James D. Fraser’s research while affiliated with Army Research Laboratory and other places

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Publications (11)


Table 2 . Land types of segments with and without recorded bald eagle use on northern Chesapeake Bay, Maryland, 1990- 92.
Perch Trees and Shoreline Development as Predictors of Bald Eagle Distribution on Chesapeake Bay
  • Article
  • Full-text available

April 1995

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64 Reads

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34 Citations

Journal of Wildlife Management

Sheri K. Chandler

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James D. Fraser

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Janis K. D. Seegar

We studied the influence of shoreline perch trees and human development on bald eagle (Haliaeetus leucocephalus) distribution on the northern Chesapeake Bay. Bald eagle distributions may be determined by available suitable shoreline perch areas. Models based on human development and shoreline habitat variables may alleviate problems associated with classifying bald eagle habitat by identifying characteristics predictive of eagle presence. We observed 2,962 eagles during 36 shoreline surveys and relocated 110 radio-marked eagles 1,350 times during 1985-92. We counted 5,928 suitable (height ≥6.1 m, diam at breast height [dbh] ≥20.0 cm, and shoreline accessibility ≥30°) perch trees in 229, 250- × 50-m segments along shoreline during 1990-91. Shoreline segments used by eagles had more suitable perch trees (x̄ = 30.3 vs. 22.0; P < 0.001) and a larger percentage of forest cover (x̄ = 54.9 vs. 39.4; P < 0.001) than unused segments. Suitable trees on segments with eagle use were closer to water than suitable trees on segments without eagle use (x̄ = 8.4 vs. 17.0 m; P = 0.009). Most segments classified as marsh (66.7%) were unused. Marsh segments had fewer suitable perch trees, less forest cover, and a greater mean distance from water to the nearest suitable perch tree than did other land types (P < 0.001). Developed segments had fewer suitable perch trees, less forest cover, and a shorter distance from water to the nearest suitable perch tree than undeveloped forested segments (P ≤ 0.01). Logistic regression models based on various measures of perch tree abundance and shoreline development correctly predicted eagle use for 65.9-71.0% of segments.

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Captive and field- tested techniques for radio-attachment in bald eagles.

January 1995

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51 Reads

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12 Citations

Journal of Field Ornithology

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James D. Fraser

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Mark R. Fuller

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[...]

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Janis K. D. Seegar

The effects of two radio transmitter attachment techniques on captive and one attachment technique on wild Bald Eagles (Haliaeetus leucocephalus) were studied. A Y-attachment method with a 160-g dummy transmitter was less apt to cause tissue damage on captive birds than an X-attachment method, and loosely fit transmitters caused less damage than tightly fit transmitters. Annual survival of wild birds fitted with 65-g transmitters via an X attachment was estimated at 90-95%. As a result of high survival, only five wild birds marked as nestlings were recovered. Two of these birds had superficial pressure sores from tight-fitting harnesses. It is recommended that a 1.3-cm space be left between the transmitter and the bird's back when radio-tagging post-fledging Bald Eagles. Additional space, perhaps up to 2.5 cm, is required for nestlings to allow for added growth and development.


Effects of scale on predictive power of two bald eagle habitat models

January 1992

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45 Reads

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2 Citations

We examined the role scale plays in determining the predictive power of bald eagle (Haliaeetus leucocephalus) habitat models. We used a bald eagle roost habitat database that included 35 roost sites and 123 random sites located and characterized on the Chesapeake Bay from 1985-1988. A micro-habitat model, based on 6 micro-scale variables, correctly classified 80% of the roost sites. A macro-habitat model, based on 10 macro-scale variables, correctly classified only 63% of the roost sites. A mixed model, incorporating the significant micro- and macro-scale variables, correctly classified 89% of the roost sites. Our results suggest there is a tradeoff between model performance (predictive power), model development costs, and model application.


