Editor’s Note: This article was originally published in the Summer 2023 issue of New Hampshire Bird Records. 

Bernd Heinrich described the sensation of finding a bird with telemetry equipment for the first time in Mind of the Raven, likening it to a superpower. I felt the same thing the first time I found a condor with a telemetry antenna, and I can raise the same feeling when I really think about Cornell’s Merlin app. Merlin uses your phone’s microphone to analyze bird sounds and suggests identification with remarkable accuracy. Keyword “suggests.” In capable hands, Merlin is a modern miracle, but beware it can lead you astray! I’ve never been a natural ear-birder. Every year, just before spring, I gather up all my resources and re-train using all the tricks and I still struggle and sometimes forget and embarrass myself. This is where I seek suggestions from Merlin. 

Walking through the wood in early spring in New Hampshire can be a little overwhelming on the ears. A dozen or more songs coming from every direction, many high up in the leaves. The ears and mind tire after filtering copious vireos and warblers. Lifting my phone before me, Merlin begins listing birds: Chipping Sparrow, Chestnut-sided Warbler, Pine Warbler, Yellow Warbler, Philadelphia Vireo, Red-eyed Vireo, Blue-headed Vireo… I’m connecting the dots between the listed birds and the songs I’m hearing. Sometimes my ears are picking up a Red-eyed Vireo right above me and another one just a little ways farther down the trail and a third one in the other direction, but I’m not sure I actually hear that Philly Vireo, and I certainly don’t see one. I guess it’s best to trust Merlin and just put it on my list, right? Not. 

Here’s where birders must engage their other resources, because Merlin should be just one of your birding tools. How well do you know your vocalizations? Is it the right time of year to find this bird here? Is the habitat right? Should you get a visual confirmation? Based on some preliminary research, it appears that Red-eyed and Philadelphia Vireos are not distinguishable by vocalization alone in New Hampshire. As Red-eyeds are ubiquitous here, they are by far more likely and NHeBird reviewers won’t typically accept a Philadelphia report without visual confirmation. Red-eyed and Philadelphia Vireo songs are similar enough that I’ve literally been looking at a singing Red-eyed and watched Merlin report it as both species simultaneously. 

Merlin takes location into consideration when suggesting IDs, so be careful if you’ve recently traveled. I’ve experienced glitches with this feature and Merlin reported a Mountain Elaenia in Concord and a Eurasian Eagle-Owl on the coast. I’ve also had Merlin mistake background sounds like cars or kids as birds. Again, consider Merlin’s suggestions, but use your other tools to confirm (preferably visually) before filling out your eBird list. Here are some Merlin mistakes I picked up during the summer of 2023 that Merlin users should watch out for. 

The above discussed Red-eyed Vireo/Philadelphia Vireo issue came up for me a few times a month. On a couple of occasions Blue-headed Vireo was added to the mix. Range is a good clue in scrutinizing this Merlin ID. Philadelphia Vireos migrate all across the state and nest in the far north, so finding one anywhere is a possibility, but visual confirmation is essential. 

I occasionally experienced confusion between Chestnut-sided Warbler and Yellow Warbler, typically at the start of a Merlin recording, as if the app had to warm up a little before making the correct ID. Chestnut-sided Warblers have an alternate song that sounds a little like a Yellow Warbler, and Yellow Warblers have an alternate song that sounds a little like a Chestnut-sided. Habitat is a good clue with these species, although there is overlap. Patience in listening to more vocalizations may clear things up. 

Confusion between Cerulean Warbler and Black-throated Blue Warbler vocalizations has been discussed in previous issues of this publication, and I have seen Merlin make this error in southern areas of the state. Cerulean Warblers are rare and any suspected birds need to be visually confirmed. 

Orchard Oriole and Baltimore Oriole each have an exciting repertoire of whistles and rattles with some overlap. Knowledge of status and distribution is the place to start. Baltimore is widespread whereas Orchard is limited to a handful of reliable spots. When in doubt, get visual confirmation. 

Lastly, a frequent issue from traveling birders in the summer was confusion between Swamp Sparrow, Chipping Sparrow, Dark-eyed Junco, Pine Warbler, and Worm-eating Warbler. Again, birders can use their knowledge of range and habitat to judge Merlin’s accuracy, then try for a visual confirmation. 

These are just the most common errors I encountered. Since Merlin is constantly being updated and (hopefully) improved, some of them may be addressed. The vast majority of the time, Merlin can be relied on to accurately get you in the ballpark, if not on an exact ID, and that alone makes it an incredible tool for most birders. It’s vital to remember that Merlin is only one tool in your birding kit and it takes some skill to use it well. I personally use Merlin all the time, juggling my phone, binoculars, and one-year-old. Next time you see somebody meandering through the woods, phone held straight up to the sky, stop and say hello!