Stopover optimization in a long-distance migrant: the role of fuel load and nocturnal take-off time in Alaskan northern wheatears (Oenanthe oenanthe)
Stopover optimization in a long-distance migrant: the role of fuel load and nocturnal take-off time in Alaskan northern wheatears (Oenanthe oenanthe)
复制标题
长途候鸟的中途停留优化：阿拉斯加北部麦穗鸟 (Oenanthe oenanthe) 的载油量和夜间起飞时间的作用
作者：
Heiko Schmaljohann;F. Korner‐Nievergelt;B. Naef;R. Nagel;I. Maggini;M. Bulte;F. Bairlein
在长途迁徙中，更多的时间和精力花在中途停留上，而不是花在飞行上。中途停留的时间和出发的决定影响随后的飞行阶段和整体迁移速度。在北极夜间迁徙的鸣禽中，相对较长的迁徙距离和较短的夜间迁徙时间之间的权衡可能会给迁徙带来很大的时间压力。因此，我们假设阿拉斯加北部小麦（Oenanthe Oenanthe）使用时间最小化的迁移策略到达15,000公里外的非洲越冬区。结果利用Cormack-Jolly-Seber模型估计了影响候鸟在穿越白令海峡前从北极中途停留的每日离境概率的因素。为了确定迁徙的方向和时间，对离境的鸟类进行无线电跟踪。在这里，我们表明阿拉斯加北部小麦没有表现为严格的时间最小化，因为它们的出发燃料负荷与燃料沉积率无关。所有的鸟离开时携带的燃料都超过了渡海所需的量。离港概率随停留时间、晚间燃油负荷和温度的降低而增加。鸟类向西南方向起飞，因此，通常遵循恒定的磁场和地理路线，而不是另一种大圆路线。夜间出发时间集中在日落之后。结论尽管鸟类在最优迁徙策略上不表现出时间最小化的行为，但从运输总能量成本最小化的角度来看，其剩余燃料负荷明显与节能策略相矛盾。与温带地区的类似研究相比，观察到的夜间起飞时间与当地夜间长度的变化较小，这表明候鸟对夜间长度的外部提示变化具有先天的反应能力。很可能，鸟类通过在夜间早些时候起飞来最大化它们潜在的夜间飞行范围，从而最大化它们的整体迁徙速度。因此，夜间出发时间可能是影响迁徙速度的关键参数，表明其在未来迁徙模型中的整合意义。
IntroductionIn long-distance migrants, a considerably higher proportion of time and energy is allocated to stopovers rather than to flights. Stopover duration and departure decisions affect consequently subsequent flight stages and overall speed of migration. In Arctic nocturnal songbird migrants the trade-off between a relatively long migration distance and short nights available for travelling may impose a significant time pressure on migrants. Therefore, we hypothesize that Alaskan northern wheatears (Oenanthe oenanthe) use a time-minimizing migration strategy to reach their African wintering area 15,000 km away.ResultsWe estimated the factors influencing the birds’ daily departure probability from an Arctic stopover before crossing the Bering Strait by using a Cormack-Jolly-Seber model. To identify in which direction and when migration was resumed departing birds were radio-tracked. Here we show that Alaskan northern wheatears did not behave as strict time minimizers, because their departure fuel load was unrelated to fuel deposition rate. All birds departed with more fuel load than necessary for the sea crossing. Departure probability increased with stopover duration, evening fuel load and decreasing temperature. Birds took-off towards southwest and hence, followed in general the constant magnetic and geographic course but not the alternative great circle route. Nocturnal departure times were concentrated immediately after sunset.ConclusionAlthough birds did not behave like time-minimizers in respect of the optimal migration strategies their surplus of fuel load clearly contradicted an energy saving strategy in terms of the minimization of overall energy cost of transport. The observed low variation in nocturnal take-off time in relation to local night length compared to similar studies in the temperate zone revealed that migrants have an innate ability to respond to changes in the external cue of night length. Likely, birds maximized their potential nightly flight range by taking off early in the night which in turn maximizes their overall migration speed. Hence, nocturnal departure time may be a crucial parameter shaping the speed of migration indicating the significance of its integration in future migration models.
影响因子：
3.3
作者：
Bairlein, Franz;Norris, D. Ryan;Schmaljohann, Heiko
通讯作者：
Schmaljohann, Heiko
影响因子：
2.3
作者：
Heiko Schmaljohann;M. Buchmann;J. Fox;F. Bairlein
通讯作者：
Heiko Schmaljohann;M. Buchmann;J. Fox;F. Bairlein