31 LOHMANN TIERZUCHT › MANAGEMENT GUIDE 31 LIGHTING The science of poultry vision is somehow new and should be still studied. Anyhow it is known that birds have a visual system which is highly developed which dif- fers a lot from that of human being. The main characteristics of poultry vison are as follows: › › Birds are able to move each single eye in- dependently and have a panoramic vision of almost 300 degrees even without turn- ing their head (see Figure 1). › › In addition to the retinal light perception in the eyes, poultry can sense light through the pineal and hypothalamic glands. › › Poultry can see a wider range of visible light spectrum (ca. 360–750 nm) than humans (ca. 410–730 nm) (see Figure 2). This ability makes it possible for the birds to perceive Ultraviolet-A light. This important charac- teristic seems to be important for birds in recognizing their environment, searching for the feed or mating behaviour. › › Other primary difference in the visual sys- tem of a bird to human is the presence of fourth retinal cone which enables layers to distinguish visual sequences of 150–200 im- ages per second. Humans can only see up to ca. 25–30 individual images per second. › › Therefore, poultry can recognize flickering of light sources operating in low frequency ranges which causes negative effects on their behaviour such as nervousness, feath- er pecking and cannibalism (e.g. some Fluo- rescent tubes and Energy-Saving lamps). It is very important to know that this flickering is not visible for human being. Vision of Poultry 100 90 80 70 60 50 40 30 20 10 0 380 395 410 425 440 455 470 485 500 515 530 545 560 575 590 605 620 635 665 680 695 710 725 740 755 770 Wavelength (nm) Relative Responese (%) Figure 2 Figure 1