Cooper's Hawks Research Articles

The Cooper's Hawk: Breeding Ecology and Natural History of a Winged Huntsman.

The Cooper's Hawk: Breeding Ecology and Natural History of a Winged Huntsman.

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.

Trophic magnification of legacy persistent organic pollutants in an urban terrestrial food web

Legacy persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), persist for generations in the environment and often negatively impact endocrine functions in exposed wildlife. Protocols to assess the bioaccumulation potential of these chemicals within terrestrial systems are far less developed than for aquatic systems. Consequently, regulatory agencies in Canada, the United States, and the European Union rely primarily on aquatic information for the bioaccumulation assessment of chemicals. However, studies have shown that some chemicals that are not bioaccumulative in aquatic food webs can biomagnify in terrestrial food webs. Thus, to better understand the bioaccumulative behaviour of chemicals in terrestrial systems, we examined trophic magnification of hydrophobic POPs in an urban terrestrial food web that included an avian apex predator, the Cooper's hawk (Accipiter cooperii). Over 100 samples were collected from various trophic levels of the food web including hawk eggs, songbirds, invertebrates, and berries and analysed for concentrations of 38 PCB congeners, 20 OCPs, 20 PBDE congeners, and 7 other brominated flame retardants listed on the Government of Canada's Chemicals Management Plan. We determined trophic magnification factors (TMFs) for contaminants that had a 50% or greater detection frequency in all biota samples and compared these terrestrial TMFs to those observed in aquatic systems. TMFs in this terrestrial food web ranged between 1.2 (0.21 SE) and 15 (4.0 SE), indicating that the majority of these POPs are biomagnifying. TMFs of the legacy POPs investigated in this terrestrial food web increased in a statistically significant relationship with both the logarithm of the octanol-air (log KOA) and octanal-water partition (log KOW) coefficients of the POPs. POPs with a log KOA >6 or a log KOW >5 exhibited biomagnification potential in this terrestrial food web.

Landscape Composition Encompassing Cooper's Hawk Nest Sites in Western North Dakota

The Cooper's Hawk (Accipiter cooperii) is often classified as a woodland species, but it exhibits marked plasticity by nesting successfully in what was previously thought to be atypical habitat such as urban areas and sparsely wooded grasslands, including the Little Missouri National Grassland in North Dakota. Forest expansion into North Dakota grasslands is likely due to the reduction of natural disturbances such as wildfires and grazing by bison (Bison bison). From the 1970s to 2001, forest cover increased in McKenzie County, North Dakota, by .1000%. From 1950 to 1972 there were two recorded instances of nesting Cooper's Hawks in McKenzie County. In 2001, we recorded 18 active nests, 13 of which were successful, four that failed, and one with unknown fate. Using the 2001 National Landcover Dataset (NLCD), we calculated that the mean proportion of forest cover in circular plots (18.1 km2) surrounding nests was 0.21. We found no relationship between nest fate and proportion of forest land cover. Additionally, we found no significant difference in proportion of forest cover between nest sites and randomly selected sites centered on forest land cover, indicating that Cooper's Hawks were using forest land cover in proportion to its availability. Understanding the relationship between the shifting landscape composition of North Dakota and its avifauna is important for monitoring and managing breeding Cooper's Hawks.

Record fledging count from a seven-egg clutch in the Cooper's Hawk (Accipiter cooperii)

Cooper's Hawks (Accipiter cooperii) typically lay 3–5 eggs per clutch, rarely 6 eggs, and there are 2 accounts of 7-egg clutches and 1 record of a maximum 8-egg clutch for the species. Brood sizes of 3–5 young are common and the previous maximum brood count is 6 young. However, in 2019, we found an urban nest in Stevens Point, Wisconsin, with 7 eggs that resulted in a record high of 7 fledglings. We genetically confirmed that the attending male sired all the offspring and the attending female laid all 7 eggs. Larger body size of the tending adults may have been a factor in the exceptional reproduction reported here.

