长距离迁徙鸟类对应于能量积累状态的取食行为调整

迁徙鸟类能够预计到迁徙过程中对能量需求的增加和迁徙途中获得能量的不确定性。最佳迁徙理论指出：迁徙停留期的一系列决策受到体内能量状态、取食机会和迁徙时间的影响。利用刚完成春季跨越墨西哥湾迁徙的鸫类，我们研究了取食行为、体内能量状态和能量积累速度的相互关系。我们用雾网捕获了停留的鸫，然后给每只鸟进行了环志和称重，并估测了表皮下积累的脂肪。为了检测体内能量积累大小对取食行为的影响，我们把在野外观察到的鸟分成肥、瘦两组。当一天里被捕获鸟的平均体重低于相关种的瘦体重时，这一天被观察到的取食鸟被归到瘦组，反之就属于肥组。我们同时对一部分鸟用有色环进行了标记，以便能在野外观察到它们时能准确地知道每一只鸟的初始能量积累状态。在春天完成跨越墨西哥湾迁徙以后的鸫大约有50％在到达停留地时就已经消耗了所有的表皮下脂肪。与肥组鸟相比，瘦组的个体在停留期扩展了取食方法和取食基底，增加了取食速度。与此相关的是，瘦鸟表现出体重积累更多、速度更快。我们的数据表明迁徙鸟在到达迁徙中途停留地时的能量状态会影响到它们停留期间的取食行为和继续迁徙时的生理机能，从而影响停留期的长短和在迁徙途中停留与否的决定动物学报51(1)：12—23，2005]。

Long-distance bird migrants adjust their foraging behavior in relation to energy stores

Migratory birds can anticipate heightened energy demand and increased uncertainty that energy demands will be satisfied during their annual migration phase.Optimal migration theory predicted that stopover decisions could be affected by energetic condition,foraging opportunity,and timing of migration.Using the stopover migratory thrushes following spring passage across the Gulf of Mexico,we examined the interactions of foraging behavior,energetic condition,and rate of fat deposit.Birds were mist-netted,weighted,estimated for fat storage,and released after being banded with a unique numbered aluminum leg band.For behavioral observation,birds were separated to two groups:"lean day birds" when daily average body mass of captured birds was near or below fat free mass and "fat day birds" when daily average body mass of captured birds was above fat free mass.A subsample of birds with known fat condition was banded with unique combination of color-band(s) for re-sight and confirmation of relationship between energetic condition and foraging behavior.Nearly 50% of the migrants had no visible fat left upon crossing the Gulf of Mexico and were near fat-free mass.Lean birds expanded their foraging repertoire,broadened their use of substrate,and foraged at a faster pace than did birds with fat stores remaining following arrival.Lean migrants tended to gain more mass and gain mass at a faster rate.Our data suggest that the energetic condition upon arrival at a stopover site affects foraging behavior and physiological conditions upon departure,which may further affect stopover length and the decisions of stopover en routeActa Zoologica Sinica 51(1):12-23,2005].