Plumage Changes in the Golden Eagle

Abstract

THE appearance of the note by Spofford (1946) entitled 'Observations on two Golden Eagles' has been the stimulus for the presentation of this material which will attempt to answer his questions and indicate points needing further study. Spofford was struck by the difference in his two specimens and said: Inasmuch as the two eagles examined were as unlike as would seem possible within the limits of variation based on age and sex, it seems worth-while to append a brief description of each. He then proceeded to describe typical juvenal and adult plumages of the Golden Eagle (with the exception of the white epaulettes of the latter). This plumage variability has puzzled taxonomists more, perhaps, than that of any other species of bird and, although we now associate the juvenal and adult birds as members of the same species and know that the plumage of the species is highly variable with age and individual, there is still need for an analysis of these variations. Such an analysis has been impossible because of lack of information regarding the manner of molt. This paper is but a preliminary report in which I will describe as fully as possible, with the materials at hand, the process of molting as it occurs in this species and the individual and age variations which have made the study of this form so difficult.