Feather Color I
• Pigments can be in the keratin
– Melanins: black to light tan or grey
– Carotenoids; red, orange, yellow, blue, green
– Porphyrins: red (magenta), brown, green
• Birds can manufacture melanins, but must
obtain carotenoids in the diet.
– Roseate spoonbills and pink flamingos need
crustaceans (e.g. shrimp) for their color
Feather Color I (cont’d)
• Except for albinos, all birds have some melanin
• Melanocytes in the skin inject melanin into cells
that become barbs and barbules
• Intermittent deposition during feather development
results in barring, speckling, other patterns
• High melanin levels correlate with
– wear resistance
– bacterial degradation
– drying damp feathers by concentrating radiant heat
– Improved camouflage in many climates
Feather Color I (cont’d)
• Carotenoids in diet can accumulate in lipid (just as
Vitamin A is lipid soluble in our bodies) in cells that
become barbs and barbules
• Porphyrins are related to hemoglobin and liver bile
pigments. Unstable, so primarily seen in new
feathers
• Structure of the feather can provide iridescence
– Blues, greens, purples, reds
• Minute structures on the surface scatter or reflect
particular wavelengths of light
• Blues and white are usually structural
• Green may be structural or pigment or both
Blue Whistling-Thrush (Myiophonus caerulea)
© Dr. Bakshi Jehangir - www.birdsofkashmir.com
Feather Color II
Ultraviolet Colors I
• Ultraviolet structural colors can be produced by two
types of structures.
• Primarily iridescent colors are produced by arrays of
melanin granules in feather barbules.
– Those structural colors are created by coherent scattering,
or constructive interference, of light waves scattered from
the layers of melanin granules in barbules.
– A few hummingbirds and European Starlings are known to
produce UV hues with coherently scattering melanin arrays
in feather barbules.
Ultraviolet Colors II
• The most commonly distributed UV hues, however, are structural
colors produced by light scattering from the spongy medullary
layer of feather barbs.
– primarily UV hues have been documented in Chalcopsitta cockatoos
(Psittacidae) and Myiophonus thrushes (Turdidae).
– Extensively UV hues with a peak reflectance in the human-visible blue
range have been observed in feather barbs of Blue Tits (Parus
caeruleus), Bluethroats (Luscinia svecica), and Blue Grosbeak
– Prum et al. (2003) have found extensive UV reflectance from apparently
blue feather barbs in many families and orders of birds including
motmots (Momotidae), manakins (Pipridae), cotingas (Cotingidae), fairy
wrens (Maluridae), bluebirds (Sialia), buntings and others.
• The structural UV hues of feather barbs, like other barb structural
colors, are produced by the keratin / air matrix of the spongy
medullary layer of the barb ramus – air bubbles.
• However, the precise physical mechanism by which the humanvisible and UV barb colors are produced remains controversial.
Bird Vision
• Birds can discriminate UV colors
• Feathers that may appear one color to us can
be very different for a bird who sees the UV
color, or patches of UV color
• Two species that look identical to humans can
be dramatically different under UV light (think
of flowers with UV patterns for bees)
Iridescence
• http://people.eku.edu/ritchisong/554notes1.html
• About 40% of the way down the page
– Sapphire vented puffleg
– Hummingbirds
Patterns within feathers
A) Representative patterns within feathers. (B) Some other basic patterns such as bars,
circles, and spots. C) There are also, of course, color patterns at the level of the
entire body (From: Yu et al. 2004).
Genetic Control of Feather Color
• Little is known about this topic in wild birds
• Does appear to be genetic variation in some species
• Some species have 2 or more distinct morphs
Red tailed hawk
Great blue heron
Bird Skin and Eyes
• Blues and greens in skin and eyes are found in
many families
• Size and spacing of parallel collagen fibers in skin
Apteria & Feather Tracts
• The spaces between feather tracts are a
taxonomic character
• Probably facilitate skin movement
• May assist in heat loss during flight
• Adjacent follicles are linked by numerous
small muscles which facilitate movement
• Variety of movements useful for display,
thermoregulation, flight, buoyancy
Abrasion plumage
• As a bird ages through the year the tips of
feathers may wear off, making the feather a
different color on the end
• Some birds, including many passerines, have
drab or cryptic winter plumage which wears
away leaving a brighter breeding plumage
Snow bunting
Motmot tail
• Feather starts out as a typical tail
feather but bird selectively preens
the brittle portions away leaving
the raquet shape
Keel-billed
Blue crowned
Feather Care
• Much grooming to maintain smooth shape, keep
barbules aligned, apply wax, remove parasites
• May groom every hour
• Uropygial gland (preen gland), on lower back at
base of tail, provides waxy secretion to:
– clean feathers
– keep them moist and flexible
– improve insulation
– maintain waterproofing and buoyancy
Uropygial gland
•
•
•
•
Waxes, fatty acids, fat and water
Also helps regulate bacteria, fungi
May discourage feather lice
Foul-smelling waxes may repel mammalian
predators
Feather Parasites
• Lice: chewing lice feed on feathers, blood and
tissue fluids
• Louse flies: flat bloodsucking flies; vectors of
numerous blood parasites, can also transport
lice and mites between hosts
• Feather mites: numerous species with many
niches including inside the shaft
• Over 250 species are
known to do anting
• Active or passive
• Ant may then be discarded
or eaten
• Pest control? Detoxifying
food?
• We don’t know
Toxic
Feathers
• Some birds have toxins in skin and feathers –
alkaloids in pitohui shrike-thrushes in New Guinea
• Unknown whether they produce the poison or
accumulate and sequester from their diet, as do
Monarch butterflies from milkweed
• Advantages?