Black Brant Branta (bernicla) orientalis (formerly nigricans) x Dark-bellied Brent Goose Branta (bernicla) bernicla

Many of the Black Brants that winter in western Europe have produced hybrids with Dark-bellied Brent Geese. Separating pure adult Black Brants from pure Dark-bellied Brent Geese is fairly straightforward but hybrids can be much less so. Some hybrids can be reasonably easy, but others may be much more like either parent species - and to complicate matters further backcrossed hybrids occur as well.

Over the years I have identified a number of Black Brant-like birds as hybrids on account of the back and belly not being dark enough. Whilst this was undoubtedly valid in some cases I had not always appreciated the extent to which these parts can vary in appearance according to light, and it may well be that I have misidentified some perfectly good Black Brants as hybrids. Under certain light conditions the black on a Black Brant's back and breast can be so dark that it doesn't contrast at all with the black neck, but on the same bird in different lights (including bright sunshine) these parts can contrast quite strongly with the neck (although they should always appear darker than on Dark-bellied Brent Geese in the same conditions).

The extent of dark feathering within the white flank patch is certainly variable with all forms of Brent Goose and the precise extent of the white neck collar is also variable. In both cases there may be little overlap with pure Dark-bellied Brent Goose but I have come to believe that a slightly less prominent white flank patch than on the most obvious birds, or a white neck collar that doesn't reach quite so far round the back of the neck as it does on some birds, are not probably not good evidence of a hybrid identity.

In view of the above I have now lost confidence in the labelling of several birds I'd originally got down as hybrids, and although I still think some of them were hybrids (I'm sure a few were) I think several of them were more likely pure birds after all. I haven't yet developed a full understanding of the limits between pure and hybrid birds - more study and more learning is needed!

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adult Black Brant x Dark-bellied Brent Goose hybrid, Burnham Overy, 9th May 2016 - note how at some angles this looks really good for a pure Black Brant while at other angles it is difficult to pick out from the Dark-bellied Brent Geese

 

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first winter Black Brant x Dark-bellied Brent Goose hybrids (with adult Black Brant and Dark-bellied Brent Geese), Wells (Norfolk, UK), 19th November 2004

 

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probable adult Black Brant x Dark-bellied Brent Goose hybrid (with Dark-bellied Brent Geese), Burnham Overy (Norfolk, UK), 30th November 2013 - I thought this to be a good candidate for a pure bird (and so it looks in this photo) but it may not have been quite the ticket; see notes below on what was presumably the same individual

 

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adult Black Brant or Black Brant x Dark-bellied Brent Goose hybrid (with Dark-bellied Brent Geese), Burnham Overy (Norfolk, UK), 11th January 2014 - I found this likely hybrid a particularly tricky individual - saw it at least 3 times before I started to doubt its purity; at least one experienced goose-watcher visited the site often during the winter and never saw what they considered to be a pure Black Brant and I presume this is the challenging hybrid he was seeing instead

 

adult Black Brant x Dark-bellied Brent Goose hybrid (with Dark-bellied Brent Geese), Burnham Overy (Norfolk, UK), 26th October 2014 - a more obvious hybrid than last winter's, in my opinion, being consistently too pale on the back and belly in a variety of lights (although looking quite dark in one or two of the photos); nevertheless it was reported on the rare bird news services as a pure bird a number of times so perhaps can look more deceiving at times

 

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adult Black Brant x Dark-bellied Brent Goose hybrid (with Dark-bellied Brent Geese), Burnham Overy (Norfolk, UK), 28th October 2014 - same bird as above

 

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adult Black Brant x Dark-belled Brent Goose hybrids (with Dark-bellied Brent Geese), Wells (Norfolk, UK), 22nd November 2006

 

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adult Black Brant x Dark-bellied Brent Goose hybrid with adult Dark-bellied Brent Goose and three presumed backcrossed juveniles, Burnham Overy, 1st January 2015

 

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adult Black Brant x Dark-bellied Brent Goose hybrid, Burnham Overy, 12th March 2016

 

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adult Black Brant x Dark-bellied Brent Goose hybrid, Burnham Overy, 26th November 2016

 

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adult Black Brant x Dark-bellied Brent Goose hybrid (with Dark-bellied Brent Geese), Burnham Overy, 7th December 2015

 

probable adult hybrid Black Brant x Dark-bellied Brent Goose (right), Wells, 19th February 2007

 

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probable adult Black Brant x Dark-bellied Brent Goose hybrid, Wells (Norfolk, UK), 7th December 2008 - this bird looked quite different in different conditions and angles to the light: at times it looked pretty good for a pure Black Brant but at other times it looked dire!

 

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adult Black Brant x Dark-bellied Brent Goose hybrids, or Black Brants, Wells (Norfolk, UK), 22nd January 2010 - I thought these were both hybrids at the time but I am not sure!

 

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adult Black Brant x Dark-bellied Brent Goose hybrids, Holkham (Norfolk, UK), 13th February 2013 - the top 4 photos are one bird and the lower 4 another bird; one of them was apparently seen to be paired to a Dark-bellied Brent Goose and accompanied by a backcrossed juvenile earlier in the winter