Geology topics

Andrew Gilbert

Publications and source records attributed to Andrew Gilbert.

4 recordsLinked to original sources

USGS2023

Assessing individual movement, habitat use, and behavior of non-breeding marine birds in relation to prey availability in the US Atlantic

Resource availability is a key factor driving marine bird movements and distributions, but direct information on prey availability is difficult to obtain at relevant scales. We present novel methods for describing multi-scale trophic associations, combining movement analyses of marine birds with estimates of forage fish surface aggregations from digital aerial survey data and species occupancy from bottom trawl survey data. We analyzed satellite telemetry data from northern gannets Morus bassanus , red-throated loons Gavia stellata , and long-tailed ducks Clangula hyemalis in the US Atlantic during the non-breeding period. Using discrete-time hidden Markov models to distinguish area-restricted (i.e. putative foraging) from transit movements, we examined how environmental factors influence movement, and how forage fish species distributions and surface aggregations influence habitat use by gannets and loons that have greater dietary reliance. Our results suggest that chlorophyll a concentration significantly affected movement behavior across species, highlighting the importance of higher-productivity areas around estuaries during colder months when regional productivity is low. Though variable across species and seasons, spatial cross-correlation analysis revealed that herring species (Family Clupeidae), including Atlantic menhaden Brevoortia tyrannus , may be important resources; it also showed positive spatial correlations with forage fish aggregations. This suggests that prey patch dynamics and factors driving aggregation formation may be as important as species composition. However, spatial patterns were generally low (<0.3), suggesting a mismatch in spatiotemporal resolution, exemplifying the challenges in quantifying trophic relationships in marine systems. Disentangling predator-prey relationships is critical to understanding the mechanisms driving marine bird behavior in rapidly changing marine systems.

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USGS2017

Determining fine-scale use and movement patterns of diving bird species in federal waters of the Mid-Atlantic United States using satellite telemetry

Offshore wind energy development in the United States is projected to expand in the upcoming decades to meet growing energy demands and reduce fossil fuel emissions. There is particular interest in commercial offshore wind development within Federal waters (i.e., > 3 nautical miles from shore) of the mid-Atlantic. In order to understand the potential for adverse effects on marine birds in this area, information on distribution and behavior (e.g., flight pathways, timing, etc.) is required for a broad suite of species. In areas where offshore wind development is likely to occur, such information can be used to identify high use areas during critical life stages, which can inform the siting of offshore facilities. It can also be used to provide baseline data for understanding broad changes in distributions that occur after offshore wind developments are constructed in a specific area.

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USGS2015

Incorporating temporal variation in seabird telemetry data: time variant kernel density models

A key component of the Mid-Atlantic Baseline Studies project was tracking the individual movements of focal marine bird species (Red-throated Loon [Gavia stellata], Northern Gannet [Morus bassanus], and Surf Scoter [Melanitta perspicillata]) through the use of satellite telemetry. This element of the project was a collaborative effort with the Department of Energy (DOE), Bureau of Ocean Energy Management (BOEM), the U.S. Fish and Wildlife Service (USFWS), and Sea Duck Joint Venture (SDJV), among other organizations. Satellite telemetry is an effective and informative tool for understanding individual animal movement patterns, allowing researchers to mark an individual once, and thereafter follow the movements of the animal in space and time. Aggregating telemetry data from multiple individuals can provide information about the spatial use and temporal movements of populations. Tracking data is three dimensional, with the first two dimensions, X and Y, ordered along the third dimension, time. GIS software has many capabilities to store, analyze and visualize the location information, but little or no support for visualizing the temporal data, and tools for processing temporal data are lacking. We explored several ways of analyzing the movement patterns using the spatiotemporal data provided by satellite tags. Here, we present the results of one promising method: time-variant kernel density analysis (Keating and Cherry, 2009). The goal of this chapter is to demonstrate new methods in spatial analysis to visualize and interpret tracking data for a large number of individual birds across time in the mid-Atlantic study area and beyond. In this chapter, we placed greater emphasis on analytical methods than on the behavior and ecology of the animals tracked. For more detailed examinations of the ecology and wintering habitat use of the focal species in the midAtlantic, see Chapters 20-22.

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USGS2015

Wintering movements and habitat use of Surf Scoter (Melanitta perspicillata) in the mid-Atlantic U.S.

Wintering habitat use and migratory pathways are key issues facing sea ducks in the mid-Atlantic U.S. and elsewhere due to the potential for offshore wind energy development. A comprehensive understanding of important winter habitats and environmental characteristics determining sea duck abundance and distribution is paramount in advising marine spatial planning efforts in the region and identifying key resource areas for sea ducks. We captured and tracked 101 Surf Scoters to investigate the spatial patterns, temporal patterns, and environmental variation in migration and winter habitat use through a combination of satellite telemetry data and remotely collected environmental covariate information. We found that Surf Scoters in core-use areas utilized shallow (<40 m) areas within 4.5 km from shore. Resource selection models suggest that other dynamic variables such as sea surface temperatures, productivity, and salinity (and selected interactions among them) may also be important in determining valuable scoter habitat. Migration chronology of birds tracked in this study suggests that Surf Scoters wintering and migrating throughout the mid-Atlantic region could encounter future offshore wind energy facilities between mid-October and early May. Our analyses indicate Surf Scoters tagged along near-shore areas of the mid-Atlantic have a minimal likelihood of overlapping with current Wind Energy Areas (WEAs) in the mid-Atlantic, though activities associated with construction within WEAs, such as installation of transmission lines or vessel traffic within nearshore areas, or possible development of wind farms closer to shore and outside currently designated WEAs, may have a higher likelihood of overlapping with wintering Surf Scoters in the mid-Atlantic.

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