Precision gain versus effort with joint models using detection/non-detection and banding data.

Capture-recapture techniques provide valuable information, but are often more cost-prohibitive at large spatial and temporal scales than less-intensive sampling techniques. Model development combining multiple data sources to leverage data source strengths and for improved parameter precision has increased, but with limited discussion on precision gain versus effort. We present a general framework for evaluating trade-offs between precision gained and costs associated with acquiring multiple data sources, useful for designing future or new phases of current studies.We illustrated how Bayesian hierarchical joint models using detection/non-detection and banding data can improve abundance, survival, and recruitment inference, and quantified data source costs in a northern Arizona, USA, western bluebird (Sialia mexicana) population. We used an 8-year detection/non-detection (distributed across the landscape) and banding (subset of locations within landscape) data set to estimate parameters. We constructed separate models using detection/non-detection and banding data, and a joint model using both data types to evaluate parameter precision gain relative to effort.Joint model parameter estimates were more precise than single data model estimates, but parameter precision varied (apparent survival > abundance > recruitment). Banding provided greater apparent survival precision than detection/non-detection data. Therefore, little precision was gained when detection/non-detection data were added to banding data. Additional costs were minimal; however, additional spatial coverage and ability to estimate abundance and recruitment improved inference. Conversely, more precision was gained when adding banding to detection/non-detection data at higher cost. Spatial coverage was identical, yet survival and abundance estimates were more precise. Justification of increased costs associated with additional data types depends on project objectives.We illustrate a general framework for evaluating precision gain relative to effort, applicable to joint data models with any data type combination. This framework evaluates costs and benefits from and effort levels between multiple data types, thus improving population monitoring designs.

Modeling the effects of environmental disturbance on wildlife communities: avian responses to prescribed fire.

Prescribed fire is a management tool used to reduce fuel loads on public lands in forested areas in the western United States. Identifying the impacts of prescribed fire on bird communities in ponderosa pine (Pinus ponderosa) forests is necessary for providing land management agencies with information regarding the effects of fuel reduction on sensitive, threatened, and migratory bird species. Recent developments in occupancy modeling have established a framework for quantifying the impacts of management practices on wildlife community dynamics. We describe a Bayesian hierarchical model of multi-species occupancy accounting for detection probability, and we demonstrate the model's usefulness for identifying effects of habitat disturbances on wildlife communities. Advantages to using the model include the ability to estimate the effects of environmental impacts on rare or elusive species, the intuitive nature of the modeling, the incorporation of detection probability, the estimation of parameter uncertainty, the flexibility of the model to suit a variety of experimental designs, and the composite estimate of the response that applies to the collection of observed species as opposed to merely a small subset of common species. Our modeling of the impacts of prescribed fire on avian communities in a ponderosa pine forest in Washington indicate that prescribed fire treatments result in increased occupancy rates for several bark-insectivore, cavity-nesting species including a management species of interest, Black-backed Woodpeckers (Picoides arcticus). Three aerial insectivore species, and the ground insectivore, American Robin (Turdus migratorius), also responded positively to prescribed fire, whereas three foliage insectivores and two seed specialists, Clark's Nutcracker (Nucifraga columbiana) and the Pine Siskin (Carduelis pinus), declined following treatments. Land management agencies interested in determining the effects of habitat manipulations on wildlife communities can use these methods to provide guidance for future management activities.

Quantifying the multi-scale response of avifauna to prescribed fire experiments in the southwest United States.

Landscape-scale disturbance events, including ecological restoration and fuel reduction activities, can modify habitat and affect relationships between species and their environment. To reduce the risk of uncharacteristic stand-replacing fires in the southwestern United States, land managers are implementing restoration and fuels treatments (e.g., mechanical thinning, prescribed fire) in progressively larger stands of dry, lower elevation ponderosa pine (Pinus ponderosa) forest. We used a Before-After/Control-Impact experimental design to quantify the multi-scale response of avifauna to large (approximately 250-400 ha) prescribed fire treatments on four sites in Arizona and New Mexico dominated by ponderosa pine. Using distance sampling and an information-theoretic approach, we estimated changes in density for 14 bird species detected before (May-June 2002-2003) and after (May-June 2004-2005) prescribed fire treatments. We observed few site-level differences in pre- and posttreatment density, and no species responded strongly to treatment on all four sites. Point-level spatial models of individual species response to treatment, habitat variables, and fire severity revealed ecological relationships that were more easily interpreted. At this scale, pretreatment forest structure and patch characteristics were important predictors of posttreatment differences in bird species density. Five species (Pygmy Nuthatch [Sitta pygmaea], Western Bluebird [Sialia mexicana], Steller's Jay [Cyanocitta stelleri], American Robin [Turdus migratorius], and Hairy Woodpecker [Picoides villosus]) exhibited a strong treatment response, and two of these species (American Robin and Hairy Woodpecker) could be associated with meaningful fire severity response functions. The avifaunal response patterns that we observed were not always consistent with those reported by more common studies of wildland fire events. Our results suggest that, in the short-term, the distribution and abundance of common members of the breeding bird community in Southwestern ponderosa pine forests appear to be tolerant of low- to moderate-intensity prescribed fire treatments at multiple spatial scales and across multiple geographic locations.

Ecomorphological relationships of a guild of ground-foraging birds in northern California, USA.

We studied habitat and morphological relationships of nine species of birds comprising a groundforaging guild within four distinct locations in northern California. Although the nine species overlapped extensively in habitat use, we observed subtle differences among species in specific characteristics of the habitats they used. About 40% of all cases were classified to the correct species based on a discriminant analysis (DA) of habitats across all study areas. Classification success from DAs on habitats within study areas ranged from 42 to 66%. Morphologies of species differed to varying degrees as 91% of all cases were classified to correct species by a DA of morphological variables. This morphological separation suggested that each species used different modes of obtaining resources. We found only weak relationships between habitat use and morphology. Morphology predicted from 13.6 to 19.0% of the variation in habitat use within each study area and only 13.9% of the habitat variation across all study areas. Habitat predicted from 6.2 to 14.6% of the morphological variation within each study area and 6.9% across all study areas. We suggest that complimentary relationships of habitat and morphology enabled species within this guild to use unique sets of resources.