Genetic confirmation of a natural hybrid between a Northern Goshawk (Accipiter gentilis) and a Cooper's Hawk (A. cooperii)

Although hybrids between captive Accipiter species are known, and hybrids between wild Accipiter species in North America have long been suspected, none have been confirmed to date. However, in 2014, a hatching year Accipiter captured at Cape May, New Jersey, during fall migration, appeared intermediate in size and plumage between a Northern Goshawk (Accipiter gentilis) and a Cooper's Hawk (A. cooperii), and was suspected to be a hybrid. We used data from mitochondrial and nuclear genes to confirm that the hawk was a hybrid female resulting from a cross between a male Cooper's Hawk and female Northern Goshawk.

ARGAS (PERSICARGAS) GIGANTEUS SOFT TICK INFECTION WITH RICKETTSIA HOOGSTRAALI AND RELAPSING FEVER BORRELIA ON WILD AVIAN SPECIES OF THE DESERT SOUTHWEST, USA

Changing climatic conditions and the northward expansion of ticks and pathogens are of immense importance to human, animal, and environmental health assessment and risk management. From 2014 through 2015, a wildlife rehabilitation center in south-central Arizona, US noted soft ticks (Argasidae) infesting 23 birds, including Cooper's Hawks (Accipiter cooperii), Gray Hawks (Buteo plagiatus), Harris's Hawks (Parabuteo unicinctus), Red-tailed Hawks (Buteo jamaicensis), Great Horned Owls (Bubo virginianus), Common Ravens (Corvus corax), and a Greater Roadrunner (Geococcyx californianus), during the late summer seasonal rainy seasons. The parasites numbered in the hundreds on individual birds. Infested birds were moribund, obtunded, or paralyzed on presentation, with no prior histories of illness or evidence of trauma. Tick and avian blood samples were collected for vector-borne pathogen analysis focusing on the molecular detection of Rickettsia and Borrelia species. Ticks were identified as the neotropical species of soft tick, Argas (Persicargas) giganteus; their occurrence in the southern US on raptors represented an expansion of host range. Pathogen testing of ticks showed that 41% of 54 ticks were infected with Rickettsia hoogstraalii and 23% of 26 ticks were infected with a relapsing fever Borrelia; both agents are associated with uncertain health consequences. Among the blood samples, one was infected with the same Borrelia spp.; this Red-tailed Hawk also had Borrelia-positive ticks. With supportive therapy, the majority of birds, 74% (17/23), recovered and were released or permanent residents. The management of soft tick-infested birds and mitigation of future disease risk will require additional characterizations of these poorly studied soft ticks and their associated pathogens.

A long‐term assessment of raptor displacement at a wind farm

Wind energy development is advancing rapidly, but the potential ramifications of this growth on wildlife, particularly birds and bats, are not fully understood. Wind energy development may affect raptor (birds of prey) populations indirectly by displacing them from their previously occupied habitat; however, there are limited empirical data demonstrating this effect. We performed long‐term raptor surveys at a wind farm previously implicated in the displacement of resident raptors and found that the duration of displacement varied among raptor species. Abundances of turkey vultures (Cathartes aura), red‐tailed hawks (Buteo jamaicensis), and accipiters (sharp‐shinned hawks [Accipiter striatus] and Cooper's hawks [Accipiter cooperii] combined) all rebounded in years 7 and 8 of wind farm operation, while the apparent displacement of northern harriers (Circus hudsonius) and American kestrels (Falco sparverius) persisted across all post‐construction monitoring periods. Our long‐term assessment indicates not only that wind farm construction and operation may displace raptors but also that these impacts can diminish over time for certain species. This finding underscores the importance of assessing potential impacts over the operational life of a given wind farm and the need for long‐term monitoring to validate predicted impacts, particularly for raptor communities.

