Akçay Çağlar, Lendvai Ádám Z, Stanback Mark, Haussmann Mark, Moore Ignacio T, Bonier Fran
Department of Biological Sciences , Virginia Tech , Blacksburg, VA 24061 , USA.
Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA; Department of Evolutionary Zoology and Human Biology, University of Debrecen, Egyetem tér 1, Debrecen 4032, Hungary.
R Soc Open Sci. 2016 Dec 14;3(12):160740. doi: 10.1098/rsos.160740. eCollection 2016 Dec.
Life-history theory predicts that optimal strategies of parental investment will depend on ecological and social factors, such as current brood value and offspring need. Parental care strategies are also likely to be mediated in part by the hypothalamic-pituitary-adrenal axis and glucocorticoid hormones. Here, we present an experiment in tree swallows (), a biparental songbird with wide geographical distribution, asking whether parental care is strategically adjusted in response to signals of offspring need and brood value and if so, whether glucocorticoids are involved in these adjustments. Using an automated playback system, we carried out playbacks of nestling begging calls specifically to females in two populations differing in their brood value: a northern population in Ontario, Canada (relatively higher brood value) and a southern population in North Carolina, USA (relatively lower brood value). We quantified female offspring provisioning rates before and during playbacks and plasma corticosterone levels (cort) once during late incubation and once immediately after playbacks. Females in both populations increased feeding rates temporarily during the first 2 h of playback but the increase was not sustained for the entire duration of playback (6 h). Cort levels from samples at the end of the playback did not differ between control females and females that received playbacks. However, females that had higher increases in cort between the incubation and nestling period had greater fledging success. These results suggest that females are able to strategically respond to offspring need, although the role of glucocorticoids in this strategic adjustment remains unclear.
生活史理论预测，亲代投资的最优策略将取决于生态和社会因素，如当前窝雏价值和后代需求。亲代抚育策略也可能部分由下丘脑-垂体-肾上腺轴和糖皮质激素介导。在此，我们对树燕（一种地理分布广泛的双亲鸣禽）进行了一项实验，探究亲代抚育是否会根据后代需求和窝雏价值信号进行策略性调整，如果是，糖皮质激素是否参与了这些调整。我们使用自动回放系统，专门对两个窝雏价值不同的种群中的雌性树燕播放雏鸟乞食叫声：加拿大安大略省的北方种群（窝雏价值相对较高）和美国北卡罗来纳州的南方种群（窝雏价值相对较低）。我们量化了播放叫声之前和期间雌性对后代的喂食率，以及在孵化后期和播放叫声后立即采集的血浆皮质酮水平（cort）。两个种群中的雌性在播放叫声的前2小时内都暂时提高了喂食率，但在整个播放期间（6小时）并没有持续增加。播放结束时，对照雌性和接受播放的雌性的皮质酮水平没有差异。然而，在孵化期到育雏期皮质酮水平升高幅度较大的雌性，其雏鸟的出飞成功率更高。这些结果表明，雌性能够对后代需求做出策略性反应，尽管糖皮质激素在这种策略性调整中的作用仍不清楚。
