Safriel Uriel N, Lavee Daphna
Department of Zoology, The Hebrew University of Jerusalem, 91904, Jerusalem, Israel.
Oecologia. 1988 Sep;76(4):611-619. doi: 10.1007/BF00397878.
Trans-Saharan insectivorous passerine night migrants stopping-over at a small oasis in Sinai were weighed as frequently as possible, throughout the entire length of fall and spring migration passages. Due to the small size of the oasis and the intensive trapping effort, most stopping-over birds were captured and weighed throughout a sizeable portion of their stopover period. Weights at first capture were either similar in both seasons, or greater in fall than in spring. In some species fall migrants that stayed one day were heavier than those staying longer. In other species, and for all species in spring, weights of birds that stayed one day did not differ from those staying longer. In most species the weight of birds that stayed for more than one day did not vary significantly between arrival and departure, and cases of weight gains were commoner in fall than in spring. Trends of weight changes of an individual during stopover were usually inconsistent, but the longer it stayed, more it gained (in fall), or less it lost (in spring). It is proposed that stopping-over birds do not always resume their migration only after their fat reserves have been replenished, but that their decision to take off, or the reappearance of the migration impulse, are also controlled by a time program incorporated into their endogenous migration scheme, which constantly updates the time left for sampling and refuelling. It seems that in spring less time is allotted for the whole migration program, hence the time constraint overrides then all other tactical considerations, such as the state of fat reserves, and the weather.
在整个秋季和春季迁徙过程中，尽可能频繁地对穿越撒哈拉沙漠的食虫性雀形目夜间迁徙鸟类进行称重，这些鸟类在西奈半岛的一个小绿洲停留。由于绿洲面积小且诱捕力度大，大多数停留的鸟类在相当长的停留期内都被捕获并称重。首次捕获时的体重在两个季节要么相似，要么秋季比春季更重。在某些物种中，停留一天的秋季迁徙鸟类比停留时间更长的鸟类更重。在其他物种中，以及在春季的所有物种中，停留一天的鸟类体重与停留时间更长的鸟类没有差异。在大多数物种中，停留超过一天的鸟类在到达和离开时的体重没有显著变化，体重增加的情况在秋季比春季更常见。个体在停留期间体重变化趋势通常不一致，但停留时间越长，（秋季）体重增加越多或（春季）体重减轻越少。有人提出，停留的鸟类并不总是在脂肪储备得到补充后才恢复迁徙，而是它们起飞的决定或迁徙冲动的再次出现，也受其内在迁徙计划中包含的时间程序控制，该程序不断更新用于采样和补充能量的剩余时间。似乎在春季，整个迁徙计划分配的时间较少，因此时间限制优先于所有其他战术考虑因素，如脂肪储备状态和天气。
