THE TIMING OF PAIR FORMATION IN HARLEQUIN DUCKS

The timing of pair formation varies within and among species of ducks. In this study we documented the chronology of pair formation in a pop ulation of wintering Harlequin Ducks (Histrionicus histrionicus) in so uthwestern British Columbia. Harlequin Ducks began forming pair bonds in October and over half of the females were paired by December. This timing is much earlier than other ducks of similar size. A segment of this population was individually marked, and we documented the reunion of mates in subsequent years. In all cases where both members of the pair returned to their wintering grounds they reunited in the fall. Ne w pair bonds, involving young males and females, were formed in the sp ring. We suggest that pair reunion in this species reduces the costs o f courtship and pair bond maintenance and arrows males to pair early i n the nonbreeding season, compared to other species.