Merlin ID - an excellent bird ID app

Merlin ID is a rather good new free app which is ideal for anyone who wants to know what birds they are listening to. Download the app to begin with.

When you are out on a walk, choose SOUND ID and press the green button.

Merlin identifies bird sounds using breakthroughs in machine learning technology to recognize species based on spectrograms—visual representations of sounds. For Merlin to learn to recognize a species by sound, we use audio recordings from the Macaulay Library that include a variety of sounds for each species to “train” Merlin.

Your smartphone's microphone will be used to record sounds in real time, and as the software identifies a match with a bird that is singing, it will appear on the screen, and you can compare the suggestion with what you are hearing.

Here's what it picked up on a walk I took yesterday's evening. 

As the bird's name popped up I heard it's call as separate from the others, which helped me potentially learn it in the future.
Each sound file can be uploaded to help Merlin ID 'learn'.

As the main website says:

Sound ID is currently available for 1,000+ species. You can view a list of all species covered by Sound ID here. Sound ID will be expanded in the future to include species worldwide, but to do that, our team needs a minimum of 150 sound recordings for each species to train Merlin to recognize their sounds. You can help us add new species to Merlin by recording the birds in your area and uploading them with your eBird checklists.

This will be a wonderful app for those who are planning to investigate bird habitats and particular species.
It's currently FREE but I wonder whether there are plans to start charging over time as the app gets more accurate.