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Tuesday, 19 August 2014

Journal of Raptor Research September 2014, Volume 48, Issue 3: Contents and Abstracts

Journal of Raptor Research

Table of Contents : SEPTEMBER 2014 : Volume 48 Issue 3 


Population Density, Home Range, and Habitat Use of Crested Serpent-Eagles (Spilornis cheela hoya) in Southern Taiwan: Using Distance-Based Analysis and Compositional Analysis at Different Spatial Scales Full Access

Bruno A. Walther, Ta-Ching Chou, Pei-Fen Lee
pg(s) 195–209

For many tropical raptors, studies of population density and habitat use are still lacking. We used radio-tracking to study population density, home-range size, and habitat use of the Formosan Crested Serpent-Eagle (Spilornis cheela hoya) in Kenting National Park, southern Taiwan, during 1995–1997 and 1998–2007. Over two years, we documented a minimum population density of 2.69 individuals/km2, which is one of the highest ever reported. Home ranges calculated using minimum convex polygons and 95% fixed kernel areas averaged 12.34 km2 and 2.86 km2 (n  =  18), respectively. Core areas represented by the 50% fixed kernel areas averaged 0.41 km2. We used distance-based analysis and compositional analysis to compare habitat use within the entire study area and the home ranges. Both methods indicated the overwhelming use (>90%) of somewhat degraded and semi-open mixed forests, followed by the use of Acacia confusaforests and grasslands to a much lesser degree. Habitat use was nonrandom both within the study area and the home range, as mixed forests covered only 24.4% of the study area. Many perch sites were near the primary monsoon forest, which was, however, almost never used for hunting. As many other species of serpent-eagles are threatened by habitat loss and human persecution, our study provides valuable information for their future monitoring and management.
Abstract & References : Full Text : PDF (2496 KB)


Use of Protected Activity Centers by Mexican Spotted Owls in the Sacramento Mountains, New Mexico Full Access

Joseph L. Ganey, James P. Ward, Jr, Jeffrey S. Jenness, William M. Block, Shaula Hedwall, Ryan S. Jonnes and Darrell L. Apprill, Todd A. Rawlinson, Sean C. Kyle, Steven L. Spangle
pg(s) 210–218

A Recovery Plan developed for the threatened Mexican Spotted Owl (Strix occidentalis lucida) recommended designating Protected Activity Centers (PACs) with a minimum size of 243 ha to conserve core use areas of territorial owls. The plan assumed that areas of this size would protect “… the nest site, several roost sites, and the most proximal and highly-used foraging areas.” The PAC concept remains an important component of the recovery strategy nineteen years later, although use of designated PACs by territorial owls has never been evaluated. We assessed use of PACs for nesting and roosting by Mexican Spotted Owls in the Sacramento Mountains, New Mexico, using location data obtained during a study of owl demography from 2004–2011. High proportions of both nest and roost locations were located within the PAC boundary for most, but not all, PACs. Many locations outside of PAC boundaries were adjacent to those boundaries, but some occurred >1 km from PAC boundaries. Proportions of roost locations within the PAC also were high for most, but not all, individual owls of both sexes, and in all years of the study. Proportions of locations within PACs remained relatively high for periods of up to 24 yr following PAC establishment, suggesting that owls continued to use these areas over relatively long periods. A number of vacant PACs were recolonized by owls during the study, and these owls also used PAC areas at high levels in most, but not all, cases. It would be desirable to assess PAC use over longer time periods, in other geographic areas, and to incorporate foraging use in such evaluations. In the meantime, however, our results suggest that most resident owls concentrated nesting and roosting activity within designated PAC areas in our study area, that some vacant PACs were recolonized, and that use levels in PACs remained high as long as 24 yr after PAC establishment, suggesting that PACs in this area are providing important habitat for owls.


