Buteo Platypterus Research Articles

David F. DeSante’s Birds of Cabo San Lucas, Fall 1968: A Historic Account

In preparation for his doctoral studies at Stanford University, the late David F. DeSante spent the fall of 1968 studying migratory landbirds at Cabo San Lucas. Although his hopes to capture numerous vagrant warblers were not met, he amassed an impressive list of distributional records for the Baja California Peninsula at a time when few ornithologists were working there. Among these were peninsular firsts for the Ring-necked Duck (Aythya collaris), Broad-billed Hummingbird (Cynanthus latirostris), Broad-winged Hawk (Buteo platypterus), Bobolink (Dolichonyx oryzivorus), and Painted Bunting (Passerina ciris). Another six species, and one subspecies, were found for the first time in Baja California Sur. Venturing away from the immediate confines of Cabo San Lucas, DeSante established the first peninsular record of the Gray-headed Junco (Junco hyemalis caniceps) and first state records for another five species and one subspecies. Although many of these records have been reported previously, the junior authors believe it is appropriate to synthesize them more completely with current context, in Dave’s honor.

Homeward bound: annual breeding home range size and overlap in Broad-winged Hawks ( Buteo platypterus ) and the effects of sex, productivity, and ecoregion

Homeward bound: annual breeding home range size and overlap in Broad-winged Hawks ( Buteo platypterus ) and the effects of sex, productivity, and ecoregion

Status and distribution of the Antillean Broad-winged Hawk (Buteo platypterus antillarum) on the island of Grenada

Status and distribution of the Antillean Broad-winged Hawk (Buteo platypterus antillarum) on the island of Grenada

Age-Class Difference in Wintering Distribution of Broad-Winged Hawks

Abstract The Broad-winged Hawk (Buteo platypterus) is one of the most easily observed North American raptors during migration, yet little is known about its distribution during the nonbreeding season. To better understand the winter distribution of Broad-winged Hawks by age, we compiled 2164 Broad-winged Hawk sightings with age data and 25,797 sightings without age data reported to eBird during the nonbreeding period from 2000–2020. The mean latitude of adult birds was significantly farther south than the mean latitude of immatures, with broad overlap in the distribution of both age classes from the United States through South America. The distribution of birds that were not aged overlapped the distribution of both age classes. A higher proportion of immatures was observed in the United States through Central America, with a mean latitude of 15.69°N, whereas adults were concentrated in Central and South America (with a mean latitude of 9.93°N). When only birds wintering south of the United States were analyzed, immatures were still found farther north than adults, although the latitude difference was less. The winter age class distribution for Broad-winged Hawks could result from short-stopping behavior occurring more often in immatures than adults. Further research is needed to understand how geographic, sex, and age class groups may differ in winter distributions and the implications of these patterns. Citizen science data from eBird proved useful in examining broad-scale patterns in Broad-winged Hawk winter distribution and is a valuable resource to scientists evaluating avian distributions.

Broad-Winged Hawk Size Varies by Sex and Latitude in North America

Abstract Divergent life histories by sex are common within species of birds; thus, the ability to accurately determine sex is essential in many studies of avian ecology and can possibly lead to more effective conservation strategies. However, sex determination can be difficult in species not displaying dimorphic plumage, including most raptors, and size dimorphism has limited use during observations but is promising for determining sex of raptors in hand. The Broad-winged Hawk (Buteo platypterus), known for its long-distance migrations between North and South America, has yet to be examined for morphometric variation across its wide range. We analyzed body mass, wing chord, and tail length data for 119 adult Broad-winged Hawks captured in eastern North America during the breeding seasons from 1974 to 2020. We found that adult female Broad-winged Hawks were larger than adult males overall. Hawks from Wisconsin were larger than hawks from Pennsylvania and Maryland, and hawks from Ontario were larger than those from other populations, suggesting geographic variation in size. Using linear discriminant analysis, we showed that it was possible to determine sex of adults with 99% accuracy in Wisconsin populations using only body mass as a predictor, and 100% accuracy in Pennsylvania and Maryland populations using body mass, wing chord, and tail length as predictors. Morphometric measurements combined with discriminant function analysis proved useful in discerning sex of breeding-season Broad-winged Hawks, and results of this study can guide researchers working in similar regions. We encourage researchers to collect body measurements for this species and other monomorphic raptors to further inform sex determination.

