The mechanism by which the wavelengths stimulate
reproductive activity has been primarily related to extraretinal
photoreceptors (Kuenzel, 1993) and the variation in
transmission of light waves through cranial tissue (Foster
et al., 1985). Photons transmitted at higher wavelengths
seem to have increased head penetration which favors
direct stimulation of the hypothalamus (Kuenzel, 1993). In
Japanese quail, red light was not as efficient as the white
LED light, suggesting that this species may have a different
mechanism of photostimulation.