The structure and behaviour of the Whooper Swan population wintering at Caerlaverock, Dumfries and Galloway, Scotland: an introductory study

摘要: Since the mid-1970s there has been an annual increase in number of Whooper Swans Cygnus cygnus wintering on Eastpark Wildfowl Refuge, Caerlaverock, Dumfries and Galloway, Scotland, which is now a site international importance for species. Between 1979-80 1983-4, 189 were marked with leg rings at Eastpark. Overall, 78% ring swans returned to least one winter 40% ringed 1979080 four successive years. first identified as pairs or families more likely return than singles yearlings. There was no significant difference rates male female swans. The population contained equal distribution two sexes. Singles formed largest social class (32.5%) showed little variation. proportion cygnets fluctuated, but average about 30% known brought young. Mean brood size ranged from 2.0 (198304) 3.5 (1982-3). Females paired earlier males. Only known-aged swan (five-year-old female) grounds offspring. Two (one firmly year old (second winter). Mates are frequently chosen flock. main arrival period during October most departed March. Yearlings arrived first, followed by families, then singles. departure patterns different classes. Single spent higher time away reserve other Sighting data support view that Icelandic breeding Caerlaverock area usually final destination these birds, rather staging migration Ireland. majority season Refuge also made use surrounding arable land especially autumn spring. Bewick's columbianus bewickii significantly less refuge. In October, fed mainly barley stubble grasses, moving potatoes aquatic river plants November December. Newly-planted grass favoured February until they left late March April. Grass species droppings. Activity budgets refuge feeding loafing water (both 30%) remainder day comfort behaviour (22%) grazing (8%). A comparison activity their seasonal variations Mute olor. Observations Islesteps (11 km NW Eastpark) indicate much (45%) (16% combined water), suggestions may benefit longer periods water. frequency aggression between Islesteps, although intense interaction occurred after grain put out. Aggression increased spring because coprophagy faeces large amounts undigested barley.