Code

CCBTR-19-02

Publication Date

2019

Abstract

The lower Susquehanna River including Exelon hydroelectric facilities falls within the Upper Chesapeake Bay Bald Eagle Concentration Area. The area supports a large and growing breeding population of bald eagles and is a convergence area for resident non-breeding eagles and migratory eagles from populations along the entire Atlantic Coast. The area represents one of the highest-use eagle areas in eastern North America and supports a growing breeding population and a network of communal roosts. In consideration of this significance, Exelon has developed a bald eagle management plan for the area that includes periodic monitoring. The objectives of this project were 1) to survey the area for pairs of breeding bald eagles and 2) to determine the occupancy status of known communal roosts. We surveyed the study area for bald eagle nests using a standard two-flight approach and examined 51 bald eagle nests. We located 35 occupied breeding territories and documented 29 breeding attempts. Breeding success was 86.2% and pairs produced at least 46 young. Average reproductive rate was 1.31/pair and 1.59/breeding attempt. This rate is above that required for population maintenance and is consistent with recent rates documented throughout the broader Chesapeake Bay. The breeding population has increased 290% since the survey conducted in 2010 representing an average doubling time of 5.2 years. This rate of growth is higher than that for the broader Bay population. We counted 230 bald eagles during 43 surveys of 19 communal roosts within the study area. More than twice (159 winter vs 71 summer) as many birds used the set of roosts during the winter compared to the summer period. Considering known-age birds, an identical ratio of juveniles to adults (44.8 juveniles: 55.2% adults) was documented for both the winter and summer periods. We found eagles within all communal roosts (N = 19) included in the survey during at least one season. Fifteen roosts were used during both winter and summer. The number of eagles associated with roosts ranged from 1 to 78 during the winter survey and from 1 to 14 during the summer survey. We discovered a new roost during the summer survey period.

Topic

Abundance/distribution, Behavior, Habitat Quality/Use/Movement, Breeding/Demography/Population Dynamics

Species

Bald Eagle

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