A palm warbler is spotted perched in a treetop. Credit: Courtesy of Bob Duchesne

Memory is a funny thing. I can recall bird songs I heard 30 years ago, but I can’t remember where I left the car keys. Birding-by-ear is my sole superpower. As superpowers go, it’s not as useful as invisibility or, say, predicting winning lottery numbers, but I’ll take it. I don’t recognize 100 percent of all the bird noises in Maine. I’m probably down somewhere around 99 percent.

So I was shocked to hear an unknown bird noise this week. It sounded like a raptor, but not one that I recognized.

It was my perfect opportunity to try out Merlin — a free app for smartphones that can identify bird sounds. I held my phone in the direction of the weird call, and Merlin instantly told me it was a sharp-shinned hawk. I’ve seen hundreds of these small woodland hawks, but they seldom make any noise except near a nest. Seconds later, a male flew over, as the female continued calling from the backside of the grove, confirming the identification.

Thus, today, I am here to recommend Merlin, an app offered by the Cornell Lab of Ornithology from its website at Merlin.AllAboutBirds.org. I don’t do so lightly. There have been several commercial attempts to produce such an app over the last decade. Generally, they have disappointed. They were often wrong, or they offered too many potential IDs to be effective. I put Merlin to the test and was quite pleased with the result, although even Merlin admits it’s not perfect.

It works like this. Merlin uses your phone to “listen” for birds. It then makes a sonogram of everything it hears. A sonogram is just a graphic representation of recorded sound — a technique that has been around since 1929. Nowadays, computing technology can compare your digital recording with a massive database of recorded songs, and the app just looks for the best match. It’s quick, and usually right. But not always.

I tried it on some tough birds over the weekend. I pointed it at a singing palm warbler — a bird you can hear right now, if you walk the back side of the Orono Bog Boardwalk. Merlin immediately identified the song as an orange-crowned warbler. Epic fail! Orange-crowned warblers are rare vagrants to Maine from their subarctic breeding grounds. They are almost never here in summer, let alone singing. Admittedly, the two birds sound similar, but I was staring directly at the palm warbler as Merlin misidentified it.

Worse, Merlin told me it was also hearing a northern cardinal. Actually, it wasn’t. I was deep in the woods west of Moosehead Lake. A cardinal wouldn’t be caught dead in those woods, and I couldn’t hear anything that might even be mistaken for a cardinal.

I continued testing, and Merlin started passing all my tests. It could tell the difference between pine warblers, chipping sparrows, swamp sparrows and dark-eyed juncos. All four birds trill in a similar fashion, but Merlin quickly figured it out. I tried it on a gray catbird. Catbirds don’t have a song of their own. They steal the songs of other birds, then meld them together into a jumble of entertaining notes. Merlin guessed correctly.

I tried Merlin near the Bangor Mall, where highway noise and other urban clamor might obscure bird song. Merlin was not fooled. If it could hear a bird, it could identify it.

I tried it on a song sparrow call note, which is just a single, solitary chip. Merlin won.

I tried it in a spot with multiple singing birds. Despite the cacophony, it correctly guessed all six species within seconds. Each time Merlin recognizes a bird, it adds a photo and link to the display, making it easy to investigate further. Impressive.

Review caveats: I found that my ears are better than my smartphone’s. I could hear and identify birds that were much farther away. However, these days some people with hearing loss are using Merlin to listen for birds they can’t hear. Thus alerted, they know what to look for. However, given that Merlin can make mistakes, I agree with the old adage: trust but verify. Don’t just assume that the bird is present, merely because Merlin says so.

I’ll continue testing, mostly because I want to see how often I can defeat it, just for fun. The songs of red-eyed and Philadelphia vireos are so similar that I often can’t tell them apart. We’ll see if Merlin can do it. Now I just have to find a Philadelphia vireo.

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Bob Duchesne, Good Birding

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.