Description

A blog mainly about birds and birding, to supplement my website www.gobirding.eu. I shall add new posts on an ad hoc basis as and when I have something I think is worth sharing, whether that’s an interesting bird, something I’ve learned, perhaps about identification, or something that’s aroused my curiosity. Often there will be questions, some of which you might be able to answer... please use the comments!

Monday, 4 June 2012

Ferruginous Ducks

A female Ferruginous Duck turned up in the Norfolk Broads a couple of years ago.  Eventually news of its presence reached the news services and lots of people went to see it.  Most of them were happy with the ID but one or two of the locals who'd originally found it and watched it for prolonged periods felt that it wasn't quite right - and was therefore a hybrid.  Last winter it returned, this time accompanied by what was certainly a hybrid, but the identity of the original bird was still doubted by some people.  I've heard three reasons cited why this bird may have been a hybrid:
  1. The head shape was wrong, looking too rounded for much of the time and lacking the peak that is associated with pure Ferruginous Ducks.  My own views confirmed that this was the case - although on occasion it could look quite peaked, most of the time it looked very round.  But was this really wrong for females?  Certainly a male looking like this would and should arouse suspicion, but I wasn't quite convinced it was wrong for a female.  However I wasn't experienced enough with females to be sure.
  2. The bill shape was considered not quite right.  Personally I thought it looked ok: although at some angles it sometimes looked a bit dubious I couldn't see anything hugely concerning in the bill shape.
  3. The white on the belly had been observed to be too indistinctly-bordered for a pure Ferruginous Duck.  I got a couple of brief views of its belly and to be honest I didn't think it was too indistinct.  Sure it wasn't as neat and tidy as it can be on a male, but it wasn't bad.
Personally I suspected it was the genuine thing, a pure Ferruginous Duck.  But although I've seen a few Ferruginous Ducks they've all be in the UK where any record is tainted with the possibility that it's escaped from a collection and may not be pure.  Also most of the birds I've seen have been males.  I simply wasn't experienced enough with wild female Ferruginous Ducks to be able to make a watertight case for it being a pure bird.  It certainly wasn't a first-generation hybrid but a hybrid backcrossed with Ferruginous Duck would be feasible in captivity and some people felt this was the most likely ID.


Ferruginous Duck, Cockshoot Broad, 12th November 2011

In Sicily I got the opportunity to study a number of Ferruginous Ducks in the wild that were free from the curse of uncertain provenance and were unlikely to be hybrids (at least not all of them!).  I learnt the following:

  1. The rounded head shape shown by the Norfolk Broads bird was perfectly normal for female Ferruginous Duck.  Just like the Norfolk bird, the females I observed in Sicily changed their head shape according to posture, sometimes looking peaked but most of the time looking rounded.  I could see no difference in head shape between the Norfolk bird and the birds in Sicily. 
  2. The apparent bill shape varied too.  Some birds, some of the time, seemed to have much less impressive bill shapes than the Norfolk bird.  Of course this has more to do with angle to the observer than anything else, but there did seem to be a little variation in the bill shape - some females seemed to have fractionally shorter and more concave bills than expected.
  3. Females seen in flight and rearing up clearly showed variation in the belly pattern.  Some were less well-defined than the Norfolk bird.  One bird was much less so, although I did wonder if the poor definition on that bird wasn't caused by dirt rather than actual plumage pattern.


 Ferruginous Duck, Granelli (Sicily), 1st May 2012










Ferruginous Ducks, Granelli (Sicily), 29th April 2012

I noticed a couple of things about the males too that I've sometimes wondered about when I've observed this on birds in Britain:
  1. The head can look rounded on males too, though with prolonged viewing it always reverted to the classic peaked shape.
  2. The contrast between the breast and the flanks varies according to angle to the light.  The same bird can change from having no discernible contrast whatsoever between the colour of the breast and the colour of the flanks to having such a strong contrast that it made me think for a moment that I must have found a hybrid. I knew this was the case on some of the British birds I've observed but it was reassuring to see that it was also the case on genuine wild birds in Sicily.



Ferruginous Ducks, Granelli (Sicily), 29th April 2012

Lots more photos of Ferruginous Ducks from Norfolk and from Sicily at http://www.gobirding.eu/Photos/FerruginousDuck.php

4 comments:

  1. Hi Dave,

    nice addition to the website

    paraphrasing comments made by locals during discussions and correspondence, the issues with the Cockshoot bird are:
    1) head shape consistently not quite right and head on the small side, not as large as expected
    2) tail habitually held down masking the utcovs
    3) colour not quite correct (not rich enough) for a pure female
    4) bill thought to be a little short, perhaps too much black on tip

    a pure female bird was also present late in 2011 on which features contra those above were noted.

    The tail feature is quite interesting. A friend of mine recently watched hundreds of Fudge in Assam and not one was seen to habitually hold its tail down over the coverts...

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  2. Thanks Tim! There are a couple of new points there that I don't recall hearing in discussions about the Norfolk bird, so interesting stuff.

    Regarding point 3, some of the Ferruginous Ducks in Sicily were at lesat as dull as the Norfolk bird - I'd say a bit duller even, so I don't think overall colouration is a point against its purity.

    Point 2, and with your friend's supporting comment, is interesting. Certainly pure Ferruginous Ducks can and do hold their tails down over the coverts so that virtually no white is visible - this was my experience and is also mentioned in Keith Vinicombe's article on the ID of Ferruginous Ducks in BB (British Birds 93: 4-21, January 2000). Keith suggests this may be the case particularly with females, and that's my impression too. My photos above weren't selected to show this feature but you can see that many of images of females have little white visible and some have no white visible under the tail. Of course this doesn't mean that it's not a valid observation, or a genuine feature when watched over a sufficiently long period of time. I realise the locals formed their views on the Norfolk bird after many hours of observation across many different days, whereas I just saw it for an hour or two on a handful of occasions.

    Cheers,
    Dave

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  3. I just came across your blog because we have our 3rd male in 6 years and believe it is a wild bird, very wary. But somebody has posted somewhere that because it has a ring on it's left leg, it must be an escapee. I don't buy it in any way, as a few used to be ringed and would love to hear your thoughts. Fraser Cottington see www.berksbirds.co.uk and my blog http://fjcsdpbirding.blogspot.co.uk/

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  4. Hi Fraser, I think we'd need a better view of the ring to be sure. A metal ring doesn't necessarily mean it's an escapee, but nor does it mean it can't be an escapee. On balance it probably shifts the balance of probability more in favour of it being an escapee, unless the ring can be seen well enough to see what's written on it. If it is indeed a BTO ring that would be a different story!

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