Bird anatomy and feathers
How identifying bird feathers could help you spot a species you might have missed
ONE AUTUMN MORNING, walking through a nearby wood, I spotted an immediately recognisable feather. For more than 30 years I have honed my specialisation in the ID of individual feathers, and this was clearly a primary wing feather from a Hawfinch, easily identifiable by having a broad, flat-edged distal portion (the furthest extremity) which was a glossy black/purple colour.
However, despite having visited this wood numerous times, I’d never seen a Hawfinch there. The feather proved their presence, so I planned more visits. As the leaves turned to red, orange and finally yellow, I scoured the lower areas of the tree canopy on ever more frequent visits. I had no success for some weeks, until, one gloriously sunny day, I set my scope up on a tripod on the edge of the wood. After about 30 minutes, I heard a scraping noise above. Looking up, I saw a beautifully-lit Hawfinch scraping the sides of his beak on a branch, to clean off the mess left behind after a good feast. The point of this story is that without having found the moulted feather, I could have walked through that wood for years without ever knowing Hawfinches were in residence. That said, the ID of a bird from an individual feather is still perhaps the most poorly-developed area of applied ornithology. This situation has most likely arisen from the relatively few experts in this field, and the consequential lack of a fully comprehensive guide on the ID of individual feathers. Yet, the sight of a freshly-moulted feather provides firm evidence of a given bird in a given area, while the discovery of a feather from a migratory species can provide valuable data on bird movements. In the cases of rare and migratory species, the bird may have made only a fleeting visit, unknown to the ornithologist, but their feathers provide a far lengthened period for discovery and ID.
Plumage and feather development
A bird is covered with various types of feathers, known in their entirety as the plumage. The number of feathers in a bird’s plumage varies depending on the size of the species, from about 1,500 on a small passerine, to 25,000 on one of Britain’s largest birds, the Mute Swan. The plumage performs numerous functions, depending on the type of feather. For example, birds are warm-blooded and so need to maintain a constant body temperature. To achieve this, if a bird gets too hot in summer, one method of keeping cool includes fluffing up its feathers in a breeze to allow circulating air to reach its warm skin, while to keep warm in winter the bird’s soft, downy area of feathers, close to its body, traps warm air against the skin. Feathers are made of keratin, a fibrous protein. Each feather has a follicle, a socket-like pit in the bird’s skin. In each follicle is a group of cells which produce feathers, once a year,
1,500 approx number of feathers on a small passerine Feathers provided a vital clue to the presence of Hawfinches é TELL-TALE SIGNS 25,000 approx number of feathers on a mute swan