Effects of Broadcasting Calls on Detection Probability in Occupancy Analyses of Multiple Raptor Species

For population studies that rely on aural or visual observations of individuals, methods that induce a detectable response can greatly improve sample sizes and reduce costs. Numerous authors have reported improved detections using broadcast surveys in forested areas for various species of raptors; however, to our knowledge, none have attempted to quantify the effects of broadcast surveys on the detection probability (p) in the context of an occupancy study for multiple species. Our objective was to determine whether broadcasting conspecific and heterospecific calls (broadcast surveys) would increase p of raptor species compared to passive surveys. This comparison was accomplished by estimating p during both types of surveys using a multiscale occupancy framework. We conducted 8400 surveys for Cooper's Hawk (Accipiter cooperii), Swainson's Hawk (Buteo swainsoni), White-tailed Hawk (Geranoaetus albicaudatus), Harris's Hawk (Parabuteo unicinctus), Red-tailed Hawk (Buteo jamaicensis), and Great Horned Owl (Bubo virginianus) in 2015 and 2016 in south Texas. We conducted 10-min passive surveys in both years, 10-min broadcast surveys in 2015 including calls from each of the target hawk species, and 10-min broadcast surveys in 2016 using calls from Great Horned Owls. Our results suggest that p is improved with multiple-hawk broadcast surveys (0.16, SE 0.04) over passive surveys (0.04, SE 0.02) for Harris's Hawks; p was not affected in broadcast surveys for the other hawk species considered. Great Horned Owls had a higher p during broadcast surveys using Great Horned Owl calls (0.35, SE 0.04) than during passive surveys (0.19, SE 0.02). Our results do not support the use of broadcast surveys to improve the detection probability of multiple species of hawks. However, our results do indicate that using broadcast surveys for occupancy studies focused on Harris's Hawks or Great Horned Owls should significantly reduce the effort required over passive surveys, resulting in improved power and reduced costs.

Nesting Density and Dispersal Movements between Urban and Rural Habitats of Cooper's Hawks (Accipiter cooperii) in Wisconsin: Are These Source or Sink Habitats?

Cites are relatively new landscapes for breeding Cooper's Hawks (Accipiter cooperii) that nest commonly in urban and rural habitats throughout North America. There is a call for data that may indicate if cities are low quality, sink habitats, as for some other raptors, or if cities function as high-quality, source habitats. Source habitats should exhibit high nesting densities, high reproductive output, and they should produce net emigration to sites that offer the potential for greater fitness. There are no reports of connectivity via dispersed individuals and their reproductive success (i.e., gene flow) between rural and urban subpopulations for Cooper's Hawks in North America. We report one of the highest nesting densities in North America, one nest/238 ha in the city of Oshkosh, Wisconsin in 2015, with regular spacing of nests suggestive of the saturated, stable population which occurs elsewhere throughout the state. Averages of 4.7 eggs and 4.1 nestlings per nest in Oshkosh, respectively, rank among the highest metrics for the species, and are similar to the stable and high reproductive indices found elsewhere throughout rural and other urban Wisconsin habitats across 34 y (1980–2015). An apparent low index of hatchling mortality rate (10%), or the loss of offspring from clutch to brood counts, was also found in Oshkosh. We detected both breeding and natal dispersal, with relatively high clutch and nestling counts, among eight individual Cooper's Hawks of both sexes moving into and emigrating from Stevens Point, Wisconsin with surrounding rural habitats. Most dispersal movements were less than 10 km. A relative similarity in maximum dispersal distances across 38 y (1980–2017) for rural-to-rural movements in males (35 km) and females (79 km), with those distances in males (27 km) and females (48 km) that moved between Stevens Point and its rural surroundings, suggest the maximum extent of natal dispersal movements is not habitat-specific in Wisconsin Cooper's Hawks. Discussion of various demographic contexts, including potentially confounding ecological variables, revealed limitations to previous reports and interpretations of reproductive output and nesting densities for the species, including assessments of habitat quality. We suggest high-quality rural and urban nesting habitats in Wisconsin are not source habitats for Cooper's Hawks within the state given none comparatively appears to offer the potential for greater fitness. Therefore, there should be no net dispersal among habitat types.

First Record of Cooper's Hawk (Accipiter cooperii) Breeding in Puebla, Mexico

First Record of Cooper's Hawk (Accipiter cooperii) Breeding in Puebla, Mexico

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.

