Leucistic Swamp Harrier

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nzsam
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Leucistic Swamp Harrier

Postby nzsam » Sat Jun 16, 2018 7:20 pm

I saw a white swamp harrier in Eastern Southland farmland today. I presume it is leucistic but of note were single bilateral black bands on both wings (see photo rear view in flight). It was twice as timid as the usual swamp harrier is when you stop your car to take it's photo so I apologise for the shocking photos plus they are cropped as well.
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kelly111
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Re: Leucistic Swamp Harrier

Postby kelly111 » Sat Jun 16, 2018 10:38 pm

This is very cool.is this the first time you have see it..
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nzsam
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Re: Leucistic Swamp Harrier

Postby nzsam » Sat Jun 16, 2018 10:49 pm

kelly111 wrote:This is very cool.is this the first time you have see it..

Yes it was the first time.
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Neil Fitzgerald
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Re: Leucistic Swamp Harrier

Postby Neil Fitzgerald » Sun Jun 17, 2018 6:40 pm

That is one neat looking harrier. If my memory is correct, bilateral symmetry is a feature of leucism, so those dark primaries suggest you could reasonably call it leucistic.
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nzsam
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Re: Leucistic Swamp Harrier

Postby nzsam » Tue Jun 19, 2018 8:30 am

Neil Fitzgerald wrote:That is one neat looking harrier. If my memory is correct, bilateral symmetry is a feature of leucism, so those dark primaries suggest you could reasonably call it leucistic.


Thank you for that confirmation Neil.
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nzsam
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Re: Leucistic Swamp Harrier

Postby nzsam » Thu Jun 21, 2018 8:33 pm

Michael posted one of the photos on New Zealand Birders Facebook page. A comment was posted by Johannes Fischer. He has given me permission to quote his comments on this forum.
"Clearly not leucistic, but more likely to be a mutation called 'Brown'. See: https://www.researchgate.net/publicatio ... s_in_birds

I then posted the flight shot and he commented - "Those black primaries suggest to me that it is indeed "Brown". "Brown" is a mutation that causes a qualitative reduction of eumelanin: it breaks down in UV light. In other words, feathers get produced in their normal colour, but quickly fade to white as they bleach in sunlight. You can see that at least the right black primary is still being moulted, suggesting exactly this mutation. Interestingly, this mutation is sex-linked and only females can have it.

So I have learned something :-)
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Neil Fitzgerald
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Re: Leucistic Swamp Harrier

Postby Neil Fitzgerald » Thu Jun 21, 2018 9:39 pm

Argh. Internet died and I lost all the really intelligent things I had written. It won't be as good second time around, I'm sure.

Now that I look properly, those primaries are not even symetrical. :shock: :roll:
Brown is common, and chances are it is a female, but it could be male. For that it would need to have a brown mother and a normal looking father that also carries the mutation. Not likely.

This thread might be of interest to those who haven't seen it:
viewtopic.php?f=3&t=247

In that (and I'll repost here) is a link to another of van Grouw's papers with a nice summary table of the common colour aberrations:
https://www.researchgate.net/publicatio ... s_in_birds

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