Although they weigh only about as much as a tablespoon of water, blackpoll warblers (Setophaga striata) migrate huge distances. Using geolocators attached to blackpoll warblers in Vermont and Canada’s Nova Scotia, scientists have determined that these tiny birds have the longest nonstop overwater flights of any migratory songbird. Although they pass through our region in the spring and fall, most do not breed here. They breed in northern forests in Canada and Alaska. Massachusetts is at the extreme southern end of their range; a few of these warblers breed around Mount Greylock in Western Massachusetts.
In the fall, blackpoll warblers fly east from their breeding territories in Alaska and Canada and amass on the New England or Southern Canadian coast. Here they spend three or four weeks fattening up for the next unbelievable leg of their migration. When they arrive on the East Coast from their northern breeding grounds, they are likely to weigh only about 11 grams (the weight of two quarters), having lost weight during their long flight. After about a month of resting and eating berries and insects – the species’ scientific name, Setophaga striata, is from the ancient Greek meaning “striped moth eater,” and these birds eat a large variety of insects including caterpillars, lice, mosquitoes, ants, worms, aphids and flies – they almost double their weight to 20 grams. After fattening up, they are ready to begin the next stage of their migration.
Tiny blackpolls, it may be surprising to hear, are yet one of the largest warblers.
The breeding male sports a black cap (or “poll”) and is mostly black and white; the female is similar but more muted. (All have orangish-pink legs.) In the fall, all blackpoll warblers, male and female, young and old, are yellowish with dull streaks.
Blackpoll warblers in the spring sing at a frequency higher than most other birds. Some people claim they sound more like insects than birds. John James Audubon said this warbler’s “notes have no title to be called a song. They are shrill, and resemble the noise made by striking two small pebbles together, more than any other sound that I know. They may be in some degree imitated by pronouncing the syllable sche, sche, sche, sche, sche, so as progressively to increase the emphasis.”
When cold winds arrive out of the north, the warblers fly at sunset out over the Atlantic Ocean. They travel nonstop for three and a half days (1,900 miles) at an average speed of 27 miles per hour to reach their overwintering grounds in northern South America. Birds with lower body weights do not survive this arduous Atlantic crossing. Once they arrive, a few hardy birds may continue their journey even farther south to northern Argentina.
In the spring, when blackpoll warblers return to the United States and Canada, they do not travel over the ocean, perhaps because they do not have favorable winds pushing them along like on their southern migration. Instead, they fly to Cuba and from there to Florida. Then they take the land route up the Eastern Seaboard to their breeding grounds. Because these birds migrate so far, they are one of the last to arrive in the spring: late May, when most other warblers are already on their breeding grounds. According to ornithologist Edward Howe Forbush, the late springtime arrival of blackpoll warblers signifies that “spring wanes and summer is at hand.”
Some of these birds breed as far north and west as Nome, Alaska – so during their fall migration, they trek thousands of miles before even reaching the Atlantic! The total distance they travel, including their Atlantic crossing, is 7,500 miles! For a tiny bird, this is an incredible feat. Perhaps for this reason, it is not surprising to learn that these are one of the fastest declining songbirds of North America.
Wildfires in Canadian forests, climate change and habitat destruction in their overwintering grounds are other possibilities why studies indicate blackpoll warblers are undergoing steep population declines. It’s striking because there was a time, ornithologist William Brewster writes, that at the height of their migration they were
so very numerous and widely distributed that they may be said to flood the entire Cambridge Region. Indeed, there are times when they occur abundantly almost everywhere – throughout upland woods; in maple swamps and dense thickets bordering brooks and ponds, in blossoming apple orchards; and scarcely anywhere more plentifully than in our city parks and gardens.
The situation is much different today. We see blackpoll warblers less and less – in part because of warming temperatures that from 2011 to 2019 saw blackpoll warblers in the Northeast shift their summer territories north by more than 50 meters. Scientists expect that as the climate continues to warm, these warblers will continue to shift their range northward. They are expected to disappear completely from New England by the end of this century.
There are still about 60 million blackpoll warblers worldwide, but those numbers may be reduced by half in as little as 16 years.
Reader photo
Maren Clark spotted this snail near Tipping Cow Ice Cream in in Somerville’s Winter Hill on April 25.
Have you taken photos of our urban wild things? Send your images to Cambridge Day and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.
Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.
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