Rojas L M, McNeil R, Cabana T, Lachapelle P
Département de sciences biologiques, Université de Montréal, Montréal, Canada.
Brain Behav Evol. 1999;53(1):29-43. doi: 10.1159/000006580.
Some shorebird species forage with the same feeding strategy at night and during daytime, e.g. visual pecking in the Wilson's Plover (Charadrius wilsonia) or tactile probing in the Short-billed Dowitcher (Limnodromus griseus). The American Woodcock (Scolopax minor) uses tactile probing, by day and by night, but sometimes pecks for insects during daytime. The Black-winged Stilt (Himantopus himantopus) is a visual pecker, both by day and by night, and sometimes forages tactilely on windy (agitated water surface) moonless nights. Territorial Willets (Catoptrophorus semipalmatus) are visual peckers during daylight and on moonlight conditions but switch to tactile feeding under lower light conditions. It could be postulated that some shorebird species would switch from visual feeding during daytime to tactile foraging at night because they have poor night vision compared to species that are always sight foragers irrespective of the time of the day. This issue was examined by comparing retinal structure and function in the above species. Electroretinograms (ERGs) were obtained at different light intensities from anesthetized birds, and the retinae were processed for histological observations. Based on ERGs, retinal sensitivity, and rod:cone ratios, both plovers and stilts are well adapted for nocturnal vision. Although they have low rod density compared to that of stilts and plovers, Willets and woodcocks have a scotopic retinal sensitivity similar to that of stilts and plovers but rank midway between plovers and dowitchers for the b-wave amplitude. Dowitchers have the lowest scotopic b-wave amplitude and retinal sensitivity and appear the least well adapted for night vision. Based on photopic ERGs and cone densities, although stilts, Willets and dowitchers appear as well adapted for daytime vision, plovers occupy the last rank of all species examined. Compared to the nighttime tactile feeders and those that switch from daytime visual pecking to tactile feeding at night, nighttime sight feeders have a superior rod function and, consequently, potentially superior nocturnal visual capabilities.
一些滨鸟物种在夜间和白天采用相同的觅食策略，例如，威尔逊鸻（Charadrius wilsonia）采用视觉啄食，短嘴半蹼鹬（Limnodromus griseus）采用触觉探测。美洲丘鹬（Scolopax minor）无论白天还是夜晚都采用触觉探测，但有时在白天会啄食昆虫。黑翅长脚鹬（Himantopus himantopus）无论白天还是夜晚都是视觉啄食者，有时在有风（水面波动）的无月夜采用触觉觅食。具有领地意识的斑腹矶鹬（Catoptrophorus semipalmatus）在白天和月光条件下是视觉啄食者，但在光线较暗的条件下会转为触觉觅食。可以推测，一些滨鸟物种会从白天的视觉觅食转变为夜间的触觉觅食，因为与那些无论白天黑夜都是视觉觅食者的物种相比，它们的夜视能力较差。通过比较上述物种的视网膜结构和功能来研究这个问题。从麻醉的鸟类身上在不同光强度下获得视网膜电图（ERG），并对视网膜进行组织学观察处理。根据视网膜电图、视网膜敏感度和视杆细胞与视锥细胞的比例，鸻和长脚鹬都非常适合夜间视觉。尽管与长脚鹬和鸻相比，它们的视杆细胞密度较低，但斑腹矶鹬和美洲丘鹬的暗视视网膜敏感度与长脚鹬和鸻相似，但在b波振幅方面介于鸻和半蹼鹬之间。半蹼鹬的暗视b波振幅和视网膜敏感度最低，似乎最不适合夜间视觉。根据明视视网膜电图和视锥细胞密度，尽管长脚鹬、斑腹矶鹬和半蹼鹬似乎同样适合白天视觉，但鸻在所有被研究的物种中排名垫底。与夜间触觉觅食者以及那些从白天视觉啄食转变为夜间触觉觅食的物种相比，夜间视觉觅食者具有更优越的视杆细胞功能，因此可能具有更优越的夜间视觉能力。
