Sokolovskis Kristaps, Bianco Giuseppe, Willemoes Mikkel, Solovyeva Diana, Bensch Staffan, Åkesson Susanne
1Department of Biology, Center for Animal Movement Research, Lund University, Ecology Building, 223 62 Lund, SE Sweden.
2Department of Biology, Molecular Ecology and Evolution Laboratory, Lund University, Ecology Building, 223 62 Lund, SE Sweden.
Mov Ecol. 2018 Oct 15;6:20. doi: 10.1186/s40462-018-0138-0. eCollection 2018.
High-latitude bird migration has evolved after the last glaciation, in less than 10,000-15,000 years. Migrating songbirds rely on an endogenous migratory program, encoding timing, fueling, and routes, but it is still unknown which compass mechanism they use on migration. We used geolocators to track the migration of willow warblers () from their eastern part of the range in Russia to wintering areas in sub-Saharan Africa. Our aim was to investigate if the autumn migration route can be explained by a simple compass mechanism, based on celestial or geomagnetic information, or whether migration is undertaken as a sequence of differential migratory paths possibly involving a map sense. We compared the recorded migratory routes for our tracked birds with simulated routes obtained from different compass mechanisms.
The three tracked males were very similar in the routes they took to their final wintering sites in southern Tanzania or northern Mozambique, in their use of stopover sites and in the overall timing of migration. None of the tested compass mechanisms could explain the birds' routes to the first stopover area in southwest Asia or to the destination in Southeast Africa without modifications. Our compass mechanism simulations suggest that the simplest scenarios congruent with the observed routes are based on either an inclination or a sun compass, assuming two sequential steps.
The birds may follow a magnetoclinic route coinciding closely with the tracks by first moving west, i.e. closer to the goal, and thereafter follow a constant apparent angle of inclination to the stopover site. An alternative would be to use the sun compass, but with time-adjustments along the initial part of the migration to the first stopover, and thereafter depart along a new course to the winter destination. A combination of the two mechanisms cannot be ruled out, but needs to be confirmed in future studies.
高纬度地区鸟类的迁徙是在末次冰期之后不到10000 - 15000年的时间里进化而来的。迁徙鸣禽依赖一种内源性迁徙程序，该程序编码时间、能量补充和路线，但它们在迁徙过程中使用哪种罗盘机制仍不清楚。我们使用地理定位器追踪了柳莺从俄罗斯分布范围东部到撒哈拉以南非洲越冬地的迁徙。我们的目的是研究秋季迁徙路线是否可以用基于天体或地磁信息的简单罗盘机制来解释，或者迁徙是否是一系列可能涉及地图感的不同迁徙路径的序列。我们将追踪鸟类的记录迁徙路线与从不同罗盘机制获得的模拟路线进行了比较。
三只被追踪的雄性柳莺在前往坦桑尼亚南部或莫桑比克北部最终越冬地的路线、中途停歇地的使用以及迁徙的总体时间上非常相似。在不做修改的情况下，没有一种测试的罗盘机制能够解释鸟类前往亚洲西南部第一个中途停歇地或东南亚目的地的路线。我们的罗盘机制模拟表明，与观察到的路线相符的最简单情况是基于倾斜罗盘或太阳罗盘，假设分为两个连续步骤。
鸟类可能沿着与轨迹紧密重合的磁倾路线飞行，首先向西移动，即更接近目标，然后以恒定的视倾斜角度前往中途停歇地。另一种可能性是使用太阳罗盘，但在迁徙到第一个中途停歇地的初始阶段进行时间调整，然后沿着新的路线前往冬季目的地。不能排除两种机制结合的可能性，但需要在未来的研究中得到证实。
