Broedende Wilde Zwaan Cygnus cygnus, onverwachte nieuwe Drentse aanwinst

In 2005 the Whooper Swan was recorded as a new breeding bird in the Netherlands. The nest was found in a riverine peatland in southwestern Drenthe (52°50’N, 6°12’E). In April six eggs were laid, and on 23 May four cygnets hatched. After 21 days all young had disappeared. With the exception of the period mid-August – mid-October 2005 the breeding birds stayed in the area. In the first week of April 2006 the same pair was found breeding, using the same nest that contained three eggs. On 4 May two cygnets hatched. After 120 days, at the end of August, the young were able to fly. Until January 2007 the family was regularly observed in the breeding area. In 2005 after hatching the cygnets stayed near the nest site and commuted to the adjacent Polder Ten Kate for feeding. In 2006, the family almost immediately moved to this polder. By the end of July they moved to a nearby sand pit. After two weeks they headed to another sand pit at 5 km distance, swimming via canals and ditches.Most of the time the incubating female was vigilant or sleeping. The male slept occasionally and was very vigilant close to the nest. Almost daily both parents made feeding trips (on average 1 hour long) to nearby marshland with dominant Water Horsetail or pastures with Ryegrass. During chick-rearing, both parents spent approximately half of the time feeding. For a third of the time, the male was vigilant. In the course of the season the time spent in vigilance diminished, and preening increased. The female always stayed close to the cygnets. On 31 August 2006, when the young were observed flying for the first time, the female had started wing moult. The male followed 15 days later. After approximately 30-38 days both adults were able to fly again. The main food resource of the parents and cygnets at the nesting site was Stonewort. In Polder Ten Kate the family predominantly fed on younger stems and leaves of Water Horsetail and to a lesser extend leaves, stems and sometimes roots of several species of sedges, grasses and some dicotyledons. In the sand pits the swans fed on rhizomes of Fennel Pondweed and leaves of Common Reed.Colonisation of The Netherlands is in line with the recent breeding range expansion of the increasing Northwest-European population.