This is probably the best use of Christmas trees (though it’s up for debate whether it’s a good idea to cut down spruce trees to begin with).
Side note: it was hard to find this story on a website that’s not exclusive access or enshitified. Even the company who built the turbine (#Modvion) has a tor-hostile website themselves.
According to the BBC Newsroom they use glue instead of bolts to hold it together.
I think they said the blades were wood when I heard it on BBC.
W.r.t killing birds, I thought that was solved a long time ago just by increasing the resistance so the blades turn slowly enough to be seen. If wood blades would have to move faster, then perhaps the birds would be threatened again.