Adenoviral infection in 5 red-tailed hawks and a broad-winged hawk.

Adenoviral infections among raptors are best described in falcons and are characterized most commonly by necrotizing hepatitis and splenitis; only one case has been reported in a hawk. Five red-tailed hawks (Buteo jamaicensis) and a broad-winged hawk (Buteo platypterus) had an adenoviral infection based on history, histopathology, negative-stain electron microscopy, and PCR. All birds had acute onset of illness resulting in death; 3 had evidence of a concurrent bacterial infection. Microscopically, all 6 birds had solitary, pale eosinophilic-to-amphophilic, intranuclear inclusion bodies within presumed hematopoietic cells in bone marrow and macrophages in spleen. Five of the 6 birds had similar inclusions within hepatocytes and Kupffer cells. All but one bird had severe bone marrow necrosis. There was moderate splenic necrosis (3 of 6) and mild-to-marked hepatic necrosis (4 of 6). Negative-stain electron microscopy demonstrated adenoviral particles in bone marrow (5 of 6), liver (1 of 5), and/or spleen (1 of 5). PCR was positive for adenovirus in bone marrow (3 of 5), liver (1 of 3), spleen (4 of 6), and/or intestinal contents (2 of 3). Viral DNA polymerase gene sequences clustered within the Siadenovirus genus. There was 99% nucleotide identity to one another and 90% nucleotide identity with the closest related adenovirus (Harris hawk, EU715130). Our case series expands on the limited knowledge of adenoviral infections in hawks. The splenic and hepatic necrosis, and particularly the hitherto unreported bone marrow necrosis, suggest that adenoviral infection is clinically relevant and potentially fatal in hawks.

Broad-Winged Hawks Overwintering in the Neotropics: Landscape Composition and Threats in Wintering Areas of a Long-Distance Migrant

The Broad-winged Hawk (Buteo platypterus) is an obligate long-distance migrant that breeds in deciduous and mixed forests of North America and migrates to Neotropical regions to overwinter. Despite advances in understanding the breeding ecology and migration of this species, the overwintering period and associated threats remain understudied. We used telemetry data to quantify land cover composition and threats during the overwintering period of seven females affixed with Argos solar-powered transmitters between 2014 and 2018. Broad-winged Hawks in our study nested in Pennsylvania, USA, and overwintered in Colombia, Brazil, and Peru. Overwintering areas varied in size (x̄ = 243.6 ± 101.2 km2) and were composed of evergreen sub-montane forests, lowland non-flooded forests, and lowland flooded evergreen forest. In general, the loss of forest cover in all areas used by Broad-winged Hawks in our study did not exceed 10% of the total overwintering area used, suggesting Broad-winged Hawks may select wintering areas with little forest disturbance. Illegal mining was a common disturbance in areas used by Broad-winged Hawks overwintering in southern Peru, and forest fires were the prevalent disturbance in the overwintering area of Mato Grosso in western Brazil. These results provide the first analysis of land cover composition and threats of Broad-winged Hawks during the overwintering period. Although more data are needed to determine specific habitat selection for this species, our study suggests large forested areas in the Neotropics are key to ensure the conservation of the Broad-winged Hawk during the overwintering period, an understudied stage of its annual cycle.

Broad-winged Hawk Buteo platypterus (Aves: Accipitridae): An addition to the Paraguayan Avifauna

The first Paraguayan records of the Broad-winged Hawk Buteo platypterus are reported from Itapúa and Central departments.