Prevalence of Sarcocysts in the Muscles of Raptors from a Rehabilitation Center in North Carolina

The life cycle of Sarcocystis species is heteroxenous (2-host), with carnivores being the definitive host and herbivores serving as intermediate hosts in predator-prey relationships. Raptors (eagles, hawks, falcons, and owls) are apex predators and are not consumed routinely by other carnivores, making the occurrence of sarcocysts in their muscles unusual. Recent reports of sarcocysts in eagles and owls with Sarcocystis encephalitis suggests that this condition may be becoming more frequent, and Sarcocystis falcatula has been implicated as the agent of encephalitis in golden ( Aquila chrysaetos) and bald eagles ( Haliaeetus leucocephalus) as well as great horned owls ( Bubo virginianus). The present study was done to determine the prevalence of sarcocysts of Sarcocystis species in the muscles of raptors from the southeastern United States. Pectoral and heart muscle from 204 raptor patients from the Carolina Raptor Center, Huntersville, North Carolina were tested for the presence of Sarcocystis species using histology. Only a few sarcocysts were seen in sections of pectoral muscle from 39 of 204 raptors (19.1%) and heart muscle from 9 that also had sarcocysts in their pectoral muscle. Two structural types of sarcocysts, thin-walled (1 μm; 62%) or thick-walled (>2 μm, 38%), were seen. Statistical analysis of raptor age and gender was done by Fisher's exact test on samples from raptors with 20 or more samples per group. The prevalence of sarcocysts by age (2 yr or more) was significant for red-shouldered hawks ( Buteo lineatus) ( P = 0.022) and Cooper's hawks ( Accipiter cooperii) ( P = 0.028). Sarcocyst prevalence in male raptors from these groups evaluated statistically were always less than in females. Prevalence in female red-tailed hawks ( Buteo jamaicensis) (42.1%) was significantly greater than in males (6.7%) using Fisher's exact test ( P = 0.047). Examination of case histories from the 39 sarcocyst-positive raptors did not reveal an association with sarcocysts in raptor pectoral or heart muscle and in a diagnosis of encephalitis. Additional studies are needed to determine the epidemiology and relationships of Sarcocystis spp. that use raptors as intermediate hosts and the importance of Sarcocystis spp. in the overall wellbeing of raptors in their natural environments.

Demographic consequences of sexual differences in age at first breeding in Cooper's Hawks (Accipiter cooperii)

Demographic consequences of sexual differences in age at first breeding in Cooper's Hawks (Accipiter cooperii)

Possible Functions of Tail-Pumping by American Kestrels (Falco Sparverius)

When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behaviour is unknown. Our objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, we noted their behaviour (e.g. landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e. rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1±0.2 pumps per 10 s) and consuming prey (mean = 2.4±0.2 pumps per 10 s). When hunting, kestrels tail-pumped at higher rates during the 30 s prior to attacking (mean = 1.1±0.3 pumps) than they did during the 30–60 s interval before an attack (mean = 0.3±0.1 pumps). During experiments where kestrels were presented with models of a conspecific and a predator (Cooper's Hawk, Accipiter cooperi), we found no difference in rates of tail-pumping prior to and during the presentation. These results suggest that tail-pumping by American Kestrels is not used either to communicate with conspecifics or as a predator-deterrent signal. Rather, kestrels appear to tail-pump to help maintain balance on perches when landing and consuming prey. In addition, prior to attacking prey, kestrels typically bob their heads (possibly to aid in judging distances), and tail-pumping may help them maintain stability as they head-bob and prepare to attack.

Molecular evidence of infection with air sac nematodes in the great tit (Parus major) and the captive-bred gyrfalcon (Falco rusticolus).

Serratospiculiasis is a parasitic disease caused by filariid nematodes of the genus Serratospiculum that parasitise the air sacs of various species of falcons, bald eagles and Cooper's hawks around the world. An infection with Serratospiculum was recently confirmed in a nonspecific host, the great tit, in Slovakia. Parasitic material from this host was fixed for molecular analysis. Nematode found in the air sacs from a captive-bred gyrfalcon was also stored. Analysis of small subunit (18S) ribosomal DNA (18S rDNA) gene indicated that sequences from Serratospiculum sp. and Serratospiculoides amaculata were closely related to a reference sequence from Serratospiculum tendo, in agreement with morphology. This study is the first to generate molecular data and infer the phylogenetic position of S. amaculata as the first representative of the genus Serratospiculoides.

