Spontaneous magnetic alignment, in which an animal or group of animals, aligns its body axis in a fixed orientation relative to the geomagnetic field has been observed across a variety of vertebrates. Although a seemingly ubiquitous spatial behaviour, the adaptive significance and sensory mechanisms underlying spontaneous magnetic alignment remain unclear. Here we report another example of spontaneous alignment during feeding behaviour from five corvid species, a well-known and geographically widespread avian taxon. Consistent with previous observational studies of magnetic alignment in free-roaming vertebrates, first- and second-order analyses show that corvids exhibit robust axial alignment corresponding with the north-south magnetic axis. In contrast, when the data is pooled relative to the sun's azimuth, the first-order analysis is indistinguishable from random and the second-order statistics, although statistically significant, are a much weaker predictor of axial orientation compared to the distribution pooled relative to the magnetic field. The magnetic alignment behaviour exhibited by foraging crows reported here is compatible with previous hypotheses proposing that spontaneous magnetic alignment may help to coordinate and structure spatial behaviours in free-living organisms. Clearly, an experimental approach in future studies is needed to help shed light on the functional significance and biophysical mechanisms mediating spontaneous magnetic alignment. These data provide support for spontaneous magnetic alignment in free-roaming corvids, a widespread taxon with exceptional cognitive abilities that may offer unique advantages for future laboratory and field-based studies of magnetoreception.

Animals use to align their body axis with respect to different cues (e.g. sun position, wind direction, magnetic field lines) and signals (informing about source of interest) in diverse behavioural contexts. Existence of alignment indicates ability to sense such cues or signals and its study can enlighten the mechanism of their sensing. Global cues (sun position, magnetic field) might provide a directional reference (direction/heading indicator) for organization of the mental map and/or for coordinated take-off. The existence of a common direction indicator may be of importance especially in birds living in large colonies and having impeded maneuverability. We measured the direction of the body axis (alignment) in flamingos of four species at 18 localities in zoological gardens and in the wild in altogether eight countries during different seasons of the year and at different times of the day. The measurements were taken from photographs in a blinded way. Flamingos in Europe showed a significant preference to align towards South during all recorded stationary activities (grooming, resting, standing) while those from Kenya tended to head towards North. On the contrary, the distribution of body alignments during locomotor activities (walking, wading, feeding) was random. Under overcast weather, and especially in the morning hours, magnetic South or North were better predictors of heading than sun position. We interpret our findings as evidence for a magnetic alignment in flamingos (depending on the weather condition) and suggest that its main function might be seen in information rather than in energy interaction. Under windless conditions, sun position and magnetic field may provide a common reference direction, i.e. a direction indicator. Visual cues (if available) and vision are in birds probably more dominant in spatial orientation than magnetic cues and magnetoreception. Magnetoreception might be "switched on", when visual sensing of relevant cues is impeded.

Introduction Landing flight in birds is demanding on visual control of velocity, distance to target, and slope of descent. Birds flying in flocks must also keep a common course of landing in order to avoid collisions. Whereas the wind direction may provide a cue for landing, the nature of the landing direction indicator under windless conditions has been unknown. We recorded and analysed landing directions of 3,338 flocks in 14 species of water birds in eight countries. Results We show that the preferred landing direction, independently of the direction from which the birds have arrived, is along the north-south axis. We analysed the effect of the time of the year, time of the day (and thus sun position), weather (sunny versus overcast), light breeze, locality, latitude, and magnetic declination in 2,431 flocks of mallards ( Anas platyrhynchos ) and found no systematic effect of these factors upon the preferred direction of landing. We found that magnetic North was a better predictor for landing direction than geographic North. Conclusions In absence of any other common denominator determining the landing direction, the alignment with the magnetic field lines seems to be the most plausible if not the only explanation for the directional landing preference under windless and overcast conditions and we suggest that the magnetic field thus provides a landing direction indicator.