The retinal binocular field of the pigeon (Columba livia: English racing homer).

An ophthalmoscopic reflex technique has shown that in sedated pigeons maximum retinal binocular field width occurs approximately 20 degrees above the bill. The binocular field has a maximum width of 27 degrees and extends vertically by 130 degrees (90 degrees above the bill, 40 degrees below it). Both the bill and cere intrude into the binocular field. Maximum optical binocularity also occurs approximately 20 degrees above the bill. The plane containing the optic axes of each eye coincides with the bill.