Hi! I wanted to share a resource page I created for Kitizen Science. I wrote an introduction to research issues and terminology, and then summarized the 35 articles that have been published in academic journals in North America that make a claim about the effects of spay/neuter. Many cat advocacy groups have similar lists, but omit the studies that conclude that spay/neuter or TNR didn't work. And, of course, bird conservation websites only list those studies, and none of the ones that you'd find listed on cat advocacy websites.
I think it's important to be familiar with the entire body of evidence and not limit ourselves to reading only research whose conclusions we agree with. There's real value to reading studies that don't support spay/neuter for free-roaming cat management, because if you're into debating these issues, they will be brought up by other people. For me, it was a good exercise to read all of these, because it's helped me understand the strengths and weaknesses of different studies so I can design better research going forward.