Monday, 10 January 2011

Ducks redux: Aythyas and hybrids

Adult male Common Pochard (Alexandra Park, Greater London, 17 February 2008).
Adult female Common Pochard (Alexandra Park, Greater London, 7 September 2009).
I’ve been meaning to revisit the subject of Aythyas for a while, and have finally been prompted to do so as hybrids and the genuine article have become something of a talking point in recent days.

I don’t know what the level of incidence of hybridisation is between different Aythya species, but having found two hybrids in a small mixed flock of about 35 Tufted Ducks and Common Pochards on my patch last month, it is a question worth considering. In this instance statistics don’t tell the full story, as the photos below show - these two lookalike (and potentially related?) birds are not Tufted Duck x Pochard hybrid spawn.

Aythya hybrid 1 (Alexandra Park, Greater London, 19 December 2010).
The structure of this bird instantly recalls Pochard/Ferruginous Duck, as do elements of the plumage ...

Aythya hybrid 2 (Alexandra Park, Greater London, 19 December 2010).
The second bird is very similar to the first, though possibly a little less contrasting. In case you were about to ask, here’s a pukka adult female Ferruginous Duck for comparison:

Adult female Ferruginous Duck (Burgess Park, Greater London, 28 November 2010). Note the uniform plumage.

In view of the head/bill profile, plumage details and other characters of the two hybrids, my feeling was that they were Common Pochard x Ferruginous Duck hybrids (surely not interbreeding anywhere near London?). Keith Vinicombe has far more experience with hybrid Aythyas than me, so I asked him for his opinion. He replied: “I'd say that the hybrids look like juveniles and that Pochard must have been one of the parents, given the ‘Pochard grey’ shading on the scapulars and flanks plus the extensive black at the tip of the bill. The bottom bird also has a dull red eye, which would also indicate that (a) it is a juvenile male and (b) that one of its parents was a Pochard. (The top one also seems to have a reddish eye too). The black ground colour to the upperparts would suggest Tufted or Ferruginous as the other parent, while I would have said that the reddish brown breast would be indicative of Ferruginous. The lack of any tuft would not favour Tufted as a parent. Overall, I would guess that they are Pochard x Ferruginous, but at the Pochard end of the hybrid spectrum.”

Tufted Duck x Common Pochard hybrid recalling Lesser Scaup (Alexandra Park, Greater London, March 2010).
These are not the only Aythya hybrids seen in Alexandra Park in 2010. The above bird, of the more classic ‘Lesser Scaup’ type, appeared back in March last year. A rather smart individual, it has tried its best, even down to the purple head sheen. But its head shape, darker grey upperparts and extensively black nail on the bill are among the characters pointing to a male Tufted x female Common Pochard hybrid. Here’s a real drake Lesser Scaup, by way of comparison (excuse the poor quality slide scan):

Firt-winter drake Lesser Scaup (Regent's Park, Greater London, March 2003).
The next bird is not a hybrid either. Present among a gathering of Tufties and other ducks, this first-winter female Lesser Scaup showed well when I was visiting Caerlaverock WWT, Dumfries and Galloway, back in February 2006. The head shape is subtly different to Tufted Duck, as in fact is the whole profile (NB do Lesser Scaups seem to sit higher on the water?), but flank/mantle pattern/colour, bill markings and smaller size also separate the two (as would, if visible, its less extensively white wing-bar, which unlike Tufted Duck and Greater Scaup is greyer on the primaries).

First-winter female Lesser Scaup (Caerlaverock WWT, Dumfries and Galloway, 15 February 2006). The tell-tale
vermiculations are beginning to emerge. Jizz-wise, it is quite distinct in both shape and posture on the water.
Here is the same first-winter female Lesser Scaup (left), with a lookalike Tufted Duck for comparison. The bill
pattern and more solidly dark upperpart coloration of the latter are among the clues to its true identity.
Back to Common Pochard x Ferruginous Duck hybrids, these links might be of interest:

4 comments:

  1. A Redhead-like Aythya hybrid photographed at Sidi Bou Ghaba (Morocco) this month. It is like the ones in Collins Bird Guide but probably this has a brighter yellow eye. The photo can be seen at this local “forum”:
    http://gomac.megaplog.com/index.php?id=3840&

    ReplyDelete
  2. Hi Dominic, a brief summary of recent hybrids here at Stoke Newington Reservoirs (several km further into the city and south of Alexandra Park) as requested:

    at least ten in the last two years, of which: five have been presumed Common Pochard x Tufted Duck (3f, 2m); one presumed Greater Scaup x Tufted Duck (female); three presumed Ferruginous Duck x Tufted Duck (together); and (most tantalisingly) a male Ring-necked Duck x ? (presumably Tufted Duck). The latter was very much at the RND end of the spectrum and needed
    prolonged views to rule out a pure nearctic vagrant.

    Numbers of aythyas here rarely exceed 150 in total (usually about 70% Tufted, 30% Common Pochard), and I've been surprised at the regularity of hybrids, especially considering genuine vagrant aythyas have numbered exactly one - an imm male Greater Scaup early last year. This is however partially a reflection of greatly increased coverage, which has shown a much more rapid changeover of birds - even on a daily basis - than otherwise assumed. Also worth mentioning that at least two of your birds at Alexandra Park were also visitors to SNR.

    Photos and videos of most of these birds are scattered throughout the latest news pages of the Hackney Wildlife site, but a few can found here:

    poor video footage of the RND hybrid (with presumed Greater Scaup x TD swimming past) - http://www.youtube.com/watch?v=oQ5M_W_I4Wo&feature=player_embedded

    drake CP x TD - http://www.hackneywildlife.org.uk/hackney-wildlife-sightings.php?newmonth=2010-2 (second entry down)

    female CP x TD - http://www.hackneywildlife.org.uk/hackney-wildlife-sightings.php?newmonth=2010-5 (10th May entry)

    two of the three presumed Ferruginous hybrids (with a female Tufted duck for comparison) - http://www.hackneywildlife.org.uk/hackney-wildlife-sightings.php?newmonth=2010-9 (14th Sep entry)

    And a Tufted Duck I found in Providence, Rhode Island last year, getting friendly with Lesser Scaup - http://northernrustic.blogspot.com/2010/02/new-england-usa-jan-feb-2010-8.html

    best,
    Mark

    ReplyDelete
  3. Interesting birds!

    I found an identical individual at Stewartby Lake in Beds last weekend:
    http://steveblain.blogspot.com/2011/01/another-hybrid-quacker.html

    The markings on my bird seem to match your top bird. Are they still on Alexandra Park?

    ReplyDelete
  4. Evening,

    I found the bird pictured here this morning:

    http://www.birdforum.net/showthread.php?t=190294&referrerid=62979

    I'd really value your comment. With thanks in advance.

    Cheers,

    Jonny

    ReplyDelete

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