Oil droplets of Wild Bird Retinas

Abstract

The retinas of several kinds of wild birds were studied to observe the effects of colored oil droplets on their spectral sensitivities. The size, optical density, and distribution of each oil droplet in the fixed area was examined. The retina of the pigeon (Columba livia) was divided into red and yellow areas microscopically. Both areas had red, orange, and pale-green oil droplets. The red area had three times more oil droplets than the other areas, but the distribution of the three kinds of oil droplets was almost the same in both areas. In microspectrophotometric measurements, the red and orange oil droplets showed a very similar spectrum in 4 species: the Japanese jungle crow (Corvus macrorhynchos), night heron (Nycticorax nycticorax), eastern house swallow (Hirundo rustica), and Japanese jungle nightjar (Caprimulgus indicus). The pale green oil droplets of Japanese jungle nightjar, however, showed a different spectrum from the other birds.