On the subject of birds, "Great tits also have age-related defects"

https://www.sciencedaily.com/releases/2011/03/110307130215.h...

Is this basically just taking a Fermi type estimation and making a paper out of it?

I was just thinking that I like doing those sorts of calculations, and given that so many people on the Internet profess to hate them, there should be an exploitable niche somewhere.

Do you have a freely accessible copy of this paper?

In that case, if you lay outdoors with your mouth open, how long does it take until a bird ... in it? Depending on the worldwide bird density and the relative size of the mouth: https://what-if.xkcd.com/11/