Well, good luck identifying mockingbirds, lol. But that's a tricky case.
Anyway, it's a nice way to use AI, unlike so many others that pop up lately.
I wish they'd open source it all though, especially if they are getting help from volunteers.
Mockingbirds do a minimum of three repeats of any particular sound before moving onto the next. So the songs are done more times in a row than the real species would and then immediately it turns into a Robin (or something else). I'm sure there's subtle audio differences between a mockingbird and the real thing too that Merlin can detect.
A feature I'd love would be if Merlin told you the call the bird was making rather than just the bird ID. eg. "Blue Jay mimicking a Red Shouldered Hawk" would be a cool bit of info it could give since it really does catch the mimics out really well. It currently just says "Blue Jay" when it hears a blue jay trying to be a red shouldered hawk.
But I agree with you that it gets those things correct most of the time and it also seems to be improving over time.
Pointing this out on HN has sometimes resulted in a lot of upvotes and sometimes in a lot of downvotes. I don't know why. In all cases, Seek identifications are unlikely to be correct.
(I also got one response saying I was wrong to try to tar iNaturalist by association with the unaffiliated app "Seek by iNaturalist". As the name of the app suggests, they are not in fact unaffiliated.)
But it’s very very good.