Satellite tracking reveals age and origin differences in migration ecology of two populations of Broad-winged Hawks (Buteo platypterus)

Recent conservation plans for long-distance Neotropical migrant birds have emphasized the importance of understanding the ecology and threats facing a species throughout its life cycle, including migration and overwintering periods. To better understand the ecology of Broad-winged Hawks (Buteo platypterus) during the nonbreeding period, we followed the movements of 14 hawks from 2 breeding populations during July 2014–April 2019 to their overwintering sites. Three juvenile and 8 adult female Broad-winged Hawks were satellite-tracked from Pennsylvania, USA, and 3 adults (2 females and 1 male) were tracked from Alberta, Canada. We documented pre-migratory movements (post-breeding) of 4 of the 14 individuals. Adults initiated fall migration on x = 25 August ± 16.38 d and 2 of the 3 juveniles began fall migration on x = 20 August ± 2 d. Adults had 1–12 (x = 5.0 ± 3.5) stopovers in autumn that lasted for 1–24 d and juveniles had 2–5 (x = 3.0 ± 1.7) stopovers that lasted 2–51 d. Adults from Pennsylvania spent the overwintering period in Nicaragua, Brazil, Peru, and Colombia (n = 8) whereas those from Alberta wintered in Suriname, Venezuela, and Bolivia (n = 3). The distance traveled on autumn migration was greater for Alberta birds (x = 10,021 ± 866 km, n = 3) than for Pennsylvania birds (x = 7,925 ± 1,631 km, n = 8). Migration distance and overwintering region varied by geographic origin with age but with some overlap between the 2 distinct geographic breeding populations. Broad-winged Hawks appear to follow a hybrid time–energy minimization strategy during fall and spring migrations with (1) energy minimization in North America, and (2) time minimization in Mexico and Central America. Stopover frequency, duration, and migration rate support this hypothesis.

Fall migration of radio-tagged Broad-winged Hawks (Buteo platypterus) in California

Little is known about migration patterns of Broad-winged Hawks (Buteo platypterus) in the western United States apart from small numbers that have been recorded at migration monitoring sites. To better understand their movements in coastal California, we radio-tracked 5 juveniles (1 in 1994, and 4 from 2012 to 2015) during fall migration from the Marin Headlands (near San Francisco) to the US–Mexico border. One hawk died near the Headlands within 2–3 d of release and the other 4 crossed into Baja California in 4–6 flight days with no stopovers beyond the Headlands. Daily straight-line flight distances ranged from about 110 to 265 km (mean = 189 ± 47 km SD). Migration began 2.5–3 h after sunrise and ended a similar amount of time before sunset. Flight paths along mountain ranges, and radio signal patterns, indicated slope-soaring was a primary strategy. The detailed flight paths we identified will be helpful to better evaluate proposed renewable energy facilities, given their current rapid development and potential for killing birds. More study is needed to determine complete migration routes and breeding and wintering grounds of Broad-winged Hawks on the Pacific coast.

Acoustic discrimination of predators by black-capped chickadees (Poecile atricapillus).

Smaller owls and hawks are high-threat predators to small songbirds, like chickadees, in comparison to larger avian predators due to smaller raptors' agility (Templeton et al. in Proc Natl Acad Sci 104:5479-5482, 2005). The current literature focuses only on high- and low-threat predators. We propose that there may be a continuum in threat perception. In the current study, we conducted an operant go/no-go experiment investigating black-capped chickadees' acoustic discrimination of predator threat. After obtaining eight hawk and eight owl species' calls, we assigned each species as: (1) large, low-threat, (2) mid-sized, unknown-threat and (3) small-, high-threat predators, according to wingspan and body size. Black-capped chickadees were either trained to respond ('go') to high-threat predator calls or respond to low-threat predator calls. When either low-threat predator calls were not reinforced or high-threat predator calls were not reinforced the birds were to withhold responding ('no-go') to those stimuli. We then tested transfer of training with additional small and large predator calls, as well as with the calls of several mid-sized predators. We confirmed that chickadees can discriminate between high- and low-threat predator calls. We further investigated how chickadees categorize mid-sized species' calls by assessing transfer of training to previously non-differentially reinforced (i.e., pretraining) calls. Specifically, transfer test results suggest that mid-sized broad-winged hawks were perceived to be of high threat whereas mid-sized short-eared owls were perceived to be of low threat. However, mid-sized Cooper's hawks and northern hawk owls were not significantly differentially responded to, suggesting that they are of medium threat which supports the notion that perception of threat is along a continuum rather than distinct categories of high or low threat.

Spectral-domain optical coherence tomography imaging of normal foveae: A pilot study in 17 diurnal birds of prey.

