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At least 145 records · Page 8Linked to original sources
USGS1991

The identity of Pennant's 'Wapacuthu owl' and the subspecific name for the population of Bubo virginianus from the western Hudson Bay

The name Strix wapacuthu Gmelin, often used for the subspecies of Bubo virginianus west of Hudson Bay, cannot be associated with certainty with either B. virginianus or Nyctea scandiaca. The subspecific name of the population of B. virginianus from Mackenzie to central-eastern British Columbia and northern Ontario should be B. v. subarcticus Hoy.

Journal of Raptor Research↗
USGS1999

Siblicide, splayed-toes-flight display, and grappling in the Saker Falcon

We observed two incidents of novel social behavior in the saker falcon (Falco cherrug) in Mongolia. First, we provide an account of a two-week-old saker falcon chick killing its nest mate, the first direct observation of siblicide in the genus Falco. We also report aerial combat between three adult saker falcons including observations of talon grappling, whirling, and Splayed-toes-flight, a previously undescribed social display.

Journal of Raptor Research↗
USGS1999

Pronounced variation in tarsal and foot feathering in the upland buzzard (Buteo hemilasius) in Mongolia

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 patterns may be best explained as the result of extensive and relatively recent hybridization between the longlegged (Buteo rufinus) and roughlegged (B. lagopus) buzzards and/or between long-legged and upland buzzards.

Journal of Raptor Research↗
USGS2002

Schizochromism in a Peregrine Falcon from Arizona

Herein, we report the first record of schizochromism in the Peregrine Falcon (Falco peregrinus). Our example is a nestling from southern Arizona. The lack of dark brown pigment in this bird made it closely resemble the blue-gray plumage of an adult. Near fledging time, the bird was eaten by its nestmates, so this article also documents cannibalism.

Journal of Raptor Research↗
USGS2003

Subadult and pale steppe eagles breeding in Mongolia

One pale morph and two rufous-tawny morph Steppe Eagles (Aquila rapax) were observed among about 20 breeding pairs found in Mongolia. All three were attending live young. Plumage features of the rufous-tawny birds suggest that they were not adults. Subadult breeding is thereby documented for the Steppe Eagle. Breeding is also documented for a pale morph bird, but the age of this bird is uncertain; either it was the first pale morph adult known for the species or, more likely, it represents breeding of a two-, three-, or four-year old bird.

Journal of Raptor Research↗
USGS1998

Breeding-season food habits of burrowing owls (Athene cunicularia) in southwestern Dominican Republic

Diet data from 20 Burrowing Owl (Athene cunicularia) nests were collected in southwestern Dominican Republic in 1976, 1982, and 1996. Invertebrates (53.3%) comprised the most numerous prey items (N = 396) delivered to nests by adult owls, but vertebrates (46.7%) were much better represented than in other studies of Burrowing Owl diet. Among vertebrates, birds (28.3% of all items) and reptiles (14.9%) were most important, whereas mammals (1.0%) and amphibians (2.5%) were less commonly delivered to nests. Vertebrates, however, comprised more than twice (69.2%) of the total biomass as invertebrates (30.8%), with birds (50.4%) and reptiles (12.8%) the most important of the vertebrate prey classes. A positive relationship was observed between bird species abundance and number of individuals taken as prey by Burrowing Owls.

Journal of Raptor Research↗
USGS1999

Bald Eagle response to boating activity in northcentral Florida

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, habitat use, interactions or age distribution indicating no alteration of eagle behavior patterns. Flush distance did not vary between weekends and weekdays (P = 0.96), but did vary by month (P = 0.0001), with a greater flush distance during months with highest boating activity. Minimal flush distances (x?? = 53m) and lack of measurable effects on behavior suggested that eagles in my study area were tolerant of boat disturbance.

Journal of Raptor Research↗
USGS1999

Poisoning of raptors with organophosphorus and carbamate pesticides with emphasis on Canada, U.S. and U.K.

