Title
Behaviour of Harlequin Ducks and three species of scoters wintering in the Queen Charlotte Islands, British Columbia
Author(s)
Goudie R.I.
Published
1999
Publisher
Occasional Paper of the Canadian Wildlife Service
Abstract
Diving behaviour and activity budgets were determined for Harlequin Ducks Histrionicus histrionicus and three species of scoters (Melanitta spp.) wintering in the Queen Charlotte Islands, British Columbia. Harlequin Ducks had the most diverse behavioural repertoires. Based on over 100 hours of behavioural sampling, the four species of sea ducks spent in excess of 60% of daylight hours in feeding activities. There was a general pattern of increased feeding from fall to winter, when daylight was shorter and inclement weather more frequent (ranging from an average of 52% of daylight hours in October to 71% in February). Harlequin Ducks did not spend significantly more time feeding than the larger scoters. Relatively mild climatic conditions, availability of energy-rich foods, and extensive shallow-water habitat may account for the lack of body size effect. Linear regression models indicated no significant relationship with environmental variables, whereas tidal regimes accounted for significant variation in proportion of time spent feeding in Black Scoters M. nigra and especially Harlequin Ducks. Harlequin Ducks decreased feeding activity with rising tides and increasing amplitudes, whereas Black Scoters increased feeding with increasing tidal amplitude. Harlequin Ducks and White-winged Scoters M. fusca exhibited the highest dive to pause ratios, although the difference from the Surf M. perspicillata and Black scoters was not marked. The analyses for sequence effects indicated that Harlequin Ducks and White-winged Scoters might defer full physiological recovery between dives during a diving sequence. Some possible explanations might include optimizing foraging during suitable tidal regimes, limited daylight hours during feeding in winter, optimal foraging of mobile prey items (e.g., crabs), and synchronized flock vigilance to minimize predation.
Keywords
activity pattern; diving behavior; feeding behavior; overwintering; waterfowl; Canada; Histrionicus histrionicus; Melanitta fusca; Melanitta nigra; Melanitta perspicillata
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PUB12771