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Pedestrians and boats (no./shoreline km) by season and geographic area, northern Chesapeake Bay, Maryland, November 1985-August 1988.
Source publication
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 seg...
Contexts in source publication
Context 1
... observed 0.15 pedestrians per km of shoreline surveyed (Table 2). Pedestrian activity was greatest in summer and least in winter (P = 0.001), but spring and fall, and spring and summer pedestrian activity did not differ (P = 0.08 and 0.83, respectively). ...
Context 2
... observed significantly more boats per shoreline km in summer than in winter (P < 0.001) ( Table 2) Pedestrians and boats were observed within 500 m of developed segments more often than would be expected if the distributions of pe- destrians and boats were independent of build- ings (P < 0.001) (Table 3). We observed pe- destrians, boats, or buildings on 2,172 of 2,532 segments (85.8%) monitored. ...
Citations
... 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%. ...
The North Cascades Ecosystem is one of the largest and most intact wilderness areas in the contiguous United States. It spans 34,965 km2 across the U.S.-Canada border between central Washington State and southern British Columbia and is bisected north to south by the Cascade Mountain range. The North Cascades National Park Service Complex (hereafter, the Park) lies in the heart of the ecosystem and is comprised of North Cascades National Park (2,044 km2), Ross Lake National Recreation Area (NRA) (473 km2), and Lake Chelan NRA (251 km2). This report focuses on terrestrial wildlife species in the Park that are federally listed under the Endangered Species Act of 1973 (ESA), state-listed under Washington Administrative Code, and/or designated by NPS as Management Priority species. We provide a detailed synthesis of information around NPS records from 1995–2020 for nine bird and nine mammal species and one mammal Order (Chiroptera [bats]), as well as a suite of invertebrate pollinators in the Park where data are available. Information for each species includes life history information, occurrence in the Park, protective status, trends when known, a summary of known threats, and a summary of conservation and research needs. We also provide brief summaries for an additional five bird and two mammal species, and one taxa group (woodpeckers) where data are more limited.
... The most negatively impactful activities are the direct cutting of trees, recreational use of the shoreline and the polluting of waterways (60 FR 36000). Therefore, leading to habitat loss, most significantly the loss of shoreline nesting, perching, and roosting sites, as well as access to aquatic foraging areas (Buehler et al. 1991). ...
... 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). ...
... Even though, this specie's nesting habitat is preferably closer to water, the human presence and settlements are enough to make them nest farther from shorelines (Fraser et al. 1985;Anthony and Isaacs 1989;Watts and Whalen 1997), with the possibility of keeping them away from available food sources and it could impair productivity (Schirato and Parson 2006). Likewise, Bald Eagles may also respond negatively to structures themselves or habitat modifications, because, even during seasons with low human activity, they avoided developed areas (Buehler et al. 1991). In the long term, the Bald Eagle's capacity to cope with human activity and the ability to manage appropriate breeding habitats will determine the size and stability of breeding populations (Watts et al. 2008). ...
... (11) People: we counted the number of people present in the park that we could see during one minute. There is evidence that some predators (including birds of prey) avoid areas frequented by people (Buehler et al., 1991;Muhly et al., 2011). Some of these 11 environmental characteristics differed between the dry and rainy seasons, specifically vegetation cover, urban noise, and people. ...
... Both the type of disturbance and its context matter: foraging raptors are often more likely to flush when approached by pedestrians than by vehicles, and large raptors are more easily flushed by pedestrians than are smaller ones (Holmes et al., 1993). In some species, individuals can habituate to high levels of human activity and do not seem to suffer negative effects on foraging, or at least a subset of birds that has greater tolerance limits is able to occupy heavily disturbed areas (Buehler et al., 1991;McGarigal et al., 1991). It is possible that a larger number of raptor species have temporarily visited areas they were not (routinely) using before the pandemic, in response to changing levels of human activity, such as urban parks, beaches, or waste management centers during operating hours. ...
