Analysis shows that New Zealand's Canada geese predominantly resemble the giant race B. c. maxima, suggesting interbreeding with B. c. canadensis.
Canada geese Branta canadensis became established in New Zealand following the introduction of 50 from central or eastern U.S.A. in 1905. In 1920 ten more were brought from western Canada. Examination of plumage, weights and measurements of the present population shows that it belongs predominantly to the giant race B. c. maxima Delacour. There is a possibility that B. c. canadensis interbred to a limited extent with it. Behaviourally and ecologically maxima appears very well suited to the South Island habitats in which it multiplied quickly.
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M. J. Imber (1971) studied this question.
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