To describe and to establish normative data for the foveae of diurnal birds of prey using spectral-domain optical coherence tomography (SD-OCT). All animals (9 red-tailed hawks, 3 Cooper's hawks, 3 American kestrels, 1 sharp-shinned hawk, and 1 broad-winged hawk) had an ophthalmic examination performed with slit lamp biomicroscopy and indirect ophthalmoscopy. Following ophthalmic examination, SD-OCT was performed in each eye that had a visible fundus and normal fovea on SD-OCT. Temporal foveae depth, central foveae depth, pecten-temporal foveae distance, and pecten-central foveae distance (PCFD) were measured using SD-OCT. Differences in measured outcomes between species were determined using generalized linear mixed effects models. The central foveae (mean±SD) displayed a small but significant depth variation between species (P=.002) and was deepest in red-tailed hawks (293±16µm), followed by American kestrels (260±12µm), broad-winged hawks (256±16µm), Cooper's hawks (250±9µm), and sharp-shinned hawks (239±16µm). The temporal foveae were shallower than the central foveae in all species tested, and there was a significant variation between species (P<.001). The temporal foveae (mean±SD) were deepest in American kestrels (137±8µm), followed by red-tailed hawks (129±3µm), broad-winged hawks (59.5±3.5µm), Cooper's hawks (20.3±6.4µm), and sharp-shinned hawks (17.5±0.7µm). Pecten-temporal foveae distance was approximately 30% shorter than PCFD in all species. There were no differences in the parameters tested between the eyes within each species (P≥.47). Normative foveae SD-OCT data were obtained in four species of diurnal birds of prey. Further studies are warranted to provide structural and functional information regarding normal and pathologic changes that can affect the foveae.

SOUTHERNMOST RECORDS OF Buteo platypterus (AVES, ACCIPITRIDAE) DURING WINTER MIGRATION: NEW OBSERVATIONS IN SOUTHERN BRAZIL

The Broad-winged Hawk ( Buteo platypterus (Vieillot, 1823)) (Accipitriformes: Accipitridae) is a migratory bird of prey that winters in Central and South America. This note reports two new records of the species in southern Brazil, which are currently the southernmost records in wintering areas. One of the observations represents the first occurrence for Santa Catarina state and the other is only the second for Rio Grande do Sul state, the first one for the central region of the state. Both observations suggest that this species may be more frequent than expected in southern Brazil and neighbouring countries.

Broad-Winged Hawk Nesting Behavior in Forested Landscapes of Pennsylvania

Broad-winged Hawks (Buteo platypterus) concentrate in large numbers during migration but several sources suggest regional declines in eastern North America may be occurring, perhaps due to increasing human development, natural resource exploitation, and suburbanization of forests. To better understand the natural history of this secretive nesting species, we used both direct field observations and video cameras to study the nesting ecology of Broad-winged Hawks in three geographic regions of Pennsylvania, each with varying degrees of forest fragmentation. We recorded adult nest attendance, prey deliveries, and nest material deliveries from incubation through fledging. During 891 hr of observation during the nestling period, adult hawks were absent from the nest >72% of the time. Of the time at least one adult was present at the nest during the nestling stage, 77% was spent standing and sheltering, 21% feeding young, and 1% consuming food. Both adults were present at the nest 16% of the total prey delivered. Prey deliveries were more frequent during the first 3 wk of the nestling period than during the last 2 wk of the nestling period, but did not vary by time of day. The most frequently delivered nesting material was deciduous sprigs, which made up 55% of deliveries. Nest materials were delivered from incubation until the young were 4 wk old, but delivery rates varied significantly by nesting stage and nestling age. The absence of adults at the nests during nestling and fledgling periods may leave young vulnerable to predators. Although our sample size of nests in fragmented forests was too small for statistical analysis, the relationship between forest fragmentation and Broad-winged Hawk nesting ecology warrants further investigation.

Artificially decreased dissolved oxygen increases the persistence of Trichomonas gallinae in water.

