Prevalence of Anticoagulant Rodenticide Exposure in Red-tailed Hawks (Buteo jamaicensis) in New York State and Diagnostic Utility of Russell Viper Venom Test for Detecting Associated Coagulopathies

Anticoagulant rodenticides (ARs) continue to be used across the United States as a method for controlling unwanted rodent species. As a consequence, wild birds of prey are exposed to toxins by eating poisoned prey items. ARs prevent the hepatic recycling of vitamin K and thereby impede the post-translational processing of coagulation factors II, VII, IX, and X that is required for procoagulant complex assembly. Through this mechanism of action, ARs cause hemorrhage and death in their target species. Various studies have documented the persistence of these contaminants in birds of prey but few have attempted to use affordable and accessible diagnostic tests to diagnose exposure in free-ranging birds of prey. In our study free-ranging red-tailed hawks were found to be exposed to difethialone and brodifacoum. Eleven of sixteen (68%) livers tested for AR exposure were positive. Difethialone was found in 1/16 (6%) liver samples, and brodifacoum was detected in 15/16 (93%) liver samples. Difethialone was found at a concentration of 0.18 ppm and brodifacoum concentrations ranged from 0.003-0.234 ppm. Two out of 34 (6%) RTH assessed for blood rodenticide had brodifacoum in blood with measured concentrations of 0.003 and 0.006 ppm. The range of clotting times in the prothrombin time (PT) and Russell’s viper venom time assays for control RTH were 16.7 to 39.7 seconds and 11.5 to 91.8 seconds, respectively. No correlation was found between PT and RVVT in the control or free-range RTH, and there was no relationship found between the presence of liver anticoagulant residues and clotting times in the PT and RVVT.

Filoplume morphology covaries with their companion primary suggesting that they are feather-specific sensors

Do birds detect and respond to forces acting on feathers through filoplumes, which appear to be unique mechanosensory feathers? If filoplumes function as sensors, their morphology should covary with the morphology of their companion feather to better detect feather movements and position. We explore covariation in filoplumes and primaries across 5 species of birds that vary in body size, molt strategy, and the functional life span of their primaries (Green-winged Teal [Anas crecca], Ring-billed Gull [Larus delawarensis], Turkey Vulture [Cathartes aura], Red-tailed Hawk [Buteo jamaicensis], and Red-winged Blackbird [Agelaius phoeniceus]). Filoplumes never extended beyond the coverts and inserted immediately adjacent to the base of their companion primaries, positioning them to detect subtle changes in feather vibration or movement. Far more variation in filoplume number and morphology was due to species differences than to individuals or position in the wing. Across species, filoplume length and number increased with calamus length of primaries. In the 2 species with growing primaries, the number and length of filoplumes were only weakly associated with molting primaries, suggesting that filoplumes were not replaced when their companion primary was replaced. Further, filoplumes associated with a growing primary were not replaced synchronously, leaving others to sense primary position and movement. Finally, filoplume number and length were greatest in Red-tailed Hawks, a species that carries individual feathers for multiple years, but links between filoplume morphology and molt strategy await broader comparative studies. Taken together, the morphology of filoplumes and their replacement schedule relative to their associated primary suggests that they are sensors, capable of detecting subtle differences in the position and movement of their companion feathers.

The degree of embryonic development influenced some eggshell characteristics of wild red-tailed hawks (Buteo jamaicensis borealis)

The influence of embryonic development on eggshell characteristics of wild birds, particularly raptors, is not well studied. Red-tailed hawk (Buteo jamaicensis borealis Gmelin 1788) eggs (n = 66) collected in central New York State during the late 1800s and early 1900s were examined to determine if eggshell mass, eggshell thickness, and a thickness index corrected for egg shape and blowhole size were influenced by the degree of embryonic development at the time of collection. Changes in these characteristics were examined with linear mixed models with year of collection and clutch size specified as random variables. Unexpectedly, length, breadth, and mass of eggshells were greater in eggs with advanced embryonic development than eggs with less developed embryos, perhaps due to sampling error or collector bias. Eggs containing well developed embryos were 13% thinner and had a thickness index 7% smaller than eggs with poorly developed embryos. Eggs with larger embryos had larger blowhole diameters; this relationship may be useful in determining degree of embryonic development in eggs of other species where development information is not explicit. Given the historical and current interest in eggshell thinning due to pollutants, degree of embryonic development should be accounted for in studies of eggshell characteristics.

Riqueza y abundancia de rapaces diurnas del Cañón de Fernández, Lerdo, Durango

El monitoreo biológico es esencial para comprender la dinámica poblacional, los procesos ecológicos y los problemas emergentes. En este estudio determinamos la riqueza y abundancia de las rapaces diurnas en el Parque Estatal Cañón de Fernández en Durango, México. Detectamos 11 especies, cinco de éstas están bajo alguna categoría de riesgo según la Norma Oficial Mexicana 059-2010: gavilán pecho canela (Accipiter striatus), gavilán de cooper (A. cooperii), aguililla negra menor (Buteogallus anthracinus), aguililla rojinegra (Parabuteo unicinctus) y aguililla pecho rojo (Buteo lineatus). Las especies más abundantes fueron Coragyps atratus, Cathartes aura y Buteo jamaicensis. El hábitat donde obtuvimos más registros fue el bosque de galería. Las rapaces del área ven amenazada su conservación por la pérdida de hábitat, cacería y electrocución.