There are no environmental drawbacks to wind energy.

Birds and bats are killed by windmill blades, but their numbers are small when
compared to the numbers of animals killed flying into glass in buildings. Nevertheless, this
is a drawback, especially if the windmill is sited in an area that is home to endangered
species.
Environmental advocates have pointed out that windmills set on mountaintops can subtract
esthetically from the esthetic experience of nature. Opponents of Cape Wind, a proposed
wind farm off Cape Cod, Nantucket, and Martha's Vineyard that would involve more than a
hundred windmills generating 420 MW, have cited esthetics in support of their position
(they don't want to have a view of the windmills and worry that it would reduce tourism).
When that argument gained little traction, opponents turned to claiming that the windmills
would interfere with radar. A decision is expected in the fall of 2007 . A similar esthetic
argument was used in Greenbriar, West Virginia against a project to build windmills to
generate 186 MW, with locals worrying that windmills on mountaintops would discourage
tourists. It did not deter the state from approving the wind farm.
Additionally, the blades make a noise when they move that many neighbors find extremely
annoying.
Overall, there are drawbacks, but also good reasons to prefer windmills to generate energy.