Age-Related Differential Migration Strategies in Northern Saw-Whet Owls (Aegolius acadicusFull Access

Ross A. Brittain and B. Casey Jones
pg(s) 219–227


We analyzed differences in wing loading and body condition indices (BCI) between hatch-year (HY) and after-hatch-year (AHY) Northern Saw-whet Owls (Aegolius acadicus) captured during autumn migration in south-central Indiana. From 2002 to 2012, banders captured 1469 owls at two sites, including 826 HY owls and 641 AHY owls. The mean BCI (mass to wing chord ratio) was 0.665 g/mm and did not vary between HY and AHY owls. BCI was lowest in 2005 (0.658 g/mm) and highest in 2008 (0.679 g/mm). During autumn 2007, the banders photographed 267 owls at the two banding sites to enable comparisons of wing loading (mass to wing surface area ratio) and BCI for different age categories. Mean wing loading was 0.242 g/cm2 and also did not vary between HY and AHY owls, confirming the BCI results and suggesting that the age classes were not gaining or losing mass differentially. The median arrival date was 3 d earlier and the nightly median capture time was 10 min later for HY owls. In addition, the mass of HY owls correlated positively with the nightly capture time, whereas this was not true for adults. Together these results suggest that HY Northern Saw-whet Owls in south-central Indiana make up for any limitations in migratory/hunting abilities by migrating earlier each night and foraging more frequently while migrating. Migrating earlier, whether by choice or as a result of density-dependent adult competition, likely affords the younger birds greater access to prey in commonly exploited foraging areas. Available data indicate the potential for regional variation in the mass to wing chord correlation for this species, which needs further research. We also suggest that future studies obtain full wingspan measurements and compare the wingtip shape (amount of point and convexity) between juvenile and adult birds.
Abstract & References : Full Text : PDF (1037 KB)


Factors Related to Northern Goshawk Landscape Use in the Western Great Lakes Region Full Access

Jason E. Bruggeman, David E. Andersen, James E. Woodford
pg(s) 228–239


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 an occupancy survey completed in 2008 (Bruggeman et al. 2011). We also combined these data with historical data of Northern Goshawk nest locations in the bioregion from 1979–2006 to evaluate the same competing hypotheses to elucidate long-term trends in use. The odds of Northern Goshawk use in 2008, and from 1979–2008, were positively correlated with average percent canopy cover. In the best-approximating models developed using 1979–2008 data, the odds of landscape use were positively correlated with the percentages of the landscape having canopy heights between 10 m and 25 m, and 25 m and 50 m, and the amount of variability in canopy base height. Also, the odds of landscape use were negatively correlated with the average height at the canopy base. Our results suggest multiple habitat factors were related to Northern Goshawk landscape-scale habitat use, similar to habitat use described at smaller spatial scales in the western Great Lakes bioregion and in western North America and Europe.


Correlation of Cere Color with Intra- and Interspecific Agonistic Interactions of Crested Caracaras Full Access

James F. Dwyer
pg(s) 240–247


Bright coloration in birds is an important indicator of individual quality often used in social displays. Structural, carotenoid-, and melanin-based colors are long-lasting, widespread, and widely studied. Hemoglobin-based colors are ephemeral, rare, and less studied. Hemoglobin-based displays occur when an individual facultatively enhances or restricts blood flow through caruncles, combs, wattles, or other highly vascularized un-feathered skin patches. In Crested Caracaras (Caracara cheriway; hereafter “caracara”) highly vascularized ceres facultatively undergo immediately reversible hemoglobin-based color changes, hypothesized to correlate with status during contests. I predicted aggressors in contests would consistently display hemoglobin-deprived ceres (hereafter “light”), and receivers would display hemoglobin-enhanced ceres (hereafter “dark”), or vice versa. To test this hypothesis, I conducted 149 30-min group observations during which I recorded outcomes of all observed intra- and interspecific agonistic interactions involving caracaras in groups including up to 46 caracaras (x¯  =  13.4, SD  =  6.9). I recorded 2586 agonistic interactions in which I could identify cere colors and ages of both caracaras involved in an intraspecific interaction (n  =  1160), or of one caracara involved in an interspecific interaction (n  =  1426). Cere colors of caracaras were consistently light when acting as aggressors in intra- and interspecific agonistic interactions, and dark when acting as receivers. Within age classes, caracaras displaying light-colored ceres were consistently aggressors toward caracaras displaying dark ceres, and between age classes, adults with light-colored ceres were aggressors toward younger birds with dark ceres. Caracaras displaying light-colored ceres were aggressors toward Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) and caracaras with dark ceres were receivers of aggression from these species. Regardless of the cere color, caracaras were subordinate to much larger Bald Eagles (Haliaeetus leucocephalus) and dominant over much smaller American Crows (Corvus brachyrhynchos). My observations support the hypothesis that cere color is correlated with agonistic behaviors and support the signaling hypothesis by correlating specific cere colors displayed with individual roles in intra- and interspecific interactions.
Abstract & References : Full Text : PDF (1895 KB) 


