Near-field visual acuity in Japanese jungle crows (Corvus macrorhynchos).

The near-field visual acuity of three Japanese jungle crows (Corvus macrorhynchos) was determined by means of operant conditioning. The task was discrimination of grating stimuli, and the threshold was measured by up-and-down method between sessions. To keep observing distance constant, a photo sensor was used and the head position was behaviorally fixed. The average visual acuity was 8.4 cycles/degree. When compared with other birds, this result is better than that of pigeons, and worse than that of predators.