Chlamydia buteonis in birds of prey presented to California wildlife rehabilitation facilities

Chlamydial infections, caused by a group of obligate, intracellular, gram-negative bacteria, have health implications for animals and humans. Due to their highly infectious nature and zoonotic potential, staff at wildlife rehabilitation centers should be educated on the clinical manifestations, prevalence, and risk factors associated with Chlamydia spp. infections in raptors. The objectives of this study were to document the prevalence of chlamydial DNA shedding and anti-chlamydial antibodies in raptors admitted to five wildlife rehabilitation centers in California over a one-year period. Chlamydial prevalence was estimated in raptors for each center and potential risk factors associated with infection were evaluated, including location, species, season, and age class. Plasma samples and conjunctiva/choana/cloaca swabs were collected for serology and qPCR from a subset of 263 birds of prey, representing 18 species. Serologic assays identified both anti-C. buteonis IgM and anti-chlamydial IgY antibodies. Chlamydial DNA and anti-chlamydial antibodies were detected in 4.18% (11/263) and 3.14% (6/191) of patients, respectively. Chamydial DNA was identified in raptors from the families Accipitridae and Strigidae while anti-C.buteonis IgM was identified in birds identified in Accipitridae, Falconidae, Strigidae, and Cathartidae. Two of the chlamydial DNA positive birds (one Swainson’s hawk (Buteo swainsoni) and one red-tailed hawk (Buteo jamaicensis)) were necropsied, and tissues were collected for culture. Sequencing of the cultured elementary bodies revealed a chlamydial DNA sequence with 99.97% average nucleotide identity to the recently described Chlamydia buteonis. Spatial clusters of seropositive raptors and raptors positive for chlamydial DNA were detected in northern California. Infections were most prevalent during the winter season. Furthermore, while the proportion of raptors testing positive for chlamydial DNA was similar across age classes, seroprevalence was highest in adults. This study questions the current knowledge on C. buteonis host range and highlights the importance of further studies to evaluate the diversity and epidemiology of Chlamydia spp. infecting raptor populations.

Inventario avifaunístico de Poza Rica, Veracruz, México

La urbanización se ha extendido de forma acelerada y ha modificado los ambientes donde habitan las aves. Generalmente, los ambientes urbanos conllevan una serie de modificaciones al entorno que derivan en cambios en la composición de aves y en la necesidad de realizar inventarios de éstas. El estado de Veracruz concentra más del 60% de la avifauna mexicana, pero hay zonas donde su conocimiento es aún deficiente, como la zona norte. En este estudio registramos la riqueza de aves de Poza Rica, una ciudad industrial, y cotejamos la categoría de conservación (nacional e internacional) y de residencia de las especies. De 2014 a 2017 realizamos una búsqueda intensiva no sistemática de aves con recorridos ad libitum en diferentes sitios del paisaje urbano. Registramos 64 especies (de 13 órdenes y 27 familias). Cuatro especies (Buteo swainsoni, Cairina moschata, Falco femoralis y Psarocolius montezuma) están protegidas por la legislación nacional. La riqueza de aves en Poza Rica fue relativamente baja, y es muy probable que sea por las condiciones industrializadas de la ciudad y su extensión. Por último, resaltamos que las zonas urbanas, aun siendo pequeñas, sirven como resguardo de especies protegidas y pueden ser espacios donde las personas observen, interactúen y protejan a las aves silvestres.

Azara’s No. 21 “Gavilán pardo obscuro” is not a Short-tailed Hawk Buteo brachyurus

Almost half of the 400+ species described in Félix de Azara’s “Apuntamientos para la historia natural de los páxaros del Paraguay y Rio de la Plata” were new to science at the time of its publication; however, not all of these have yet been correctly identified. Azara’s No. 21 “Gavilán pardo obscuro” has long been misidentified as a dark phase of the Short-tailed Hawk Buteo brachyurus. However, the description of plumage, jizz, habitat and measurements are inconsistent with that species and Azara’s No. 21 can, in fact, be convincingly identified as a juvenile Swainson’s Hawk Buteo swainsoni, the earliest Paraguayan report of this species. No scientific names were apparently ever based on Azara No. 21.

Aerial attack strategies of bat-hunting hawks, and the dilution effect of swarming

Aggregation behaviors can often reduce predation risk, whether through dilution, confusion, or vigilance effects, but these effects are challenging to measure under natural conditions, involving strong interactions between the behaviors of predators and prey. Here we study aerial predation of massive swarms of Brazilian free-tailed bats Tadarida brasiliensis by Swainson’s hawks Buteo swainsoni, testing how the behavioral strategies of predator and prey influence catch success and predation risk. The hawks achieved high overall catch success, but they were no more successful against lone bats than against bats flying in column formation. There was therefore no evidence of any net vigilance or confusion effect, and hawks attacking the column benefitted from the opportunity to make several attempted grabs. Even so, the bats’ overall risk of predation was an order of magnitude higher when flying alone. Attacks on lone bats (∼10% of attacks) were greatly overrepresented relative to the proportion of bats classified as flying alone (∼0.2%), so dilution is both necessary and sufficient to explain the higher survival rates of bats flying in the column. From the hawks’ perspective, their odds of catching a bat more than trebled if the attack involved a stoop rather than level flight, or a rolling rather than pitching grab maneuver. These behavioral tactics were independently deployed in nearly three-quarters of all attacks. Hence, whereas the survival rate of a bat depends principally on whether it flies alone or in a group, the catch success of a hawk depends principally on how it maneuvers to attack.Lay summaryBats emerging by daylight from a massive desert roost are able to minimise their predation risk by maintaining tight column formation, because the hawks that attack them target stragglers disproportionately often. Whereas the predation risk of a bat therefore depends on how it maintains its position within the swarm, the catch success of a hawk depends on how it maneuvers to attack. Catch success is maximised by executing a stooping dive or a rolling grab.