Control of the onset of nocturnal migration

夜间迁徙的候鸟在没有社会指导的情况下在繁殖区和越冬区之间旅行。为了到达正确的地点和时间，它们天生的迁徙程序定义了鸟类迁徙的时空组织以及它们对环境线索的典型反应。当鸟类在迁徙过程中被关在笼子里时，它们会表现出夜间活动，称为迁徙不安。迁徙不安的时间模式和强度是受内在控制的。然而，光周期，温度和身体状况的变化调节季节模式。这些因素也影响移徙者在中途停留地离开的可能性。虽然通过笼内实验和对野生鸟类的跟踪（无线电遥测、雷达、稳定同位素等）对候鸟的昼夜节律和实际的迁徙行为进行了很好的研究，我们几乎没有关于以下方面的信息：（i）夜间迁徙不安的确切开始和夜间迁徙的开始，（ii）这两种特征是否在时间上相关，（iii）是强烈的内源性控制，以及（iv）哪些外源性因素显著影响这两种特征的时间。然而，了解这一点对于认识造成移徙的一般时间和最近观察到的移徙时间变化的机制至关重要。夜间迁徙的开始定义了每晚的潜在飞行范围。夜间所有潜在飞行范围的季节性总和影响迁移的总速度，这反过来又影响迁移的总体时间。因此，对于我们了解鸟类迁徙，有必要调查哪些内源性和外源性因素显着影响夜间迁徙的发生。通过结合笼实验，以确定开始的夜间迁徙不安和无线电遥测，以确定发病的夜间迁徙为同一个人，我将（i）描述的时间模式的两个特征，（ii）找出是否这两个特征的时间相互关联，并确定如何（iii）内源性和（iv）外源性因素的影响，这两个特征的时间在夜间。为此，北方小麦（Oenanthe oenanthe）将在黑尔戈兰岛被捕获。由于岛屿的小尺寸，可以精确地确定无线电标记的鸟类的存在和不存在。在迁徙过程中，斯堪的纳维亚的指名亚种和冰岛、格陵兰和加拿大的银合欢亚种经常在黑尔戈兰岛繁殖。由于所有的北方小麦在撒哈拉以南非洲过冬，种群根据其繁殖区域的不同总迁移距离，不同的剩余迁移距离Helgoland在春季，但不是在秋季。该框架允许测试两种性状在总迁移距离[内源性因素]、剩余迁移距离、光周期、季节日期、温度、身体状况和天气[所有外源性因素]方面的差异。

Nocturnal migrants travel without social guidance between the breeding and wintering areas. To arrive at the correct place and time, their innate migration program defines birds` spatiotemporal organisation of migration and their typical reactions to environmental cues. When birds are kept in cages during migration, they show nocturnal activity, called migratory restlessness. The temporal pattern and intensity of migratory restlessness is endogenously controlled. However, changes in photoperiod, temperature and body condition modulate the seasonal pattern. These factors also influence the departure probability of a migrant at a stopover site. Although the circannual and circadian rhythms in migrants and the realised migration behaviour are well studied by cage experiments and tracking of wild birds (radio telemetry, radar, stable isotopes, etc.), we have little information (i) about the exact start of nocturnal migratory restlessness and onset of nocturnal migration within the night, (ii) whether both traits are temporally related, (iii) are strongly endogenous controlled and (iv) which exogenous factors significantly influence the timing of both traits. Knowledge about this is, however, essential for recognizing the mechanisms responsible for the general timing of migration and for the recently observed temporal change in migration. Onset of nocturnal migration defines the potential flight range per night. The seasonal sum of all potential flight ranges per night influences total speed of migration which in turn affects the overall timing of migration. For our understanding of bird migration it is hence essential investigating which endogenous and exogenous factors influence significantly the onset of nocturnal migration. By combining cage experiments to determine the start of nocturnal migratory restlessness and radio telemetry to identify the onset of nocturnal migration for the same individual I will (i) describe the temporal pattern of both traits, (ii) find out whether both traits correlate temporally with each other and identify how (iii) endogenous and (iv) exogenous factors influence the timing of both traits within the night. To this end, Northern Wheatears (Oenanthe oenanthe) will be caught on Helgoland. Due to the small size of the island presence and absence can be precisely determined for radio-tagged birds. On migration the nominate form breeding in Scandinavian and the leucorhoa subspecies breeding on Island, Greenland and in Canada occur regularly on Helgoland. As all Northern Wheatears winter in sub-Sahelian Africa, populations have depending on their breeding areas different total migration distances, different remaining migration distances from Helgoland in spring but not in autumn. This framework allows testing differences in both traits in respect of total migration distance [endogenous factor], remaining migration distance, photoperiod, date of season, temperature, body condition and weather [all exogenous factors].