Birds have the largest eyes relative to their size within the animal kingdom and eyesight is described as the most important sight for these feathered killers. <br />Nocturnal species have tubular eyes with low numbers of colour detectors, but a high density of rod cells which function well in poor light. Birds can resolve rapid movements better than humans, for whom flickering at a rate greater than 50 Hz appears as continuous movement. For example a Cooper's hawk can pursue agile prey through woodland and avoid branches and other objects at high speed; to humans such a chase would appear as a blur.
