Temeles Ethan J, Roberts W Mark
Department of Zoology, University of British Columbia, V6T 1Z4, Vancouver, British Columbia, Canada.
Oecologia. 1993 May;94(1):87-94. doi: 10.1007/BF00317307.
We examined whether sexual differences in trophic morphology are associated with sexual differences in foraging behavior through two laboratory experiments on rufous hummingbirds (Selasphorus rufus) designed to compare probing abilities (maximum extraction depths) and handling times of sexes at flowers. Bills of female S. rufus are about 10.5% longer than bills of males, and this difference was associated with sexual differences in foraging abilities. Maximum extraction depths of female S. rufus were significantly greater than those of males, and no overlap between the sexes was observed. Moreover, handling times of females were shorter than handling times of males at flowers having longer corollas (≥15 mm). Thus, because of their longer bills, female S. rufus have the potential to feed from longer flowers than males, and can do so more quickly. We suggest that no single mechanism is responsible for the evolution of sexual dimorphism in bill lengths of hummingbirds, but rather that the dimorphism probably reflects the combined effects of reproductive role division and intersexual food competition, and possibly, sexual selection.
我们通过两项针对棕煌蜂鸟（Selasphorus rufus）的实验室实验，研究了取食形态上的性别差异是否与觅食行为的性别差异相关，这两项实验旨在比较两性在花朵上的探刺能力（最大吸食深度）和处理时间。雌性棕煌蜂鸟的喙比雄性长约10.5%，这种差异与觅食能力的性别差异有关。雌性棕煌蜂鸟的最大吸食深度显著大于雄性，且未观察到两性之间有重叠。此外，在花冠较长（≥15毫米）的花朵上，雌性的处理时间比雄性短。因此，由于喙较长，雌性棕煌蜂鸟比雄性有潜力从更长的花朵中取食，并且能更快地做到这一点。我们认为，没有单一机制可解释蜂鸟喙长两性异形的进化，相反，这种两性异形可能反映了生殖角色分工、两性间食物竞争的综合影响，也可能还有性选择的影响。
