Hi! I understand you're not getting any sound for bird songs in the Merlin Bird ID app on your iPhone running iOS 18.5. I'd love to help you get this sorted. To make sure I suggest the best next steps, could you tell me if the issue is that you don't hear the bird song sounds that the app is trying to play back, or if the app is not picking up bird sounds when you try to record or identify them? Also, is this happening with all birds or just some specific ones?

In the meantime, here are some common things to check:
1. Make sure the volume on your iPhone is turned up and not muted or on silent mode.
2. Verify that Merlin Bird ID has permission to access your microphone: Go to Settings > Merlin Bird ID and check Microphone is enabled.
3. iOS 18 introduced a Sound Recognition feature that might need to be turned on for the app to pick up bird sounds properly. You can check this at Settings > Accessibility > Sound Recognition, and toggle it on if it’s off.
4. Try closing the app completely and restarting it. If that doesn’t work, restart your iPhone as well.
5. Ensure your Merlin Bird ID app is fully updated to the latest version from the App Store.

If the problem persists after these, I'd be happy to guide you through more advanced checks or settings. How does that sound?