Assessing Bias in Studies of Bald Eagle Food Habits

January 1992

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266 Reads

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102 Citations

Journal of Wildlife Management

Although studies of bald eagle (Haliaeetus leucocephalus) food habits are numerous, few authors have quantified biases inherent in the techniques used. In our study of food habits of nonbreeding bald eagles on the northern Chesapeake Bay, we examined biases associated with pellet analysis, food remains analysis, and direct observation. We assessed these biases through controlled feedings of 2 captive bald eagles and through observations of free-ranging eagles. Fish fed to 2 captive bald eagles were underrepresented (P < 0.001) in egested pellets. Most bird and mammal food items were detected in ≥1 pellet; however, species and carcass condition affected frequency of occurrence. Analysis of captive eagles' food remains overrepresented birds, medium-sized mammals, and large bony fish (P < 0.001); small mammals and small fish were underrepresented (P < 0.001). This bias increased over time due to greater persistence of some remains in shoreline plots. Direct observations of free-ranging eagles resulted in biases toward easily identified species such as eels and catfish, but also documented the use of small, soft-bodied fish, which were not well documented by the other techniques. Because of the variety of biases present, accurate assessment of bald eagle foods requires use of multiple techniques.


Survival Rates and Population Dynamics of Bald Eagles on Chesapeake Bay

October 1991

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176 Reads

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53 Citations

Journal of Wildlife Management

Survival of 39 radio-tagged Haliaeetus leucocephalus in the Chesapeake Bay region was 100% in the first year of life. Mean minimum survival per year of all eagles was 91%, mean maximum survival 98%. A deterministic life-table model predicted a finite growth rate of 5.8% per year; growth rate based on the maximum survival estimates was 16.6% per year. The breeding population actually increased 12.6% per year from 1986-1990. Intrinsic growth rate was 6.9% based on natality and minimum survival data and 19.2% based on maximum survival data. -from Authors


Factors Affecting Piping Plover Productivity on Assateague Island

July 1991

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21 Reads

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76 Citations

Journal of Wildlife Management

We studied piping plovers (Charadrius melodus) on Assateague Island (Md., Va.) in 1986-87 to estimate population size and to identify factors affecting productivity. Fledging rates (0.19-1.11 chicks/pair) appeared to be lower than the level necessary to maintain a stable population. Fifty-four percent of the nests were unsuccessful. Predators accounted for most (91%) of the known causes of nest losses. Only 1 nest (2.2% of losses with known cause) was lost due to direct human destruction, and we found no evidence that suggested recreational disturbance was a factor affecting productivity. Mean chick fledging success was 69% for broods foraging at bay flats or tidal pools and 19% for broods foraging on ocean beach (P < 0.05).


Winter Microclimate of Bald Eagle Roosts on the Northern Chesapeake Bay

July 1991

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38 Reads

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8 Citations

Ornithology

From 11 November 1988 to 1 April 1989, we studied the microclimate and nightly energy budgets at three separate Bald Eagle (Haliaeetus leucocephalus) communal roost sites; one used in winter, one used in summer, and another used year-round. We compared the roost sites with the microclimate and nightly energy budgets at randomly selected inland forested sites and eagle shoreline perch sites on the northern Chesapeake Bay. Mean and minimum air temperatures were similar among all sites. Mean and maximum wind speeds were greater at the shore than at other sites. Wind speed did not differ between roosts and inland sites. Among roost sites, mean and maximum wind speeds were lowest at the winter roost. The year-round roost and summer-roost winds did not differ. Mean net radiation was greater at inland sites than at the shore sites, whereas mean net radiation of roost and inland and of roost and shore sites did not differ. Minimum net radiation was greatest at inland sites, whereas roost and shore minimum net radiation did not differ. We calculated that roosting eagles would have expended 205.9 kcal per night at traditional roost sites, 206.6 kcal per night at shoreline perches, and 203.7 kcal per night at inland sites. Calculated energy expended on the 10 coldest nights was similar among roost, shoreline, and inland sites. Adding the estimated cost of transport from shoreline perches to roosts (x = 5.3 kcal/round trip) did not produce significant differences in nightly energy expenditure between eagles roosting in communal roosts vs. those roosting on the shore.


