Farshid S. Ahrestani | USGS Science

USGS2020

Resource use by American black bear in suburbia: A landholder step selection approach

Range expansion of American black bear ( Ursus americanus ; bear) and residential development has resulted in a growing presence of bear in suburbia. Suburban landscapes exhibiting patchworks of variable-sized parcels and habitats and owned by landowners with diverse values, can create large areas of suitable habitats with limited public access. These landscapes thereby may limit the effectiveness of hunting as a traditional bear population management tool. Managers require better information regarding suburban landowner attitudes regarding hunting before implementing changes intended to increase bear harvest to management populations. To address this need, in 2013, we surveyed landowners to identify properties that allowed bear hunting in three suburban areas of Pennsylvania where bear sightings have increased. We then used location data obtained for 29 bears equipped with global positioning system (GPS) transmitters from 2010 to 2012 to model their resource selection in the study area. We assessed the influence of hunting access, housing density, land cover, and topographic variables on radio-marked black bear monitored 10 days before, during, and after the bear hunting season. We found that resource selection of radio-marked bear was similar for all three periods and bears selected for forested land in all three seasons and herbaceous cover in the pre- and hunting periods. Resource selection by bears was not influenced by whether land was open or closed to hunting in the pre-hunting and hunting periods, but in the post-hunting period lands not open to hunting had support as the second-best model. All radio-marked bears in our study were vulnerable to harvest. However, they did not change resource selection during the hunting season nor did they avoid areas open to hunting. Integrating human dimension data with bear habitat use studies, especially in suburban landscapes, has the potential to address bear space use and population management needs often overlooked in traditional research designs.

Pennsylvania↗

USGS2017

An integrated population model for bird monitoring in North America

Integrated population models (IPMs) provide a unified framework for simultaneously analyzing data sets of different types to estimate vital rates, population size, and dynamics; assess contributions of demographic parameters to population changes; and assess population viability. Strengths of an IPM include the ability to estimate latent parameters and improve the precision of parameter estimates. We present a hierarchical IPM that combines two broad‐scale avian monitoring data sets: count data from the North American Breeding Bird Survey (BBS) and capture–recapture data from the Monitoring Avian Productivity and Survivorship (MAPS) program. These data sets are characterized by large numbers of sample sites and observers, factors capable of inducing error in the sampling and observation processes. The IPM integrates the data sets by modeling the population abundance as a first‐order autoregressive function of the previous year's population abundance and vital rates. BBS counts were modeled as a log‐linear function of the annual index of population abundance, observation effects (observer identity and first survey year), and overdispersion. Vital rates modeled included adult apparent survival, estimated from a transient Cormack‐Jolly‐Seber model using MAPS data, and recruitment (surviving hatched birds from the previous season + dispersing adults) estimated as a latent parameter. An assessment of the IPM demonstrated it could recover true parameter values from 200 simulated data sets. The IPM was applied to data sets (1992–2008) of two bird species, Gray Catbird ( Dumetella carolinensis ) and Wood Thrush ( Hylocichla mustelina ) in the New England/Mid‐Atlantic coastal Bird Conservation Region of the United States. The Gray Catbird population was relatively stable (trend +0.4% per yr), while the Wood Thrush population nearly halved (trend −4.5% per yr) over the 17‐yr study period. IPM estimates of population growth rates, adult survival, and detection and residency probabilities were similar and as precise as estimates from the stand‐alone BBS and CJS models. A benefit of using the IPM was its ability to estimate the latent recruitment parameter. Annual growth rates for both species correlated more with recruitment than survival, and the relationship for Wood Thrush was stronger than for Gray Catbird. The IPM's unified modeling framework facilitates integration of these important data sets.

Ecological Applications↗