Wednesday, 4 June 2014

Herring Gull x Lesser Black-backed Gull

Herring Gull x Lesser Black-backed Gull hybrid, Blakeney (Norfolk, UK), 13th February 2016 - copyright Dave Appleton
(photo ID: 2703)


A Herring Gull x Lesser Black-backed Gull hybrid has been seen at Blakeney on a number of occasions during the winter of 2015/16, though sometimes reported as a Yellow-legged Gull.  In my photos the legs look quite pinkish but in the field they looked more yellow, albeit a very dull greyish yellow.





Herring Gull x Lesser Black-backed Gull hybrid (same bird as in photo ID 2703 above), Blakeney (Norfolk, UK), 13th February 2016 - copyright Dave Appleton
(photo IDs: 2704-2708)


I managed to get a couple of sound recordings of this bird, including this one here.  To my ears the nasal call sounded distinctly lower pitched than Herring Gull, if perhaps not so low as Lesser Black-backed and Yellow-legged Gulls.

video
Herring Gull x Lesser Black-backed Gull hybrid (same bird as in photo IDs 2703-2708 above), Blakeney (Norfolk, UK), 13th February 2016 - copyright Dave Appleton
(media ID.: 2709)


What was presumably the same bird returned to the same location the following winter.



Herring Gull x Lesser Black-backed Gull hybrid (presumably same bird as in photo IDs 2703-2708 above), Blakeney (Norfolk, UK), 18th January 2017 - copyright Dave Appleton
(photo IDs: 2840-2842)


Herring Gull x Lesser Black-backed Gull hybrid (same bird as in photo IDs 2840-2842 above), Blakeney (Norfolk, UK), 21st February 2017 - copyright Dave Appleton
(photo ID: 3090)


Yellow-legged Gull is a rare bird in Scotland so when Stephen clocked a fairly bulky bird with intermediately dark grey mantle, red orbital ring, solid yellow legs and a thick band on P5, it deserved a closer look!  The account of his find is on his blog and you'll see there that Stephen was wise to the problem of hybrids and suspected his bird would not prove to be a pure Yellow-legged Gull.  Sure enough when it started preening he saw that the thick band on P5 was only on the outer web, with nothing on inner (see the close-up picture below) - an even band is needed for Yellow-legged Gull.  Steve notes the narrow dark subterminal band on the bill, concluding that it was probably immature, perhaps 4th summer.



Herring Gull x Lesser Black-backed Gull hybrid, Fenton Barns (East Lothian, UK), 20th April 2014 - copyright Stephen Welch
(photo IDs: 2273-2275)


This bird was back the following spring, paired with a Herring Gull:


Herring Gull x Lesser Black-backed Gull hybrid, Fenton Barns (East Lothian, UK), 15th March 2015 - copyright Stephen Welch
(photo IDs: 2177-2178)


On his blog Steve describes this bird's call when he saw it again two weeks later:
"For first time, long call was observed, with head vertically down initially coming up to 45 degrees during the brief (truncated) call, followed by mate behind; thus in contrast to the vertical upward angle shown by Yellow-legged Gull and Lesser Black-backed Gull.  Red gonys spot clearly confined to lower mandible, also contra Yellow-legged Gull.  However the orbital is pretty reddish, thus closer to Lesser Black-backed Gull."



Herring Gull x Lesser Black-backed Gull hybrid, Fenton Barns (East Lothian, UK), 29th March 2015 - copyright Stephen Welch
(photo IDs: 2379-2382)


Dean writes about the next two birds:
"These are far more common than people think, some are like Herring Gulls (the Spalford bird) whilst others are more like Lesser Black-backs (the Cotham bird) and many get passed off as Yellow-legged Gulls; interestingly it’s only adults that seem to get picked up but there must be plenty of younger birds escaping detection.  These two were both in Nottinghamshire on 23rd Oct 2013 and 5th Feb 2015 respectively.  No two are seemingly the same with and should be taken on their individual merits.....head streaking and bare colouration are variable, as is mantle tone and primary pattern.  One consistent feature however seems to be the broad white tertial crescents.  Although subtle, with practice they do stand out as looking different to their congeners..."
Interestingly I was chatting with another UK gull expert a few days ago (watching but failing to photograph another Herring Gull x Lesser Black-backed Gull hybrid) and he made the same point about only adults getting picked up at the moment.





Herring Gull x Lesser Black-backed Gull hybrid, Spalford (Nottinghamshire, UK), 23rd October 2013 - copyright Dean Nicholson
(photo IDs: 2655-2659)






Herring Gull x Lesser Black-backed Gull hybrid, Cotham Tip (Nottinghamshire, UK), 5th February 2015 - copyright Dean Nicholson
(photo IDs: 2660-2664)


Dean says of the following bird,
"It was obviously paler mantled than the adult graellsii present (best appreciated in photo ID 2943) with a subtle but definite bluey tinge, the legs were dull yellow, primary projection relatively short and the white tertial fringe is pretty broad. It was hard to age accurately as the plumage was adult-like (no obvious dark in tail or coverts) but the bill is obviously immature.... its an odd time for an adult type to have head/nape streaking- recalling heuglini/taimyrensis although no black on p4 not good for that fanciable option!... thin band on p5 and a decent sized tongue (for a Lesser Black-backed Gull) on the underside of p10 (photo ID 2945)"








Herring Gull x Lesser Black-backed Gull hybrid, Norton Disney (Lincolnshire, UK), 23rd June 2016 - copyright Dean Nicholson
(photo IDs: 2940-2948)


For the next one Dean writes:
"I first thought it was a Yellow-legged Gull when I saw it scuffling about in the ‘bread melee’ on account of its dark mantle and obviously yellow legs but on settling on nearby rocks I could see immediately that it wasn’t.  I then considered a dark mantled and yellow legged ‘Baltic Herring Gull’ but this too didn’t seem right especially when it stretched showing much black in the wing tip, especially with a solid band across p5 (most dark mantled yellow legged argentatus show very little or no black at all on p5) so then I started looking at a hybrid.  Lesser Black-backed x Herring was the most obvious candidate and would fit quite well with others I’ve seen, especially the dark mantle tone (darker than michahelis), broad white tertial crescents and orangey red eye ring.  The broad p5 band did make me wonder about possible michahelis involvement so I forwarded a few pics to my usual gulling contacts as well as putting some shots on the birdforum ID page for comment and the general consensus was overwhelmingly a Lesser Black-backed x Herring combo......"











Herring Gull x Lesser Black-backed Gull hybrid, Scalby Mills, Scarborough (Yorkshire, UK), 20th January 2017 - copyright Dean Nicholson
(photo IDs: 2949-2960)



Herring Gull Larus argentatus
Lesser Black-backed Gull Larus fuscus
Yellow-legged Gull Larus michahellis

1 comment:

  1. Thanks for adding to blog Dave - we have in fact a spate of records of apparent hybrid in recent years, some will be returning birds, but also many different (older) immatures, see Geoff Morgan's blog:

    http://morgithology.blogspot.co.uk/search/label/Hybrid

    I agree juveniles and younger immatures would be hard/impossible to detect. If we have resident adults then maybe this explains some of the younger birds, though enquiries to those monitoring local seabird colonies have drawn a blank thus far...

    ReplyDelete