Differences in Distribution of Breeding, Nonbreeding, and Migrant Bald Eagles on the Northern Chesapeake Bay

May 1991

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59 Reads

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22 Citations

Ornithological Applications

We compared the distributions of resident breeding, resident nonbreeding, and northern and southern migrant Bald Eagles (Haliaeetus leucocephalus) on the northern Chesapeake Bay from 1984-1988. Breeding eagles were dispersed throughout most of the study area and were resident all year. Dispersion of Chesapeake nonbreeding eagles was similar to the dispersion of breeding birds on the northern Chesapeake in summer and winter. Chesapeake nonbreeding eagles moved throughout most of the bay, ≤5% of radio-tagged eagles were off the bay during any month. Radio-tagged northern migrants arrived in late fall (x̄ = 21 December, n = 7, range = 61 days) and departed in early spring (x̄ = 27 March, n = 14, range = 43 days). In contrast to local eagles, northern migrants were concentrated almost exclusively on Aberdeen Proving Ground, Maryland. Radio-tagged southern migrants arrived throughout April-August (x̄ = 6 June, n = 11, range = 94 days) and departed from June-October (x̄ = 3 September, n = 22, range = 119 days). Southern migrants were more dispersed than the northern migrants but less dispersed than the resident eagles. Northern Chesapeake eagle abundance peaked twice annually; in winter (e.g., 261 eagles, December 1987), due to the presence of northern eagles, and in summer (e.g., 604 eagles, August 1988), due to the presence of southern birds.


Fig. 2. Distance from the shoreline (m) of bald eagles, pedestrians, boats, and buildings during aerial surveys of the northern Chesapeake Bay, Maryland, 1985-88.
Table 2 . Pedestrians and boats (no./shoreline km) by season and geographic area, northern Chesapeake Bay, Maryland, November 1985-August 1988.
Effects of Human Activity on Bald Eagle Distribution on the Northern Chesapeake Bay

April 1991

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218 Reads

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58 Citations

Journal of Wildlife Management

Only 55 of 1117 locations of radio-tagged Haliaeetus leucocephalus (4.9%) occurred in the developed land-cover type ≥4 buildings/4 ha), although 18.2% of potential eagle habitat was developed. Eagle use of the shoreline was inversely related to building density and directly related to the development set-back distance. Few eagles used shoreline segments with boats or pedestrians nearby. Only 360 of 2532 segments (14.2%) had neither human activity nor shoreline development. Eagle flush distances because of approaching boats were greater in winter than in summer (mean 264.9 vs. 175.5 m, respectively), but were similar for adult and immature eagles (203.7 vs. 228.6 m, respectively). Of 2472 km of shoreline on the N Chesapeake, 894 km (36.2%) appears to be too developed to be suitable for eagle use, and an additional 996 km (40.3%) had buildings within 500 m, thereby reducing eagle use. The projected increase in developed land in Maryland (74%) and Virginia (80%) from 1878 to 2020 is likely to determine the future of the bald eagle population in this area. (See also 91L/12673). -from Authors


Nonbreeding Bald Eagle Communal and Solitary Roosting Behavior and Roost Habitat on the Northern Chesapeake Bay

