Another mass of migrated birds we recently found at Cley and Salthouse Marshes in Norfolk was these Brent Geese. The white patch on the neck is distinctive of this bird.

These appear to be dark-bellied Brent Geese, which migrate back to their breeding grounds in the tundra of northern Siberia via the Baltic in April. The other sort are light-bellied, and these migrate the other way, to Iceland and then Canada.

According to Wikipedia these are also known as Brant Geese, after the genus Branta. Apparently, the Brent Oilfield, off the Shetland Isles, is named after these geese.

Whilst we were watching, these geese stuck together, occasionally flying off in unison to a nearby field, almost taking turns with a herd of cows to feed on a particular area. Maybe there is some synergy there.