Of course course even wind isn't the perfect energy source. Wind turbines depend on the air actually moving in order to produce electricity, and unlike the water flowing through a dam wind tends to be less than continuous. That means that the energy needs to be stored for downtimes. When the wind does blow, the turbines spin and anything moving through the path of the blades tends to meet an untimely demise. As more wind turbines are put up more birds and bats are getting killed.
[Source: American Wind Energy Association]