A WHITER SHADE OF TAIL? LEUCISM IN BIRDS
And not just the tail*. Other parts of a bird. Sometimes most of a bird. More rarely, an entire bird. Whichever, a bird affected by leucism stands out from the crowd – out of the ordinary and therefore startling to the eye. I’d be very surprised if the fine turkey vulture in the header image didn’t make you look twice – maybe even to check if some devious photoshop trickery had been at work. Yet it’s just a normal TUVU in the Florida Keys, living a normal vulturine life.
LEUCISTIC DISCOVERY ON ABACO
LEUCISM? EXCUSE ME, AND THAT IS?
First, what it is not. It is not albinism, which results from diminished or lost melanin production that affects pigmentation. One characteristic of the condition is the tendency to pink eyes, which of course is seen in humans as well as animals and birds. Meet the perfect example…
WELL, WHAT IS IT THEN?
Put simply, melanin is only one of many ingredients of pigmentation. Leucism is caused through pigment loss involving many types of pigment, not just melanin. In birds this results in unnaturally light or white colouring of feathers that may be partial or entire. The eyes of a bird with leucism are unaffected. At one extreme, if all pigment cells fail, a white bird will result; at the other extreme, pigment defects cause patches and blotches of pale or white on the bird, often called a ‘pied’ effect. The condition can be inherited.
A mallard on Abaco. The species is known for its wide colour variations in both sexes. Sometimes the variations go beyond the usual range: this is a leucistic bird
BAHAMA (WHITE-CHEEKED) PINTAIL: A PIGMENT PUZZLE
I have found more examples of leucism in the ‘Bahama Duck’ than any other local species on Abaco. But there is also scope for confusion. First, here’s a pintail that is undoubtedly leucistic – note that the eyes and beak are unaffected by pigmentation deficiency:
But not all pale variants can be so confidently labelled. In the first picture, bottom right, there is an obviously an ‘odd’ pintail, silvery rather than ruddy brown like the rest of them (and yes, I do see the coot in the pack as well…). The second photo shows the same bird on dry land.
This is known as a ‘silver pintail’. These are said to be a leuchistic variant, and they are stocked by poultry dealers as ornamental ducks at a higher price than the much-loved standard brown version. However this bird clearly retains the essential markings of a normal pintail that you might expect to be absent (at least in patches) in the ‘true’ leucistic bird. I’ve seen it described as a ‘gray morph’. I wonder where the line is drawn between a noticeable colour variant or morph in a bird; and an obviously pigment-abnormal, leucistic bird where the incidence and extent of the condition seems to be random.
A fine example of a ‘pied’ American Robin, an occasional visiting species on Abaco
PIPING PLOVERS CAN BE LEUCISTIC TOO
These photos of a leucistic female were featured by Audubon Alliance for Coastal Waterbirds, Audubon Connecticut. They were taken by Jim Panaccione, a Biological Science Technician at Parker River National Wildlife Refuge, Newburyport, Massachusetts. I hope he won’t mind their illustrative use here… Despite the theory that leucistic birds may find it hard to find a mate – and might even be attacked by its own species – this pair successfully nested.
OPTIONAL MUSICAL & CULTURAL DIGRESSION
A WHITER SHADE OF PALE
*Obviously, it had to be ‘tail’ in the title to justify one of my clunky ‘jokes’ and an accompanying musical diversion. That’s just the way it is, I’m afraid. Bach’s well-known descending chord sequence of was of course
shamelessly ripped off by ingeniously adapted by Procol Harum for ‘A Whiter Shade of Pale’, their first single in 1967. Relive a Summer of Love right here and now.
Any fret-tweakers might like to see the sheet music of Bach’s Air for guitar – you could even play it on Air Guitar – which is relatively easy, being in C major.
‘BACH IN A MINUET’
The best known commercial use of the tune was in the famed series of adverts that equated a mild cigar called Hamlet with happiness, accompanied by an excerpt from a jazzy version of Bach’s ‘Air on the G String’. Here is one of the best – and possibly the only advert to my knowledge to feature not one, but two excellent Sir Walter Raleigh jokes.
Credits: thanks to Amy Evenstad (PoweredByBirds.com) for use permission for her wonderful TUVU & AMRO photos; other photos by Keith Kemp & Bruce Hallett (Spindalis); Pinterest (rabbit); Nina Henry (mallard); Tony Hepburn (moorhen); Wiki (pigeon); Jim Edmonson (leucistic pintail); Keith Salvesen (silver pintail); Jim Panaccione / Audubon (piping plovers); Procol Harum, esp. Robin Trower for building a great career round being ‘reminiscent of Jimi Hendrix’; J.S. Bach for a nagging tune; Hamlet cigars for ingenuity & making me laugh