As top-level piscivores, Bald Eagles are a compelling subject for the study of territory dynamics and are highly representative of the distinctive suite of avian species that occupy Florida Bay. Despite successful recovery of Bald Eagles (Haliaeetus leuocephalus) throughout the species range, the population breeding within Florida Bay has not mirrored this trend. Beginning in the late 1980s, Florida Bay has suffered in its capacity to support species diversity and abundance as a result of extreme changes in hydrology related to altered flows of incoming freshwater. In fact, Bald Eagle territory use in Florida Bay has declined by as much as 43% as year to year variation and sensitivity to transitions between territory states have increased. Florida Bay’s populations of other large, conspicuous fish-eating birds, including Ospreys, Great White Herons, Roseate Spoonbills, and Reddish Egrets each exhibit a similar pattern of decline. The effects of environmental degradation throughout Florida Bay are magnified at higher trophic levels. The negative trend in territory occupancy is most pronounced in southeast Florida Bay whereas effects on territory occupancy in the northwest are minimal. The presence of spatial patterns in territory occupancy, despite regionally available breeding birds, suggests that individuals are evaluating differences in habitat quality for which certain territories are no longer considered viable. Building on our current understanding of the health of this population of Bald Eagles, we have successfully implemented modeling approaches that identify key territory breeding decisions. Loss of early breeding season activity (occupied and active territories) despite maintaining high breeding success indicates that changes in territory dynamics are the result of a failure to breed and not a reproductive failure. As such, future conservation actions should promote early breeding season activity (decisions by breeding pairs to initiate nesting) in areas of Florida Bay that were historically occupied but are now abandoned. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Forested shoreline is important perching habitat for bald eagles (Haliaeetus leucocephalus). Bald eagles hunt, feed and loaf on shoreline perches. I measured trees suitable for bald eagle perches along the northern Chesapeake Bay during 1990-1991 to determine the influence of shoreline perch tree availability on bald eagle distribution. The shoreline was divided into 250 x 50 m segments. A segment was considered used if at least 1 eagle had perched on it during 1985-1992. I determined the number of suitable shoreline perch trees, percent forest cover, and distance from the water to the nearest suitable perch tree for each segment. Segments along the Chesapeake Bay had an average of 1 suitable perch tree per 10 m of shoreline. Shoreline segments used by eagles had more suitable perch trees (P = 0.0008) and a larger percent of forest cover (P = 0.0008). Suitable trees on segments with eagle use were closer to water than suitable trees on segments without eagle use (P = 0.0087). The differences in segments with and without eagle use appear to be largely due to the lack of trees in marshes which were used only seldomly. Marsh had few suitable perch trees, less forest cover and a greater mean distance from water to the nearest suitable perch tree than the other land types (P < 0.0001). These factors are unfavorable for foraging eagles and most marsh segments (66.7%) were unused, probably for this reason. The number of suitable perch trees and the percent of forest cover were lower on developed areas than undeveloped, forested areas (P < 0.01 for both tests). Also the distance from water to the nearest suitable perch tree was greater on developed land than forested land (P < 0.01). Thus, development appears to decrease the availability of suitable shoreline perch trees when compared to forested areas. Logistic regression models were created to predict the probability of eagle use, given the conditions at the time of this study. Varying values of development density, percent forest cover, number of suitable perch trees and distance from water to the nearest suitable tree were inputs used in these models to create curves to predict eagle use under different conditions. These curves indicated that, for a given development density, the probability of eagle use increased as the number of suitable perch trees or percent forest cover on the segment increased. Also, for a given development density, the probably of eagle use increases as the distance to water decreases. / Master of Science

During 1991-1993, I studied movements of 23 adult and 7, 8-10 week old nestling bald eagles captured in Glacier Bay National Park and Preserve, Alaska. I estimated locations by homing and satellite telemetry. During the breeding season, the distances adult eagles moved from successful, unsuccessful, and mixed-success nests were not significantly different (£ = 0.148). Regardless of nest success, the proportion of adult eagle locations within 750 m of their nest were not significantly different during the breeding season (£ = 0.152) and between the breeding and non-breeding seasons (£ = 0.075). On average, bald eagles were perched 91 % of the time; and perching was the most frequently observed activity (£ < 0.001). Adult eagles perched more often in conifers than cottonwoods, snags, or intertidal debris (£ < 0.001). Perch types selected (£ = 0.473), as well as eagle activity (£ = 0.126) were not significantly different during the breeding and non-breeding seasons. Fifty-eight percent of radio-ma~ked adult eagles used 3 watersheds in Glacier Bay from August through January 1991-1993. Six adult (26%) and 6 (86%) fledgling eagles moved out of Glacier Bay during the non-breeding season. Four adult eagles (17%) traveled to the Chilkat Bald Eagle Preserve in late November and December (mean distance from nest to preserve = 74 km) and 57% of the fledgling eagles were on the Chilkat River in October, where they remained for 2-12 weeks. After leaving the Chilkat River, all fledgling eagles traveled in a southeasterly direction; one male fledgling traveled 435 km in 28 days to Prince Rupert, British Columbia. / Master of Science

