Second North American Sea Duck Conference - Patuxent Wildlife ...

SECOND NORTH AMERICAN SEA DUCK CONFERENCE
MOVEMENT PATTERNS OF WINTERING SURF SCOTERS
IN COASTAL BRITISH COLUMBIA:
THE ROLES OF HABITAT AND PREY TYPE
Molly Kirk¹, Daniel Esler¹, Deb Lacroix¹, Sam Iverson¹ and Sean Boyd²
¹Centre for Wildlife Ecology, Simon Fraser University, Burnaby, BC; mkkirk@sfu.ca
²Pacific Wildlife Research Centre, Canadian Wildlife Service, Delta, BC.
Local movement patterns are important for understanding wildlife habitat associations, resource use,
and population structure. We evaluated the importance of habitat attributes, including prey type, on
movement patterns of surf scoters (Melanitta perspicillata) wintering in coastal British Columbia. Surf
scoters typically feed on mussels in rocky areas and on clams in soft-bottom areas. We hypothesized
that there are trade-offs associated with each habitat, which may influence foraging and movement
decisions. Radio telemetry was used to track surf scoter movements in two distinct locations with
different habitat types. Baynes Sound has extensive sand and mud flats with dense clam resources (n =
106 radio-marked surf scoters). The Malaspina Complex is a rocky fjord-like inlet where mussels grow
both on reefs and on shellfish farming structures (n = 74 radio-marked surf scoters). In Baynes Sound,
where clams are the principal prey resource, surf scoters exhibit low levels of movement and have
small winter home ranges (mean 95% khr = 5.09 km² ±1.19 SE). In this clam habitat, site fidelity was
evident within and between years. Preliminary results from the Malaspina Complex indicate that surf
scoters in mussel habitats display higher levels of movement and have larger home ranges (mean 95%
khr = 22.45 km² ± 3.25 SE). Mussels growing on aquaculture structures were preferentially depleted
and birds subsequently shifted into intertidal habitats or made long distance movements dispersing
from the study area. Survey data substantiate these distribution trends; surf scoter abundance estimates
within survey blocks were more consistent over time in Baynes Sound than in the Malaspina Complex.
These findings indicate that surf scoter movement strategies are environmentally-mediated, i.e.: the
foraging landscape dictates how scoter habitat use varies over space and time. Conclusions from our
study will assist in the conservation and management of surf scoter populations in British Columbia’s
changing coastal environment.
NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA
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