Invasive Alien Species in Northern Ireland

Branta canadensis, Canada Goose

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Branta canadensis
© Tom Ennis
Branta canadensis
© Tom Ennis
Branta canadensis
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Branta canadensis (L.)
Recent taxonomic changes (see links) have resulted in the former Canada goose being ‘split’ into two species greater and lesser Canada geese B.hutchinsii). The latter species occur as vagrants from North America, usually in the company of other wild geese and are thought to be rare amongst the feral populations. The greater Canada goose is the main subject of this web page.
As its name implies, the greater Canada goose is not a native species, but was introduced into wildfowl collections in England over 300 years ago. Since then it has spread throughout Britain where a large free-flying population (feral) has become established. It is also often associated with town park lakes and it has been identified as a pest in many areas, where it can damage both amenity grassland and agricultural crops. It has been slower to colonise Northern Ireland where most introductions date from the early twentieth century. It is now resident around Lough Erne, County Fermanagh and Strangford Lough, County Down, occasionally.
The greater Canada goose is a large bird with a long black neck, and brown body, paling on the breast and belly. It has distinctive white face patches which extend under the chin on an otherwise black head. In flight the bird shows large, dark wings and a U-shaped white rump. Its distinctive musical honking call often introduces its presence around the large waterbodies where it occurs. In their native North America a number of different forms of the goose occur. Indeed, the British and American Ornithologists’ Unions have recently divided the Canada goose into two species: the one discussed here, greater Canada goose (Branta Canadensis) and the other being named lesser Canada goose (B. hutchinsii), which is generally a smaller and darker bird. Originally a total of eleven subspecies of Canada goose were recognised. Since the division of the species into two, there are now considered to be seven races of greater Canada goose and four of lesser Canada goose.
Country of origin
The two species of Canada geese are native to North America. Greater Canada geese occur naturally along the eastern seaboard of Canada and the United States.
Current distribution
Well in excess of half a million greaters and lessers occur throughout the US and Canada. They have also been introduced to large parts of that continent through breeding programmes, expanding the range along both Atlantic and Pacific coasts. They were originally introduced into England in 1665 to St James’ Palace for the delight of Charles II. Many further introductions took place over the following centuries, usually associated with stately homes and estates. Many of these birds escaped to form self-sustaining feral populations. The population in Britain has increased in recent years and now numbers around 100,000 birds.
Location in Ireland
In Ireland, colonisation took place in the twentieth century. In Northern Ireland by 1953 a maximum of only 120 birds were estimated. Today this has increased to nearly 1,000 birds, most of which occur at two main sites, Lough Erne and Strangford Lough. In the Republic of Ireland breeding occurs mainly in Counties Cork, Cavan and Monaghan.
Life cycle
In its native North America the two species 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 or Strangford Lough for nesting.
The greater Canada goose lays five to six eggs, the young fledging in 68 to 78 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.
Wildlife and habitat impacts
In Northern Ireland there are no known major impacts on other wildlife, although the aggressive nature of nesting birds plus their colonial habits could affect some other species at a very local level, for example, on nesting islands and smaller loughs.
Flocks of geese can dramatically change grassland and wetland habitats through trampling, grazing and enrichment caused by their droppings. In parkland this is often more of an aesthetic problem but can still pose an enormous challenge to the management of amenity grassland. Some authorities also consider that abundant droppings in public places could be a health hazard due to the bacteria they contain.
Human impacts
Damage to amenity areas and agricultural land has brought this introduced species into conflict with humans. The problems are greatest in parts of Britain where numbers are highest. In Northern Ireland the birds, and therefore any problems, are very localised, although conflicts with farming interests do occur around the shores of Lough Erne in particular. The species is included as a quarry species under the Wildlife (NI) Order 1985 (as amended) which permits Canada geese to be killed or taken between 1 September and 31 January. Outside this period, where geese are causing damage to crops or other grassland, licences can be issued by the Department of the Environment for control purposes. Control measures in Britain have resulted in the establishment of various lobbying groups opposed to such actions.
Key vectors
Since the species is now established in the wild (feral) in Ireland, it is possible that it may spread to other suitable sites. Indeed it is somewhat surprising that it currently remains so localised. Further introductions to wildfowl collections could help to accelerate expansion if escapes are not prevented.
What you can do as an individual
Assist in monitoring the Northern Ireland population by participating in any censuses or reporting large groups of geese to the Northern Ireland Birdwatchers’ Association, Flightline (details below).
Report concerns about agricultural damage to Environment and Heritage Service of the Department of the Environment (Northern Ireland) and any possible health-related issues to the Area Environmental Health Officer.
Advice to specific groups relevant to this species
Groups should follow the guidelines listed above.
Management measures
Most species management relates to population control through egg pricking (that is, making them infertile) aimed at slowing down population growth. In some cases there may be a case for direct culling of adults if serious health risks have been identified.
Management groups
Department of Environment, Food and Rural Affairs (DEFRA) — Helpline Tel: 08459 335577 — responsible for UK policy.
Environment and Heritage Service (NI). Tel: 028 9025 1477 — responsible for licensing issues in Northern Ireland.
Wildfowl and Wetlands Trust — the leading authority on wildfowl issues in the UK. Slimbridge, Gloucester, GL2 7BT. Tel: 01453 891916.
RSPB, The Lodge, Sandy, Beds, SG19 2DL — Leading bird-based charity — provides information leaflets on the species and problems. The Lodge, Sandy, Beds., SG19 2DL. Tel: 01767 680551.
BASC — BASC Northern Ireland Centre, 33 Castle Street, Lisburn, County Down, BT27 4SP. Tel: 028 9260 5050. Control measures and hunting issues.
Northern Ireland Birdwatchers Association — reporting numbers and sightings, especially of potentially wild birds. Flightline for reporting sightings. Tel: 028 9146 7408.
Further information
A full explanation of recent taxonomic changes can be found on these web sites.
A simple, identification web-page.
Relevant legislation in Northern Ireland
Canada goose groups opposed to any control measures. Official line on control methods.
Banks, R.C., Cicero, C., Dunn, J.L., Kratter, A.W., Rasmussen, P.C., Remsen, J.V., Rising, J.D. and Stotz, D.F.. (2004). Forty-fifth supplement to the American Ornithologists' Union Check-list of North American Birds. Auk 121: 985-995.
Bellrose, F.C. (1976). Ducks, geese and swans of North America, 2nd edition. Stackpole Books, Pennsylvania.
Browne, A.M., O’Halloran, J. and Smiddy, P. (1999). Introduced Canada and Greylag Goose Populations in Ireland 1994. Irish Birds 6: 233-236.
Cramp, S. and Simmons, K.E.L. (1977). The Birds of the Western Palaearctic. Vol 1. Oxford University Press, Oxford.
Madge, S.C. and Burn, H. (1988). Wildfowl of the World: an identification guide. Croom Helm, Bromley.
Rehfisch, M.M., Austin, G.E., Holloway, S.J., Allan, J.R. and O’Connell, M. (2002). An approach to the assessment of change in the numbers of Canada Geese Branta canadensis and Greylag Geese Anser anser in southern Britain. Bird Study 49: 50-59.
Text written by:
Allen & Mellon Environmental Ltd.