Raptor with white bits, Benacre, Suffolk (2 Viewers)

[HH75]

Hi there,
Edited my posts above.
I don't have much of a library of photos myself, and Google won't help when I put in 'juvenile raptor wear' as a search, so I have asked Dick and Killian in case they might have photos of juvenile raptors with this much wear (and, by the way, I would imagine that a raptor like Marsh Harrier would generally be more succeptible to wear to begin with, through its habit of hunting and roosting in tall vegetation, and a partial albino bird's feathers would be expected to be weaker as a result, though I concede that this doesn't PROVE my theory that the bird was a juv). I will also try to give a look through a few old journals etc.
Note that, if my efforts come back fruitless, or if Killian or Dick tells me that the bird CAN'T have been a juvenile, I'll accept that too, and live and learn. If it IS a juvenile, then I won't gloat either: what's the point, when knowledge rather than oneupmanship is my main goal here?
I'm cool with anyone, man! I just don't like the tone that recent posts had been taking: that's NOT the same as me having a problem with you or anyone else as a person.
Peace out!
Harry

 

[tittletattler]

Thanks Harry.

This bird HAS to be a juvenile Marsh Harrier. I just won't sleep properly until someone proves it. That's really all I ever wanted from this thread.

Cheers,

Andy.

 

[HH75]

Hi Andy,

This bird HAS to be a juvenile Marsh Harrier. I just won't sleep properly until someone proves it. That's really all I ever wanted from this thread.

It seems that I misunderstood your position on the ageing of the bird, and that we are both in broad agreement that it must be a juvenile Marsh Harrier: I also acknowledge the world of difference between believing something to be so, and being able to prove it!
I'll try my best, with what limited resources that I have.
Regards,
Harry

 

[James Lowther]

I have made it clear that I would be happy to admit I'm wrong as soon as there is some evidence to support what has been said.

Jane provided stacks and stacks of evidence that anyone trying to use feather wear to definitively age a bird with partial albinism is out on a limb

Chris Benesh produced a compelling argument (based on the photos at hand) that you were overstating the degree of wear in the subject bird anyway (which you dismissed as a whim, presumably because he hadn't gone to the trouble of tacking on a completely irrelevant photo, such as your perched intermediate morph Swainson's hawk)

there you go,

no good reason to believe this bird can not possibly be a juvenile

 

[Frenchy]

Andy,

Theres not much more we can do for you really Andy. If you don't want to accept the conclusions of most of the people on this thread, two of the worlds leading raptor experts, a member of BBRC and the news that a pair of Marsh Harriers are known to be producing partially leucistic young (at least one of which looked like the bird in question) at Minsmere as proof, then it looks like you're in for some long nights.

For me, thats good enough. But then i always trust my own eyes and experience over anyone elses (and learn from it if i'm wrong), which is why i can respect your stance on this. Although maybe now is the time for us all to finish this thread before it stretches to 11 pages!!!

 

[Strandman]

... so I have asked Dick and Killian in case they might have photos of juvenile raptors with this much wear

I think that to meet the Grosser challenge it has to be juvenile raptor with this much wear by late autumn- that's right isnt it, G?

I only ask because it would be shame to see anyone with a pic of a worn Feb juvenile being disappointed...

 

[HH75]

I think that to meet the Grosser challenge it has to be juvenile raptor with this much wear by late autumn- that's right isnt it, G?

I only ask because it would be shame to see anyone with a pic of a worn Feb juvenile being disappointed...

I specified first calendar year raptors, though I concede that this could throw up a few November/ December pics.
Harry

 

[Strandman]

I specified first calendar year raptors, though I concede that this could throw up a few November/ December pics.
Harry

Understoood.

The pic re-posted by Frenchy above was apparently taken in April, so presumably a bird well into calendar year 2.

When that pic was first published, the white pigmentation was put down to poor food supply pre fledging rather than (or in addition to?) genetic abnormality. Whether poor food supply at that stage leads to feathers which are weak and prone to rapid wear as well as being white I hardly dare speculate..

 

[tittletattler]

The following was sent to me by Dick Forsman and he has kindly agreed to allow me to post this here:

Andrew,
To me, no doubt about its age: it is a juv. All non-juv Marsh Harriers
should show CLEAR signs of moult in Sep, which this bird doesn't. The
moult always starts with the inner primaries and proceeds outwards,
therefore the inner primaries should always be fresher than the outer
ones. In this bird the case is rather the opposite, and the only
explanation I can think of, is that the feathers along ther trailing
edge are, for one reason or another, of a poor quality and have
therefore become frayed at this unusually early age. These things
happen, and it is not rare to see young birds with a similarly damaged
plumage also in other species.

