Use of Satellite Transmitters to Delineate Bald Eagle Communal Roosts within the Upper Chesapeake Bay

Watts, Bryan D.; Mojica, Elizabeth K.

doi:10.3356/jrr-10-86.1

Cited by 9 publications

(7 citation statements)

References 14 publications

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“…Major activity centers along the shorelines that were delineated in this investigation are comparable to foraging areas delineated in the 1980s (Millsap et al 1983, Buehler et al 1987. Similarly, of the 17 communal roosts delineated in the 1980s (Buehler et al 1991b), 13 remained active during the present study (Watts and Mojica 2012). Stability in activity patterns suggests that investments made in mitigation will provide benefits far into the future.…”

Section: Discussionmentioning

confidence: 56%

“…Unlike conventional home-range techniques where UD surfaces are produced by a set of independent locations, BBMMs take advantage of both the order of locations and the time between them to delineate areas of high use that can be used to identify activity centers and movement pathways. Activity centers for bald eagles within the upper Chesapeake Bay study area include communal roosts (also used as daytime loafing areas) and major foraging areas (Watts and Mojica 2012). Eagles repeatedly use movement corridors that connect communal roosts to foraging areas, communal roosts to communal roosts, and foraging areas to other foraging areas.…”

Section: Discussionmentioning

confidence: 99%

“…As indicated above, activity centers are consistent with patterns observed 30 years previous and during the intervening decades (SWCA, Inc. 1996). In addition, the entire network of communal roosts (n ¼ 170) was revealed by the cohort of birds within the first year of tracking (Watts and Mojica 2012), suggesting that birds tracked are integrated within the broader population and are freely moving throughout the study area.…”

Section: Discussionmentioning

confidence: 99%

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Using Brownian bridges to assess potential interactions between bald eagles and electrical hazards within the upper Chesapeake Bay

2015

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One of the most effective means of minimizing mortalities of large raptors from collisions with hazards is to locate hazards away from major activity centers. A reliable means of delineating bird activity centers on the landscape has been a significant impediment to progress in proactive infrastructure planning. We used Brownian bridge movement modeling to develop a population-wide, utilization probability surface for bald eagles (Haliaeetus leucocephalus) within the upper Chesapeake Bay. We used locations (n ¼ 320,304) for individuals (n ¼ 63) tracked with global positioning system (GPS) satellite transmitters between 2007 and 2011 in the analysis. We intersected the electrical network on the probability surface within Aberdeen Proving Ground, a 350-km 2 military installation to identify overlap between power lines and eagle activity centers. We also overlaid locations of eagle mortalities attributed to the lines (n ¼ 67) on the installation to assess the relationship between mortality rates and utilization probabilities. Areas of high bald eagle use were relatively rare on the landscape with only 0.1% and 5% of the area accounting for 10% and 30% of estimated utilization. Most electric lines were along roads and distributed away from eagle activity centers, with only 0.3% of lines located within areas with the highest estimated eagle use. Eagle mortalities were highly skewed to lines that overlapped with eagle activity centers. Eagle mortality rates (birds/100 km/yr) were 42 times higher along lines associated with the highest 10% of eagle use compared to lines associated with the lowest 10% use, suggesting that estimated utilization may be an effective proxy for mortality risk associated with electric line hazards. The majority (71.9%) of high-use bald eagle areas delineated within the study area have no existing electric lines. Utilization probabilities may be a potential tool for site-specific infrastructure planning. Ó 2015 The Wildlife Society.

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Section: Discussionmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Using Brownian bridges to assess potential interactions between bald eagles and electrical hazards within the upper Chesapeake Bay

2015

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“…Nonbreeding bald eagles are very social and move freely throughout roost networks (Southern , Buehler et al , Isaacs et al ). Previous studies within the study area reported that use of the roost network is independent of migratory status or age class (Watts and Mojica ). For this reason and because we were interested in patterns across populations and age classes that could inform management, we lumped data from all individuals into a single analysis.…”

Section: Methodsmentioning

confidence: 83%

“…Nonbreeding eagles within the upper Chesapeake Bay study area vary their space use according to season (Watts et al ). Within the available network of roost sites, roosts used exclusively during winter or summer are referred to as seasonal and roosts used consistently throughout the year are referred to as year‐round (Buehler et al , Watts and Mojica ). Much of the annual shift in space use corresponds to activation and use of seasonal roosts (SWCA ).…”

Section: Methodsmentioning

confidence: 99%

Mapping bald eagle activity shadows around communal roosts

Watts

Turrin

2017

J Wildl Manag

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We assessed diurnal activity patterns associated with communal roosts (n ¼ 26) by tracking nonbreeding bald eagles (Haliaeetus leucocephalus; n ¼ 58) within the upper Chesapeake Bay, USA, 2008-2013. We used daytime locations (n ¼ 54,165) to map activity shadows (using home range analytics, 90% kernel) around communal roosts, to evaluate the spatial structure and to delineate diurnal activity centers. We overlaid a range (100-3,200 m) of buffers around the perimeter of each roost to estimate the benefits of management scenarios in extending protection to daytime activities. Activity shadows around roosts varied from 1.5 km 2 to 116 km 2 ( x ¼ 30.3 AE 5.48 [SE]), reflecting landscape context. Roosts with small (<10 km 2 ) activity shadows tended to have simple shapes with roosts centrally located and positioned along primary shorelines. Roosts supporting large (>50 km 2 ) activity shadows tended to have complex shapes with roosts not centrally located and set back from primary shorelines. Daytime locations were highly concentrated in areas near communal roosts (76% of locations within 2 km of roost perimeters). Diurnal activity centers (n ¼ 38) included areas surrounding roosts and secondary activity centers that were primarily located along prominent shorelines. Communal roosts play a more significant and multi-faceted role in the eagle life cycle than we previously understood. Many of the roosts positioned along the shoreline provided resting places during the night and day, served as social gathering places during the day, and functioned as feeding locations. Evaluation of management buffers supports current management guidelines that recommend the establishment of 800-m buffers. Establishment of 800-m buffers within the study area would enclose 54% of all daytime locations, 66.7% of the area enclosed within activity centers associated with roosts, and 12.1% of the area enclosed in secondary activity centers. Ó 2017 The Wildlife Society.

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Movements and landscape use of Eastern Imperial Eagles Aquila heliaca in Central Asia

Poessel

Bragin

Sharpe³

et al. 2018

Bird Study

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Use of Satellite Transmitters to Delineate Bald Eagle Communal Roosts within the Upper Chesapeake Bay

Cited by 9 publications

References 14 publications

Using Brownian bridges to assess potential interactions between bald eagles and electrical hazards within the upper Chesapeake Bay

Using Brownian bridges to assess potential interactions between bald eagles and electrical hazards within the upper Chesapeake Bay

Mapping bald eagle activity shadows around communal roosts

Movements and landscape use of Eastern Imperial Eagles Aquila heliaca in Central Asia

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