Comparison of scotopic sensitivity in diurnal (Anas platyrhynchos) and crepuscular (Dendrocygna autumnalis) ducks.
Scotopic visual adaptation curves were obtained from 4 mallard ducks. A curve of best fit was used to compare the mallards' mean adaptation curve to the curve previously reported for the black-bellied tree duck, a crepuscular species. The curves did not differ significantly in either their slopes or base levels (thresholds). The mallards curve had a rod-cone "break" at approximately 25 min. This break is evident in the scotopic curve for pigeons, but is absent from the black-bellied tree ducks' curve. Examination of retinal tissues indicated that the black-bellied tree ducks had significantly more rods and cones, and a larger rod:cone ratio than the mallards. The mallards' scotopic visual threshold is exceeded by the natural illumination present under several nocturnal conditions.
D000221:Adaptation, Ocular; D000818:Animals; D002940:Circadian Rhythm; D003216:Conditioning, Operant; D003623:Dark Adaptation; D004192:Discrimination, Psychological; D004372:Ducks / Q000502:physiology*; D008029:Lighting; D010786:Photoreceptor Cells / Q000033:anatomy & histology; D013045:Species Specificity