Birds are most sensitive to sounds with frequencies between 1 and 5 kHz. Humans can hear sounds with frequencies as low as 0.02 kHz and as high as 17 kHz. Vision is a diurnal bird of prey's most important sense for hunting and reacting to danger. Diurnal birds of prey have excellent vision. The eyes are proportionally larger than the eyes of other vertebrates, providing larger and sharper visual images.
More sensory cells mean better visual acuity.
As in humans, the point of sharpest vision is the fovea. Humans have one fovea per eye, while diurnal birds of prey have two. In addition, many diurnal birds of prey have proportionately more sensory cells in the upper half of the retina. This helps a bird perceive images when looking toward the ground from a perch or when flying. As a consequence, to scan the sky, they must turn their heads upside down.