Canoes have the potential to be a more serious problem, as curious canoeists can penetrate nest clusters, where they may tip over nests and disturb adults and chicks. Predation Caspian and Common terns nest in dense colonies on the ground and this makes them particularly vulnerable to predation by mammals. This is why they prefer to nest on islands. Islands are relatively inaccessible and this gives some protection from disturbance by ground predators and humans. Dogs can also be a serious problem in mainland colonies because they trample on eggs and chicks and cause major disruption, although they do not normally eat eggs or birds.
Avian predation can also occur.
Spawning carp may knock eggs into the water, while muskrats, rebuilding their houses after storms and heavy rain, may cover over or damage nests and their contents. Information herein is provided by the Government of Canada. Its use and reference is unlimited, upon condition that the source is correctly attributed.