I doubt that wind turbines are the only power source that kills birds. Marginal bird deaths per unit of power production is the interesting statistic. This MIT post [1] links to a 2009 study [2] which provides that comparison:

  Wind/nuclear: 0.3-0.4 birds/GWh
  Fossil: 5.2 birds/GWh

So if you’re pro bird you’re pro wind power.

[1]: https://climate.mit.edu/ask-mit/do-wind-turbines-kill-birds

[2]: https://www.sciencedirect.com/science/article/abs/pii/S09601...