Bird collisions with vehicles cause serious safety, financial and conservation concerns worldwide, but the causes of such collisions are poorly described. We investigated how experience with vehicles influenced avian avoidance responses. We trained three groups of vehicle-na€ ıve rock pigeons Columba livia with 32 near-miss vehicle approaches over 4 weeks at 60 and 120 km h À1 , and also included individuals that heard but did not see the approaches (control group). We subsequently measured flight initiation distance (FID) and whether individuals 'collided' with a virtual vehicle directly approaching at 120 or 240 km h À1 using video playback. We found that inexperienced individuals (i.e. the control group) had longer FIDs than experienced birds, although only one of 90 individuals across groups successfully avoided virtual collision. Vehicle approach speed during video playback and the interaction of approach speed and training group did not influence FID. Our results suggest that a habituation-like effect based on repeated observations of passing vehicles could contribute to ineffective vehicle avoidance responses by birds when collisions are imminent. Novel strategies should be developed to enhance avoidance responses to high-speed vehicles to minimize bird mortality.

A key aspect in the conservation of endangered populations is understanding patterns of genetic variation and structure, which can provide managers with critical information to support evidence-based status assessments and management strategies. This is especially important for species with small wild and larger captive populations, as found in many endangered parrots. We used genotypic data to assess genetic variation and structure in wild and captive populations of two endangered parrots, the blue-throated macaw, Ara glaucogularis, of Bolivia, and the thick-billed parrot, Rhynchopsitta pachyrhyncha, of Mexico. In the blue-throated macaw, we found evidence of weak genetic differentiation between wild northern and southern subpopulations, and between wild and captive populations. In the thick-billed parrot we found no signal of differentiation between the Madera and Tutuaca breeding colonies or between wild and captive populations. Similar levels of genetic diversity were detected in the wild and captive populations of both species, with private alleles detected in captivity in both, and in the wild in the thick-billed parrot. We found genetic signatures of a bottleneck in the northern blue-throated macaw subpopulation, but no such signal was identified in any other subpopulation of either species. Our results suggest both species could potentially benefit from reintroduction of genetic variation found in captivity, and emphasize the need for genetic management of captive populations.