April 1991

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24 Reads

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43 Citations

Journal of Wildlife Management

We studied roosting behavior and habitat use of nonbreeding bald eagles (Haliaeetus leucocephalus) on the northern Chesapeake Bay during 1986-89. In summer and winter, 11 and 13 communal roosts, respectively, and many solitary roosts were used simultaneously in the 3,426km23,426-\text{km}^{2} study area. Radio-tagged eagles roosted solitarily with differing frequency by season (60, 21, 39, and 44% of 81 eagle nights in summer, fall, winter, and spring, respectively) (P < 0.05). Roost trees, predominantly oaks (Quercus spp.) or yellow poplars (Liriodendron tulipifera), were larger in diameter and provided greater canopy cover than random trees (P < 0.05). Roost sites had snags present more often than did random sites (P < 0.01). Most roosts (86%) were in woodlots >40 ha, and none were in human-developed habitat. In contrast, only 23% of random sites were in woodlots >40 ha, and 9% were in developed areas. Roosts were farther from human development than were random sites (P < 0.05); 57% of the roosts were found on public lands, compared to only 20% of the random sites (P < 0.001). Winter roost sites were protected from prevailing northerly winds more often than were summer sites (P < 0.05). We prescribe a 1,360-m-wide shoreline management zone that extends 1,400 m inland to encompass roost sites and provide a buffer from human disturbance.


Citations (11)


... These inconsistent findings indicate that variations among roosts may be significant, but have been insufficiently studied. Only a few studies have emphasised the seasonal variation of roosts (Barrows 1981;Buehler et al. 1991;Gorenzel and Salmon 1995). Despite the enhanced understanding of roost site selection, knowledge regarding seasonal switching remains limited. ...

Reference:

Microhabitat characteristics related to seasonal roost switching: implications from a threatened and introduced cockatoo species in an urban landscape
Winter Microclimate of Bald Eagle Roosts on the Northern Chesapeake Bay

Ornithology

... Ravens used in this study were trapped at 16 different locations (11 of which were inside Yellowstone National Park), and it often took hours or even several days before ravens landed in front of the trap. We fitted solar-powered GPS transmitters (e-obs GmbH; Bird Solar UMTS, 25 g) on ravens as backpacks with a Teflon harness (after Buehler et al., 1995) that weighed 35-37 g (i.e., 3.1%-3.7% of the raven's body mass). The GPS transmitters recorded data between approximately sunrise and sunset at 30-minute intervals with fully charged batteries (i.e., above 3,900 mV), at 1-hour intervals with a lower battery voltage (i.e., below 3,900 mV), and temporarily stopped GPS data collection when the voltage was extremely low (i.e., below 3,700 mV). ...

Captive and field- tested techniques for radio-attachment in bald eagles.
  • Citing Article
  • January 1995

Journal of Field Ornithology

... We created 2 buffers around each nest: one representing the immediate nest area (500-m radius) and the other representing the territory area (3000-m radius). We selected these spatial scales based on previous studies of Bald Eagles in the eastern United States, including satellite telemetry data from a nesting eagle in Kentucky (Buehler 2020, Buehler et al. 1994, Watts et al. 1994, Zehnder 2012. To calculate the proportion of each land-cover class, we intersected the buffers with the National Land Cover Database (NLCD), a Landsat-imagery-based, 30 m x 30 m resolution land-cover classification for the conterminous United States (Homer et al. 2020). ...

Effects of scale on predictive power of two bald eagle habitat models

... The distance and duration of disturbance has also been indicated as an important factor for recreational boating impacts on nesting success, leading managers to recommend boat exclusions within 100 m of nests, and the implementation of no-stopping-zones in the proximity of nest trees (Grubb et al. 2002). Eagle presence has been positively correlated with the distance of human development from shorelines, and negatively correlated with pedestrian use on beaches and near-shore boat traffic (Buehler et al. 1991). Camping within 100 m has been observed to impact bald eagle behavior, reducing the quantity of prey fed to nestlings by nearly 30%. ...

Effects of Human Activity on Bald Eagle Distribution on the Northern Chesapeake Bay

Journal of Wildlife Management

... Research on Hg in Bald Eagles (Haliaeetus leucocephalus) has been conducted in numerous eastern states including South Carolina (Jagoe et al. 2002), Florida (Wood et al. 1996), Maine (Welch 1994), New York (DeSorbo et al. 2008, and the Great Lakes region of the US (Bowerman et al. 1994). Although the Bald Eagle has been studied extensively in the Coastal Plain of Virginia (Buehler 1990;Buehler et al. 1991;Watts et al. 2011), little research on Bald Eagles has been conducted in the inland regions, due in part to a lack of knowledge of the inland distribution. Wiemeyer et al. (1984) analyzed nonviable eggs from Bald Eagles in the Chesapeake Bay, and reported concentrations of Hg between 0.03 and 0.17 mg/ kg, and Cristol et al. (2012) found that eagles residing near the Chesapeake Bay exhibited low concentrations of Hg in molted feathers. ...

