When Sapsuckers Attack

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20170504.jpg dominci herony, WC

Male yellow-bellied sapsucker. Photo: dominick herons, Wikimedia Commons

Sapsucker: it sounds rather disgusting, doesn’t it? Yet sapsuckers are actually quite pretty birds… with the nasty habit of damaging trees.

Sapsuckers are woodpeckers, belonging to a small genus of 4 species, Sphyrapicus, strictly limited to North America. Readers in other parts of the world can therefore stop reading now… unless you’re curious about a unique type of bird that failed to evolve on your continent.

The best-known species and the one with by far the widest range is the yellow-bellied sapsucker (Sphyrapicus varius), the species common east of the Rockies. The other 3 are limited to various Western ranges. But they all have the same habits.

The yellow-bellied sapsucker is a medium-sized woodpecker, about 8 to 9 inches (20 to 23 cm), long. It’s black and white with a red crown and, in the case of the male, also a red throat. The other species are similar, with more or less red on their heads. As the name suggests, the yellow-bellied species also has a pale yellow breast and upper belly, although that isn’t always very obvious.

Sapsuckers Love Sap

What makes sapsuckers unique among woodpeckers is that they mostly live on sap while other species are essentially insect eaters, making holes in bark to scoop up insect larvae. Since grubs and bugs are most common in dead or dying trees, they’re the main hosts for the average woodpecker, but not so for sapsuckers: they only attack living trees.

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Paper birch showing many years of sapsucker wells,,, and serious bark damage! Photo: Cephras, Wikimedia Commons

They make horizontal rows of shallow, equally spaced oval or square holes called sap wells, piercing the bark to reach the sapwood. The tree reacts to this intrusion by producing sap in order to plug the holes. The sapsucker then returns to drink the sap with its brush-like tongue (it doesn’t really suck sap, it’s more like it laps it up). This reopens the wound, causing the tree to release more sap. Then the sapsucker returns… and the cycle continues. Some experts even believe that sapsuckers inject a substance into the wells that prevents the sap from hardening, thus prolonging the usefulness of the row of holes they drill.

The sap that flows from the wells also attracts insects… that the sapsuckers gleefully harvest, as they need protein as well as sugar. When the sap finally stops flowing in a given row of wells, the sapsucker drills another row and starts over. Usually it will return to the same tree for years. Often, a foot (30 cm) or more of the trunk is entirely ringed in rows of holes! The outflow of sap is such that it often discolors the surrounding bark.

The Tree Recovers… or Dies

A healthy tree that with only a few rows of wells may recover and eventually bark may cover the holes, leaving no trace. But if the trunk is entirely ringed in holes, or if the tree was already in trouble to begin with, this constant drilling can seriously reduce the movement of sap within the tree and thus weaken it.

And sapsuckers do seem to favor either weakened or stressed trees, ones naturally less able to withstand the attack. Also, pathogenic insects or fungi can penetrate the tree through the wells and cause secondary damage. Thus you’ll often see “sapsucker trees” weaken and die a few years after the bird has abandoned it.

Migratory

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Male yellow-bellied sapsucker on a pine. Photo: Ltshears, Wikimedia Commons

The yellow-bellied sapsucker is the most migratory of the sapsuckers, although it tends to travel rather short distances. It winters in warmer parts of North America, plus Central America and the Caribbean, then comes back north in spring, nearly to the tree line, spending the entire summer there.

It does have its favorite trees, especially species known for their sweet sap or thin bark, such as birch, aspen and maples, but in fact will also feast on in over 1,000 species of trees, both native and imported, including conifers (it seems to favor Scots pine) and even palms.

It’s interesting to note that it doesn’t attack all the trees in a forest. It chooses a tree here and there for no apparent reason, then frequents it all summer long and often for several years in a row.

The yellow-bellied sapsucker is a very typical woodpecker when it comes to nesting, digging a large cavity in a dead or dying tree. Both males and females prepare the nest and rear the young. There is only one generation of 4 to 7 eggs per year.

A Role to Play

In nature, sapsuckers are actually fairly innocuous. They mainly choose as hosts either weak trees or trees near the end of their lifespan, so the eventual death of the tree simply leaves move room for its neighbors. Thus it plays a role in maintaining the health and vigor of the forest.

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Female ruby-throated hummingbird visiting sap wells. Photo: Fun Kynd, Flickr

Hummingbirds also visit holes that “bleed” sap and indeed, early in the season when there are few flowers, hummingbirds in northern areas depend entirely on the sapsucker’s wells for their survival. Other birds, including nuthatches and warblers, also take advantage of the sweet sap, as do porcupines and squirrels.

On the other hand, sapsuckers are less appreciated when they encroach on human territory, notably when they pick a tree the landowner planted and wants to see thrive.

Thunderous Drum Rolls

In addition to drilling trees for sap, male sapsuckers like to drum, beating their beak repeatedly against an object just to make noise. They have their own special pattern that distinguishes them from other woodpeckers. Not only does this attract females at the beginning of the season, but it warns other males that this spot is its territory. They prefer trees with good resonance, but sometimes discover an even noisier surface to beat on: metal sheeting!

They often choose metal surfaces—a sheet-metal roof, chimney flashing, siding, even street signs!—which amplify the noise and then come back day after day… much to the frustration of the families they wake up at dawn through their staccato drumming. Oddly enough, banging their beak against metal doesn’t seem to harm them at all.

Putting Sapsuckers in Their Place

Sapsuckers are protected throughout their territory by the Migratory Birds Convention Act: you’re not allowed to kill or capture one, nor to destroy its eggs. And it is very difficult to get a sapsucker to abandon a tree it is feeding on.

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Sticky Tanglefoot can discourage sapsuckers.

One method is to cover the affected part of the trunk with Tanglefoot, a sticky product sold essentially as a barrier to prevent insects from climbing into a tree. (Wait for a warm day: it’s hard to apply in cold weather.) Not that the sapsucker will actually become stuck, but it doesn’t seem to appreciate having sticky feet and may well move away.

Other people claim success by wrapping strips of cloth or tape over the rows of sap wells, then removing the barrier in the fall.

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Scare-eye balloon

Early in the season you can try hanging visual repellents—objects that move in the wind, such as strips of cloth, foil tape, aluminum pie plates or scare-eye balloons—from branches of the tree, but once the bird has settled on a favorite spot for the year, it’s unlikely to remain away long.

Live and Let Live

Of course, the easiest, most laidback treatment of all is just to leave the bird alone. It’s a pretty enough bird if a bit noisy, and fascinating to observe. Since it always comes back to the same spot, it will add interest to your yard. True enough, it will be harming one of “your” trees, but usually only one, and you can always plant a replacement later. Plus it tends to choose its “victim” in a wooded area: you probably already have substitute trees all around. Is losing one—to natural causes at that!—so bad?

Of course, you have to draw a line somewhere and a sapsucker drumming on your house really is going too far. Try one of the treatments recommended above to dissuade it. Maybe you can encourage it to move to your neighbor’s house!20170504.jpg dominci herony, WC

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