Visual fields in woodcocks Scolopax rusticola (Scolopacidae; Charadriiformes)

Woodcocks, Scolopax rusticola, are long-billed terrestrial wading birds (Scolopacidae; Charadriiformes) which forage primarily by probing in soft substrates for invertebrates. Visual field topography in restrained alert birds was investigated using an ophthalmoscopic reflex technique.

1. Eye movements of significant amplitude are absent.
2. The retinal binocular field is long and narrow. It extends through 190° in the median sagittal plane. When the head adopts a normal posture (bill at an angle of 40° below the horizontal) the binocular field stretches from 25° above the bill to 5° above the horizontal behind the head. Thus, woodcocks have comprehensive visual coverage of the hemisphere above them but the bill falls outside the visual field. Maximum binocular field width equals 12° and occurs perpendicular to the line of the bill. To the rear of the head binocular field width is less than 5° except in an area 40° above the horizontal where it increases to 7°.
3. Monocular retinal fields in the horizontal plane are 182° wide. There is no blind sector at the margin of the optical fields.
4. The general structure of woodcock skulls facilitates panoramic vision in a horizontal plane.
5. Interspecific comparisons are consistent with the hypothesis that visual field topography among birds is closely associated with the role of vision in foraging. Comprehensive visual coverage of the celestial hemisphere probably occurs only in species, such as woodcocks, which rely primarily upon senses other than vision to guide foraging.