Water containing organic material has been shown to increase the persistence of the avian pathogenic protozoa, Trichomonas gallinae. We hypothesized that the decrease in dissolved oxygen due to microbes in the organic material could increase persistence of the microaerophilic trichomonads. Using simulated birdbaths, we determined 1) the levels of dissolved oxygen in distilled water with various amounts of organic material, 2) the concentration of the oxygen-scavenging enzyme Oxyrase® needed to achieve the dissolved oxygen levels obtained in organic material contaminated water, and finally, 3) the persistence of two T. gallinae isolates in Oxyrase®-supplemented water. An average of 9.6% dissolved oxygen was obtained with the addition of 15 g organic material to 500 ml of distilled water, whereas organic material-free water had 86.2% dissolved oxygen. The addition of 0.5% and 1.0% (vol/vol) Oxyrase® to organic material-free water yielded dissolved oxygen of 18.6% and 6.9%, respectively. Using 0.5% and 1.0% concentrations of Oxyrase®, we evaluated the persistence of two trichomonad isolates by inoculating ∼1 million trichomonads into 500 ml distilled water in triplicate. At various time-points, 0.5 ml aliquots of trichomonad-inoculated water were obtained and placed into Hollander Fluid media, incubated at 37 °C, and read by light microscopy every other day for 5 days. In our 1% Oxyrase® treatments, the longest recorded persistence of broad-winged hawk 1 increased from the previously reported 4hrs to 30hrs and Cooper's hawk 4 from 16hrs to 30hrs. These results indicate that the mechanism for organic material-mediated trichomonad persistence is associated with decreased dissolved oxygen, further demonstrating the importance of keeping birdbaths free of organic debris to discourage trichomonad persistence.

Raptor and large soaring bird migration across the Isthmus of Tehuantepec, Mexico: distribution, seasonality, and phenology

SummaryWe present the first study of the spatial and temporal dynamics of raptors and large soaring birds from the Isthmus of Tehuantepec, Mexico. Using systematic migration counts from multiple localities in the southern states of Oaxaca and Chiapas, as well as observations of their flight trajectories during eight consecutive years (2007–2014), we describe the magnitude of these movements, their geographic extent, and the phenology of the most abundant species in both spring and fall seasons. The most abundant species were Turkey VultureCathartes aura, Swainson’s HawkButeo swainsoni, Broad-winged HawkButeo platypterus, Wood StorkMycteria americana, American White PelicanPelecanus erythrothynchos, Franklin’s GullLeucophaeus pipixcan, and American KestrelFalco sparverius. In spring, the seasonal average magnitude of migration was over 28,000 birds, while in autumn the average was over one million. The aggregated seasonal phenologies recorded illustrate a variety of migration patterns. The inter-annual variation is lower in autumn than in spring. Migrating raptors and other soaring birds did not seem to use any topographical feature as a leading line for their movements in spring, while in autumn they did. We estimated the main axis of spring flights to run along a SE–NW vector, while autumn migration follows a WNW–ESE general trajectory. Our results place the isthmus as one of the five most important sites in the world for raptors and soaring migrants. Sustaining annual migration counts at these sites is of high importance to track substantial portions (&gt; 90%) of the global population of Turkey Vulture and Swainson’s Hawk, as well as over 10% of the global population of Broad-winged Hawk. Autumn migration counts have the potential for long-term population monitoring.

Turkey Vulture Scavenging Prey at a Broad-winged Hawk Nest

Turkey Vulture Scavenging Prey at a Broad-winged Hawk Nest

Amblyomma auricularium(Ixodida: Ixodidae) in Florida: New Hosts and Distribution Records

Previous published evidence for the occurrence of an exotic armadillo tick, Amblyomma auricularium (Conil), in Florida is scant, but we found it is fully established and integrated into the state's tick fauna. We collected 11,192 specimens of this tick from naturalized nine-banded armadillos, Dasypus novemcinctus L., and 14 other species of wild native mammals and birds in Florida, while sampling statewide during 2004 through 2007. In all, we document its specific presence only in 14 contiguous South Florida counties. Moreover, we report the first collections of A. auricularium from the Virginia opossum (Didelphis virginiana Kerr), common raccoon [Procyon lotor (L.)], cotton deermouse [Peromyscus gossypinus (Le Conte)], gray fox [Urocyon cinereoargenteus (Schreber)], eastern spotted skunk [Spilogale putorius (L.)], and white-tailed deer [Odocoileus virginianus (Zimmerman)]. For the first time on birds, we report the collection of this tick from the broad-winged hawk [Buteo platypterus (Vieillot)], northern cardinal [Cardinalis cardinalis (L.)], Carolina wren [Thryothorus ludovicianus (Latham)], gray catbird [Dumetella carolinensis (L.)], and yellow-rumped warbler [Setophaga coronata (L.)]. In addition, we report unattached A. auricularium collected from humans for the first time, and additional new collections from domestic dogs, Canis lupus familiaris L.

