iOS app "Requires iOS 13 or later" :-/ . Too bad I can't use this on my still functional-and-receiving-security-upgrades iPhone 6. I suspect an overlap between the population enjoying birds and the population not buying a new phone every year, so I hope they can reconsider and broaden support.

I contacted the authors at the email on the page, asking them to support iOS 12. Maybe email them too if you're also impacted.