One of the most fun aspects of spring migration is you can step outside almost every day and see or hear some new bird species arriving for the summer. Keeping track of the arrival timing of migrants, or other phenological indicators like crocuses blooming, has been a major interest and area of study for naturalists for centuries. One of the most common questions I get this time of year concerns the arrival timing of different species, so I want to point out some key indicators to look and listen for, as well as tools to help.

Let’s start with hummingbirds because that will cover 90% of the timing questions we get. By late April we start seeing the first reports of ruby-throated hummingbirds making it back to Maine, but the real push won’t hit until May. The easier date to remember, which is well-timed with the mass arrival of hummingbirds, is Mother’s Day. I’ll encourage caution for early lookers because I think a lot of people get confused by early bumblebees or other winged insects taking flight on warm days. The earliest reports we get are usually from people thinking they saw female hummingbirds, which makes me skeptical since males migrate before females.

Before mentioning the next couple of birds to watch for, I want to make a plug for downloading the Merlin Bird ID app. I’ve written about this many times, but as a reminder, this is a free mobile app from the Cornell Lab of Ornithology that can identify birds in several ways. If you see the bird, you can answer five questions (where, when, size, color and behavior) and it uses the eBird database to suggest the most likely options. It can also identify birds from a photo and perhaps most impressively, also by their song. If you’ve ever used Shazam to learn the name of a song, it works just like that: Hold your phone up to a singing bird and it lists the names of what it hears.

With Merlin downloaded, see if you can detect blue-headed vireos. They tend to favor evergreen forests but can be found in any mixed woods during migration. The song is typically described as a slow repetition of varying paired notes, sounding like “Look-up. Over-here. See-me? Up-here.” Blue-headed vireos arrive in mid-April and are usually the dominant vireo through the first week of May. So now is the best time to learn their song because by the second week of May, red-eyed vireos will arrive and then become one of the most common songs for the rest of the summer. Red-eyed songs are a faster series of three-parted notes, often described as asking a question, then giving an answer: “Here-I-am! Where-are-you?” This switch in vireos is a fun indicator that birds wintering from farther south will arrive soon, like some long-distance flycatchers and warblers from South America.

We tend to think of warblers as just arriving in May, but each species has slightly different arrival timings, with some even completing their migration through Maine before others have arrived. One late warbler is the blackpoll warbler. This mostly black-and-white colored warbler might be mistaken for a chickadee if you aren’t looking closely, but check Merlin for good ID tips —and use it to help hear their high-frequency rapid song, often given as they migrate through. Blackpolls are often called “the beginning of the end” as far as migrating warblers go, because they and mourning earblers are some of the latest to pass though.

Our annual bird walks at Evergreen Cemetery in Portland are starting on Tuesday, May 6. I’ll be there each morning (except weekends) through May 16 to help point out birds and talk about how migration is progressing. We meet at the ponds in the back, near the trails, at 7 a.m., and I’ll have extra binoculars for anyone who needs them. Join me to hear the switch from blue-headed to red-eyed vireos, or see when a blackpoll warbler shows up during those two weeks. Learn more at maineaudubon.org/events.

Have you got a nature or wildlife question of your own? It doesn’t have to be about birds! Email questions to [email protected] and visit www.maineaudubon.org to learn more about birding, native plants, and programs and events focusing on Maine wildlife and habitat. Maine Audubon Staff Naturalist Doug Hitchcox and other naturalists lead free bird walks on Thursday mornings starting at 7 am, at Maine Audubon’s Gilsland Farm Audubon Sanctuary in Falmouth.