Is that bird an albino? Aberrant plumage definitions and terminology info

General birdwatching discussion, help with bird identification, and all other things relating to wild birds and birding in NZ that don't fit in one of the other forums.
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Brent Stephenson
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Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Brent Stephenson » Fri Apr 26, 2019 3:56 am

Hi all,

I've had a passing interest in this sort of thing for a while, and definitely don't profess to be an expert. But following the recent pictures and sightings of the Tolaga Bay oystercatcher, thought it might be useful to share the attached documents. Unfortunately, they both take a completely different approach to naming conventions, which really doesn't help the matter! But it is very useful in out lining the different kinds of aberrant plumages in birds, what causes them, and the fact that the term albino is used, when in many cases this is not correct.



Davis-2007-Color-Abnormalities.pdf
(3.22 MiB) Downloaded 26 times


I suspect the variable oystercatcher at Tolaga Bay is a 100% leucistic individual, similar to the Eurasian oystercatcher pictured in image 108 of 'Not every white bird is an albino' by Hein van Grouw.

Hope some find these of interest.
Cheers,
Brent Stephenson
Wrybill Birding Tours, NZ - Great birds, real birders
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Adam C
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Re: Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Adam C » Fri Apr 26, 2019 10:23 am

Nice to clarify it!
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Neil Fitzgerald
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Re: Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Neil Fitzgerald » Sat Apr 27, 2019 5:41 pm

van Grouw's more recent paper on the subject is also worth reading. There is a link to it on page four of the long "white birds" thread: viewtopic.php?f=3&t=247&hilit=white+birds&start=30#p22394
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Re: Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Brent Stephenson » Tue Apr 30, 2019 8:12 pm

Cool - thanks Neil!
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Peter Frost
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Re: Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Peter Frost » Wed May 15, 2019 1:25 am

The paper by Davis has an interesting set of illustrations showing the progressive loss of melanin from the plumage of a Stellar's Jay over the course of a single moult (see p. 39). In the last three years we've had a female house sparrow regularly visiting our garden in Whanganui East that seems to show similar progressive loss of melanin over successive moults. Although the bird is unbanded, I'm assuming that it is the same bird, based on the regularity of its occurrence (at least once a week) and that I've never seen two aberrant coloured females in the garden at the same time or even within a short time of each other. In fact, it appears to be the only aberrant coloured female in the vicinity. She reared two broods during the last breeding season (2018/19) and, on each occasion, her 2-3 chicks appeared to be normal coloured (she fed them for about a week post-fledging with grain put out for the birds).

Here is a set of photographs showing this progressive loss (assuming that it is the same bird). Her post-breeding moult is in late-February - March, during which time she replaces all of her body feathers.

Leucistic female sparrow_Dec 2017_lowres.jpg
December 2017
Leucistic female sparrow_Dec 2017_lowres.jpg (563.41 KiB) Viewed 337 times


Leucistic female house sparrow_May 2018.jpg
May 2018
Leucistic female house sparrow_May 2018.jpg (464.58 KiB) Viewed 337 times


Leucistic female house sparrow_LHS_April 2019.jpg
April 2019
Leucistic female house sparrow_LHS_April 2019.jpg (459.1 KiB) Viewed 337 times

This progressive loss of melanin over time suggests either creeping old age or some environmental cause. I've no idea what the latter might be as the bird looks healthy and is lively (sprightly might be a better term). Interestingly, when flying, she seems to have a faster wing beat than ordinary sparrows but this could just be an optical illusion. Alternatively is could be that with much reduced melanin in her flight feathers, they do not have the same rigidity of normal feathers, and this may require faster wing beats to compensate. This draws attention to the question of what the consequences of plumage abnormalities could be, apart from the obvious one of (perhaps) increased vulnerability to predation.

Peter
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Re: Is that bird an albino? Aberrant plumage definitions and terminology info

Postby Neil Fitzgerald » Wed May 15, 2019 8:31 pm

Looks like progressive greying to me. Apparently one of the more common conditions, although people usually jump to other conclusions which is understandable when a bird's history is unknown. The NZ pigeon I photographed near Hamilton and the white-faced heron in Northland come to mind.

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