Within-Season Moulting And Wintering Site Philopatry In Harlequin Duck

Robertson, Gregory J.
Cooke, Fred
Fraser, Simon
Goudie, R. I.
Canadian Wildlife Service

A small population of moulting and wintering Harlequin ducks were monitored between July 1994 and May 1995 near White Rock, B.C. In all 72 birds were captured during the wing moult and were banded with individually identifiable coloured tarsal bands. Males arrived in mid-June, moulted in August, and were in their alternate plumage by early October. Females arrived in mid-August and moulted in September. There were three patterns of habitat use over the winter season; some individuals spent the entire period (Aug. - May) in the study area, other birds permanently left the area in the fall, and finally, some birds appeared to leave the study area in the winter only to reappear in the spring. Adult birds paired in October and November, while 2 (a second and a third winter) females did not pair until March, 31% of 29 adult males never found a mate. Unpaired males were seen at a greater variety of sites than paired males. Before pairing, males were seen at a greater variety of sites than females. Within sea son observations of individuals show that individuals use very specific stretches of shoreline within the available habitat. Three pairs seen during the 1994-1995 winter period re-paired in the fall of 1995. One female marked on the breeding grounds in Montana and one pair marked in Banff have been sighted in the area. 28 of 39 (71.8%) banded males and 19 of 29 (65.5%) females returned to moult in White Rock in the fall 1995, demonstrating a high site fidelity to the moulting grounds.