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We compared the breeding biology of sympatric nesting Red-tailed Hawks (Buteo jamaicensis), White-tailed Hawks (Buteo albicaudatus), and Crested Caracaras (Caracara cheriway) in south Texas during 2003 and 2004. We monitored 46 breeding attempts by Red-tailed Hawks, 56 by White-tailed Hawks, and 27 by Crested Caracaras. Observed nesting success was similar for Red-tailed Hawks (62%) and Crested Caracaras (61%), but lower for White-tailed Hawks (51%). Daily survival rates (0.99) were the same for all three species. Red-tailed Hawks and White-tailed Hawks both fledged 1.13 young per nesting pair and Crested Caracaras fledged 1.39 young per nesting pair. All three species nested earlier in 2004 than in 2003; in addition,...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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The Puerto Rican Broad-winged Hawk (Buteo platypterus brunnescens) is an endemic and endangered subspecies inhabiting upland montane forests of Puerto Rico. The reproductive ecology, behavior, and nesting habitat of the Broad-winged Hawk were studied in Ri??o Abajo Forest, Puerto Rico, from 2001-02. We observed 158 courtship displays by Broad-winged Hawks. Also, we recorded 25 territorial interactions between resident Broad-winged Hawks and intruding Red-tailed Hawks (Buteo jamaicensis jamaicensis). Broad-winged Hawks displaced intruding Red-tailed Hawks from occupied territories (P = 0.009). Mayfield nest survival was 0.67 across breeding seasons (0.81 in 2001, N = 6; 0.51 in 2002, N = 4), and pairs averaged 1.1...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Compared to other regions of North America, little information exists regarding Northern Goshawk (Accipiter gentilis) ecology and population dynamics in the western Great Lakes Region. We examined productivity and nesting habitat characteristics of goshawks in Minnesota from 1998-2001. Apparent nesting success varied annually from as low as 38% to as high as 83%. The Mayfield estimate of daily survival for nests was 0.992 ?? 0.002 (SE). The mean fledgling number across years was 1.85 ?? 0.14 for successful nests and 1.14 ?? 0.17 for all nesting attempts. Twenty-one percent of all nesting attempts failed, primarily due to predation or suspected predation (52%) and inclement weather (35%). Overall, productivity of...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Radio transmitters provide data that enhance understanding of raptor biology (Walls and Kenward 2007) and are now used to answer a multitude of research questions (Meyburg and Fuller 2007). However, transmitters affect the birds that carry them (Barron et al. 2010), and it is important to document and evaluate such effects (Casper 2009). For example, decreased survival has been documented in Prairie Falcons (Falco mexicanus; Steenhof et al. 2006), Northern Goshawks (Accipiter gentilis; Reynolds et al. 2004), and Spotted Owls (Strix occidentalis; Paton et al. 1991) tagged with radio transmitters. However, no such effects were reported for Peregrine Falcons (Falco peregrinus; Fuller et al. 1998, McGrady et al. 2002)...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Long-term research in Greenland has yielded 1 8 years of incidental sightings and 2 years of surveys and observations of gyrfalcons(Falco rusticolus) around Sondrestromfjord, Greenland. Gyrfalcons nest on cliffs along fjords and near rivers and lakes throughout our 2590 sq. km study area. Nestlings are present mid-June to July. In 1990, we marked one adult female gyrfalcon with a 65 g radio-transmitter to obtain location estimates via the ARGOS polar orbiting satellite system. The unit transmitted 8 hours/day every two days. We obtained 145 locations during 5 weeks of the nestling and fledgling stage of breeding. We collected 1-9 locations/day, with a mean of 4/day. We calculated home range estimates based on the...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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The Peregrine Fund has published proceedings of several conferences over the years and has become experts, and this 2 volume set is no exception. The title of the proceedings sounded especially interesting in this era of almost daily accounts in the media about climate change, its causes and its effects on the planet, including its flora and fauna. This 772-page Proceedings is loaded with useful information regarding Gyrfalcons and their prey and should be in the library of all serious raptor bibliophiles. The sponsors are to be commended for supporting the conference and for publishing the proceedings. Proceedings are available at http://www.peregrinefund.org/gyr-conf Review info: Gyrfalcons and Ptarmigan in a...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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http://elibrary.unm.edu/sora/jrr/v028n03/p00194-p00196.pdf
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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I examined the effects of weekend and weekday boating activity on Bald Eagle (Haliaeetus leucocephalus) use of three lakes in northcentral Florida during 1988-89. On Lake Lochloosa, which had the highest number of boats of the three lakes, boating activity significantly reduced the numbers of all age classes of eagles using the lake (P < 0.025). Increased boating activity on Lake Wauberg was not related to use by eagles (P = 0.06) likely because boating activity was concentrated during midday while eagles typically foraged early and late in the day. On Newnan's Lake, the number of eagles observed also was not different between weekends and weekdays (P = 0.20). Weekend boating activity did not relate to perch use,...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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We predicted sex of 140 Snowy Owl (Bubo scandiacus) nestlings out of 34 nests at our Barrow, Alaska, study area to develop a technique for sexing these owls in the field. We primarily sexed young, flightless owls (3844 d old) by quantifying plumage markings on the remiges and tail, predicting sex, and collecting blood samples to test our field predictions using molecular sexing techniques. We categorized and quantified three different plumage markings: two types of bars (defined as markings that touch the rachis) and spots (defined as markings that do not touch the rachis). We predicted sex in the field assuming that males had more spots than bars and females more bars than spots on the remiges and rectrices. Molecular...