Geology topics

Tania Lewis

Publications and source records attributed to Tania Lewis.

2 recordsLinked to original sources

USGS2020

Using a bayesian multistate occupancy model to assess seabird and shorebird status in Glacier Bay, Alaska

The U.S. Department of Interior National Park Service is charged with both monitoring avian communities and evaluating the influence of visitors to National Parks on sensitive species; however, this task is challenging considering that sampling programs often involve multiple species, each with differing behavior, habitat requirements, and detectability. Our objectives were to build a model to describe the status of waterbirds in Glacier Bay National Park, Alaska, USA, and assess effects of area closures on these species. We used a Bayesian multistate occupancy model to describe the status of multiple species and make the best possible use of existing survey data. We modeled up to 5 states per species and evaluated predictors of occupancy, nesting, and abundance, as well as survey-related predictors of state-dependent detection probability. We found that occupancy probability varied across species and habitats (islands vs. glacial outwashes). For most species, occupancy probability was substantially greater at sites occupied in the year previous (site persistence). We found weak evidence that area closures affected the occurrence of species in the study, but this was largely because most sites were closed for the entirety of the study period. The probability of detecting occurrence, nesting, and abundance varied across species and survey methods (ground vs. vessel). Detection parameters provided valuable information for enhancing the efficiency of future surveys, by identifying preferred survey methods and sampling periods for specific waterbird species. © 2020 The Wildlife Society.

Alaska↗

USGS2009

Black and Brown Bear Activity at Selected Coastal Sites in Glacier Bay National Park and Preserve, Alaska: A Preliminary Assessment Using Noninvasive Procedures

A number of efforts in recent years have sought to predict bear activity in various habitats to minimize human disturbance and bear/human conflicts. Alaskan coastal areas provide important foraging areas for bears (Ursus americanus and U. arctos), particularly following den emergence when there may be no snow-free foraging alternatives. Additionally, coastal areas provide important food items for bears throughout the year. Glacier Bay National Park and Preserve (GLBA) in southeastern Alaska has extensive coastal habitats, and the National Park Service (NPS) has been long interested in learning more about the use of these coastal habitats by bears because these same habitats receive extensive human use by park visitors, especially kayaking recreationists. This study provides insight regarding the nature and intensity of bear activity at selected coastal sites within GLBA. We achieved a clearer understanding of bear/habitat relationships within GLBA by analyzing bear activity data collected with remote cameras, bear sign mapping, scat collections, and genetic analysis of bear hair. Although we could not quantify actual levels of bear activity at study sites, agreement among measures of activity (for example, sign counts, DNA analysis, and video record) lends support to our qualitative site assessments. This work suggests that habitat evaluation, bear sign mapping, and periodic scat counts can provide a useful index of bear activity for sites of interest.

Open-File Report↗