Post-fledging Dependence Period in the Eurasian Kestrel (Falco tinnunculus) in Western France Full Access

Nicolas Boileau, Vincent Bretagnolle
pg(s) 248–256


The post-fledging dependence period (PDP) of 25 Eurasian Kestrel (Falco tinnunculus) fledglings was studied in a coastal marsh in western France in 2002 and 2003. Body condition at fledging was the only parameter that had a positive effect on the length of the PDP, which averaged 18 d (range 3–31 d). Mean daily distance from the nest increased 15 m per day until independence, and mean area used during the PDP was 7.3 ha. Male kestrels provided food for fledglings during the PDP (though decreasing their delivery rate with time). Females stopped feeding their young 3 d after they fledged. First fledglings received more food than others and food per fledgling decreased with brood size.
Abstract & References : Full Text : PDF (354 KB) 


Raptor Presence Along an Urban–Wildland Gradient: Influences of Prey Abundance and Land Cover Full Access

Stan Rullman and John M. Marzluff
pg(s) 257–272


Native animals are affected differently by urbanization. Some species respond favorably and thrive in human-dominated landscapes, but others are extirpated. Raptors are often sensitive to changes in land cover and prey abundance. We therefore used a combination of broadcast surveys and incidental observations while spot-mapping to evaluate the influences of these two variables on the presence of raptors at 21 sites from 2004–2008 along an urban-to-wildland gradient in western Washington, U.S.A. We detected three species of hawks: Sharp-shinned Hawk (Accipiter striatus), Cooper's Hawk (Accipiter cooperii), and Red-tailed Hawk (Buteo jamaicensis); and five species of owls: Northern Pygmy-Owl (Glaucidium gnoma), Western Screech-Owl (Megascops kennicottii), Barred Owl (Strix varia), Great Horned Owl (Bubo virginianus) and Barn Owl (Tyto alba). Models that included specific land-cover elements as independent variables explained presence for all species better than models including only prey abundance. Cooper's Hawks and Barred Owls showed a positive response to human-altered landscapes, specifically the edges between deciduous-mixed forest and light intensity urban land cover. Raptor species richness was consistent across the gradient of urbanization (  =  3.67 species/site) and not correlated with land-cover diversity, songbird species richness, or total forest cover.
Abstract & References : Full Text : PDF (1848 KB)


Abundance and Distribution of Overwintering Red-tailed Hawks and American Kestrels in an Agricultural Landscape in Northeastern Arkansas Full Access

Melissa M. Bobowski, Virginie Rolland and Thomas S. Risch
pg(s) 273–279


Although Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are common raptors in the U.S.A., their wintering population abundance and distribution has not been studied recently in Arkansas. We assessed the temporal and spatial variation in population abundance of Red-tailed Hawks and American Kestrels over the winter in northeastern Arkansas. We conducted weekly surveys from an automobile in Craighead and Poinsett counties, Arkansas, October 2012–March 2013. Abundance of Red-tailed Hawks (n  =  854 total observations) and American Kestrels (n  =  165 total observations) along the transect increased during winter months. The overall abundance indices were 7.05 Red-tailed Hawks per 10 km (highest ever recorded) and 1.36 American Kestrels per 10 km. We found no significant differences in the utilization of the various cover types (i.e., short rice stubble, soybean stubble, and fallow areas/roadsides) for either species. However, both species differed in their use of perch types (i.e., utility poles, utility crossbeams, utility wires, trees, and other [such as ground, signs, or farming equipment]). Red-tailed Hawks perched on trees and crossbeams significantly more than on other perches. American Kestrels used utility wires as perches significantly more than any of the other perch types. We concluded that northeastern Arkansas is an important wintering area for migrating Red-tailed Hawks and American Kestrels, despite the large-scale agricultural fields present year-round in the landscape.
Abstract & References : Full Text : PDF (276 KB) 