Antibody Prevalence and Isolation of Viable Toxoplasma gondii from Raptors in the Southeastern USA.

Raptors are good indicators of the prevalence of Toxoplasma gondii in the environment because they prey on small mammals and birds. These prey species are a major source of infection in domestic cats ( Felis catus ), which shed the environmentally resistant oocysts. We assessed T. gondii infection in 281 opportunistically available raptors at a rehabilitation facility between 2012 and 2014. Antibodies to T. gondii were assayed by a modified agglutination test (cutoff 1:25) and found in serum of 22/71 Red-tailed Hawks ( Buteo jamaicensis ), 25/54 Barred Owls ( Strix varia ), 9/41 Red-shouldered Hawks ( Buteo lineatus ), 13/28 Great Horned Owls ( Bubo virginianus ), 6/20 Broad-winged Hawks ( Buteo platypterus ), 2/16 Eastern Screech Owls (Megascops asio), 12/13 Bald Eagles ( Haliaeetus leucocephalus ), 6/12 Cooper's Hawks ( Accipiter cooperii ), 1/8 Black Vultures ( Coragyps atratus ), and 1/1 Golden Eagle ( Aquila chrysaetos ). Antibodies were not detected in 5 Barn Owls ( Tyto alba ), 3 American Kestrels ( Falco sparverius ), 1 Mississippi Kite ( Ictinia mississippiensis ), and 1 Osprey ( Pandion haliaetus ). Viable T. gondii was isolated from the tissues of 1 antibody-positive Barred Owl and identified as a strain having type II alleles at all 10 loci tested, except one (ToxoDB polymerase chain reaction-restriction fragment length polymorphism genotype 3). Type II strain is the most common strain in the US. Results of this study indicate a high prevalence of T. gondii in some raptor species and the first reported genotyping from a Barred Owl.

Response of migrating raptors to an increasing number of wind farms

SummaryFlying birds have been documented to respond in different ways to the presence of wind farms. Such responses are species‐ and site‐specific, with wind farm design playing an important role. Between 2009 and 2014, the length of rows of wind turbines within our study area increased from 3·4 km to ∼7·5 km, and the total area occupied by wind farms increased from 6·47 km2to 14·21 km2. This area is located on an important migratory corridor in southern Mexico.We used marine radar and hawk‐watch monitoring stations to collect data during six consecutive autumn seasons from a single wind farm. We analysed the response of migrating raptors to the presence of two new wind farms by comparing the mean bearing of flight trajectories and the number of intersections km−1of trajectories with wind farm areas between 2009–2011 and 2012–2014, representing the pre‐ and post‐construction stages of the new wind farms.Mean raptor count was &gt;600 000 individuals for the six seasons. The most abundant species were Turkey VultureCathartes aura, Swainson's HawkButeo swainsoniand Broad‐winged hawkButeo platypterus. Between 79% and 97% of migration occurred in October. Radar monitoring overlapped with the peak migratory activity each season.We observed significant differences between periods, involving more scattering in flight bearings and less intersections km−1of trajectory in the post‐ than in the pre‐construction period, implying an avoidance of the new wind farms.Synthesis and applications. We show that migrating raptors adjusted their flight trajectories to avoid new wind farms, but also discuss the extent and limitations of our findings. Our results from our hawk‐watch monitoring station, which represent the first published account about the seasonality and intensity of raptor migration in the area, could be used by decision‐makers for careful planning of future wind energy developments in the area. Our results might aid in the conservation of those species of raptors that migrate through the Isthmus of Tehuantepec.