By Michael Caduto
Sugar maples have already produced several strong runs of sap during the 2022 season, and steam has been rising from sugarhouses throughout the North Country. But this sweet elixir is nature’s springtime bounty for more than just people; some of our feathered friends will soon be working the trees for sap that will be pecked and lapped, rather than tapped.
One day some years ago, while out for a walk on North Bridgewater Road, I heard a loud buzz and looked up to marvel at a hummingbird moving methodically along the bark of a basswood tree, lapping up sap that oozed from small holes chiseled by a yellow-bellied sapsucker. Although the sapsucker is saddled with a name that sounds like an insult, it plays a critical role in the lives of hummingbirds and many other animals.
Yellow-bellied sapsuckers are lively birds with a sporty plumage. Pastel yellow feathers on the breast are highlighted by a bright red cap and striking zigzag bars of black and white on each side of the head and neck. They also have a white wing stripe and a red neck with a bib-like black crescent.
“Sapsucker” comes from their habit of pecking neat, horizontal rows of holes in tree bark. Male sapsuckers migrate northward earlier than females, in late March or early April, in order to establish breeding territories. As soon as the sapsuckers return, they start pecking lattice-like patterns of 1/4-inch holes across trunks and branches to tap into the sap of the inner bark (phloem) that carries sugar and other nutrients down from the treetops. They periodically clean out and renew the holes to keep the sap flowing, and are especially fond of tapping basswood, apple, hemlock, sugar maple, aspen, white birch and mountain ash.
Unlike sap drawn from the xylem (sapwood), which is tapped in the deeper holes drilled by farmers to make maple syrup and which contains from 2-3 percent sugar, phloem sap may contain 20-30 percent sugar. Sapsuckers use brush-like tongues to lap the sap that accumulates at the top of each hole. Once the flow subsides, sapsuckers move up the bark and start another row of holes. They also eat cambium and inner bark as they chisel.
The mix of sugar and other nutrients contained in the sweet sap is similar to flower nectar, so it’s no surprise that the northernmost range of the ruby-throated hummingbird coincides with the summer breeding territory of the yellow-bellied sapsucker. When hummingbirds arrive in New England in early spring, enough sapsucker holes are already exuding sweet sap to supplement the nectar from early-blooming flowers. Hummingbirds continue to feed on sapsucker wells throughout the summer—they even shadow sapsuckers making the rounds of the best sap wells, chasing away other birds (except for sapsuckers) that come to feed.
But the impact of sapsucker activity extends well beyond hummingbirds. Their sap wells are nature’s soda fountains for about three dozen different species of birds, including other woodpeckers, yellow-rumped warblers, Cape May warblers, eastern phoebes, ruby-crowned kinglets, nuthatches and chickadees. The sap also nourishes a host of mammals and insects, including squirrels, bats, porcupines and insects from at least 20 different families, such as bees, wasps, hornets and moths.
Some animals, like red squirrels, feed directly on the sap, while many others, including hummingbirds, also feast on insects drawn to the sweetness. Some fungi colonize the oozing sap, including one called “black bark” that forms dark, canker-like patches. Many bacteria and fungi that can decay and discolor wood enter trees through sapsucker holes.
Studies show that species diversity, as well as the size of the population within each species, are both greater in forests with high levels of sapsucker activity. Because of this effect, sapsuckers are considered a keystone species—they have a critical impact on the surrounding ecological community that goes beyond what would normally be expected from their numbers. Beavers are another example of a keystone species—their ponds provide critical food, water and cover for an array of plants and animals. Late sleepers, however, might describe sapsuckers as more of a hammer-stone species as males bang their notoriously loud “rat-a-tat-tat” territorial calls on metal roofs, chimney caps and other resonant surfaces.
In our region, sapsuckers often chisel nest holes in the punky wood of aging aspens infected with white trunk rot fungus. They also nest in cottonwood, beech, pine, fir, maple, birch, elm, butternut, willow and alder. Females lay from 2 to 7 white eggs that are incubated by both sexes. Hatchlings call incessantly for adults to bring insect meals, some of which are coated in sweet sap like a bug fondue. Adults feed on tree sap and a smorgasbord of insects, including ants, which comprise up to a third of their diet.
Sapsuckers lap at their sap wells several times a day throughout the growing season. As summer advances and the sap wanes, sapsuckers tap the species of trees that have the best sap flow at any particular time. They also supplement their diet by eating more insects and partaking of ripening berries and nuts. Overall, their signature sap-tapping has a positive influence on the world around them, even as it remains the source of their dubious moniker.
Insects feeding on sap oozing from holes that a yellow-bellied sapsucker has chiseled into the bark of a white birch. Sapsuckers lap up the sap, and they also feed on the insects that are attracted to the sweetness. Photo: Michael J. Caduto.
Don’t miss the Vermont Maple Sugar Makers’ Association‘s official 2022 Maple Open House weekends: March 19-20 and March 26-27.