Visual pigment and oil droplet characteristics of the bobolink (Dolichonyx oryzivorus), a new world migratory bird.

The retinal photoreceptors of a New World migratory bird, the bobolink (Dolichonyx oryzivorus) were examined using microspectrophotometry. Based on the absorbance spectra of their visual pigments and oil droplets, retinal photoreceptors include five classes of single cones, one double cone, and one rod. The single cones contain a long-wavelength pigment (lambda(max)=564nm) paired with a red or clear droplet, a medium-wavelength pigment (lambda(max)=505nm) with an orange or yellow droplet, and an ultraviolet pigment (lambda(max)=372nm) with a transparent droplet. No violet- or blue-sensitive single cone was found. The Bobolink double cone is unique: the Accessory member possesses the violet sensitive pigment (lambda(max)=403nm), in contrast to the long-wavelength sensitive pigment present in the double cones of other avian species.