Only two cygnets have been born and 12 eggs have disappeared. Staff at the Dawish town's aviary say they have never known a year like it and believe seagulls are to blame.
Dawlish waterfowl warden Derek Porter said if the swans leave their nest the seagulls are there straight away, the eggs are fairly big but the gulls manage to take them and damage them.
The blach swans have been a major tourist attraction in Dawlish and have been used as the town's emblem for more than 40 years.