Tuesday, 20 April 2010

Invasive Species: Canada Goose

Canada goose
Branta canadensis (Linnaeus, 1758)
Anatidae; Anseriformes; Aves; Chordata
Enfield Town
May 2009

Apart from the mallard (Anas platyrhynchos), the most ubiquitous anseriform (the term used to refer to ducks, geese, swans, and their kin) in British ponds, lakes, rivers, canals, and reservoirs is the Canada goose. The mallard is a native bird, but the Canada goose, as its name suggests, is North American in origin. It is a large bird, close in size to the smaller swan species, and is a vocal one too: gaggles (or skeins if they’re airborne, don’t forget that!) honk loudly.

Canada geese
Verulamium Park, St. Albans, Hertfordshire
July 2009

Canada geese were first introduced to Britain in the late 17th Century to St. James’s Park in London. Today, the park still boasts an impressive array of exotic waterfowl, including pelicans, but back then it was at the wishes of King James II to own flocks and gaggles of birds from other lands. The Canada geese escaped and bred, and they spread to all parts of Great Britain in decades.

Canada goose gosling
Original photograph taken in Enfield Town in June 2006
Popart version created in 2006

I was unfortunate (or fortunate, depending on how you look at it) enough to witness a young coot (Fulica atra) being drowned by a Canada goose. The goose was most likely being protective of its own offspring, a chain of eleven goslings taking up the rear of the two parent birds. If this happens on a regular basis, the geese could be responsible for declines in the population of other birds. I reported my concern to the RSPB (Royal Society for the Protection of Birds) at the time, but they said there was nothing that could be done with relation to culling the goose population, despite them being detrimental to other, native, bird species. It is now legal (since last year) to shoot Canada geese without a license, as well as several other invasive species.

Cackling goose
Branta hutchinsii (Richardson, 1832)
Anatidae; Anseriformes; Aves; Chordata
Slimbridge Wetland Centre, Gloucestershire
September 2009

Occasionally, the odd truly wild Canada goose enters the UK, within groups of migratory geese. Some of these belong to a different species (some consider it just a subspecies), the cackling goose, which is recognised by being smaller and with a white ‘collar’ at the base of the neck. The cackling goose is native to arctic Canada and Alaska, spending the winter further south towards Mexico. The British populations of Canada goose are non-migratory.

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