I will never not be amazed at the Sound ID feature. And I have spent a concerning amount of time trying to fake a bird call good enough to fool the app. It is my White Whale
No joke about a month ago I found out about that app, and now I'm obsessing over bird feeders and trying to run away house sparrows. This app is DANGEROUS, it's probably more addictive than cocaine.
Merlin identifies birds as soon as it thinks it hears one; that is quite nice. I can click on the listed bird and it will jump to the section(s) of the recording where it heard the bird. Iirc birdnet makes you create a selection. I am no expert but they both seem accurate.
WhoBIRD has been working well for me. Doesn't have the visual ID stuff that Merlin has, but it's FOSS and identifies by sound, based on location and time of year.
Granted, I don't know enough to know when it's wrong, and I bet it's not great for identifying rare birds, but it's fun.
I did use BirdNet for quite some time before whoBIRD was available, but it's so great to be able to open up the app (whoBIRD) wherever and have it identify the birds we're hearing without having to wait for a network round trip. The somewhat recent feature of showing bird photos in whoBIRD is nice as well.
Running the app from time to time has had me notice birds in the area I would've otherwise missed.
Thanks to the app, I saw a long tailed tit for the first time and even managed to get a few photos! (They were mixed in with other bird song, but the app said they were singing in the area too. After a little searching, we found them.)
It's definitely an app that would make someone install F-Droid on Android if they haven't already. (As it's only available on F-Droid and not Google Play.)