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The global potential for wind power generation is vast, and the number of installations is increasing rapidly. We review case studies from around the world of the effects on raptors of wind-energy development. Collision mortality, displacement, and habitat loss have the potential to cause population-level effects, especially for species that are rare or endangered. The impact on raptors has much to do with their behavior, so careful siting of wind-energy developments to avoid areas suited to raptor breeding, foraging, or migration would reduce these effects. At established wind farms that already conflict with raptors, reduction of fatalities may be feasible by curtailment of turbines as raptors approach, and offset...
We used video-recording systems to collect diet information at 13 Northern Goshawk (Accipiter gentilis) nests in Minnesota during the 2000, 2001, and 2002 breeding seasons. We collected 4871 hr of video footage, from which 652 prey deliveries were recorded. The majority of prey deliveries identified were mammals (62%), whereas birds (38%) composed a smaller proportion of diet. Mammals accounted for 61% of biomass delivered, and avian prey items accounted for 39% of prey biomass. Sciurids and leporids accounted for 70% of the identified prey. Red squirrel (Tamiasciurus hudsonicus), eastern chipmunk (Tamias striatus), and snowshoe hare (Lepus americanus) were the dominant mammals identified in the diet, while American...
ABSTRACT.--The Jolly-Seber model is a capture-recapture model that can provide less-biased survival and population size estimates than those produced from simple counting procedures. Parameter estimation by simple counts and Jolly-Seber methods are based on certain assumptions that directly determine the validity of estimates. Evuluation of assumptions for parameter estimation is a focus of this paper and used as a basis for determining which methods are more likely to produce better estimates. An example of population size and survival estimation for a peregrine falcon(Falco peregrinus) population in western Greenland is used to compare the two methods.Based on results from the Greenland peregrine population, and...
We studied home-range characteristics of adult Mexican Spotted Owls (Strix occidentalis lucida) in southern Utah. Twenty-eight adult owls were radio-tracked using a ground-based telemetry system during 1991-95. Five males and eight females molted tail feathers and dropped transmitters within 4 wk. We estimated cumulative home ranges for 15 Spotted Owls (12 males, 3 females). The mean estimate of cumulative home-range size was not statistically different between the minimum convex polygon and adaptive kernel (AK) 95% isopleth. Both estimators yielded relatively high SD, and male and female range sizes varied widely. For 12 owls tracked during both the breeding and nonbreeding seasons, the mean size of the AK 95%...
To investigate whether Northern Goshawk textit(Accipiter gentilis) reproduction is food-limited, we evaluated the reproductive output from 401 goshawk breeding opportunities on the Kaibab Plateau, Arizona during 1999-2002. Concurrently, we estimated densities of 10 goshawk prey species (seven birds, three mammals) using distance sampling. We then assessed the relationship between goshawk productivity (number of fledglings produced) and prey density within and among years by relating the contribution of individual prey species and total prey density to goshawk productivity. We also estimated the proportion of total diet and biomass for each species that contributed ?3% of all prey items. Total prey density was highly...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Journal Of Raptor Research,
Predator?prey dynamics,
accipiter gentilis,
diet,
distance sampling,
Four manufacturers now produce transmitters in the size range suitable for raptors (3-5% of body mass). Dummies of these transmitters will be displayed and harnessing techniques will be demonstrated. Estimates will be given for: cost, reliability, longevity, mass, availability, programmability, power output and other information essential in deciding on manufacturer and model.
Gyrfalcon (Falco rusticolus) museum specimens in Moscow (73) and St. Petersburg (132) were divided into four color classes (gray, light gray, white gray, and white) and four longitudinal belts representing major physiographic regions of northern Russia. Gray variants predominated in the west and central regions. White birds were most common in extreme eastern Siberia, but were occasionally found even west of the Ural Mountains. Frequencies were as follows: European Russia 4% white, 50% gray (the remainder were intermediates); western Siberia 0% white, 58% gray; central Siberia 15% white, 42% gray; and eastern Siberia 47% white, 33% gray. Remarkably, in the easternmost subregion, white birds predominated even near...
A literature review of the effects of pesticides on owls in North America showed that relatively few studies have been undertaken. Owls used in experiments seem as sensitive to organochlorine pesticides (OCs) as other birds of prey, but wild owls experienced few serious problems, primarily because they were exposed to lower residues in their predominately mammalian or invertebrate prey. For example, the great horned owl ( Bubo virginianus ) and the common barn-owl ( Tyto alba ) neither experienced marked changes in mortality or recruitment rates nor was there any evidence of population decreases even during the maximum period of OC pesticide use. Also, eggshell thinning was not a widespread problem. There were adverse...
Uncertainties about factors affecting Northern Goshawk (Accipiter gentilis) ecology and the status of populations have added to the challenge of managing this species. To address data needs for determining the status of goshawk populations, Hargis and Woodbridge (2006) developed a bioregional monitoring protocol based on estimating occupancy. The goal of our study was to implement this protocol and collect data to determine goshawk population status in the western Great Lakes (WGL) bioregion, which encompasses portions of Minnesota, Wisconsin, and Michigan, and is a mixture of private and public property. We used 366 goshawk nest locations obtained between 1979 and 2006 throughout the WGL bioregion to develop a...