We reviewed cases of raptor mortality resulting from cholinesterase-inhibiting pesticides. We compiled records from the U.S., U.K. and Canada for the period 1985-95 (520 incidents) and surveyed the relevant literature to identify the main routes of exposure and those products that led to the greatest number of poisoning cases. A high proportion of cases in the U.K. resulted from abusive uses of pesticides (willful poisoning). The proportion was smaller in North America where problems with labeled uses of pesticides were as frequent as abuse cases. Poisoning resulting from labeled use was possible with a large number of granular pesticides and some seed treatments through secondary poisoning or through the ingestion of contaminated invertebrates, notably earthworms. With the more toxic products, residue levels in freshly-sprayed insects were high enough to cause mortality. The use of organophosphorus products as avicides and for the topical treatment of livestock appeared to be common routes of intoxication. The use of insecticides in dormant oils also gave rise to exposure that can be lethal or which can debilitate birds and increase their vulnerability. A few pesticides of high toxicity were responsible for the bulk of poisoning cases. Based on limited information, raptors appeared to be more sensitive than other bird species to organophosphorus and carbamate pesticides. Some of the more significant risk factors that resulted in raptor poisonings were: insectivory and vermivory; opportunistic taking of debilitated prey; scavenging, especially if the gastrointestinal tracts are consumed; presence in agricultural areas; perceived status as pest species; and flocking or other gregarious behavior at some part of their life cycle. Lethal or sublethal poisoning should always be considered in the diagnosis of dead or debilitated raptors even when another diagnosis (e.g., electrocution, car or building strike) is apparent. Many cases of poisoning are not currently diagnosed as such and, even when diagnosed, the information is often not made available to regulatory authorities. The importance of pesticide intoxications relative to other sources of mortality is highly variable in time and place; on a regional level, the increased mortality of raptors resulting from cholinesterase-inhibiting pesticides can be significant, especially in the case of rare species.

Journal of Raptor Research↗
USGS2000

First-year movements by juvenile Mexican spotted owls in the Canyonlands of Utah

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 a feeding experiment, using Mongolian gerbils ( Meriones unguicuculatus ), to test the influence of increased food supply on dispersal onset. The mean dispersal date of five owls that received supplemental food (Julian day no. 255 ?? 2.6 SD) was significantly different than a control group (day no. 273 ?? 12.3).

Journal of Raptor Research↗
USGS2003

Temporal and spatial stability of red-tailed hawk territories in the Luquillo Experimental Forest, Puerto Rico

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 having high slope and easterly aspects. Territory size was small compared to that reported for other parts of the species' range. In addition, there was remarkably little temporal change in the spatial distribution, area, and boundaries of Red-tailed Hawk territories among the study periods. Further, there was substantial boundary overlap (21-27%) between defended territories among the different study periods. The temporal stability of the spatial distribution of Red-tailed Hawk territories in the study area leads us to believe the area might be at or near saturation.

Journal of Raptor Research↗
USGS1993

Are Bald Eagles important predators of Emperor Geese?

Bald Eagles ( Haliaeetus leucocephalus ) and geese often occur together, especially at sites used by geese for migrational staging and wintering. Although numerous studies have been directed at these taxa, there are only anecdotal accounts (Parris et al. 1980, Bennett and Klaas 1986, Bartley 1988) of Bald Eagles killing healthy geese at any time of the year (but see Raveling and Zezulak 1991). Most species of geese may be too large, as suggested by Shetrod et al. (1976) and Palmer (1988), or they may not regularly allow eagles an advantageous attack position (J.M. Gerrard in litt .). Here we report observations of attacks on Emperor Geese ( Chen canagica ) by Bald Eagles on the Alaska Peninsula in autumn. We discuss these and other observations of eagle-goose interactions vis-a-vis the role of Bald Eagles as predators of Emperor Geese.

Alaska↗
USGS1991

Estimating wintering Bald Eagle densities in the Mississippi Alluvial Valley

Surveys on the winter distribution of Bald Eagles have been concentrated in the northern USA (Hastings 1988, Mattson 1988), where Bald Eagles are most common. Few density estimates for wintering Bald Eagles exist. In the past, different survey techniques with little standardization have been used. Statistical analyses and error measurements of existing winter survey data usually are not possible. The National Wildlife Federation's "midwinter Bald Eagle survey," the largest operational winter survey, is not systematic. Observers concentrate on areas where large numbers of Bald Eagles winter. We collected Bald Eagle density and distribution data in the Mississippi alluvial valley (MAV) while conducting four regional aerial surveys for Mallards ( Anas platyrhynchos ) during the winters of 1988-89 and 1989-90. Our objectives were to determine if the relatively large sample size and experimental design used in our Mallard surveys would provide accurate population estimates and additional distribution data not provided by current Bald Eagle surveys

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