Migratory shorebirds show highly organized seasonal cycles in physiological and morphological traits (body mass and composition, plumage, hormone levels, etc.), which in captivity is accompanied by restless behaviour at times when free-living birds would start migration. We introduce the idea that seasonally changing preference for habitat could motivate migrants to embark on migration and that this cognitive process could also guide them to seasonally appropriate places. We explored this by testing whether red knots (Calidris canutus), which also in captivity maintain marked circannual phenotypic rhythms, show evidence of seasonal change in preference for pictures of seasonally appropriate habitats. We first developed a method to verify whether red knots are able to memorize and discriminate contrasting pictures projected by LCD projectors. This was followed by two different experiments in which we tested for a seasonally changing preference for breeding or non-breeding habitat. When carried out during the pre-breeding season, the red knots are expected to prefer pictures of mudflats, their non-breeding habitat. At the start of the breeding season, they should prefer pictures of the tundra breeding habitat. We established that knots are able to distinguish and memorize projected images. We failed to demonstrate the predicted change in vision-based habitat preference, but for reasons of test design we do not interpret this as a strong rejection of the hypothesis. Instead, we suggest that experiments with greater numbers of individuals tested once, perhaps in combination with the provision of additional cues such as smells and sounds, will help the development of these ideas further.

中文翻译：

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长距离迁徙滨鸟栖息地季节性变化视觉偏好的实验测试

迁徙的滨鸟在生理和形态特征（体重和成分、羽毛、激素水平等）方面表现出高度有组织的季节性周期，当自由生活的鸟类开始迁徙时，它们在圈养期间伴随着不安的行为。我们引入了一个想法，即对栖息地的季节性变化偏好可以激励移民开始迁移，并且这种认知过程也可以引导他们到季节性合适的地方。我们通过测试红结（Calidris canutus）是否在圈养中保持明显的昼夜节律，显示季节性变化的证据，即偏爱季节性适当栖息地的图片，从而探索了这一点。我们首先开发了一种方法来验证红节是否能够记住和区分 LCD 投影仪投影的对比图像。随后进行了两个不同的实验，其中我们测试了对繁殖或非繁殖栖息地的季节性变化偏好。在繁殖前季节进行时，预计红结节更喜欢泥滩的照片，这是它们的非繁殖栖息地。在繁殖季节开始时，他们应该更喜欢苔原繁殖栖息地的照片。我们确定结能够区分和记忆投影图像。我们未能证明基于视觉的栖息地偏好的预测变化，但出于测试设计的原因，我们不会将此解释为对假设的强烈拒绝。相反，我们建议对更多的个体进行一次测试，也许结合提供额外的线索，如气味和声音，将有助于进一步发展这些想法。