Question

Owls move freely during night since they have

• A. Adjustable pupil
• B. Only cones in retina
• C. Only rods in retina
• D. Vitamin A deficiency

Answer 1

Answer: (C)

Only rods in retina

Nocturnal bird species have low numbers of colour detectors, but a high density of rod cells, which function well in poor light. Rods are more sensitive to light, but give no colour information, whereas the less sensitive cones enable colour vision. In diurnal birds, 80% of the receptors may be cones, whereas nocturnal owls have almost all rods.