From late September thousands of Barnacle Geese arriving from Greenland congregate on the tidal mudflats at the head of Loch Gruinart and Loch Indaal which are also their main roosting sites. Barnacle Geese are distinguished from other black geese such as the Canada Goose and smaller Brent by its creamy white face contrasting boldly with the black hind crown, neck and breast. They are highly gregarious, often noisy and quarrelsome, throughout the year with thousands in winter flocks as seen on Islay.

(https://www.islay.blog/article.php/islay-seasonwatch-barnacle-goose)