Merlin Bird and Audubon Bird Guide are both amazing resources and are well maintained and updated. They are both free and have a lot of the same features. At first, these apps might seem very similar. However, there are some big differences. I’ll start off with Merlin Bird. The Cornell Lab of Ornithology’s birding app has a couple of standout features. The app has a much cleaner interface with a simpler bird ID feature. You’ll answer five basic questions and it gives you a list of possible birds. It is very easy to use and is perfect for novices that do not have a lot prior knowledge about birds.
Another point for Merlin Bird is the variety of regions covered from all over the globe. They also let you download these regions individually, so you don’t have to fill up your device with information you don’t need. Merlin bird has a unique feature that allows you to take a photo of a bird and it will attempt to identify it. While it isn’t always accurate (or easy to get a good photo of a bird!) I am impressed by how often it gets it right. Even with photos I’ve taken at a distance the app has managed to identity the bird correctly.
Another nice feature is that the app integrates with Cornell’s other app, eBird. If you have a bird in eBird that you’ve identified it will display that in the Merlin app. It also has a nice ability that shows you a list of birds based on how likely it is that you’ll see them in your area.
The Audubon app has a lot of good features too. When trying to identify a bird, it has a lot more in-depth choices you can make to help narrow down the results. This is especially useful for more experienced birders. There is also a very useful feature that shows a map of local birding “hotspots” where other users have logged identifying a lot birds. If there is a specific bird you are looking for you can even look for places where it has been spotted recently. It also has a well organized catalog that makes it easy to look through birds.
I also think Audubon app has much more in-depth descriptions. Whereas the Merlin app just has a general description, the Audubon app has very detailed descriptions on everything from breeding patterns, nesting, eggs, and other behavior that might help you identify them or distinguish them from another similar bird.
Overall, I prefer to use the Audubon app while I’m in the states. Sadly, Audubon only covers birds that are in the United States and Canada regions. If you are outside of the United States, or if you are a beginner birder looking for a more user friendly interface, the Merlin app is for you.