Kiwis see no profit in night vision
“New and Noted” in PLoS ONE
Kiwi Forego Vision in the Guidance of Their Nocturnal Activities
Martin GR, Wilson K, Wild JM, Parsons S, Kubke MF, et al. (2007) PLoS ONE 2(2): e198. doi:10.1371/journal.pone.0000198
The Kiwi is a bird both flightless and nocturnal, circumstances which might predict the evolution of large sensitive eyes—but in fact, the opposite is the case. Eyes and visual areas of Kiwi brains have regressed, while the senses of smell and touch have become more sensitive, as is also seen in some nocturnal mammals. The costs of maintaining effective night vision must be too high in the Kiwis’ forest floor habitat.