Filoplumes of petrels and shearwaters

Abstract

Filoplumes occur on the head and neck of most dark‐crowned procellariiform birds, but do not seem to have been reported before. Their pattern of distribution is apparently related to the bird's feeding habit. The filoplumes, many of which project beyond the feathers, are more abundant in breeders than in fledgelings, and in males than in females. Their value in sexing birds before egg‐laying was compared with that of culmen lengths, bill widths and body weights, by using data from Grey‐faced Petrels (Pterodroma macroptera gouldi) on Whale Island, Bay of Plenty, and sexual dimorphism was demonstrated. © 1971 Taylor & Francis Ltd.