Research is underway around the world to examine how a wide range of animal species have responded to reduced levels of human activity during the COVID-19 pandemic. In this perspective article, we argue that raptors are particularly well-suited for investigating potential ‘anthropause’ effects, and that the resulting insights will provide much-needed impetus for global conservation efforts. Lockdowns likely alter many of the extrinsic factors that normally limit raptor populations. These environmental changes are in turn expected to influence – mediated by behavioral and physiological responses – the intrinsic (demographic) factors that ultimately determine raptor population levels and distributions. Using this framework, we identify a range of research opportunities and conservation challenges that have arisen during the pandemic. The COVID-19 anthropause allows raptor researchers to address fundamental and applied research objectives in a large-scale, quasi-experimental, well-replicated manner. Importantly, it will be possible to separate the effects of human disturbance and anthropogenic landscape modifications. We explain how high-quality datasets, accumulated for a diverse range of raptor species before, during, and after COVID-19 lockdowns, can be leveraged for powerful comparative analyses that attempt to identify drivers of particular response types. To facilitate and coordinate global collaboration, we are hereby launching the ‘Global Anthropause Raptor Research Network’ (GARRN). We invite the international raptor research community to join this inclusive and diverse group, to tackle ambitious analyses across geographic regions, ecosystems, species, and gradients of lockdown perturbation. Under the most tragic of circumstances, the COVID-19 anthropause has afforded an invaluable opportunity to significantly boost global raptor conservation.
... We found that movement distances of fledglings were shorter in areas of the Chesapeake Bay with lower salinity, but that they were longer in areas with lower human density. Although urban areas are considered lower quality habitat (Buehler et al. 1991b), eagles that fledged from nests in more populated areas tended to stay closer to the nest than did fledglings in less densely populated areas. Fraser et al. (1985) reported that eagles nesting near developed shorelines built nests farther from the water than those nesting along less-developed shorelines. ...
... However, in our study human population density and nest distance to water were not correlated (r ¼ À 0.08) and thus it may be that disturbance and competition are comparatively more important for eagles in the Chesapeake Bay. In more heavily developed areas, eagles may be disturbed more often (Buehler et al. 1991b). For example, post-fledging eagles from suburban nests in Florida were disturbed more often and, like the eagles we tracked, also stayed closer to the nest than did eagles from rural nests (Tinker 2000). ...
... For example, post-fledging eagles from suburban nests in Florida were disturbed more often and, like the eagles we tracked, also stayed closer to the nest than did eagles from rural nests (Tinker 2000). The nest and area closely surrounding it may provide safety for fledgling eagles in these areas because eagles may avoid people (Buehler et al. 1991b). In addition, the higher habitat quality of less-developed areas used by eagles in the Chesapeake Bay (Buehler et al. 1991b) may result in increased intraspecific competition with densitydependent effects. ...
Bald eagle (Haliaeetus leucocephalus) aircraft strikes have increased since 1998 because their populations have recovered to near historical sizes. Their attraction to airfields and their large body size makes them a danger to aircraft and therefore important to airfield managers. However, bald eagle management is complicated by their special protected status and the place they hold in the eyes of the public. To help airfield managers plan monitoring efforts and make informed management decisions, we studied the movements of 32 bald eagles telemetered as nestlings in the Chesapeake Bay, Virginia, USA, 2013–2018. Managers often need to know when fledged eagles are most likely to move enough to encounter airfields near nests. As fledglings aged, they moved progressively farther from the nest and spent more time away from the nest. Twenty-eight days after fledging, eagles spent most of the day (81 ± 10% [95% CI]) near the nest (<500 m) and only 7 ± 7% of the daytime away from the nest (>1 km). By day 55 fledglings ventured beyond 2.5 km from the nest and spent 32 ± 15% the day >1 km away from their nest. Distances moved, however, were influenced by proximity of the nest to water, the salinity of that water, and human population density. Eagles left their natal nests and generally migrated out of the Chesapeake Bay 60.5 ± 7.7 days (4 Aug) after fledging and returned to the Chesapeake Bay approximately 220 days later (Mar–Apr). Eighty-four percent (27 of 32) of the eagles that we tracked encountered 164 airfields across the east coast with 91% of those airfields located within 10 km of the Chesapeake Bay. Encounters with airfields outside the Chesapeake Bay occurred mainly during the first 1.5 years of life, peaking in late fall and early spring. We recorded eagles on Chesapeake Bay airfields during each year, but encounters peaked in April of the first year of the bird's life. April coincides with the height of reported strikes of eagles by aircraft in the region. Our results suggest that eagles fledging from the Chesapeake Bay are an issue for airports near the Chesapeake Bay and for airports across the east coast. Given the continued growth of the population, this issue is likely to continue and grow in significance.
