Structural changes in the lyrate feathers in the development of the tail plumage of the Superb Lyrebird, Menura novaehollandiae

Abstract

The tail plumage of the Superb Lyrebird, Menura novaehollandiae, proceeds through a succession of annual moults over about eight years for the male and about seven for the female in which the feathers change in dimensions, shape, structure and pigmentation. Male lyrates increase in length from 245 mm to ~700 mm, and in weight from 0.37 g to 2.4 g; adult female lyrates are ~305 mm long and weigh 0.55 g; but details vary from bird to bird. The asymmetry (defined in paper) of the first two generations of lyrates is low, but increases at each generation. The shape of the feather is determined by the lengths of the barbs in both vanes and the angle of growth, and the curvature pattern of the shaft, which is curved concave to the long axis of the bird over the proximal part and convex over the distal part. The degree of curvature is greatest in the distal part and increases as the bird matures. Lyrates have yellow-orange-brown bars along the inner vane; the number increases from 16 for the second generation to 20–25 at maturity; adult female lyrates have 8–12 bars. Lyrebirds from Sherbrooke Forest differ from one another in the details of the properties studied; lyrates from other districts had characteristics that fell within the ranges of values for the Sherbrooke birds. The data for a particular mature male bird from Healesville indicate that, once a male bird has matured, the dimensions and structural details remain (practically) unchanged. The lyrates of adult females from different districts differed in some respects, but were similar in others.