Hint: In order to answer this question, you must be aware about the different types of cells present in the retina of the eye. There are two types of photoreceptors in the human retina, rods and cones. Rods are responsible for scotopic vision and cones are responsible for photopic vision.
Complete answer: An owl is a night bird with fewer cones and more rods in the retina, therefore, it can see well at night but not during the day. Since rods work in low-light environments, an owl can see well at night. Cones are needed to see well throughout the day, but there aren't enough of them in an owl's retina. Moreover, an owl has a large cornea and a large pupil to allow more light to enter its eye during the night. Hence, vision is more clear during the night in an owl.
Note: There is a small, central pit composed of closely packed cones in the eye known as Fovea Centralis. It is located in the center of the macula lutea of the retina and contains a maximum number of cones and no rods. It is responsible for sharp, central vision.