Regards,
Dick

 

[Jane Turner]

Hope you can sleep now Andy.

 

[Pie Face]

See you in the Virkie willows next year.

Mark

 

[gerdwichers8]

By the way,
What was that Real Grosser on your list Andy?

 

[Jane Turner]

http://www.surfbirds.com/media/gallery_photos/20070112063121.jpg

Pointd out to me by Nice Mr Gosser.

Seems wear/breakage patterns can vary between individuals. That said the tail is or gives the appearance of being pretty well mashed.

 

[ruggiel]

I think that's exactly what it is. Loks very like a Marsh to me on structure- head looks a bit bulky, but that I think is down to the absence of light markings to break it up.

Uneven patches of white on wings and upperbody apart, this raptor shows five primaries, a long tail and a proportional long wing span, dark iris and beak with culmen dark and cere yellow. Legs are also yellow.
This matches with a juvenile Marsh Harrier rather than a Buteo sp.

The most intriguing feature is the white spot on belly and throat and the irregular white feathers on the upperwing which of course are not good for a regular juvenile Marsh Harrier.
(probably some leucistic gene flow?)

The other odd feature is the irregular wing shape with many feathers looking really abraded. (I guess this bird is not a local individual...)

Very nice!

 

[bitterntwisted]

I had some forewarning of this and have now spent longer comparing leucistic Marsh Harriers than is healthy. I was convinced at the time the subject bird was a Marsh Harrier and, pace William of Ockham, I am still certain that it is a Marsh Harrier. However, the Surfbirds image does support Andy's argument about feather wear very well. So how can a September bird show the wear of the Benacre subject while the bird on Surfbirds, presumably four months older, with the same leucism, shows no such excessive abrasion?

Graham

 

[martin kitching]

So how can a September bird show the wear of the Benacre subject while the bird on Surfbirds, presumably four months older, with the same leucism, shows no such excessive abrasion?

Because, as Jane has already pointed out, wear/breakage patterns can vary between individuals (this is the simple answer of course; the factors involved could make for a very long discussion). If anything, when combined with the fact that the Benacre bird was ably shown to be a juvenile, the surfbirds image only reinforces the point that in aberrant birds feather wear is an unreliable guide to age.

martin

 

[bitterntwisted]

Because, as Jane has already pointed out, wear/breakage patterns can vary between individuals (this is the simple answer of course; the factors involved could make for a very long discussion). If anything, when combined with the fact that the Benacre bird was ably shown to be a juvenile, the surfbirds image only reinforces the point that in aberrant birds feather wear is an unreliable guide to age.

If I may play devil's advocate one more time? Variance I can accept, and "unreliable" is fine, but the feather condition of the bird on Surfbirds is good, better than many individuals without the pigment condition which usually causes excess wear. By contrast the Benacre bird's "wings must be about to drop off", to quote Andy. Is no further explanation needed for even this extent of variation?

 

[Frenchy]

If I may play devil's advocate one more time? Variance I can accept, and "unreliable" is fine, but the feather condition of the bird on Surfbirds is good, better than many individuals without the pigment condition which usually causes excess wear. By contrast the Benacre bird's "wings must be about to drop off", to quote Andy. Is no further explanation needed for even this extent of variation?

Ask Dick Forsman. Or spend half a day re-reading this monster thread. All the answers are contained within...

 

[Jane Turner]

Thanks Harry.

This bird HAS to be a juvenile Marsh Harrier. I just won't sleep properly until someone proves it. That's really all I ever wanted from this thread.

Cheers,

Andy.

Look at the state of "wear" or apparent wear on this juv Marsh Harrier - In Aug - 8 weeks earlier than the Benacre bird.

http://www.cleybirds.com/images/Marsh Harrier02.04_08_2007.jpg

Also highlights the propensity of the East Anglian Harriers to show white bits!

 

[scott m]

This bird is 100% a marsh Harrier. It fledged at Minsmere 2 years ago along with 2 or 3 similarly marked siblings. 1 of the birds has remained in the area on and off and I have seen it on at least 2 occasions since it fledged. Hope this clears all the questions up. Should have noticed this thread a while ago to solve the problem straight away..cracking bird though.