Seasonal and diurnal patterns of behaviour and movements of the Canada goose (Branta canadensis) In Christchurch City and Central Canterbury, New Zealand
The growing conflict between wildlife and humans continues as we expand our reach and movements globally. In New Zealand, the Canada goose (Branta canadensis) was introduced last century as a game species but recent increases in their populations present concern for civil and military aviation in the region as there is little information on the movements and behaviour of geese in this region. Utilising GPS tracking technology, I investigated the spatial and temporal patterns of Canada goose movements in central Canterbury. Transect surveys were also used to identify key habitats and quantify behaviours of urban goose populations in Christchurch. Field surveys and tracking of geese were conducted from November 2018 to January 2020. GPS- collars were fitted on 10 Canada geese at three habitats; Lake Ellesmere/Te Waihora (n = 3), Lake Grasmere (n = 3) and central Christchurch city (n = 4). A detailed study comparing the behaviour of geese fitted with GPS collars and control birds (no collars) found no major differences, indicating the collars likely had little effect on the geese. Long distance movements of Canada geese mostly occurred during spring with birds flying >20 km and as far as 115.6 km from point of being tagged. The long-distance flights coincided with a dispersal of geese away from the coast to inland breeding sites. Long distance movements took place again in early summer when geese returned to coastal moulting sites, travelling up to 128.8 km. Home range size varied between individuals, with the range of a Lake Ellesmere/Te Waihora goose spanning 20,540 km2 during November 2019. In contrast, city birds only averaged ranges of 9.47 km2 for the whole year, with a single goose peaking at 80 km2 in August. Data on altitude and velocity of flights showed peaks during September and two distinct increases in diurnal activity from 05:00 to 08:00 am and 16:00 to 20:00 pm. Foraging behaviour was seen most often in ‘red zone’ paddocks and showed significant increases from spring to summer, and then decreases from autumn to winter. These trends coincide with the moult period and increase in body condition for winter, respectively. A large resident population of Canada geese in the Christchurch area, along with overwintering densities reaching 112.8 geese/ha on urban lakes, poses questionsabout whether this increase is the result of an influx from rural populations or a consolidation of urban birds in fewer sites. This study presents results that may assist future management of Canada geese and improve the assessment of the risk they pose to civil and military aviation in the Canterbury region.