Lifestyles

Is that sap that you’re sucking?

By BILL CHAISSON
Of a Feather
Yellow-bellied sapsucker was for pretty obvious reasons the bird name that sitcoms would trot out to make birdwatching and birdwatchers seem vaguely ridiculous. As in, “So, Chad, have you seen any yellow-bellied sapsuckers lately?”

As it happens, I have. Some woodpeckers, like the hairy and the downy woodpeckers, stick around all year. But many of them migrate south for the winter and return in the spring. This past Wednesday I heard the familiar “wik-a-wik-a-wika-a” call along the hedgerow between my yard and the next and saw two sapsuckers chasing each other around on a tree trunk. David Sibley calls this their “close contact call,” and indeed these two were about a foot apart and spiraling up the trunk until one of them flew off. They were both males, so this was likely an early season territorial squabble. This kind of acrobatics, however, is also associated with pre-courtship behavior between males and females. They will also face each other on the ground with the bill and tails raised and their throat feathers puffed out.

Like most woodpeckers, the sapsucker’s plumage is a combination of black, white, and red. The best field mark for them is the vertical white bar on their wing. The males have a red throat and a red forehead with a thick black stripe through the eye and white stripes above and below the eye. The back is black heavily barred with white. The eponymous yellow belly is almost impossible to see unless you see the bird from below in flight.

The females have a white throat, but are otherwise a lower contrast version of the males. The juveniles, which we will see wandering around by July, lack any red and have plumage that looks as if a female sapsucker has been photocopied several times. The consistent field mark, even in the juveniles, is the vertical white bar on the wing.

Interestingly, all four species of sapsucker have that vertical white bar. All are members of the genus Sphyrapicus and have overlapping characteristics that show their relatedness. The other three species, however, are all western birds, found between the Rocky Mountains and the California coast. Sibley notes that this is a good example of a cline, a biogeographical term for species with adjacent ranges and from one to the next you can see a gradual change in one or more characters. In sapsuckers, as Sibley describes it, they vary “from more red and less white in the west to less red and more white in the east.”

All the species, except the Williamson’s sapsucker, make very similar calls, which are described as “cat-like” or mewling “nee-ah” or “quee-ah.” Sapsuckers also have one of the more identifiable drumming patterns. It begins with a burst of several taps then gradually slows, with occasional double taps.

The name “sapsucker” is something of a misnomer, you will be disappointed to find out. I knew that there were sapsuckers in my neighborhood before I saw any because the pattern of holes (“sapwells”) they drill in tree trunks are distinctive. Sapsuckers make neat horizontal rows of holes that are perhaps a quarter inch in diameter and often less than an inch apart. The holes are excavated down into the sapwood and do indeed fill with sap, but when the bird return to eat it is eating the insects that have been attracted to the sweep sap and gotten caught in its stickiness. They do drink the sap too, but it involves lapping it up with their tongue rather than sucking it.

Generally, sapsuckers prefer trees with smooth tight bark and they are especially fond of apple and other fruit trees. Away from fruit trees they gravitate toward areas that have recently been cut over in logging operations. These areas have abundant young trees with smooth bark. While many woodpecker species are drawn to dead or dying trees because they tend to be filled with ants and other insects, sapsuckers prefer living trees for feeding. They do, however, search out older trees in order to excavate their nesting cavities.

According to allaboutbirds.org, the excavation of sapwells varies seasonally. Early on the spring the sapsucker excavates more deeply to reach the xylem where the sap is rising as the tree comes out of dormancy. These are the holes in horizontal rows. Later, after leaf out, the birds drill more shallow holes into the phloem. These holes are drilled in vertical columns above the early row. The sap coming down from the leaves can be more than 10 percent sugar. The birds have to constantly maintain their sapwells, staying ahead of the trees’ efforts to heal themselves.

Like other woodpeckers, sapsuckers probe into the crannies of bark to search for insects. They will also sally out to take flying insects on the wing, like tyrant flycatchers. When they are drilling for sap in orchards, they will also eat the fruit.

Yellow-bellied sapsuckers may migrate as far south as Central America or stay as far north as Long Island. The females tend to migrate further south. Generally they are due back on their breeding grounds in May. My early arrivers last week were perhaps short-distance migrators who have not come very far. I haven’t yet seen a bird that looked like a female. We are at the southern edge of their breeding range in New England; they are absent from Connecticut and Rhode Island and breed only in the Berkshires in Massachusetts.

According to the National Audubon Society, the yellow-bellied sapsucker is disappearing from the southernmost areas where it has bred historically, which they attribute to climate change. The bird is, however, not just common, but increasing in numbers, according to the North American Breeding Bird Survey.

Because of the way they drill, maintain and expand the number of holes they drill to feed, sapsuckers can actually kill trees. Some species are more susceptible than others. Gray birch is the most vulnerable, with 67 percent of them dying after being fed upon by sapsuckers. Fifty-one percent of paper birches die and 40 percent of red maples. Coniferous species, which are important to the winter diet of sapsuckers, are far less vulnerable, with fewer than 5 percent succumbing.

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