Potential factors influencing increasing numbers of Canada Geese Branta canadensis in west Greenland

Abstract

This paper reviews the increase in abundance of Canada Geese Branta canadensis, particularly
those of the subspecies interior, in west Greenland over the last 20 years. Potential reasons
for the increase, such as displacement from traditional breeding areas on mainland North
America and regional variation in the breeding success of the population are discussed.
Breeding biology of Canada Geese nesting in Isunngua, west Greenland (67°N) was
monitored for the first time in 2010. The geese had identical mean first egg dates (27 May
2010) but greater mean clutch size compared to those nesting 1,300 km further south at
Ungava (58°N) in the same year (4.57 and 3.80 eggs, respectively). Mean May temperatures
in Isunngua were on average 2°C higher than in Ungava during 1979–2010, suggesting that
females may have been able to enhance reproductive investment in Isunngua relative to
Ungava in those years. Moreover, although data are currently only available for one year in
Greenland, nesting success there was as high as in other parts of the Canadian range of this
subspecies. Compared to the traditional Canadian nesting grounds, milder spring conditions,
potentially lower predation rate, availability of abundant food and lack of competition for
nest sites may have combined to help explain the rapid expansion of this goose population
in west Greenland.