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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The quantification of shifts in bird distributions in response to climate change provides an opportunity to gain a deeper understanding of the processes that influence species persistence. We used data from the North American Breeding Bird Survey (BBS) to document changes in the distributional limits of the western Burrowing Owl (Athene cunicularia hypugaea) from 1967 to 2008. We used logistic regression to model presence probability (p) as a function of longitude, latitude, and year. We modeled a linear trend in logit(p) through time with slope and intercept modeled as a double Fourier series of longitude and latitude. We found that the western Burrowing Owl has experienced an intriguing southward shift in the...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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During 1994, 1995, 1997, and 1998 expeditions across Mongolia, we located over 250 upland buzzard (Buteo hemilasius) nests. At these, we noted considerable morphological variation in plumage coloration and in leg pterylosis. In 1997 and 1998, we examined 131 nests scattered across eastern and central Mongolia and report here the tarsal condition of 119 nestlings from 59 broods where young were at least 2 weeks of age. Of 119 birds carefully examined, 50 (42%) had less than fully feathered tarsi and 4 of the 69 with fully feathered tarsi had scattered feathers on their toes. Thus, 54 of 119 birds (45%) in some way deviated from the feathered tarsibare toes condition. This extraordinary degree of variability in feather...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Blood samples collected in 1979-81 from wintering Bald Eagles (Haliaeetus leucocephalus) in Oregon and northern California, residents in Oregon, migrants in Montana and residents in Washington were analyzed for lead (Pb), mercury (Hg) and organochlorines. Lead was detected infrequently (5%) and at low concentrations (<0.25 ppm) in nestlings from Oregon, more frequently (41%) and at occasionally elevated concentrations (>0.40 ppm) in wintering Bald Eagles in Oregon and north California and migrants in Montana, and most frequently (56%) in nestlings from Washington but at low concentrations (<0.40 ppm). Mercury concentrations were low (<0.70 ppm) in samples from Washington nestlings and higher in samples from Oregon...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Birds face challenges in how they allocate energy during the reproductive season. Most temperate zone species do not breed and molt at the same time, presumably because of the high energy demands of these two activities (Espie et al. 1996 and citations therein). However, representatives of at least four raptor genera are known to molt during the nesting season (Schmutz and Schmutz 1975, Newton and Marquiss 1982, Schmutz 1992, Espie et al. 1996). Molt strategies vary among raptor species depending on prey abundance, migration strategies, and the relative costs of reproduction. Sexually-dimorphic raptors typically have different roles in parenting, which result in different strategies for energy allocation. Male and...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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Dispersal is a behavioral process having consequences for individual fitness and population dynamics. Recent advances in technology have spawned new theoretical examinations and empirical studies of the dispersal process in birds, providing opportunities for examining how this information may be applied to studies of the dispersal process in raptors. Many raptors are the focus of conservation efforts; thus, reliable data on all aspects of a species' population dynamics, including dispersal distances, movement rates, and mortality rates of dispersers, are required for population viability analyses that are increasingly used to inform management. Here, we address emerging issues and novel approaches used in the study...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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We studied first-year movements of Mexican Spotted Owls (Strix occidentalis lucida) during natal dispersal in canyonlands of southern Utah. Thirty-one juvenile Mexican Spotted Owls were captured and radiotracked during 1992-95 to examine behavior and conduct experiments related to the onset of natal dispersal. Juvenile Spotted Owls dispersed from their nest areas during September to October each year, with 85% leaving in September. The onset of movements was sudden and juveniles dispersed in varied directions. The median distance from nest area to last observed location was 25.7 km (range = 1.7-92.3 km). Three of 26 juveniles tracked (11%) were alive after one year, although none were observed with mates. We conducted...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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We studied nest use by Golden Eagles (Aquila chrysaetos) from 1966 to 2011 to assess nest reuse within territories, ascertain the length of time that elapses between uses of nests, and test the hypotheses that reproductive success and adult turnover influence nest switching. Golden Eagles used 454 nests in 66 territories and used individual nests 1 to 26 times during 45 continuous years of observation. Time between reuse ranged from 1 to 39 yr. Distances between nearest adjacent alternative nests within territories ranged between <1 and 1822 m, and distances between 90% of adjacent nests were <500 m. Of all nests used, 21% fell or disintegrated, and 31% were newly constructed during the study. Nest switching was...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research
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For this study, I compared sequentially molted feathers for a few captive raptors from year to year and symmetrically matched feathers (left/right pairs) for many raptors to see if color patterns of sequential feather pairs were identical or if symmetrical pairs were mirror-image identical. Feather pairs were found to be identical only when without color pattern (e.g., the all-white rectrices of Bald Eagles [Haliaeetus leucocephalus]). Complex patterns were not closely matched, but some simple patterns were sometimes closely matched, although not identical. Previous claims that complex color patterns in feather pairs are fingerprint-identical (and therefore that molted feathers from wild raptors can be used to identify...
Categories: Publication; Types: Citation; Tags: Journal of Raptor Research