J. Mikola et al., THE EFFECTS OF DISTURBANCE CAUSED BY BOATING ON SURVIVAL AND BEHAVIOROF VELVET SCOTER MELANITTA-FUSCA DUCKLINGS, Biological Conservation, 67(2), 1994, pp. 119-124
We studied the consequences of human disturbance and gull predation on
brood survival of velvet scoter Melanitta fusca in the Archipelago of
South-West Finland in 1990 and 1991. Each brood was exposed to distur
bance by boats on average 8.5 times a day in 1990 and 3.5 times a day
in 1991. Disturbance lengthened the swimming distances of ducklings an
d reduced the time used for feeding. Broods disturbed more frequently
than average were smaller than those disturbed less frequently. At lea
st 60% of ducklings died before the age of three weeks. The common pre
dators of ducklings in the study area are the herring gull Larus argen
tatus and the great black-backed gull Larus marinus. The daily predati
on rate by gulls on velvet scoter ducklings was 4.7%, which means that
56% of ducklings are caught by gulls during the first three weeks. Th
e frequency of gull attacks was 3.5 times higher in disturbed than in
undisturbed situations.