Winter Philopatry In Harlequin Ducks: Implications For Their Conservation In The Strait Of Georgia, BC

Robertson, Gregory J.
Goudie, R. I.
Boyd, W.S.

Habitat use and requirements for wintering birds has only recently received attention compared to breeding habitat use and requirements. For waterfowl, quality wintering habitat is important for not only surviving the winter period, but for courtship and pair bond formation as well. Harlequin Ducks are a small sea duck that nest on mountain streams and winter on coastal rocky shores. We have been marking a portion of the Harlequin Duck population in the Strait of Georgia with small tarsal leg bands annual ly since 1993. One of our main objectives is to estimate the rate at which individuals utilize the same wintering sites between years. A focal population at White Rock, BC consisting of about 100 individuals has been intensively studied to achieve this ob jective. Over half and up to 3/4 of the individuals marked in one year returned to the site in a later year. If both members of a pair return to the same wintering grounds they will re-unite. Limited data for younger age classes suggest that they have low er return rates. This tendency for individuals to return to the same site year after year has significant conservation implications for these birds. One, is that local populations may be genetically isolated reducing the effective population size. Second ly, major local habitat degredation may result in the loss of local populations with no subsequent recolonization even if the habitat is restored. Thirdly, chronic disturbances and minor habitat degredation may cause birds to lose body condition which may result in poor productivity in the following breeding effort. Harlequin Ducks are currently listed as endangered on the east coast of North America, as such, they are known to be a very sensitive species. Threats to this species and its' habitat should be considered very real conservation concerns.