GIS (Geographic Information Systems) and remote sensing techniques were used to predict relationships between bald eagle nest presences and land type, distance to land type and impervious surface cover area. Data plots revealed bald eagle nest presence decreases in response to an increase in area of bareland; increases with an increase in area of forested land; decreases with an increase in distance (m) to shoreline, and decreases in response to an increase in area of impervious surfaces. Logistic regression models identified impervious surfaces as an indicator for bald eagle nest presence (P 24% as unsuitable. Unsuitable area covered 17.82% of the total study area, impacted area covered 13.40%, and, sensitive area covered 68.77%. The projected increase in population in the state of Virginia and subsequent increase in impervious surfaces presents a challenge to the future viability of the Virginia Chesapeake Bay bald eagle population. The threshold analysis identified areas of prime conservation concern for bald eagle nest presence within the defined study area. These areas provide the basis for a conservation management plan and for further scientific study.

Influence of historic landscapes and contemporary species management on Chesapeake Bay Bald Eagles and Osprey Catherine B. Viverette Co-distributed species with well documented demographic histories can provide good models for testing alternative hypotheses about the impact of evolutionary history, contemporary landscapes, and species management on current distribution and population structure. The Osprey (Pandion haliaetus) and Bald Eagle (Haliaeetus leucocephalus) have been extensively studied, managed and monitored across their North American breeding range, particularly in the Chesapeake Bay. We used a combination of ecological niche modelling, diet reconstruction, and population genetic modeling to understand the role of historic events--both shallow and deep time--on contemporary species distribution. The first objective of this study was to develop contemporary and paleo-distributional models for North American Bald Eagles and Osprey in order to explore the geographic histories of the two species, including the identity of possible Pleistocene refugia. Potential distribution during past (e.g. Last Glacial Maximum, LGM) and possible future climate scenarios were developed with species occurrence records for Osprey (n = 3034) and Bald Eagles (n = 8859) combined with 19 bioclimatic variables representing current conditions using the maximum entropy model (MaxEnt). Paleoclimatic models predict multiple putative refugia that may explain differences in migratory behavior between the two currently co-distributed species, as well as geographically defined sub-populations within each species. We conducted bulk stable isotope analysis of feathers collected from museum specimens and contemporary nests to investigate the influence of historic declines in critical prey species on distribution of Bald Eagles (n = 41 ) and Osprey (n = 45) in the Chesapeake Bay over the past 140 y. Stable Isotope Analysis in R (SIAR) was used to estimate the relative contribution of potential prey items in order to test the hypothesis that migration of estuarine-dependent and anadromous clupeid fishes represents an historically important seasonal subsidy in the form of marine-derived organic matter (MDOM). SIAR results demonstrate that MDOM contributed approximately 50% of the carbon and nutrients to Bald Eagle and Osprey occupying the upper estuary historically but declined to less than 5% of contemporary diets. Declines in anadromous prey in the diet correspond with historic spatial shifts in distribution and population growth of avian predators over the same period. Finally, we tested the hypothesis that conservation efforts, specifically translocation or “hacking” programs, rather than biogeographical history, best explains the current pattern of genetic variation exhibited by Osprey across their North American breeding range. We genotyped 11 microsatellite loci and a 513 base pair sequence of the cyt b region from 433 Osprey samples in order to investigate current population substructure, the genetic consequences of historic demographic bottlenecks, and the influence of hacking programs on contemporary gene flow. We calculated genetic differentiation (Dest) and Isolation-By-Distance (IBD) among regional populations and spatially cohesive genetic clusters identified using the program STRUCTURE. Our results indicate that although Osprey nesting in North America are subdivided into multiple cohesive genetic clusters, genetic differentiation among groups is low and unrelated to geographic variation. The findings of this study are discussed in light of past and present management practices and broader issues salient to species management and conservation of genetic diversity and adaptive response to future environmental change.