... Outside of the literature concerning the European Herring Gull There are many reasons why an urban-nesting population of gulls could enjoy greater reproductive success compared to non-urbannesting conspecifics. Most obviously, predatory species like the Bald Eagle Haliaeetus leucocephalus are often deterred from urban environments due to the extreme human presence (Buehler et al. 1991, Steidl & Anthony 2000. More importantly, because the size of one rooftop often allows only a single nest, the practice of rooftop nesting can equip breeding pairs with a structural territorial boundary that cannot be physically breached by any chicks that have not yet learned to fly. ...
The present study investigated the reproductive success and breeding ecology of 102 Glaucous-winged Gull Larus glaucescens pairs nesting in downtown Vancouver, British Columbia during the summer of 2015. These urban breeders enjoyed a remarkably high level of post-hatch fledging success (≥ 85%) compared to previous records for non-urban subpopulations in the region (≈ 70%). A relatively small average initial clutch size of 2.43 eggs was observed, which aligns with a historical analysis of the literature and corroborates the inference that clutch size has declined substantially in the region over the past century. I argue that the high level of post-hatch fledging success is likely attributable to a tendency of urban Glaucous-winged Gulls to establish isolated nesting territories, often on the rooftops of individual buildings, which leads to low intra-and interspecific predation. Given that offspring commonly return to their natal sites to breed later in life, the evolutionary impact of this reproductive differential could be significant for the ecological future of Glaucous-winged Gulls in the region.
... Nest-site selection on a local level has been extensively studied, indicating that Haliaeetus leucocephalus L. (Bald Eagle) typically select nest sites in large mature trees (Andrew and Mosher 1982, Anthony and Isaacs 1989, Harris et al. 1987, McEwan and Hirth 1979, Saalfeld and Conway 2010, Wood et al. 1989 in close proximity to open water (Andrew and Mosher 1982, Anthony and Isaacs 1989, Harris et al. 1987, McEwan and Hirth 1979, Wood et al. 1989. Other factors that influence nest-site selection include size of water bodies (Anthony and Isaacs 1989, Dzus and Gerrard 1993, Gerrard et al. 1975, prey availability (Gende et al. 1997, Isaacs et al. 1983, human activity/disturbance (Andrew and Mosher 1982, Anthony and Isaacs 1989, Buehler et al. 1991, Guinn 2013, Mundahl et al. 2013, Saalfeld and Conway 2010, and habitat surrounding a site (Andrew and Mosher 1982, Anthony and Isaacs 1989, Buehler 1995, McEwan and Hirth 1979, Mundahl et al. 2013, Saalfeld and Conway 2010, Wood et al. 1989. Harris et al. (1987) examined nest-site characteristics at a local level in southcentral and southeastern Louisiana during 1977Louisiana during -1980, and reported that nests were located primarily in Taxodium distichum (L.) Rich. ...
Mating pairs of Haliaeetus leucocephalus (Bald Eagle) nest during winter in Louisiana, and numbers of nests have increased exponentially since the mid-1970s. Active nests have remained relatively concentrated within the south-central and southeastern part of the state, in an area primarily consisting of inland swamps, coastal marshes, and barrier islands, which is referred to as the Basin. However, as the number of nests continues to grow, it is expected that nesting will continue to expand geographically into new habitats. In order to manage an expanding population, it is imperative to first determine parameters that influence nest-site selection. To evaluate site selection and success, we conducted GIS-based analyses to evaluate geographic variables such as proximity to water, landcover, human activity, and other nests. We compared 387 active nests from the 2007–2008 winter nesting season and 1935 random sites, which represented available habitat for site selection. Our results suggest that success of a nest within the Basin was not greatly influenced by the physical characteristics around a site, but sites with the highest probability of being selected for nesting generally had a higher probability of success. Initial selection of a nest site was most influenced by distance to road, number of houses per km 2 , and landcover within 3 km, but the influence of these variables varied between sites within and outside the Basin. Our results should assist managers in making informed decisions about effects of future developments, conservation activities, and human use on current and future suitable nesting habitat.
