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Virginia Bald Eagle breeding survey: A twenty-five year summary (1977-2001)
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... Our study area included lands surrounding all major water bodies in the coastal plain of Virginia. The study area is described by Watts and Byrd (2002). We conducted systematic surveys for Bald Eagle nests and breeding activity during 1999-2005 as part of the Virginia monitoring program. ...
We evaluated the impact of Hurricane Isabel on nest loss and reproductive performance of Bald Eagles (Haliaeetus leucocephalus) in the lower Chesapeake Bay. Approximately 40% of Bald Eagle nest trees (n = 527) were damaged and 127 nests were lost during the storm. Nest loss was significantly higher than in years prior to and after the storm. Only 46% of pairs that lost nests attempted to breed the following season, compared to 85% of pairs that did not lose nests. Of the pairs that made breeding attempts, only 69% of pairs that lost nests during the hurricane produced young compared to 83% of pairs that did not lose nests. Average brood size was also reduced for pairs that lost nests. The disparity in reproductive performance between the two groups narrowed in the second breeding season after the storm. Hurricane Isabel had a significant but short-lived impact on the Bald Eagle breeding population in the lower Chesapeake Bay.
... The species was proposed for endangered status within Virginia during both 1978 and 1989 (Byrd 1979b(Byrd , 1991b due to the reduced population status, contaminant-induced reproductive suppression and ongoing habitat loss. Since this time, the population has undergone a dramatic recovery with an average doubling time of approximately 8 years (Watts and Byrd 2002, 2008 reaching 726 pairs by 2011 (Watts and Byrd 2011). The population is now estimated to exceed 1,000 pairs (Watts and Byrd, unpublished data). ...
Virginia supports a diverse community of breeding birds that has been the focus of investigation for more than 400 years. The avifauna reflects the latitudinal position of the state and the fact that the border extends from the Atlantic Ocean to the Appalachian Mountains. A total of 224 species have been recorded breeding in Virginia, 214 of which are extant. Twenty species have colonized the state since 1900 including 14 since 1950. Of all extant species, 102 (48%) are considered common at least somewhere in the state and 64 (30%) are rare to very rare. Diversity varies by physiographic region with 179 (83%), 168 (78%) and 141 (66%) in the Coastal Plain, Mountains and Piedmont, respectively. Two significant landscape features make significant contributions to the statewide diversity including tidal waters along the coast and isolated spruce-fir forests of the Appalachians that represent Pleistocene-era relicts. In all, nearly 25% of the statewide avifauna is either wholly or nearly confined to tidal water and 10% is confined to "sky island" refugia. Since 1978, 25 species of birds throughout Virginia have been identified as requiring immediate conservation action. A retrospective assessment shows that 5 of these species including osprey (Pandion haliaetus), bald eagle (Haliaeetus leucocephalus), peregrine falcon (Falco peregrinus), brown pelican (Pelecanus occidentalis) and piping plover (Charadrius melodus) have recovered to or beyond historic numbers. Three species including Bewick's wren (Thryomanes bewickii), Bachman's sparrow (Peucaea aestivalis) and upland sandpiper (Bartramia longicauda) have been lost from the state and the black rail (Laterallus jamaicensis), loggerhead shrike (Lanius ludovicianus) and Henslow's sparrow (Ammodramus henslowii) are in imminent danger of extirpation. Several species including the peregrine falcon, piping plover, Wilson's plover (Charadrius wilsonia) and red-cockaded woodpecker (Picoides borealis) are the focus of intensive monitoring and management programs. The underlying causes of imperilment remain unclear for several species of concern, limiting our ability to development effective conservation strategies.
... The Bald Eagle breeding population within Virginia and the broader Chesapeake Bay reached a low in the early 1970s (Abbott 1974)but has been growing exponentially over the past three decades with an average doubling time of less than 8 years (Watts and Byrd 2002, Watts et al. 2007, 2008. Bald eagles in Virginia nest almost exclusively in trees, including primarily loblolly pines (Pinus taeda) and various hardwoods (Jaffee 1980, Watts 2005. ...
... This study included the tidal reaches of the lower Chesapeake Bay and the lower Delmarva Peninsula in Virginia (Watts et al. 2006). The breeding population within this location and the broader Chesapeake Bay reached a low in the early 1970s but has been growing exponentially over the past 3 decades with an average doubling time of less than 8 years (Watts and Byrd 2002;Watts et al. , 2008. Nests within the study area have a high turnover rate (Watts and Duerr 2010) due primarily to wind throw . ...
