ArtikelDilemma in een ganzenfamilie

Dilemma in een ganzenfamilie
Omslag Dilemma in een ganzenfamilie

A pair of Greater Canada Geese Branta canadensis hatched six chicks on a small island in a public park in Haren, Groningen, The Netherlands on 17 May 2013. Two chicks were white Domestic Geese Anser anser f. domestica, resulting from eggdumping.

One of these died, but the other thrived within its foster family. A second pair had bred successfully elsewhere in the village since 2011 and took one 24-25 days old chick to the park on 5 June, accompanied by two of their young of 2011 and five of 2012, plus two partners. These 12 individuals moulted their flight feathers in the park and remained together within the larger group of moulting birds. From early July onwards the two families increasingly foraged together.

Both families left the park together on August 8, when their young were 81-83 and 88-89 days old. The young Domestic goose stayed behind as it remained unable to fly, calling loudly. In the next three days it was visited several times by a foster-sister, once by a group of at least 13 marked geese, probably members of both families, and once by three marked (unidentified) birds, each visit involving much social interaction and calling.

These observations illustrate the strong bond between geese and their (foster) young of the year, but also between members of the wider family: the young of previous years and their partners in the second family remained in the park for at least a week after they had regained flight until their youngest sibling could fly as well, while other geese left the park as soon as they finished moult.