As I enjoy the spring, a constant thought keeps circling in my mind: "What kind of bird is the one whose song I hear?" Birdsong is the sound of this season for me, and a free iPhone app adds more color to this mystery.

Merlin Bird ID, a great free app for identifying birds by sound

There are many iPhone apps that can identify birds visually or audibly. However, most of these apps require a paid subscription.

My curiosity about the source of bird song hasn't reached that level yet, but it might over time.

Fortunately, there is a great free iPhone app from the Cornell Ornithology Lab that can solve the great mystery of spring: Which bird is singing?

Merlin Bird ID is available for free on both iPhone and Android, and there's a reason it has a 4.9-star rating from 109K reviews on the App Store.

How to identify birds in your backyard with iPhone?

This app helps you identify the sound you hear by combining your general location with the sounds of birds singing or chirping. You can also take a photo of a bird and label it, but I mostly appreciated the Sound Recognition feature.

The transformation of this app from curiosity into a hobby happens with the Life List feature of Merlin Bird ID. This feature allows you to "collect" bird identifications by date, location, and of course, bird species.

For me, when I hear birds chirping, I pull out the app and try to memorize the song and the bird species. The next step is to invest in a smart bird feeder with a camera that can take pictures of the birds.

In the meantime, I’m happy to get to know local birds like the American Robin, Northern Cardinal, Tufted Titmouse, Carolina Wren, Chimney Swift, House Sparrow, and Fish Crow better.

You can learn more about Merlin Bird ID or download it for free from the App Store.