Prompted by an ID query I cam across on the internet earlier this evening thought I'd right something about one of the other races of brent geese that occasionally can be seen in Dublin in the winter. There were at least 3 (the true figure is probably far higher) dark-bellied brent geese wintering in North Dublin this winter and I saw them fairly regularly during the course of my work. Normally dark-bellied brents winter elsewhere in Europe - they are common for example back in the south east of England where I grew up. To start with they can often look surprisingly similar to the light-bellied in certain light, but after weeks of looking at brent geese telling them apart soon becomes second nature! Below are some pics I took at Red Arches at the end of February.
Picture 1: Note how much darker the underparts and flanks are, and how the dark area extends further towards the belly and up the flanks
Picture 2: This picture shows another useful feature quite well. The back colour of dark-bellied brents is subtly different to that of light-bellies being more slate-grey. Additionally the colour of the back tends to be a bit more solid, lacking the narrow pale fringes that are more common on light-bellues
Picture 3: Note the dark smudgy area that extends beyond the legs on the otherwise white belly. I think this is the easiest feature to split the two subspecies - its particularly obvious when ring reading!
I'll try to add some more stuff about the science soon when work is keeping me a bit less busy!