A robotic falcon induces similar collective escape responses in different bird species.

Patterns of collective escape of a bird flock from a predator are fascinating, but difficult to study under natural conditions because neither prey nor predator is under experimental control. We resolved this problem by using an artificial predator (RobotFalcon) resembling a peregrine falcon in morphology and behaviour. We imitated hunts by chasing flocks of corvids, gulls, starlings and lapwings with the RobotFalcon, and compared their patterns of collective escape to those when chased by a conventional drone and, in case of starlings, hunted by wild peregrine falcons. Active pursuit of flocks, rather than only flying nearby by either the RobotFalcon or the drone, made flocks collectively escape more often. The RobotFalcon elicited patterns of collective escape in flocks of all species more often than the drone. Attack altitude did not affect the frequency of collective escape. Starlings escaped collectively equally often when chased by the RobotFalcon or a wild peregrine falcon. Flocks of all species reacted most often by collective turns, second most often by compacting and third by splitting into subflocks. This study demonstrates the potential of an artificial aerial predator for studying the collective escape behaviour of free-living birds, opening exciting avenues in the empirical study of prey-predator interactions.

Early conversion of maternal androgens affects the embryo already in the first week of development.

Maternal androgen exposure has potent effects on offspring development. As substantial levels of maternal androgens are deposited in avian egg yolks, avian eggs are frequently used to study maternal effects, with a strong focus on post-natal development. However, the underlying pathways are largely unknown. Since the hormones are taken up during the embryonic phase, and these are rapidly metabolized by avian embryos into metabolites such as etiocholanolone, we studied the effects of yolk androgens (testosterone and androstenedione) and their metabolite etiocholanolone during the first few days of embryonic development. As embryonic heart rate is often used as an indicator of embryonic development, we measured the heart rate from day 3 to day 6 of incubation by using a shell-less culture technique in rock pigeon eggs (Columba livia). Increased androgen exposure increased heart rate, and increased etiocholanolone mimicked this effect, albeit in a small sample size. This indicates that exposure to maternal androgens increases embryonic overall metabolism which may account for the developmental outcomes found in previous studies such as increased growth. Moreover, etiocholanolone is likely to be an important metabolite in a non-genomic pathway underlying the androgen-mediated maternal effect.