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The Other Sap Tappers

"A singular habit...and one with which all are familiar, is that which has gained him the name of 'sap-sucker.' He bores little round holes just through the bark of the tree, usually an apple tree, not penetrating into the wood of the branch. These holes form a complete circle around the branch of the tree, about half an inch apart. No theory has yet been advanced that explains satisfactorily the object of the bird in making these perforations. The theory that they are made for the purpose of sap-sucking is after all the most rational one."

So wrote Wilson Flagg in the September 1879 issue of Atlantic Monthly. The bird he was talking about, however, wasn't the yellow-bellied sapsucker, nor was it the red-naped, red-breasted, or Williamson's sapsucker. The bird Flagg described was, in fact, the downy woodpecker.

These days, when we see holes drilled in the trunks and limbs of trees with sap oozing from them, we automatically assume they were made by a sapsucker. But would we be right?

Presumably, Wilson Flagg was wrong about his observation, but he wasn't alone in his assertion. A number of naturalists of the time, including Jared Kirtland, Thomas Nuttall, and Alexander Wilson, likewise believed it was the downy, as well as the hairy woodpeckers that made the well-recognized perforations in trees.

Others, however, disagreed with this. Realizing that the migratory sapsuckers were the birds responsible for making the holes, they sought to set the record straight, laying the blame where it belonged, at the bill of the Sphyrapicus species.

"Indirectly," wrote Charles E. Bendire describing the habits of the yellow-bellied sapsucker in his 1895 book Life Histories of North American Birds, "it also causes the death of many a Hairy and Downy woodpecker...these species being frequently shot through ignorance of their habits or because they are mistaken for Sapsuckers."

It's not hard to see how the downy and hairy were misidentified as the makers of such holes. They are often found in the same areas as the sapsuckers, especially when the latter species are on their spring and fall migrations. Also, like many birds, downies and hairies enjoy drinking sap, and are not above pilfering the sweet liquid brought about through the sapsuckers' hard work. If one were to come upon these birds drinking at sapsucker wells, it could easily be assumed that they were the culprits that made the holes.

Does this mean, then, that the downy and hairy are incapable of procuring sap on their own? Not necessarily. Edward H. Forbush, in The Birds of Massachusetts, tells of how his assistant, Charles E. Bailey, watched a downy woodpecker tap a swamp maple and subsequently feed on the sap that flowed from the wounds.

"He tapped the tree by picking it a few times very lightly; it looked like a slight cut, slanting a little," reported Bailey. "The cut was so small the sap did not collect very fast. The bird would go and sit for a long time in a large tree and not move, then it would come back and take more sap. It did this three times while I was watching it. It did not care to take any food but the sap...."

Afterward he cut off the limb the downy had fed on. He presented it to Forbush, who concluded, "The perforations passed from the bark to the wood, but did not enter it, and they do not in the least resemble in shape those made by the yellow-bellied sapsucker."

Even though some experts of the time realized that neither the downy nor hairy woodpeckers were the ones making the familiar perforations, there were still those who got it wrong. To them, it was the red-bellied woodpecker that did it.

A number of people in the 1800s thought the red-bellied woodpecker was the "true" sapsucker. Thus were they described in the First Annual Report of the Geological Survey of Indiana by state geologist E.T. Cox. In the section "Birds of Franklin County, Indiana," he writes, "This is the bird which bores holes in the sugar maple, apple trees, etc., for the purpose of drinking sap. These holes, when bored in the bark of the apple tree in October, fill up with viscid sweet sap, which the bird collects from day to day...." (The yellow-bellied sapsucker was mentioned in the same article, listed as the yellow-bellied woodpecker-with no mention of sap eating!)

As with downies, it's easy to understand why redbellies were misidentified as sapsuckers because they are also enamored with sap. I have on many occasions watched the local redbellies flock to the sugar maple in my yard to imbibe the sugary liquid procured by yellow-bellied sapsuckers. However, I also had the opportunity to watch a redbelly dig its own sap wells.

On February 2, 1995, a male of the species came to the maple and pecked at a limb for several minutes. He then flew to another branch and repeated the process. Looking at the areas through binoculars, I could see a line of liquid oozing from a single hole in each spot. For the next six weeks, the redbelly returned regularly to these sites, pecking at them, then sticking his bill into the holes.

Several other woodpeckers have also been reported to tap trees for sap. Among these are the Nuttall's, ladder-backed, American three-toed, and red-headed woodpeckers.

About the last, E.L. Youmans wrote in The Galaxy:

The red-headed woodpecker has been seen by Professor C.A. White piercing holes in the bark of the maple tree. On examining the trees Professor White found their trunks perfectly sound; but the birds had bored many holes of the usual size through the bark and into the cambium layer, where they stopped. The sap was flowing freely from the holes, and on watching the movements of the birds after they had returned to the tree, it was plain that they were sucking the sap, and that they had pecked the holes for the purpose of obtaining it.

Did this red-headed woodpecker actually produce the wells, or is this another example of mistaken identity? Whichever the case, it's unlikely that the red-headed woodpeckers would pass up a chance to get a free drink courtesy of the sapsuckers.

There is, however, one non-sapsucker species in North America that unquestionably drills a series of sap wells-the acorn woodpecker. From late winter throughout summer, communal assemblages of these birds bore holes similar to those of the sapsuckers, usually in the limbs of oak trees.

Michael MacRoberts observed acorn woodpeckers in California from October to December 1966, and from April to September 1968. He deemed them proficient sapsuckers, noting in a 1972 issue of The Condor that, "in one particular live oak, about 1,800 sap holes were counted, although only a part of the tree was used by the birds for this purpose." He continued, saying, "The woodpeckers repeatedly visited and probed into these sap-filled holes. I would estimate that during the height of the sapsucking period [June and July] each hole was visited on an average, 4-10 times per hr..."

The birds staunchly defend these sap wells against interlopers, but have no qualms about stealing a drink of the sweet juice from holes drilled by sapsuckers. Yet when acorns begin to mature, the woodpeckers switch to eating the nuts, abandoning their sap trees.

It's possible for the sap wells dug by acorn woodpeckers to be attributed to sapsuckers, just as holes made by sapsuckers have been credited to other woodpeckers. Other woodpeckers, on the other hand, sometimes excavate their own sap wells. So the next time you see holes drilled in trees with sap seeping from them, you may want to find out who made them-it might turn out to be one of the other sap tappers.