12 September 1997

Successful goose ruffles feathers

THE Canada goose, Britains biggest wild goose, is a handsome bird.

With black head and neck, broad white cheek flashes which extend under the chin, white front and grey-brown wings, it is readily identified and a gaggle in full sail under a summer sun is a fine sight.

It was first introduced to Britain in 1664 into the St James Park waterfowl collection of King Charles II, but the numbers of Canada geese in Britain remained low, despite further introductions.

However, in the 1950s, the Wildfowlers Association of Great Britain and Ireland promoted translocation of the geese throughout the country as a quarry species for its members and the spread was started. Encouraged by feeding on park ponds and introduced onto estate lakes, its elegant frame is as familiar today as the ubiquitous mallard on many still waters.

Its success has ruffled more than a few homo sapiens feathers on the way. Living in large groups and family parties, they feed on farmland and their droppings sour grass and foul park lakes and watersides.

Some pundits say the Canada goose has been too successful for its own good and that numbers should be controlled.

Population increase

Ornithologist Graham Austin of the British Trust for Ornithology (BTO) says that the birds population had increased from 3900 individuals in 1953, to 64,000. "Thats quite a lot of weight. At the moment there may be over 400t of adult Canada geese in the country."

According to statistics, a Canada goose will consume more grass than a sheep a day and that, say affected farmers, is too much.

The main concern among farmers is the species habit of grazing new spring growth and newly emerged arable crops in autumn, as well as trampling and stripping the grain from ripening crops in July and August. In addition to causing direct loss, the damage may lead to uneven ripening of crops and increased susceptibility to disease. In spring these geese may compete directly with livestock for scarce forage.

However, past control methods have shown only very local effect and any future attempts should be based on sound ecological knowledge if they are to be both successful and humane.

The Department of the Environment has established a Canada goose working group and provided funding for a joint project between the BTO and the Wildfowl and Wetlands Trust aimed at understanding the population dynamics of the species in this country.

Regional control measures are likely to be taken to curb their numbers and the results of BTO findings have clear implications for the seasonal timing of any attempt to control local populations of Canada geese.

Late June through to August is the best time for control. In the autumn populations are at their most mobile when a far higher proportion of geese in a given locality will not be of local origin. Before this time, adults which have bred successfully will still be in their breeding areas together with their progeny.

It is usually assumed that young birds generally have a lower survival rate than older birds because the young are at risk while they learn to feed, avoid predation (and shooting in the case of wildfowl) and generally get used to life without the protection of their parents.

Not so with our Canada geese. Unlike North American Canada geese, British Canada geese are largely non-migratory. The young remain in tight family groups during their first autumn and winter, giving them the protection they need.

Increased competition between individuals for a limited amount of food could in itself be a controlling factor. Data from the BTOs Wetland Bird Survey showed that Canada goose populations in several parts of Britain appear to be stabilising, suggesting that density-dependent processes might be in operation.

Michael Edwards

&#8226 The British Trust for Ornithology is a charity dedicated to researching birds found in the UK. If you would like to know more about their work with Canada geese or other birds contact:

The National Centre for Ornithology,

The Nunnery, Thetford, Norfolk IP24 2PU. (01842-750050).

Canada geese look smart and have been introduced to country estates as ornamental waterfowl, but may now be too numerous for their own good.