I'm a big proponent of alternative energy solutions. On a broad scale, I think producing energy that doesn't rely on simply burning fossil fuels, combined with a reduced consumption, is the only long-term solution to global climate change issues.
However, global climate change is only one step of the environmental issues we're facing as a society. We're also threatening the healthy functioning of ecosystems by eliminating species through habitat destruction, introducing new species, etc.
Wind power is one of the most cost-effective alternatives to coal available today. The physics are simple, the mechanics are well-understood, and the supply of wind is abundant in many locations. Indeed, wind power is growing so fast the suppliers of turbines are having a hard time keeping up. The overall picture is that wind power is going to become an increasingly important part of our energy budget.
The downside? Like just about everything else we push up into the sky, wind turbines may take a pretty heavy toll on the bird populations. This paper suggests that most of the birds killed by a Minnesota wind farm were migrants, and in case anyone forgot, we have a treaty that covers migrants. Overall though, I haven't been able to find a lot of hard data on the magnitude of effects on birds, but as I've mentioned before, I have terrible journal access here. I'll be at the library later this week and I'll have to see if I can find out more then.
There seems to be some inherent reason to believe that this might be similar to what happens with bird-kills around cell and radio towers. The basic idea with the towers is that lights on the towers reflect off clouds, creating a "false dawn" that the birds respond to en-masse. The response? Flying around in circles while waiting for the sun to come up. Unfortunately, flying around a 400 foot tower supported by guyed wires isn't a great idea, even for birds with as much dexterity as a sparrow. Of course, the wind turbines don't have wires supporting them (at least, not as many), but the swinging blades might pose a similar hazard.
I mention this because a battle over the environmental impacts of wind is raging down in Texas. Essentially, the use of wind is going to lead to whole new areas of land being given over to energy production that were previously being used for something else. I think the large-scale, long-term benefits of increasing wind production and subsequently decreasing coal/petroleum use probably outweigh the impacts on migratory birds, but I'm not sure. I'm not sure enough information about the effect of wind turbines on bird populations is even known to answer that question.