Diel variation in corticosterone and departure decision making in migrating birds
Diel variation in corticosterone and departure decision making in migrating birds
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DOI：
10.1016/j.yhbeh.2020.104746
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发表时间：
2020-06-01
影响因子：
3.5
通讯作者：
Schmaljohann, Heiko
中科院分区：
文献类型：
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作者：
Eikenaar, Cas;Schaefer, Jana;Schmaljohann, Heiko
动物通常表现出明显的昼夜活动期和非活动期。糖皮质激素（皮质酮和皮质醇）的循环基线水平通常在一天中从非活动期到活动期的过渡期之前或过渡期达到峰值。糖皮质激素的这种上调可用于动员储存的能量并使动物准备增加活动。通常，活跃期和非活跃期的交替是高度可预测的;然而，有一组动物并不总是如此。许多白天活动的鸟类在迁徙季节表现出夜间活动。夜间迁徙飞行与中途停留交替进行，在此期间，鸟类补充燃料和休息。中途停留的时间长短不一，这意味着夜间迁徙者在某些夜晚（当他们继续中途停留时）不活动，但在其他夜晚（当他们离开并整夜飞行时）非常活跃。这为测试糖皮质激素是否上调以准备增加活性提供了理想的自然条件，我们在本研究中使用了这一条件。我们发现，在北方小麦（Oenanthe oenanthe）中，皮质酮水平在日落前几个小时达到峰值，在当晚离开中途停留的鸟类中，重要的是，这个峰值在继续中途停留的鸟类中没有。这表明，皮质酮在面对能量需求增加时上调，强调了皮质酮的准备代谢功能（能量动员）。皮质酮上调的时间也提供了一个第一次洞察，在白天时，迁徙的鸟类决定是否恢复迁移。
Animals usually show distinct periods of diel activity and non-activity. Circulating baseline levels of glucocorticoid hormones (corticosterone and cortisol) often peak just before or at the transition from the non-active to the active period of the day. This upregulation of glucocorticoids may function to mobilize stored energy and prepare an animal for increased activity. Usually, the alternation of active and non-active periods is highly predictable; however, there is one group of animals for which this is not always the case. Many otherwise diurnal birds show nocturnal activity during the migration seasons. Nocturnal migratory flights are alternated with stopover periods during which the birds refuel and rest. Stopovers vary in length, meaning that nocturnal migrants are inactive in some nights (when they continue their stopover) but extremely active in other nights (when they depart and fly throughout the night). This provides an ideal natural situation for testing whether glucocorticoids are upregulated in preparation for an increase in activity, which we used in this study. We found that in northern wheatears (Oenanthe oenanthe), corticosterone levels peaked in the few hours before sunset in birds departing from stopover that night, and, importantly, that this peak was absent in birds continuing stopover. This indicates that corticosterone is upregulated in the face of an increase in energy demands, underlining corticosterone's preparative metabolic function (energy mobilization). The timing of upregulation of corticosterone also gives a first insight in when during the day nocturnally migrating birds decide whether or not to resume migration.