When I started birdwatching in 1969 Brent Geese were just starting to recover
from a severe population crash that almost led to the extinction of the species. The global population went down to just a few tens of thousands at one point. Now you can see several thousand on the Fleet alone. This video shows a group of Dark-bellied Brent Geese with a high proprtion of young birds (the ones with the bars across their wings) and also features their distinctive call.
Here is a closer video of a young Dark-bellied Brent.
The geese we see around Weymouth breed in the north of Russia, on the Arctic coast. Further west at Svalbard a dlifferent form of the species is found, the Pale-bellied Brent Goose. Just a handful of these winter with the Dark-bellied birds on the Fleet.
Even further west in Arctic Canada is a very dark form, the Black Brant. Each year one or two of these can be found in our Brent flock if you look hard enough.