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Austin, G.A., Rehfisch,
M.R., Allan, J.R. & Holloway, S.J. 2007. Populaton size and differential
population growth of introduced Greater Canada Geese Branta canadensis
and re-established Greylag Geese Anser anser across habitats
in Great Britain in the year 2000. Bird Study 54: 343-352.
Abstract
Capsule
Both populations are increasing at a similar rate.
Aims
During 2000, an extensive survey of introduced Greater Canada
Geese and re-established Greylag Geese in Great Britain was undertaken
in order to update population estimates last made between 1988 and 1991.
Methods
A randomized stratified sample of 1329 of the 61 510 tetrads
(2km x 2km unit) in Great Britain was surveyed. The habitat categories,
or strata were based on the proportion of water cover, urbanization,
and upland/lowland in each tetrad. Non-urbanized strata were further
divided into northern and southern reporting areas.
Results
In 2000 there were an estimated 88 866 full-grown Greater Canada Geese
and 24 522 full-grown Greylag Geese in Great Britain. Since the 1988-91
survey, Greater Canada Geese have increased by 166% and Greylag Geese
by 170%, an average per annum rate of increase of 9.3% for Greater Canada
Geese and 9.4% for Greylag Geese. The increase in Greater Canada Goose
numbers since the 1988-91 survey has occurred mainly in habitats which
had previously held low goose population densities, particularly the
‘no water’ lowland habitat. Although densities were still
relatively low in this habitat (<0.5 geese per km2), because
of its extent it supported 56% of the total Greater Canada Goose population
in 2000. The greatest increase in re-established Greylag Goose numbers
has arisen from an expansion into lowland habitat with some water cover.
Conclusion
There was no obvious decline in the 8.3% per annum Greater Canada Goose
growth rate that caused the population to treble between 1976 and 1991.
Greylag Goose numbers are increasing at a similar rate to those of the
Greater Canada Goose.
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