I didn't know that birds can overheat. Got to wave 7 with 3800 score.
The game is simple to understand, and the tutorial did a nice job. I wish it explained you can't connect one bird with multiple lines though. Having multiple colors of threats is a nice touch.
The only issue I found was the controls - these definitely work but I think it could use some polish e.g. have larger click radius when connecting birds. Also, I think making maximum connection radius have more contrast could help.
Overall, I think this game could find its place in time killers realm. Nicely done!