Many temperate and arctic animals and birds react to daylight length. Photoperiodism entrains their physiology and behavior, which helps them respond to adapt to seasonal changes in the environment. Although bird species vary in their responses, daylight length drives the annual cycle of temperate and arctic birds overall. How do birds detect changes in day length? Like many other creatures, they use photoreceptors – specialized cells that detect light and initiate a physical response. The photoreceptors in birds are not
The Raptor Resource Project