Canada geese, or Branta canadensis, easily recognised by their distinctive black head and neck and white chin-strap, are widespread in Britain. As their name suggests, they originated in the Canadian tundra and many winter in the southern swamplands of the United States. Some scientists claim that they are now choosing to winter in Europe because of global warming.
Nonsense. The birds that are causing problems in the U.K. and in America aren’t migratory birds, but local populations that have set up home in protected areas and are thriving due to the lack of natural predators.
And as for the U.K. in particular, although some Canadian Geese have found their way east on their own, the birds were introduced to the area in the 17th century. Wikipedia:
Canada Geese have reached northern Europe naturally, as has been proved by ringing recoveries. The birds are of at least the subspecies parvipes, and possibly others. Canada Geese are also found naturally on the Kamchatka Peninsula in eastern Siberia, eastern China, and throughout Japan.
Greater Canada Geese have also been introduced in Europe, and have established populations in Great Britain, the Netherlands, Belgium, and Scandinavia. Semi-tame feral birds are common in parks, and have become a pest in some areas. The geese were first introduced in Britain in the late 17th century as an addition to King James II’s waterfowl collection in St. James’s Park.