Mute Swans

Scientific Name: Cygnus olor

Damage:

There is a debate surrounding this exotic species (it is not a native of North America as it was imported from Europe in the late 1800's), regarding whether or not it is a threat to native ecosystems.

Here are the facts:

Their longer necks allow them to remove pond vegetation at deeper levels then other birds possibly harming the ability of native geese to reach food.
Mute swans tend to pull up plants by the roots thereby hindering the plant's ability to replenish.
Must swans are very aggressive in defending their territory. (some people have imported them in hopes of keeping Canada Geese away. This has met with mixed results. Warning: no one should translocate wildlife without explicit permission from their state's wildlife agency.)