However, the frequency of collisions did not – the additional calls obviously help the zebra finches to coordinate their flight paths well despite the limited visibility. Under light conditions equivalent to a clear full moon night, where the birds were just able to fly, call rates increased. They darkened the wind tunnel to limit the visual information available to the birds. To test their hypothesis, the researchers examined how limited visibility and background noise affect the frequency of call emission in flight. When turning their head by about 90°, one of the bird’s eyes looks to the side while the other eye looks straight ahead – a brief shoulder check, so to speak, before changing direction. While zebra finches announce vertical position changes by a call, the birds use vision to coordinate horizontal position changes. "The calls indeed seem to announce a change in the caller’s position, and to draw the conspecifics’ attention towards the calling bird." "We didn't expect such a close relationship between the vocalizations of a bird in a group and its flight maneuvers," Hoffmann recalls. This could enable them to observe the flight path of the calling bird and to avoid collisions. The scientists also observed that the flight speed of the other zebra finches briefly decreases after an emitted call. From such a position, the animal probably can’t see group members above and behind itself. When calling, this bird was usually located at frontal and bottom positions in the group. The researchers found that the zebra finches’ short vocalizations during flight are almost always followed by an upward flight movement of the calling bird. Video cameras simultaneously tracked the flight movements of the group. This allowed Hoffmann and her colleagues to record the chirping of individual birds in the institute's own wind tunnel, even during flight. These can be easily carried by the birds, which weigh about 15 grams. To investigate the zebra finches’ vocalizations in more detail, the researchers used very small and lightweight wireless microphones developed at the institute. The connection between flight calls and the birds’ flight maneuvers hasn’t been studied yet. In the wild, these talkative songbirds live in colonies and also vocalize during flight. To approach these questions, Hoffmann studied acoustic communication in a small group of zebra finches.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |