Good vibrations: Remote-tactile foraging success of wading birds is positively affected by the water content of substrates they forage in

Some taxa of wading birds can locate buried prey by detecting vibratory cues in their foraging substrates while probe-foraging, using a sensory modality called “remote-touch”. As more saturated substrates transmit vibrations better, we predict that these birds can detect prey in wetter substrates more easily. We used sensory assays to test whether substrate water content affects the remote-touch foraging success rate of Hadeda Ibises, Bostrychia hagedash. The birds were more successful at locating prey using vibratory cues than when relying on random direct contact with the beak alone. Their remote-touch foraging success rate was positively affected by increasing water contents of the soil, but water content had no effect on their direct contact foraging success (indicating this is not an artefact of ease of probing). This may partially explain the link between the range expansion of this species in southern Africa and increased soil irrigation, as it is easier for the birds to detect prey in wetter substrates. Thus, it is likely that the distribution of other remote-touch foraging birds is affected by substrate water content, and as many of these species are endangered and rely on sensitive wetland habitats, it is vital to understand their sensory requirements for foraging.

部分涉禽类群在啄探觅食过程中，可通过感知觅食基质中的振动信号定位埋藏的猎物，其所采用的感知方式被命名为“远程触觉（remote-touch）”。由于基质饱和度越高，振动传导性能越好，我们推测此类涉禽在湿度更高的基质中更易发现猎物。本研究通过感知实验，测试了基质含水量是否会影响哈达朱鹭（Hadeda Ibises，学名：Bostrychia hagedash）的远程触觉觅食成功率。实验结果表明，相较于仅依靠喙部随机直接接触的觅食方式，该朱鹭通过振动信号定位猎物的成功率显著更高；随着土壤含水量升高，其远程触觉觅食成功率呈正向提升趋势，但基质含水量对其直接接触觅食的成功率无显著影响，这说明该结果并非由啄探难度降低所导致的人为假象。该发现可部分解释该物种在南非的分布范围扩张与土壤灌溉面积增加之间的关联，因为哈达朱鹭在湿度更高的基质中更易发现猎物。因此，其他采用远程触觉觅食的鸟类的分布大概率也会受到基质含水量的影响；由于此类鸟类中有许多处于濒危状态，且依赖对环境变化敏感的湿地生境，明确其觅食所需的感知条件至关重要。