... The southwestern portion of the study area includes urban expanses of Baltimore and Annapolis, Maryland, which are dominated by extensive residential and commercial development. These areas support very little eagle activity (Buehler et al. 1991a, Watts et al. 2015a. Remaining portions of the study area are primarily rural, with forest lands interspersed with agriculture. ...
... The disturbance of eagles within foraging areas has received much attention by researchers over the past 30 years (Stalmaster and Newman 1978, Knight and Knight 1984, McGarigal et al. 1991, Brown and Stevens 1997. Frequent human activity associated with land development has led to the avoidance of hunting areas by foraging birds or presumptive habitat loss (Buehler et al. 1991a, Clark 1992, Chandler et al. 1995. Episodic human activities from the water (Knight and Knight 1984, McGarigal et al. 1991, Brown and Stevens 1997, air (Stalmaster and Kaiser 1997), or land Kaiser 1988, Grubb andKing 1991) flush eagles and disrupt hunting behavior. ...
We assessed diurnal activity patterns associated with communal roosts (n = 26) by tracking nonbreeding bald eagles (Haliaeetus leucocephalus; n = 58) within the upper Chesapeake Bay, USA, 2008–2013. We used daytime locations (n = 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 km2 to 116 km2 ( = 30.3 ± 5.48 [SE]), reflecting landscape context. Roosts with small (<10 km2) activity shadows tended to have simple shapes with roosts centrally located and positioned along primary shorelines. Roosts supporting large (>50 km2) 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 = 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.
... As eagle numbers grew, so did Louisiana's human population, which increased by about 25% from 1970 to 2010 (US Census Bureau 2010). In the past, human activity has been a strong predictor of Bald Eagle nest-site selection (Andrew and Mosher 1982, Buehler et al. 1991b, Saalfeld and Conway 2010. Eagles may select areas away from human activity to nest, but as populations expand they could alter their preferences and move into populated areas (Guinn 2013). ...
The population of nesting Haliaeetus leucocephalus (Bald Eagle) in Louisiana reached precariously low numbers in the early 1970s after experiencing marked declines similar to the rest of the continental population. From 1975 to 2008, aerial surveys of all known nests have been conducted within the state to monitor the population. We used data collected over the 34-year nest-monitoring program to quantify the recovery of the nesting population in Louisiana. Active nests increased exponentially from 7 to 387, exhibiting a mean annual rate of increase of 11.1 ± 0.3% per year with no indications of slowing. Accounting for increases in nests over the monitoring period, we found relatively slight changes in reproduction, with productivity and brood size peaking in 2000 and 1999. By 1990, the nesting population in Louisiana had exceeded each goal of the Southeastern States Bald Eagle Recovery Plan, and the species was removed from the federal list of endangered and threatened wildlife in 2007. However, the continued stability and growth of the nesting population may depend on the ability of Bald Eagles to cope with increasing levels of human activity, as well as the protection and availability of current and future nesting habitats.
... Human activity is the best predictor of eagle distribution within the tidal portion of the Bay. Indicators of human activity such as housing and road density, shoreline use, and boating activity have been related to nest distribution (Watts et al. 1994), shoreline use (Buehler et al. 1991b, Watts and Whalen 1997), and the likelihood of nest abandonment (Therres et al. 1993 ) or recolonization (B. D. Watts, Center for Conservation Biology, unpublished data). ...
We conducted annual aerial surveys (1991-2011) for breeding Bald Eagles (Haliaeetus leucocephalus) within Aberdeen Proving Ground (APG), a 350-km2 military installation located along the northwestern shoreline of the upper Chesapeake Bay in Maryland. The population increased exponentially from 1 pair in 1977 to 58 pairs in 2011 with an average doubling time of 5.8 years. This rate was higher than that documented for the broader Chesapeake Bay and is comparable to the highest reported throughout the species range. Annual population increase was highly variable and exhibited no indication of any systematic decline. A total of 646 chicks were produced from 464 breeding attempts during this period. The population has exhibited tremendous forward momentum such that more than 50% of young produced
over the 21-year period were produced in the last 6 years. Average success rate was high (79.8%) and reproductive rates exceeded conservation targets in nearly all years. Due to the expansion of urban development throughout the Chesapeake Bay watershed, APG plays an increasingly important role in the recovery and maintenance of the Chesapeake Bay Bald Eagle population.
