Temeles Ethan J
National Zoological Park, Smithsonian Institution, 20008, Washington, DC, USA.
Oecologia. 1996 Mar;105(4):517-523. doi: 10.1007/BF00330015.
The close correspondence between the bills of hummingbirds and the lengths of the flowers they feed from has been interpreted as an example of coadaptation. Observations of birds feeding at flowers longer and shorter than their bills, however, and the lack of experimental evidence for any feeding advantage to short bills, seem to contradict this interpretation. I address this problem by considering a little-studied dimension of floral morphology: corolla diameter. In laboratory experiments on female ruby-throated hummingbirds (Archilochus colubris), probing abilities (maximum extraction depths) increased with increasing corolla diameter. Handling times increased with decreasing corolla diameter, resulting in "handling time equivalents", i.e., flowers having the same handling times but different lengths and diameters. Longer-billed birds had greater maximum extraction depths and shorter handling times than shorter-billed birds at all corolla diameters greater than the width of the bill. In contrast, shorter-billed birds made fewer errors inserting their bills into narrow flowers. Hence, differences in bill lengths apparently are associated with trade-offs in foraging abilities, whereby longer-billed birds are able to feed at long flowers and may do so more quickly, whereas shorter-billed birds are able to feed more successfully at narrow flowers.
蜂鸟的喙长与它们所取食花朵的长度之间的紧密对应关系，一直被视为协同适应的一个例子。然而，观察到鸟类取食比它们喙长或短的花朵，以及缺乏关于短喙具有任何取食优势的实验证据，似乎与这种解释相矛盾。我通过考虑花卉形态学中一个研究较少的维度：花冠直径，来解决这个问题。在对雌性红玉喉北蜂鸟（Archilochus colubris）进行的实验室实验中，探取能力（最大探取深度）随着花冠直径的增加而提高。处理时间随着花冠直径的减小而增加，从而产生了“等效处理时间”，即具有相同处理时间但长度和直径不同的花朵。在所有大于喙宽的花冠直径下，喙较长的鸟类比喙较短的鸟类具有更大 的最大探取深度和更短的处理时间。相比之下，喙较短的鸟类将喙插入窄花时犯错较少。因此，喙长的差异显然与觅食能力的权衡有关，即喙较长的鸟类能够取食长花，并且可能速度更快，而喙较短的鸟类能够在窄花上取食得更成功。
