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 (λmax = 564 nm) paired with a red or clear droplet, a medium-wavelength pigment (λmax = 505 nm) with an orange or yellow droplet, and an ultraviolet pigment (λmax = 372 nm) 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 (λmax = 403 nm), in contrast to the long-wavelength sensitive pigment present in the double cones of other avian species.