Responses of Blue Jays (Cyanocitta Cristata) to Raptors that Differ in Predatory Threat

Some species of birds use their vocalisations to communicate predator presence and the level of threat they pose, including two species of corvids (Corvidae), American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus). Our objective was to determine if Blue Jays (Cyanocitta cristata), another corvid, also use specific calls or vary the characteristics of certain calls to convey information about the level of threat posed by aerial predators. During the non-breeding seasons of 2014 and 2015, we recorded and analysed the vocal responses of Blue Jays to study skins of six species of raptors that varied in size and the level of threat they pose to Blue Jays. Experiments were conducted at seven locations in Madison County, Kentucky. The mean number of Blue Jays present during trials was 2.6, and Blue Jays uttered five different vocalisations during trials, with ditonal and monotonal jeers given most frequently. The rate at which Blue Jays uttered ditonal jeers differed among trials, with rates highest during trials with an Eastern Screech-Owl (Megascops asio) and a Sharp-shinned Hawk (Accipiter striatus). However, the characteristics of ditonal and monotonal jeers (duration, low frequency, high frequency, and peak frequency) did not differ among trials. These results suggest that Blue Jays may either perceive Eastern Screech-Owls and Sharp-shinned Hawks as the greatest threats or, alternatively, as potential, but less threatening predators, and, therefore, they were willing to take greater risks when mobbing them. In contrast, Blue Jays mobbed the other raptors, i.e. American Kestrels (Falco sparverius), Red-tailed Hawks (Buteo jamaicensis), and Great Horned Owls (Bubo virginianus), with much less intensity, likely because they posed less of a threat or, in the case of Cooper's Hawks (Accipiter cooperii) that are known predators of Blue Jays, perhaps because mobbing with greater intensity, e.g. approaching more closely, posed too great a risk. Blue Jays in our study used the same calls with the same characteristics when responding to potential predators, only calling rates differed. However, such variation in calling rates when mobbing would likely provide useful information about the presence of, and possibly the threat posed by, potential predators for conspecifics and, perhaps, heterospecifics.

Lifestyle shapes bird of prey binocular visual field

Swooping toward a victim with its vicious talons extended, a bird of prey homes in for the kill with meticulous precision. ‘Birds, particularly birds of prey [raptors], are believed to forage primarily using visual cues’, says vision scientist Simon Potier from Lund University, Sweden, who was inspired by his father's love of birds of prey to take up falconry as a small child. Yet, Potier explains that it was not clear how the birds use the region where the views from the two eyes overlap (the binocular zone) during their rapier-like attacks. As the hunting strategies of birds of prey span low-speed scavenging to high-speed aerial and ground prey capture, Potier, Francesco Bonadonna and Olivier Duriez from Université de Montpellier, France, and an international team of collaborators wondered whether the binocular vision of these precision hunters might vary depending on their lifestyle.Potier turned to his own collection of almost 60 birds at Les Ailes de l'Urga theme park in France and other birds from Le Grand Parc du Puy du Fou to measure the binocular visual fields of birds ranging from carrion-feeding vultures to predatory Cooper's hawks and eagles that target victims on the ground. ‘We used a non-invasive procedure to measure visual field characteristics in alert birds’, says Potier, recalling the difficulty of holding the large eagles steady for 20 min while measuring the limit of the view from each eye in order to calculate the binocular region where the visual fields overlapped. ‘The experience of the falconers who helped was essential’, he says. In addition, he had to custom build individual bill holders for each species to keep their heads in place, ‘which took me quite some time to fit perfectly’, he laughs. However, Potier was relieved when the birds appeared unfazed after they were released: ‘Directly after the experiment, they still flew to me, which indicates that they were not stressed’, he smiles.Initially, Potier and his colleagues had anticipated that the binocular visual fields of the hunters would be wider than those of the scavengers, as the hunters have to precisely target a moving victim with their talons while the scavengers’ aim may not need to be as precise. However, the width of the binocular visual fields was remarkably similar. The contrasts were more apparent when the team plotted the full projections of the binocular region, showing that the zone above the beak where the view from the two eyes overlapped tapered more rapidly in the ground-hunting eagles than it did in Cooper's hawks (which target birds on the wing) and the scavenging vultures. There was also an extensive blind zone above the heads of the ground predators – which do not have to outmanoeuvre agile targets on the wing. Considering the various hunting strategies and differences in the head shapes of the 15 species, Potier and his colleagues suspect that the ridge of bone that shades the eyes of the ground-hunting species could partially obscure the upper portion of their binocular field to produce the large blind zone. In addition, their short, but wide, powerful beaks appear to shade the lower portion of their view.‘Our results show that the binocular field configuration is specialized to foraging tactics in raptors’, says Potier, who is keen to scrutinise the vision of the almost exclusively terrestrial secretary bird. ‘They have very large eyes… I would love to estimate their visual field’, he muses.

