The color vision of birds. I. The spectrum of the domestic fowl. (1916)

Evidence bearing upon the color vision of birds has come, thus far, chiefly from three sources; tests for the Purkinje phenomenon, discrimination tests with pigments, and photoe 1 '~ic studies of the retina.Hess ('07) advanced the first e\ oe for the Purkinje phenomenon in birds.He placed whn rice grains on a matt-black background, illuminated them with a spectrum, and placed fowls before them.The birds, light adapted, pecked first from the region of the orange through the red to the limit of the human spectrum, then in the yellow to blue-green, never in the blue or violet.Dark adapted and with a spectrum of low intensity they began to peck in the region of the yellow or orange-yellow and reached somewhat farther into the blue-green but never into the blue.Similar behavior was observed in the pigeon.The point of greatest stimulating value seemed to shift from the longer to the shorter wave-lengths with darkness adaptation.These results also led Hess to conclude that the spectrum of the day-bird is shortened at the violet end.In view of Watson's proof ('15) that the spectrum of the fowl is fully as extensive as that of man the validity of such a method as that of Hess becomes questionable.Katz and Revesz ('07 and '09) reported experiments with color-papers and stained rice grains in which fowls, when dark adapted and in dim light pecked more frequently at grains reflecting the shorter wave-lengths than when light adapted and 2 K. S. LASHLEY in bright light.A somewhat more conclusive test was made by Hess ('08) in measurements of the pupillary opening.The maximum contraction of the iris was produced by longer light waves in light adaptation than in darkness adaptation.A preliminary report of the writer's experiments was given by Watson ('14).They are recorded at length in the following pages.Yerkes ('15) using a similar method, obtained evidence of the change in the relative brightness values of.the red and green with change of adaptation in the ring-dove.Students of color discrimination in birds have usually employed color-papers or dyes with no certain control of intensity or saturation.Porter ('06) records tests with the English sparrow and cow-bird in which red, yellow, green, blue, and two shades of gray paper were used.The birds learned very readily to distinguish between these.Rouse ('06) used almost identical methods with the pigeon and secured like results.Katz and ReVdisz ('07) trained chicks to pick out colored rice grains from among gray ones.As Hess ('12, p. 21) points out for the work of Katz and Rev6sz, all these results might have been obtained with completely color blind animals.Hess ('12) reports tests with rice grains stained to match the Seebeck-Holmgren wools.Fowls distinguished the reddish grains from the greens and grays of this series, which were confused by a red-green blind man.From this Hess concludes that the fowl is sensitive to the wave-length of the red and green rays.The uncertainty of conclusions as to the color vision of animals drawn from analogy with the condition of brightness vision in color blind men has been pointed out by Frisch ('14) and the evidence of Hess himself for a shortening of the fowl's spectrum in the blue-green tends to invalidate his evidence for color vision.The careful work of DeVoss and Ganson ('IS) shows in a practical way the justice of the most severe criticisms that have been urged against the use of color-papers in the study of animal vision.Rouse ('05), by recording the rate of respiration in the pigeon after stimulation with light, was able to show an increase in rate progressive with change from the longer to the shorter wave-lengths.He was not able to find like changes with alteration in the intensity of light of constant wave-length.The tests with wave-length and intensity were not carried out under