Spring comes grudgingly to New England, and this year is certainly no exception. But on a cold, dreary day a few weeks ago I heard a harbinger of warmer, sunnier days to come -- a pine warbler singing from a cluster of big white pines.
I’m not a birder, but many of my friends are, and the arrival of warblers in the spring seems to be a big deal to birders. So why are these little birds so appealing?
Fair enough, but what makes warblers so awesome?
“I think it’s mostly a matter of their diversity and beauty, combined with their ephemeral qualities,” said Wood. “On a good spring morning in much of the East, you can see 20 species. But at any location, that peak only lasts about 10 days.”
Wayne Petersen, Mass Audubon’s Director of the Massachusetts Important Bird Areas program, said warblers appeal to birders for a variety of reasons.
“Warblers are small, active, and brightly colored,” said Petersen. “And there’s a lot of species that arrive in big numbers.”
Petersen said their songs are memorable as well, although warblers don’t warble.
“It’s a misnomer,” said Petersen. “Warblers tend to have high thin songs. Some warblers even have wispy or buzzy sounds, almost like insects.”
The Cornell Lab website said North America has over 50 warbler species. About 26 of those species breed regularly in Massachusetts, said Petersen.
Palm, pine, and yellow-rumped warblers are the first to arrive in April, Petersen said, but May is prime time for warblers in Massachusetts.
The North Shore is one of the best areas in the Boston suburbs to view migrating warblers, Petersen said, with peninsulas like Nahant, Marblehead Neck, and Plum Island being particularly good spots.
Plum Island, especially the Parker River National Wildlife Refuge, is on the Atlantic Flyway so it is visited by many migratory birds, David Larson, Science and Education Coordinator at Mass Audubon’s Joppa Flats Education Center in Newburyport, said in an e-mail.
“Songbirds migrating at night often get a bit off course and end up over the ocean, and head to the nearest land,” said Larson. “The scrubby maritime forest on the island provides food and shelter for migratory birds, especially the refuge, which has many off-limits areas where the birds can rest and feed in peace.”
But the pandemic is affecting warbler watching this spring. People should check online before heading to observation areas to make sure they are open to the public.
“Unfortunately, most of the best spots on Plum Island are more difficult to access this year due to construction closure of the Hellcat Observation Area boardwalks and the pandemic-induced closure of the refuge to vehicle traffic,” said Larson. “Access is by foot or bicycle only and there are very few places to park a car on Plum Island to walk onto the refuge.”
Places like Mount Auburn Cemetery in Cambridge and Watertown, and the Manomet Bird Observatory in Plymouth are also well known sites for observing migrating warblers, said Petersen, but as of this writing both locations remained closed to bird watching because of the pandemic.
Warblers are small, said Petersen, with most about 4.5 to 5.5 inches long, which can make them hard to spot, so you need to know how to look for them. Look up into trees or shrubs for little movements, he suggests.
One way to attract warblers is by pishing – making a “pish, pish, pish, pish, pish” sound -- which basically imitates the alarm call of some birds and can draw in curious warblers, said Wood.
Walking through the woods in the Middlesex Fells recently I decided to give pishing a try. I stood behind a big oak tree and repeated “Pish, pish, pish, pish, pish” several times. It worked! Within a couple minutes about half a dozen warblers were flitting around in the branches above me, including a pine warbler and a black-and-white warbler.
Warblers lay three to five eggs during the breeding season, said Petersen, and they live about five or six years, which is typical for small birds. But they face a variety of threats.
One unusual threat is brood parasites, like brown-headed cowbirds, which don’t build their own nests or raise their own young. Instead, cowbirds lay their eggs in other birds’ nests, including warblers, said Petersen. Some warblers are fooled into raising the cowbird chicks, which may outcompete baby warblers for food or even push warbler eggs or chicks out of the nest.
Predators like sharp-shinned and Cooper’s hawks, snakes, and mammals, including domestic cats, will feed on warblers.
Warblers migrate at night because they use the stars for navigation, and because there is less wind and fewer predators, said Petersen. But one of the hazards of night flying is that sometimes flocks of migrating birds accidentally fly into tall buildings and towers, which can kill significant numbers of birds.
Warblers feed mainly on insects and insect larvae, like caterpillars, so insecticides can have an adverse effect on warblers by reducing their food supply or by poisoning the birds directly, said Petersen.
Bad weather, especially hurricanes and big storms in the fall, can wipe out large numbers of warblers during southward fall migrations, which typically begin in late August and continue into September, Petersen explained.
But habitat destruction and modification remain the biggest factor adversely affecting warblers. Some habitat destruction is here, said Petersen, but it’s also in the tropics where warblers spend the winter.
Among warblers and other small birds, numbers are declining, Petersen said.
“The problems are additive – habitat changes here and in the tropics, pesticides, tall buildings, predators, etc.,” said Petersen. “It’s not easy to be a little bird. There are a lot of things that can go wrong.”
Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to firstname.lastname@example.org.