Hatching Rank Influences Nutritional Condition in the Common Buzzard: Evidence from Ptilochronology Full Access

Péter Fehérvári, Szabolcs Solt, Károly Erdélyi, Reuven Yosef
pg(s) 280–284


It is believed that the chicks that hatch first in a clutch have a better condition than their siblings. To test this hypothesis, we monitored six clutches of Buteo buteo in Jászság area, Hungary. Note the order of hatching chicks ( n  = 21) and prior to fledging measure the length of the central tail feather pen, tarsus length and body mass of all chicks. To assess the nutritional status on, cut the central tail feather for a blind ptilochronological analysis. The average length of the central tail feathers was 69.5 mm, tarsus length was 77.0 mm, body mass was 824.9 g and the average growth bar width was 4.05 mm / day. The first chicks hatched bars had wider growth compared with chicks hatched second or third and assume that this represented a better nutritional status. The data corroborate existing information for other species of Buteo and suggest that sibling competition on nutrition affects younger chicks a clutch.
Abstract & References : Full Text : PDF (229 KB) 


Focal Activity of Nesting Golden Eagles near Unused Nests Full Access

James W. Watson, Robert Marheine and Thad Fitzhenry
pg(s) 284–288


Protection of nests used by individuals Aquila chrysaetos and implementation of buffer zones to minimize the effects of human activities associated conservation practices are accepted. The need to protect and create buffer zones unused nesting eagles is less clear. Analyzing the intensity of the functional behavior, or focal activity of 14 adults of A. chrysaetos tracked by telemetry used and unused nests in relation to their home ranges full in eastern Washington and Oregon between 2005 and 2013 The focal activity of eagles nesting in unused areas was variable and typically lower than that occurred near the nests used, but almost all unused nests were located within the core areas of the areas of action of the eagles. Nests were located in unused areas of high use of home ranges, even when they were separated by> 1 km of nests used and pretended to have been unused for several years. The Eagles may have been attracted to areas near nests unused due to the preference of hangers or flight conditions, or focal activity near nests without use may have played a territorial function. Because eagles moved to nests located up to 2.5 km of nests and used, could not identify nests that would not benefit from the protective buffer zone and concluded that all nests without using merit protective buffer zones.
Abstract & References : Full Text : PDF (318 KB) 


Improved Satellite Transmitter Harness Attachment Technique Full Access

John S. Humphrey and Michael L. Avery
pg(s) 289–291


Satellite telemetry often requires the attachment of a transmitter on the bird using a backpack harness configuration. The proper fit of the harness on the bird is essential for effective deployment and for the welfare of the birds. Introducing an improved harness attachment technique that uses inexpensive and available immediately rivet. This method reduces handling time and allows researchers to adjust the guides harness then secure them quickly and efficiently without sewing, gluing or screwing hot plastic.
Abstract & References : Full Text : PDF (935 KB) 


Cannibalism in Bonelli's Eagle (Aquila fasciataFull Access

Jesús Caro, Diego Ontiveros and Juan M. Pleguezuelos
pg(s) 292–294
Citation : Full Text : PDF (55 KB)  

Proning Behavior in Cooper's Hawks (Accipiter cooperiiFull Access

Robert N. Rosenfield, Larry E. Sobolik
pg(s) 294–297
Citation : Full Text : PDF (4926 KB) 

Observations of Predatory Behavior by White-headed Vultures Full Access

Campbell Murn
pg(s) 297–299
Citation : Full Text : PDF (49 KB) 

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