This study employed satellite telemetry to document dispersal and migratory behaviour of nine juvenile Bald Eagles (Haliaeetus leucocephalus) and two adult and five hatch-year Osprey (Pandion haliaetus) from central Labrador between 15 Aug 2002--31 Dec 2003. Autumn average departure dates were 20 October 2002 and 13 November 2003 for the eagles and 13 October for both 2002/2003 Osprey, siblings migrating independently. Juvenile Osprey travelled at an average rate of 200 km/d during fall migration; one adult travelled at a rate of 188 km/d enroute to the Dominican Republic. Eagles travelled an average distance of 1200 km over 40 days at a rate of 81 km/d, wintering as far south as Virginia. Eagles departed wintering areas by 25 March 2003, travelling at an average rate of 76 km/d using similar waterways, river valleys and corridors as taken in the fall. Eagles and Osprey were not documented travelling overnight or crossing large bodies of water.

A significant bird hazard to aircraft occurs at times at Port Hardy Airport through the presence of numbers of northern bald eagles in the vicinity of the airport and its approaches. This study investigated bald eagle abundance, distribution, movement patterns, productivity and feeding habits within the airport vicinity and satellite region. Findings were analyzed in the light of comparable ecological information available on the species. The study extended from October 1972 to October 1974. The resident summer and winter population within the airport vicinity approximated 3 eagles. Numbers increased gradually from late August until early November (when salmon were spawning in the Keogh River) and when 11 eagles were continuously present. The maximum number of eagles at any one time was 35. Even a relatively small spawning run of salmon was adequate to attract the eagles and the very large runs did not attract eagles in the same ratio. Eagle numbers decreased from early November until the herring spawning season in March and April when at least 5 eagles were continuously present. The potential hazard to aircraft, expressed as the maximum number of eagle sightings and the number of eagles observed per hour, was greatest during the fall salmon spawning season and the spring herring spawning season for each of the 5 observation areas within the airport vicinity. The population within the study area (200-250 resident eagles) was sufficiently large to dismiss a killing program, even if this was socially acceptable. Mean nesting density in the study area was at least .1 active nest/lineal km of coastline with .2 active nest/lineal km of coastline in the airport vicinity. Fifty seven per cent of the nests failed but those that produced young averaged 1.4 young/nest. Five active nests were within the area of airport activity and they did not differ in success rate or fledged young per successful nest from nests more remote. Statistical analysis of distribution data within the airport vicinity revealed that eagle use was significantly greater in the Keogh River mouth region and significantly lower in the inland region than in the remaining observation areas. The aggregation area along the KeoghiiRiver in the southeast flight path for runway 1028 presented the greatest hazard to aircraft. Direct eagle flights across the flight path occurred at frequent intervals in September and October and were often at the same elevation as approaching or departing jet aircraft. Since it is not likely that the behaviour of the eagles can be changed, ways of altering the flight paths of the aircraft were considered so as to lessen the frequency of interaction. This can be done by extension of runway 102 8 (by about 610m) to allow approaching or departing Boeing 737 jets to pass over, instead of through, the hazardous zone above the Keogh River. / Science, Faculty of / Zoology, Department of / Unknown

The diurnal behavior and nocturnal roosting patterns of 28 bald eagles outfitted with tail-mounted radios were investigated in Rush Valley, Utah between January and March 1982-1984. Casting analysis and feeding observations indicated the principal food source was jackrabbit carrion. Jackrabbit availability declined from 1982 to 1984 and eagles responded by; 1) roosting closer to feeding sites, 2) shifting from canyon to valley roosts, 3) arriving later at and departing earlier from roosts, 4) decreasing diurnal activity, and 5) decreasing residence time. Foraging efficiency appeared to be maximized by experienced eagles using familiar feeding areas and by naive birds monitoring their activity. There appeared to be a slight (8.6%) energetic advantage to roosting at valley sites because of their proximity to feeding areas. This saving was presumably dissipated under adverse weather conditions when eagles selected the sheltered microclimate of canyon slopes. Twelve eagles were tracked during spring migration and all followed northward routes.

Bald Eagles on Amchitka Island, Alaska, were studied from 1969-1972. From 1970-1972 the population averaged 214.6 eagles. The average ration was 66% adults to 34% subadults. The eagles move to and from the island in relation to significant food sources (especially the garbage dump). An increase in active nests occurred from 1969-1972 due to an increase in food. The average percentage of nests containing young from 1970-1972 was 71.28%. During these three years, the average number of young known in a nest per nesting attempt was 1.24, and the average number of young known in a nest per nest containing young was 1.75. In 1972, .86 young fledged per nesting attempt, and 1.42 young fledged per nest fledging young. Prey remains from 1971-1972 averaged 23% mammalian, 61% avian, 14% fish, and 1% invertebrate as calculated by numbers. Bald Eagles were found to regularly prey on sea otter pups.

No description available.