The best way to find a Red-tailed Hawk is to go for a drive, keeping your eyes peeled along fenceposts and in the sky. Chances are good that the first hawk you see will be a Red-tailed Hawk. Just make sure to look for the buteo shape (broad, rounded wings; short tail), then check field marks like the dark bars on the leading edge of the wing. Across most of the continent, Red-tails are more numerous in winter, when birds from the far north arrive to join the birds that live in your area year round.
Here, we report a new species of Sarcocystis with red-tailed hawk (RTH, Buteo jamaicensis) as the natural definitive host and IFN-γ gene knockout (KO) mice as an experimental intermediate host in which sarcocysts form in muscle. Two RTHs submitted to the Carolina Raptor Center, Huntersville, North Carolina, were euthanized because they could not be rehabilitated and released. Fully sporulated 12.5 9.9-μm sized sporocysts were found in intestinal scrapings of both hawks. Sporocysts were orally fed to laboratory-reared outbred Swiss Webster mice (SW, Mus musculus) and also to KO mice. The sporocysts were infective for KO mice but not for SW mice. All SW mice remained asymptomatic, and neither schizonts nor sarcocysts were found in any SW mice euthanized on days 54, 77, 103 (n = 2) or 137 post-inoculation (PI). The KO mice developed neurological signs and were necropsied between 52 to 68 days PI. Schizonts/merozoites were found in all KO mice euthanized on days 52, 55 (n = 3), 59, 61 (n = 2), 66, and 68 PI and they were confined to the brain. The predominant lesion was meningoencephalitis characterized by perivascular cuffs, granulomas, and necrosis of the neural tissue. The schizonts/merozoites were located in neural tissue and were apparently extravascular. Brain homogenates from infected KO mice were infective to KO mice by subcutaneous inoculation and when seeded on to CV-1 cells. Microscopic sarcocysts were found in skeletal muscles of 5 of 8 KO mice euthanized between 55-61 days PI. Only a few sarcocysts were detected. Sarcocysts were microscopic, up to 3.5 mm long. When viewed with light microscopy, the sarcocyst wall appeared thin (
Secondary exposure to anticoagulant rodenticides (ARs) through consumption of contaminated prey has been documented worldwide in many non-target species, especially raptors. The Red-tailed Hawk (Buteo jamaicensis), a raptor that frequents agricultural areas and eats primarily rodents, is particularly susceptible. Because there is documentation of Red-tailed Hawk exposure to ARs in California, this study aims to describe the extent to which migrating juvenile Red-tailed Hawks are exposed to ARs, as well as any sublethal effects of AR ingestion. We collected blood samples and body morphometrics from 97 juvenile Red-tailed Hawks migrating through the Marin Headlands, Marin County, CA, from August to December in 2013 and 2015, and screened samples for the presence of ARs. Eight hawks (8.2%) tested positive for some amount of ARs. We detected first-generation (diphacinone, chlorophacinone) and second-generation (brodifacoum, bromadiolone) ARs. Although some juvenile Red-tailed Hawks are exposed to ARs either along their migration route or as resident birds in the Marin Headlands, we did not find any relationship between body condition and presence of ARs. Although this method of AR sampling of live birds is novel and increases our sampling capabilities, the short half-lives of ARs in blood make it difficult to estimate population-wide exposure rates. Future studies should focus on resident raptors near agricultural areas where AR exposure can be tested over time to better understand how this technique can be used to estimate exposure rates across whole populations.
Central and Southwestern Ontario is one of the largest migratory flyways for raptors in North America. The expanse of airfields and prey availability make airfields attractive to migrating raptors, which may result in an increase in over wintering birds. These birds do not readily scare with conventional wildlife control methods and have high public profile. Even though the strike risk is moderate, raptors routinely make the top ten list for strikes from all bird species (8%) at Canadian Airports. The potential for damage from a collision with raptor species is high due to their size and weight. It has been suggested that the live trapping and relocation of raptors has limited application and success. The banding of trapped and relocated raptors from Lester B. Pearson International Airport (Toronto, ON) and Windsor Airport (Windsor, ON) suggests that this approach to control is very effective. Of the 1502 Red-tailed Hawks (Buteo jamaicensis) relocated from Pearson International Airport over the past 15 years, 4 % returned to the airfield and that less than 2% returned within the same migratory period (90 days from initial encounter). The data collected also indicates that the concept of resident birds being replaced by naïve birds is not accurate because the majority of birds caught at Pearson are trapped during migration and therefore are by definition not resident birds.
Interpretive Summary: Toxoplasma and Sarcocystis are related single celled parasites of livestock and humans. While Toxoplasma has long been recognized to cause neurologic disease in many warm-blooded hosts, several species of Sarcocystis also cause a variety of disorders in livestock, pets, and wild animals and some of them are zoonotic. Neurological sarcocystosis simulating toxoplasmosis has been reported in raptors, including eagles. Additionally, raptors are definitive hosts (reservoirs) of several species of Sarcocystis that cause fatal pneumonia in several species of birds. In the present investigation, the authors confirm that immunodeficient (knock out) mice can serve as experimental intermediate hosts for Sarcocystis jamaicensis of red tailed hawk; KO mice fed sporocysts from the feces of naturally infected hawk developed neurological signs and mature sarcocysts were found in their muscles. The results will be of interest to biologists, zoo veterinarians, and parasitologists, and help search for the natural intermediate host of S. jamaicensis.
Technical Abstract: Here, we report confirmation of sarcocysts of Sarcocystis jamaicensis in an experimental intermediate host, IFN-' gene knockout (KO) mice orally inoculated sporocysts from its natural definitive host, red-tailed hawk (RTH). A RTH submitted to the Carolina Raptor Center, Huntersville, North Carolina, was euthanized because it could not be rehabilitated and released. Fully sporulated sporocysts from intestinal scrapings of the RTH were orally fed to 2 laboratory-reared outbred Swiss Webster mice (SW) (Mus musculus) and to 2 KO mice. The sporocysts were infective for KO mice, but not to SW mice. Both SW mice remained asymptomatic, and neither schizonts nor sarcocysts were found in their tissues when euthanized on day 54 post-inoculation (PI). The KO mice developed neurological signs,and were necropsied between 38 or 54 days PI. Schizonts/merozoites were found in both KO mice euthanized and they were confined to the brain. The predominant lesion was meningoencephalitis. Microscopic sarcocysts were found in muscles of both KO mice. When viewed with light microscopy, the sarcocyst wall appeared thin (
Nest sites and nest habitats used by Red-tailed (Buteo jamaicensis), Ferruginous (B. regalis), and Swainson's (B. swainsoni) hawks in Washington state were quantitatively described. Discriminant function analysis showed that each species used specific nesting areas with significant variation among species in the distance to water, distance to human disturbance, nest tree diameter, nest height, nest exposure, type of nest structure, and percentages of grass, shrub, and juniper habitats surrounding nests. Red-tailed Hawks nested closest to water, in the tallest and oldest trees, and in areas with large amounts of shrub and grassland habitat. Ferruginous Hawks nested at lower elevations in locations that were farthest from water and at heights of less than 10 m. Swainson's Hawk nests were closest to roads and human structures and nearly half were in areas where the surrounding habitat was dominated by wheat fields. 59ce067264