For over 30 years, bald eagle (Haliaeetus leucocephalus) nests and nest trees have been managed using a combination of spatial buffers and time-of-year restrictions. Most management standards include the protection of nests currently in use as well as alternate nests and trees that have lost nests. Protection is extended to alternate nest structures under the assumption that they provide value to the breeding population. However, the notion that these structures hold enough residual value to warrant the cost of their protection has not been fully explored. I used nest histories (n > 2,250) from a long-term (1962–2011) dataset collected in the lower Chesapeake Bay to evaluate the relationship between management costs and residual value across the range of management scenarios currently in use. I used a joint, multistrata, live-recapture/dead-recovery model in Program MARK to estimate probabilities of annual survival for active and alternate nests and transition probabilities between active and alternate nests. My primary objective was to assess the residual biological value of alternate nests and trees relative to the management costs required to protect them. I estimated the per capita management costs and the residual value of alternate nests and trees. Survival rates were 0.902 ± 0.007 (mean ± SE) and 0.703 ± 0.017 for active and alternate nests, respectively. Of 1,163 alternate nests, 352 (30.3%) were determined to be re-used within 5 years. However, the likelihood of re-use declined with time. Most re-used nests were re-used in the first year (76.4%), with virtually all (98.6%) being re-used in the first 3 years. Only 9.9% (168 of 1,699) of trees that had lost nests were re-used within the first 10 years. Nests were rebuilt in 32% (equating to 3.1% re-use) of re-used trees in the first year and in 71.4% of these trees in the first 3 years. Implementation of current national management guidelines resulted in 2.35 nest equivalents of management cost for each active nest in the population. The residual value and cost functions diverged over time such that the return on social investment diminishes over the management periods. The cost-to-benefit relationship is particularly poor when the protection of alternate nests is extended beyond 3 years and when protection is extended to trees that have lost nests. © 2015 The Wildlife Society.
We evaluated the impact of Hurricane Isabel on nest loss and reproductive performance of Bald Eagles (Haliaeetus leucocephalus) in the lower Chesapeake Bay. Approximately 40% of Bald Eagle nest trees (n = 527) were damaged and 127 nests were lost during the storm. Nest loss was significantly higher than in years prior to and after the storm. Only 46% of pairs that lost nests attempted to breed the following season, compared to 85% of pairs that did not lose nests. Of the pairs that made breeding attempts, only 69% of pairs that lost nests during the hurricane produced young compared to 83% of pairs that did not lose nests. Average brood size was also reduced for pairs that lost nests. The disparity in reproductive performance between the two groups narrowed in the second breeding season after the storm. Hurricane Isabel had a significant but short-lived impact on the Bald Eagle breeding population in the lower Chesapeake Bay.
With the DDT ban enacted in the early 1970s, piscivorous bird populations have grown exponentially throughout the tidal reach of the Chesapeake Bay. However, avian population growth is not uniform throughout the Chesapeake Bay watershed; several species including Bald Eagles (Haliaeetus leucocephalus) and Ospreys (Pandion haliaetus) experienced significantly greater population growth rates in riverine tidal freshwater and oligohaline regions than in higher salinity portions of the bay. Shifting fish prey resources may provide an explanation for the observed influence of salinity on distribution of piscivorous bird populations. Changes in the fish resources available to avian predators over the past 40 years include changing temporal and spatial distribution of fish prey, as well as shifts in taxonomic and trophic structure of resident and migratory fish assemblages. Historical ecological changes, including long- and short-term changes in the abundance of anadromous clupeid fishes, Atlantic Menhaden (Brevoortia tyrannus), and the relatively recent introduction and establishment of non-indigenous fishes, within tidal freshwater rivers may be influencing piscivorous bird distributions and abundance, particularly for Bald Eagles and Ospreys, in the Chesapeake Bay. Predator-prey interactions among piscivorous birds and fish prey have received little attention from wildlife managers. Collaborative efforts between fishery scientists and avian ecologists will ultimately lead to better ecosystem management of the Bay’s living resources.
Aimed to determine 1) the frequency and causes of error in aerial surveys at different stages of the breeding season of Haliaeetus leucocephalus on the Chippewa National Forest, and 2) the aerial survey schedule that would provide the most accurate estimates of nesting parameters of the bald eagle population. -from Authors
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