Avian - Feathers
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- Created by: Becky_Berry
- Created on: 08-12-20 20:15
Introduction to Feathers
- Feathers are a uniquely avian trait
- it is now well established that feathers also occurred in dinosaurs
- In the 1990s feathers were described in a series of non-avian coelurosaurs, mostly from the Chinese Liaoning deposits
- Feathers are what enable birds to fly
- thought to have evolved as a thermoregulatory device
- Feathers are lightweight but strong
- the surface is made up of tightly spaced, overlapping filaments that hook together
- overlapping feathers form the wings which birds fly
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Types of Feather
- For example
- Vaned or contour
- down
- semiplume
- filoplume
- bristle
- powder down
- There are two main categories of feathers
- Plumaceous - downy for insulation
- Pennaceous - linked, vaned feathers. Wing and contour feathers.
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Feather Structure
- Made of keratin
- an inert substance that consists of insoluble microscopic filaments embedded in a protein matrix
- also found in hair, nails, claws and scales of other animals
- bird keratin is unique and differs from that of modern reptiles
- a contour feather has a long central shaft and a broad flat vane
- the hollow base of the shaft (quill) anchors the feathers to the follicle under the surface of the skin
- the rest of the shaft (rachis) supports the vanes
- branching of the rachis are barbs
- each barb has barbules projecting either side that interlock with the barbules of adjacent barbs
- barbs and barbules form an interlocking, but flexible, surface
- vane of a typical body feather consists of a hidden downy base (for insulation) and an exposed cohesive outer portion (for streamlining)
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Feather Structure: Pennaceous Feathers
- give birds a streamlined shape, protection from moisture, and the ability to manoeuvre freely in the air
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Feather Structure: Plumaceous Feathers
- the body feathers of most birds include an aftershaft that emerges from the underside of the shaft where the first basal barbs of the vane branch off
- the aftershaft is almost always downy
- functions to increase insulation
- in the ptarmigan winter plumage, the aftershaft is 3/4 as long as the main feather
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Other uses for feathers: Make Sounds
- male club-winged manakins
- use the feathers as mating calls as part of an elaborate dance
- when the feathers rub against each other they make a high-pitched sound
- the feather vibrates at 1500 cycles per second, stridulation
- male American woodcocks clap their wings fast high in the air which creates twittering sounds
- have narrow gaps between their feathers which create the sound
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Other uses for feathers: Reduce sound
- Owls
- 3 feather features
- comb-like structures where the air first hits the wing, reducing the turbulence and overall noise
- on the trailing edge, there are wispy fringes which scientists thinks help smooth airflow
- soft-velvet covering on the top of the wings
- 3 feather features
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Other uses for feathers: Hearing
- facial discs in owls
- the feathers reflect sound which help them pinpoint soft noise
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Other uses for feathers: Digestive Aid
- Grebes eat their feathers to slow digestion and stop fish bones etc. damaging their digestive tract
- feathers can fill up half the gizzard
- don't swallow stones like other birds
- the pyloric pouch is where the smaller feather ball filters out sharp bones
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Other uses for feathers: Fishing
- form an umbrella which it then hunts under
- thought the shade could either reduce glare or draw fish in, or scare away smaller fish and leave medium and large fish
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Other uses for feathers: Water transport, snowshoe
- Water Transport
- Sand grouse use specialised belly feathers to transport water back to their young
- a single bird can pick up 40ml
- when wet the feathers such in water
- Snowshoes
- the feathers quadruple the area of their foot which makes it less likely to sink into the snow
- thought to reduce the sinking by half
- save energy while travelling
- some species grow these feathery snowshoes every year
- Courtship displays
- birds of paradise
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