Wiltschko R, Walker M, Wiltschko W
Fachbereich Biologie, Zoologie, der J. W. Goethe-Universität Frankfurt a.M., Siesmayerstrasse 70, D-60054 Frankfurt a.M., Germany.
J Exp Biol. 2000 Mar;203(Pt 5):889-94. doi: 10.1242/jeb.203.5.889.
Birds using their sun compass must compensate for the apparent movement of the sun with the help of their internal clock. The movement of the sun is not uniform, being much faster around noon than near sunrise and sunset. If the sun-compass mechanisms are not adjusted to these variations, considerable errors might arise. To learn whether birds are able to take the different rates of sun azimuth change into account, we subjected homing pigeons to a 4 h fast clock-shift. The experiments were performed near Auckland, New Zealand, at a latitude of 37 degrees S, where the expected deflections for a 4 h shift in summer vary from less than 40 degrees to more than 120 degrees, depending on time of day. One group of birds was released just after sunrise or during the corresponding period in the afternoon when the expected deflections were minimal, the other group during late morning when they were maximal. The different sizes of the observed deflections - between 26 degrees and 51 degrees in the first group, and between 107 degrees and 153 degrees in the second group - clearly show that the birds' compensation mechanisms are closely tuned to the varying rates of change in sun azimuth. The results suggest that pigeons have a rather precise internal representation of the sun curve, which makes the avian sun compass a highly accurate mechanism of direction finding.
利用太阳罗盘导航的鸟类必须借助其生物钟来补偿太阳的视运动。太阳的运动并不均匀，在中午时分比日出和日落附近要快得多。如果太阳罗盘机制没有根据这些变化进行调整，就可能会出现相当大的误差。为了了解鸟类是否能够考虑到太阳方位变化的不同速率，我们让归巢鸽经历了4小时的时钟快速调整。实验在新西兰奥克兰附近进行，纬度为南纬37度，在夏季，4小时的时钟调整所预期的偏移量根据一天中的时间不同，从小于40度到超过120度不等。一组鸽子在日出后或下午相应时段放飞，此时预期偏移量最小，另一组在上午晚些时候放飞，此时偏移量最大。观察到的偏移量大小不同——第一组在26度到51度之间，第二组在107度到153度之间——清楚地表明，鸟类的补偿机制与太阳方位变化的不同速率密切相关。结果表明，鸽子对太阳轨迹有相当精确的内部表征，这使得鸟类的太阳罗盘成为一种高度精确的定向机制。
