Environment and Climate Change Canada, Wildlife Research Division, National Wildlife Research Centre, Ottawa, Ontario, Canada.
Cambrian College, Sudbury, Ontario, Canada.
PLoS One. 2018 Oct 8;13(10):e0205236. doi: 10.1371/journal.pone.0205236. eCollection 2018.
Nest predation is an important determinant of reproductive success and ground-nesting birds exhibit a variety of nest defence strategies to mitigate the risk. Many small-bodied, ground nesting birds rely on deceptive behaviours such as injury-feigning to reduce nest predation: we call this behaviour active deception. However, active deception may entail risks to adults, and passive deceptive behaviour, where individuals effectively sneak away from the nest by flushing at long distances, may be an alternative means of avoiding nest predation. We provide a simple model to demonstrate that these tails of the flush distance distribution could minimize predation risk; an intermediate strategy of moderate flush distances means that birds flush more often than with short-distance flushes, and once flushed, the nest is more easily located than for long-distance flushes. We tested this model using two species of ground nesting shorebirds, the White-rumped Sandpiper (Calidris fuscicollis) and the Red Phalarope (Phalaropus fulicarius). We demonstrate that short-distance flushes are associated with active deception and intermediate-distance flushes are associated with an increased risk of nest predation. However, we found no evidence that this potential selective pressure against intermediate strategies has produced a bimodal distribution of nest defence traits. The heritability of defence behaviours, or the ability of individuals to learn, is unknown and other factors such as energetic constraints or risks to adults might also influence flush distances and defence behaviours.
巢寄生是生殖成功的一个重要决定因素，地面筑巢的鸟类表现出多种巢防御策略来降低风险。许多小体型、地面筑巢的鸟类依赖欺骗行为来减少巢捕食：我们称之为主动欺骗。然而，主动欺骗可能会对成鸟造成风险，而被动欺骗行为，即个体通过远距离惊飞有效地从巢中溜走，可能是避免巢捕食的另一种手段。我们提供了一个简单的模型来证明这些惊飞距离分布的尾部可以最小化捕食风险；中等惊飞距离的中间策略意味着鸟类比短距离惊飞更频繁地惊飞，一旦惊飞，巢比长距离惊飞更容易被定位。我们使用两种地面筑巢的涉禽——白腰杓鹬（Calidris fuscicollis）和红喉潜鸟（Phalaropus fulicarius）来测试这个模型。我们发现，短距离惊飞与主动欺骗有关，而中等距离惊飞与增加巢捕食的风险有关。然而，我们没有发现这种针对中间策略的潜在选择性压力已经产生了防御特征的双峰分布的证据。防御行为的遗传力，或者个体学习的能力，是未知的，其他因素，如能量限制或对成鸟的风险，也可能影响惊飞距离和防御行为。
