External, Middle, and Internal. Overall, the range of optimal hearing in birds is narrower than that in mammals. Because of this they can capture prey by sound alone. Use low frequency clicks. This differs from the high frequency ultrasound used by bats and is not nearly as effective.
Vision is the most important sensory input for birds, as they are visual animals.
Generally, birds have higher powers of accommodation as both the cornea and the lens change curvature while focusing. Only the lens changes curvature in mammals. Most birds see laterally better than forward due to the lateral position of eyes on the head and little overlap in fields of view.