Developed by the Cornell Lab of Ornithology, this smartphone app available on Apple earlier this year is now available for Android devices which run OS 4 or higher. The app covers 400 of the most common birds. By answering simple questions such as What size was the bird? or What were the main colours? or types of activities of the bird Merlin will come up with the answer based on results of more than 70 million sightings submitted to eBird. This free app has more than 1000 bird photos, ID text, range maps and you can listen to the birds song. Beware though that with all these features the app is 443 MB in size, now version 1.0.60.
Paid apps include iBird Pro is the best digital app in my opinion and many birders like The Sibley eGuide to Birds and last but not least National Geographic Birds app. The three paid apps are also available in the Windows Store.