Dark-bellied Brent Goose Branta (bernicla) bernicla x Pale-bellied Brent Goose Branta (bernicla) hrota hybrid

In the winter of 2013/14 a family part of Brent Geese spent most of the winter at Cley/Salthouse. The adults were one each Dark and Pale-bellied Brent Geese and the young were presumed to be their offspring. Despite several attempts I never managed to catch up with these but the following winter I got another chance. It took me a few goes again but I did eventually manage to see them.

It seems to be surprisingly rare for these two closely-related taxa to produce hybird young. One of Norfolk's finest goose-watchers told me he'd never seen a mixed family party like this before, athough I think he and I have both seen one or two adult birds that we have suspected as being hybrids. Having said this, I think there have been quite a few records in north Norfolk more recently, perhaps involving the same parents?

first-winter Dark-bellied Brent Goose x Pale-bellied Brent Goose hybrids with adult Pale-bellied Brent Goose and Dark-bellied Brent Geese, Salthouse (Norfolk, UK), 18th December 2014

In April 2017 I discovered the following bird which stood out from the accompanying Dark-bellied Brent Goose in having a more conspicous pale flank patch. Usually that is a pointer to Black Brant hybrids, but this bird showed no other features of Black Brant hybrid - the upperparts and belly were no darker than the other Brent Geese - a fraction paler and browner if anything - and the neck collar was not larger (at times it looked smaller, at least not extending so far round to the front, which is often a feature of Pale-bellied Brent Goose). It reminded me more of Pale-bellied Brent Goose and supporting the idea that this taxa was involved was the way that the pale flanks extended downwards further into the belly. The bottom of the belly was dark, including between the legs, ruling out pure Pale-bellied.

Interestingly this bird seemed to be paired to a colour-ringed Dark-bellied Brent Goose, a bird ringed in Taimyr in July 2008 and reported a number of times since here in Norfolk, in Netherlands, in Germany and in France. So far I have not been able to establish if the hybrid was accompanying this bird on any of the previous occasions it was seen..

adult Dark-bellied Brent Goose x Pale-bellied Brent Goose hybrid with Dark-bellied Brent Goose, Burnham Over (Norfolk, UK), 20th April 2017

I found the bird again a few days later and took the following photos.

adult Dark-bellied Brent Goose x Pale-bellied Brent Goose hybrid with Dark-bellied Brent Geese, Burnham Over (Norfolk, UK), 2nd May 2017

For comparison, here are photos of the parent species.

Dark-bellied Brent Goose, Wells (Norfolk, UK), 14th February 2012 and Pale-bellied Brent Goose, Burnham Norton (Norfolk, UK), 13th March 2010

For more photos of these taxa follow the links below:

• Dark-bellied Brent Goose
• Pale-bellied Goose