The Cackling Goose
Branta hutchinsii (pres leucopareia)

The Cackling Goose was long considered just a small race of the Canada Goose. The smallest four of the eleven recognized races were recently determined to be distinct enough to be their own species. Cackling Goose includes the races known as Taverner's, Richardson's, Aleutian, and Cackling geese. Confusingly, the "Lesser Canada Goose" is still a race of the Canada Goose.
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All About Birds: Cackling Goose

Length of neck in flight can be a useful indicator of species (shorter for Cackling Geese, longer for Canada Geese); however, because geese can elongate or retract their necks, neck length can be difficult to determine in swimming or sitting birds. Due to their smaller size, Cackling Geese (especially B.h. minima) display a faster wingbeat than Canada Geese and their wings appear longer proportionally to their body size in flight.

Cackling Geese do not show any seasonal variation and sexes are alike, although males are slightly larger.
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Cackling Goose - BirdWeb

Population: Down to less than 500 birds in the 1970s, the Aleutian Cackling goose is a success story in waterfowl management. Presently, population estimates based on observations of neck-banded Aleutian Cackling geese during winter 2006-07 was 118,700, 13% greater than the previous year. Estimates for Aleutian Cackling geese increased an average of 14% per year from 1997-2006. This year's fall estimate of Cackling geese is 173,400 geese. The estimate for Taverner's Cackling geese (a pooled estimate of Taverner's and Lesser Canada geese) was 74,400 birds for 2007. The Richardson's (Hutchins's) goose subspecies is thought to be increasing, with population estimates greater than 680,000 in 2007.
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Cackling Goose Facts, Figures, Description and Photo

Life cycle
In its native North America the various races of Canada goose occupy a wide range of different habitats from tundra to woodland lakes and prairie. In Britain and Ireland the species is closely associated with larger waterbodies, both coastal and freshwater. The birds feed on adjacent grassland and can gather in large flocks during the winter months. In the breeding season it is loosely colonial and in Northern Ireland favours islands on Lough Erne, County Fermanagh or Strangford Lough, County Down for nesting.
The Canada goose lays five to six eggs, the young fledging in sixty-eight to seventy-eight days from the time of laying. In Britain, the much longer established populations have new migration routes within the country, mimicking their natural behaviour. In Ireland, movements are much more localised and between favoured feeding sites.
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Branta canadensis :: Invasive Aliens in Northern Ireland ::