Airspeed of the Song Thrush in relation to the wind during autumnal nocturnal migration

Birds possess behavioural and physiological adaptations which permit them to minimize time and energy expenditure during migration in a broad spectrum of winds, for instance, by varying their airspeed. Nocturnally migrating birds were recorded by an optical-electronic matrix system, which permitted recording their images and flight parameters in the dark. Among medium size birds, Song Thrushes (Turdus philomelos) were identified by their silhouette, linear size, wing-beat pattern, and phenology. The equivalent airspeed at sea level (VEq) of the observed thrushes without wind assistance (mean value 14.4 m/s) was close to the maximum range speed (Vmr) predicted from flight mechanical theory. This indicated an energy-selected migration strategy of the thrushes in autumn. The characteristic speed Vmr is wind-dependent: it increases with increasing velocity of head- and sidewinds. The airspeeds of the Song Thrushes showed a similar pattern of wind-dependence

Visual lateralization in flight : Lateral preferences in parent‐offspring relative positions in geese

Visual lateralization arises from the differential processing of information by the two brain hemispheres and can manifest itself in animal behaviour in the form of lateral preferences. Current evidence suggests that social coordination serves as a driving force for the emergence of one-sided behavioural preferences in the populations. Collective movement is one of the most basic and ubiquitous examples of coordinated behaviour. Very little is known, however, about lateralized social interactions in such a complex and sensory demanding movement mode as flight. In the present study, we aimed at investigating lateralization in parent-offspring interactions during migratory and nonmigratory flights in greater white-fronted geese. Analyzing the GPS tracks of 19 goose families, we showed individual lateral preferences in the position of juvenile birds relative to a parent in nearly half of the juveniles. A population-level preference to follow the mother on her left side was shown in juveniles during migratory flights but not in other analyses. This preference, differently from previous findings in mammals implicating a right eye bias, may be explained by the left hemisphere advantage for the functions involved in following behaviour of migrating birds, e.g., focussed attention. This highlights different drivers of lateralization in collective movement in relation to situation-specific demands.publishe