Habitat change and timing of dusk flight in the Eurasian woodcock: a trade-off between feeding and predator avoidance?
Habitat change and timing of dusk flight in the Eurasian woodcock: a trade-off between feeding and predator avoidance?
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DOI：
10.5735/086.047.0305
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发表时间：
2010-06-30
影响因子：
0.7
通讯作者：
Gonzalez-Quiros, Pablo
中科院分区：
文献类型：
--
作者：
Brana, Florentino;Prieto, Laureano;Gonzalez-Quiros, Pablo
在西班牙北部越冬的欧亚林鸡(Scolopax Rusticola)遵循从林地的白天地点到放牧地区的夜间地点的每日活动模式，这与之前关于其他欧洲种群的报告一致。与林地相比，田野里蚯蚓的丰度和生物量要高得多，而蚯蚓是林鸡的主要猎物，但只有在晚上鸟类才会使用，大约在日落后30分钟出现。除了11月下半月较早外，羽化时间在每两周一次中相当一致，这可能反映了候鸟对能量的较高需求导致的活动延长。伍德科克的羽化时间与日落呈负相关，因此当天空阴天时，鸟儿活动得更早。此外，鸟类倾向于在低气温下更早地移动，这一模式是可以预测的，因为由于体温调节成本的增加，山雀在低温下对能量的需求更高。在低光强下出现较晚，可避免暴露在猛禽身上，但会导致能量增加，因此移动到捕食场的时间可能会因能量考虑而改变。我们讨论了林地和农田之间食物和安全的时空梯度不同的观点，因此捕食风险是越冬林鸡夜间羽化时间的重要决定因素。因此，它们的日常活动周期反映了取食和躲避捕食者之间的权衡。林鸡视野的特殊特征，可以在很远的距离探测到捕食者，鸟嘴上的化学感受器可以通过使用非视觉线索探测和捕获猎物，包括有助于在夜间成功进食并降低捕食风险的适应。
Eurasian woodcock (Scolopax rusticola) over-wintering in northern Spain follows a pattern of daily movement from diurnal sites in woodlands to nighttime sites in grazed fields, congruent with previous reports on other European populations. Fields have a much higher abundance and biomass of earthworms, the main prey of woodcock, than woodlands, but are only used by birds at night, when they emerge about 30 minutes after sunset. Emergence time was quite uniform among fortnightly periods except for the second half of November when it was earlier, probably reflecting extended activity resulting from the higher energy requirements of migrating birds. Woodcock emergence time relative to sunset was negatively related to illumination, so that birds moved earlier when the sky was overcast. Also, birds tended to move earlier at low air temperatures, a pattern which is to be predicted since woodcock have higher energy requirements at low temperatures because of the increased cost of thermoregulation. Emerging late, at low light intensity, avoids exposure to raptors but results in reduced energy gains and therefore the timing of moving to feeding fields may be modified by energy considerations. We discuss the idea that there is a divergent spatio-temporal gradient of food and safety between woodlands and fields and, therefore, that predation risk is an important determinant of the timing of evening emergence of over-wintering woodcock. Thus, their daily activity cycle would reflect a trade-off between feeding and predator avoidance. Special features of the visual fields of the woodcock, allowing detection of predators at long distances, and chemoreceptors in the bill enabling detection and capture of prey by probing using non visual cues, comprise adaptations that facilitate successful feeding at night with reduced predation risk.