Differences in Distribution of Breeding, Nonbreeding, and Migrant Bald Eagles on the Northern Chesapeake Bay

Ornithological Applications

... Within a sample, the count of individual items for each species was the minimum consistent with the numbers of the most frequent remains. There was bias towards the recovery of robust bone remains from large birds and mammals and against those of softtissue items that left few long lasting remains, or those with small bones that were wholly consumed and digested, so small birds and fish were under-represented (Wille & Kampp 1983, Mersmann et al. 1992, Marquiss, Madders & Carss 2003a. ...

Assessing Bias in Studies of Bald Eagle Food Habits
  • Citing Article
  • January 1992

Journal of Wildlife Management

... Characteristics of acceptable resting or roosting locations are often species-specific and uncommon on the landscape such that sites are frequently limited in number and act to constrain distribution (Hayward and Garton 1984, Krapu et al. 1984, Rogers et al. 2006. Use of communal roosts is documented for bald eagles (Haliaeetus leucocephalus; Swisher 1964, Steenhof et al. 1980, Keister and Anthony 1983, Curnutt 1992, Wilson and Gessaman 2003, and roost characteristics have been described for many locations throughout their range (Griffin 1978, Steenhof et al. 1980, Chester et al. 1990, Stohlgren 1993, Dellasala et al. 1998). The recognition that communal roosts are essential elements within the life cycle of bald eagles led to their protection under the disturb clause of the Bald and Golden Eagle Protection Act (BGEPA) of 1940 (16 U.S.C. 668-668d), and their management is incorporated into the National Bald Eagle Management Guidelines (U.S. Fish and Wildlife Service [USFWS] 2007). ...

Habitat Use by Nonbreeding Bald Eagles in North Carolina
  • Citing Article
  • April 1990

Journal of Wildlife Management

... In these systems, predator control commonly is used in shorebird management . Wild canines, such as the red fox (Vulpes vulpes), sometimes are top predators in barrier island communities and are thought to contribute to the regulation of bird and mammal populations (Patterson et al. 1991;Radford et al. 2018;Hunt et al. 2019;Stantial et al. 2021;Robinson et al. 2024). There is some evidence that red foxes suppress smaller predators (e.g., Stantial et al. 2021), including domestic cats (Felis catus; Rees et al. 2023). ...

Factors Affecting Piping Plover Productivity on Assateague Island
  • Citing Article
  • July 1991

Journal of Wildlife Management

... BUA, TC, DGD, DOS, DWB and DBL) as continuous explanatory variables. In this analysis, each roosting site was considered as a sampling unit and the individual roosting substrates within a roosting site was not considered to be independent following Buehler et al. (1991). Bonferroni post hoc tests were performed for the explanatory variables which were significant. ...

Nonbreeding Bald Eagle Communal and Solitary Roosting Behavior and Roost Habitat on the Northern Chesapeake Bay
  • Citing Article
  • April 1991

Journal of Wildlife Management

... Human disturbance and alterations of habitat, such as tree cutting, can influence nest distribution, since Bald Eagles tend to prefer nest sites in undeveloped areas (Fraser et al. 1985;Anthony and Isaacs 1989;Buehler et al. 1991;Gende et al. 1998) containing suitable perch trees for foraging and other activities (Chandler et al. 1995). Furthermore, nest productivity is also affected, hence higher nesting success in places where there is less human intrusion (Anthony and Isaacs 1989;Gende et al. 1998). ...

Perch Trees and Shoreline Development as Predictors of Bald Eagle Distribution on Chesapeake Bay

Journal of Wildlife Management