The Loup City Northwestern

How Birds Change Plumage

Prof. Joseph Grinnell Makes Some Interesting Discoveries Which Agree Not With Common Belief.

It has been generally believed that the brilliant plumage exhibited by the males of many species of birds during spring—that is, during the mating season—is directly connected with the physiological condition of the birds at this time, and various theories have been formulated to account for the facts. Prof. Joseph Grinnell has found in the Californian linnet some facts that do not agree with the common belief. In this bird the male presents a brilliant red breast and neck during the mating season, whereas in the autumn and winter the feathers have a dull grayish coloring, with a mere suggestion of pink. But the bird does not moult (change its feathers) in the spring, nor is there new pigment formed in the feathers. By collecting a series of feathers from August, when the bird does moult, to the following spring, and examining these carefully, it was found that in the new feathers the brilliant red is confined to a narrow band, which is overlapped by the edge of the adjacent feathers. The overlapping portions are white and brittle. During the winter these delicate portions are rubbed off and lost, so that when the mating season arrives the bird has its brilliant coat. Mr. Grinnell emphasizes especially the fact that this brilliant coloring is actually produced in the autumn, after the mating season, at a time of the year when the vitality of the birds is supposed to be at its lowest ebb.