We studied diets of Northern Spotted Owls (Strix occidentalis caurina) in three different regions of Washington State during 1983-96. Northern flying squirrels (Glaucomys sabrinus) were the most important prey in most areas, comprising 29-54% of prey numbers and 45-59% of prey biomass. Other important prey included snowshoe hares (Lepus americanus), bushy-tailed woodrats (Neoloma cinerea), boreal red-backed voles (Clethrionomys gapperi), and mice (Peromyscus maniculatus, P. oreas). Non-mammalian prey generally comprised less than 15% of prey numbers and biomass. Mean prey mass was 111.4 ?? 1.5 g on the Olympic Peninsula, 74.8 ?? 2.9 g in the Western Cascades, and 91.3 ?? 1.7 g in the Eastern Cascades. Diets varied...
We mapped Red-tailed Hawk (Buteo jamaicensis) territories in the Luquillo Experimental Forest (LEF) of Puerto Rico in 1998. We combined our 1998 data with that collected during previous studies of Red-tailed Hawks in the LEF to examine population numbers and spatial stability of territorial boundaries over a 26-yr period. We also investigated potential relationships between Red-tailed Hawk territory sizes and topographic and climatic factors. Mean size of 16 defended territories during 1998 was 124.3 ?? 12.0 ha, which was not significantly different from our calculations of mean territory sizes derived from data collected in 1974 and 1984. Aspect and slope influenced territory size with the smallest territories...
We reviewed the literature to assess status and population trends and to identify mortality factors affecting Golden Eagle populations in the U.S. and Canada. Nesting populations in Alaska and Canada are stable, but some nesting populations in the western U.S. have declined. Small but steady declines in the intermountain West have been associated with shrub loss and declining jackrabbit populations; declines in southern California have been attributed to urbanization. Migration counts in the eastern U.S. suggest a decline in Golden Eagles from the 1930s to the early 1970s, with a stable or increasing trend since the early 1970s. No significant trends in migration counts were reported for Golden Eagles in the western...
Peregrine Falcons (Falco peregrinus) captured in the spring at Padre Island, Texas, nest across the arctic and subarctic from Alaska to Greenland and winter throughout Latin America. Padre Island, located immediately north of the Mexican border, is the peregrines' first landfall in the U.S.A. after spending about 6 mo in Latin America. Blood plasma was collected from spring migrants at Padre Island between 1978 and 2004 to monitor trends in organochlorine (OC) pesticides and their metabolites. Geometric mean concentrations of p,p'-DDE (??g/g, ww) decreased throughout the study: 1978-1979 (0.879), 1980 (0.617), 1984 (0.551), 1994 (0.406) and 2004 (0.013). Most other OC pesticides, with detection limits used during...
Concern for the welfare of animals used in research and teaching has increased over the last 50 yr. Animal welfare legislation has resulted in guidelines for the use of animals in research, but the guidelines can be problematic because they focus on animals used in laboratory and agriculture research. Raptor biologists can be constrained by guidelines, restrictions, and oversight that were not intended for field research methods or wild animals in the wild or captivity. Field researchers can be further hampered by not understanding animal welfare legislation, who is subject to oversight, or that oversight is often provided by a committee consisting primarily of scientists who work with laboratory animals. Raptor...
Raptors were observed on a 5200 km expedition from Ulaan Baatar through the Hangay Mountains to the Russian Altay Mountains with return through the Gobi Altay Mountains. The focus of the expedition was on nesting ecology of the Saker (Falco cherrug) and Altay falcons (F. altaicus) (25 eyries were located), but nests were also found for seven other species including more than 30 nests found of the upland buzzard (Buteo hemilasius). We conducted 21 day-long counts and 10 more formal raptor road counts. Raptors were concentrated in areas where perches were common and where food was most abundant. Western Mongolia remains a vast undeveloped land where camel trains and yak carts are normal. No developed highway network...
Northern Goshawks (Accipiter gentilis) are a species of special conservation concern in the western Great Lakes bioregion and elsewhere in North America, and exhibit landscape-scale spatial use patterns. However, little information exists about Northern Goshawk habitat relations at broad spatial extents, as most existing published information comes from a few locations of relatively small spatial extent and, in some cases, short durations. We used an information-theoretic approach to evaluate competing hypotheses regarding factors (forest canopy cover, successional stage, and heights of the canopy top and base) related to odds of Northern Goshawk landscape use throughout the western Great Lakes bioregion based on...
Urban ecosystems are attractive to several raptor species, including the Mississippi Kite (Ictinia mississippiensis). To better understand the niche filled by urban-nesting Mississippi Kites, we observed nesting kites at 10 nests for a total of 269 hr during the breeding seasons of 2010 and 2011. We assessed prey delivery rates and prey use within and between years, evaluated the influences of nestling age, time of day, day of year, and local atmospheric conditions on delivery rates, and examined provisioning rates by male and female kites. A 62% decrease in the prey delivery rate, measured by the number of prey deliveries, from 2010 to 2011 was likely attributable to extreme heat and drought during the 2011 breeding...
Twenty-six (23 traveling and three point) raptor roadside surveys were conducted during a 29,000 km expedition through nine nations of South America. During roadside surveys, we tallied 41 of the 87 (47%) diurnal raptor species (including vultures) that occur in South America. The number of species observed per route varied from 17 in the wet savanna of Venezuela to only two species recorded in the harsh Atacama Desert and the dry montane grasslands of Chile and Peru. Raptor density (non-vultures) varied from 1 per 67 km in the Atacama Desert to more than 1 per km in agricultural areas where caracaras and other species that utilize disturbed habitats were common. Responses of raptor communities to deforestation...
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