May is a busy time for a naturalist at Maine Audubon. Just look at our events calendar and you can find us delivering programs somewhere in the state almost every single day (though on Mother’s Day, we have higher priorities). With songbird migration nearing its peak, we are out each day looking for new waves of arriving birds. That said, the most common question I am getting right now is, “Doesn’t it seem slow this year?” So let’s take a look.

First we should look at the whole picture: Ducks have pretty much moved through and are settled in to their breeding grounds. Shorebirds are a mixed bag, with local breeders like piping plovers already nesting in Maine, while longer distance migrants like least sandpipers are still blasting through on their way to the subarctic tundra. Even some of the early warblers are already starting to nest — on a walk at Evergreen Cemetery in Portland last week, we watched a female pine warbler gathering spiderwebs she’ll use to build a nest — while species wintering farther south are mostly yet to arrive, like blackpoll or mourning warblers. The real peak will come around the third week of May, though some species are already “past,” and migration will settle down after the first week of June. 

It is important to consider that average, because day by day, the fluctuations in birds we see makes it seem pretty dismal at times. As a quick comparison, our first “warbler walk” at Evergreen last week was a bit slow. We had to make an effort to find a warbler. One day later, we were greeted by a dozen yellow-rumped warblers all flycatching from the small island in the back ponds, and then we were quickly distracted by a scarlet tanager, a Baltimore oriole, and about 40 other species that day. 

Ornithologists have built a tool called BirdCast that uses radar data to quantify the number of birds migrating on any day. It is pretty cool that the same NEXRAD radar that detects droplets of rain can also be used to detect birds in the air. Most meteorologists will filter out the birds (and bats and insects) as “noise” in generating a weather map you’d see on the evening news, but now ornithologists can filter out the rain and generate bird migration density maps. 

Let’s look at those counts during the two days mentioned above, our slow day and our busy day. During our slow day, BirdCast estimated 135,800 birds had crossed over Cumberland County the evening before. That sounds like a lot of birds until you consider the 3,018,300 estimated to have moved the evening before our much busier day. 

The weather plays a really big role in helping birds get here. Sticking with our examples, the slow day had less favorable conditions. Most obvious to us onlookers was the chilly start to the day: it was only 36 degrees when I got into my car to head to the walk. The next day, though, we had a southerly breeze that brought with it much warmer air — it was in the 50s and 60s during the morning walk. 

More important than the temperature is the direction of the wind. These birds are traveling long distances and moving north as quickly as they can, and a tailwind is most helpful for that. We see fewer birds move when they’ve got a strong headwind, and they’ll stop altogether if they are heading into a low pressure system where rain is likely. 

The last point I’ll emphasize is about that rain: We are unlikely to see new migrants coming into Maine when it is raining here, but even if we have clear conditions, if it is raining where the birds are coming from, then they will need to wait for a window to make their next jump. So even when we seem to have perfect weather here, you should take a look at the mid-Atlantic or southern New England and make sure there isn’t a wall of rain holding the birds back.

Long story short, things seem a little slow this year, but so far the weather has been the biggest factor. Despite some of the warblers being a little behind, we are seeing some “winter birds” lingering later than usual. Like the bohemian waxwings I wrote about a month ago, I said you had “a couple more weeks” to see them, but there are still quite a few hanging around this month! 

I highly recommend going to BirdCast.org to follow along with the daily pushes of migrants. Download the free Merlin app to help identify the birds you are seeing and hearing. Download eBird to explore where you can find more birds. Or join us on a “warbler walk” or any of the upcoming birding festivals!

Have you got a nature or wildlife question? It doesn’t have to be about birds! Email questions to [email protected] 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 8 am, at Maine Audubon’s Gilsland Farm Audubon Sanctuary in Falmouth.