DETERMINING RAPTOR SPECIES AND TISSUE SENSITIVITY FOR IMPROVED WEST NILE VIRUS SURVEILLANCE.

Raptors are a target sentinel species for West Nile virus (WNV) because many are susceptible to WNV disease, they are easily sighted because of their large size, and they often occupy territories near human settlements. Sick and dead raptors accumulate at raptor and wildlife rehabilitation clinics. However, investigations into species selection and specimen type for efficient detection of WNV are lacking. Accordingly, we evaluated dead raptors from north-central Colorado, US and southeast Wyoming, US over a 4-yr period. Nonvascular mature feathers ("quill"), vascular immature feathers ("pulp"), oropharyngeal swabs, cloacal swabs, and kidney samples were collected from raptor carcasses at the Rocky Mountain Raptor Program in Colorado from 2013 through 2016. We tested the samples using real-time reverse transcriptase-PCR. We found that 11% (53/482) of raptor carcasses tested positive for WNV infection. We consistently detected positive specimens during a 12-wk span between the second week of July and the third week of September across all years of the study. We detected WNV RNA most frequently in vascular feather pulp from Cooper's Hawk ( Accipiter cooperii). North American avian mortality surveillance for WNV using raptors can obviate necropsies by selecting Cooper's Hawk and Red-tailed Hawk ( Buteo jamaicensis) as sentinels and targeting feather pulp as a substrate for viral detection.

TetratrichomonasandTrichomonasspp.-Associated Disease in Free-Ranging Common Eiders (Somateria mollissima) from Wellfleet Bay, MA and Description of ITS1 Region Genotypes

During an outbreak of Wellfleet Bay virus (WFBV) in common eiders ( Somateria mollissima) from the Cape Cod region of Massachusetts, several birds were diagnosed with trichomonosis consisting of multiple trichomonad species. Six birds were examined, with trichomonads found in ceca in four birds and associated typhlitis in three of these four birds. PCR and DNA sequencing utilizing trichomonad-specific primers targeting the ITS1 region of the ribosomal DNA (rDNA) revealed the presence of Tetratrichomonas gallinarum in the gastrointestinal tracts of five birds and Trichomonas spp. in the livers of two birds, one of which had a dual Te. gallinarum-Trichomonas gallinae infection. Sequence analysis revealed no variation between Te. gallinarum sequences whereas the ITS1 sequences obtained from the other Trichomonas spp. demonstrated the presence of multiple genotypes. One sequence had 100% identity to a Trichomonas sp. previously isolated from a Cooper's hawk ( Accipiter cooperii) and the other sequence was 100% identical to a previously described Tr. gallinae isolate obtained from a Pacific Coast band-tailed pigeon ( Patagioenas fasciata monilis). These findings suggest Te. gallinarum and other Trichomonas spp. possibly contributed to morbidity and mortality in this species. Furthermore, to the authors' knowledge, this is the first report of trichomonad-associated disease in a free-ranging sea duck.