What is a Yellow-bellied Sapsucker?
A male yellow-bellied sapsucker (Photo: Patrick Colin, Flicker Sharing).
How are Yellow-bellied Sapsuckers Beneficial to the Environment?
Outside of the fact that they have an awesome name, yellow bellied sapsuckers are an amazing type of woodpecker that acts sort of like nature's equivalent of the convenience store keeper of a 7-11. How does this work? Let's start with what they look like and how they are built.
Yellow-bellied Sapsuckers (Sphyrapicus varius) are smaller woodpeckers (length from snout to tail of about 8.5") that have a straight bill and tapered/pointed tail feathers that help them sit against trees. Their bodies are mostly black and white, with black and white barring on their back and sides. The males have a red chin and forehead, along with a bright black bib. These colors scream "I'm a cute male woodpecker!!" to the females!
Females have a white chin and red forehead with a smaller black bib. Males and females both have a dapper black mask, with white above and below the mask. They also have a white stripe along their outer wing margin. Males usually have a yellow belly, which can extend into their chest. Females may have a lighter yellow wash of color.
Yellow-bellied sapsuckers are found in hardwood and coniferous forests. They love aspens, maples, and soft wood trees. Their summer range is in Canada and the Eastern US, while their migratory and winter range is in the Mid-west and Southern US.
So here's the question: Do they really "suck sap" as their name implies? Nope. Their beaks aren't built like a straw, but they are built for hammering and chiseling holes, and their tongues are like a bottle-brush that can sweep up tree sap and move it through capillary action into their throat. As the picture below suggests, a group of sapsuckers is called a "slurp." Do you think yellow-bellied sap-slurper sounds better than sapsucker? I kind of like it, but it's hard to pronounce.
Yellow-bellied sapsuckers are super interesting, because in the Spring they use those chisel-like beaks to make precisely rounded deep holes into trees (they like over 1,000 species of trees, but mostly they prefer maples and soft woods that have a good sap flow) in horizontal rows. These deep holes are called "sapwells" and they go through the bark, into the tree's xylem (zy-lum), this is the inner most part of a tree's trunk. By drilling these holes in early spring they are able to feed on the sap as it begins to flow into the new tree branches, leaves, and buds of the tree's new Spring growth.
After the tree leafs out the sapsuckers switch to making another type of hole. These are more shallow sapwells that are rectangular and only reach into the phloem (flow-um) of the tree's trunk (not as deep).
Because the y are shallow and heal over easily, these shallow wells have to be maintained and regularly opened to keep the sap flowing. It's important to note here that they aren't killing the tree, and usually sapsuckers only drill into sick or previously wounded trees, not healthy ones.
So what's the big deal about sap and all these holes? Well, sap is about 10% sugar, which is a great energy source for the birds. Insects like ants and spiders can be attracted to the sap too, which is another food source for the yellow-bellied sapsucker. This is also where the 7-11 idea comes in. All of these holes, leaking sap, are some of the first sources available to nectar drinking hummingbirds. This is super important when hummingbirds begin their migration in early Spring. Because at this time there may be very few flowers blooming, and food may be scarce, hummers can use the sapsucker trees as a pit-stop for sugary sap or tiny insects to eat. Sapsuckers are one of the few truly migratory birds, and their migration/movement corresponds with the migration of hummingbirds that follow them. The northwest range of hummingbirds correlates to the summer breeding range of sapsuckers too (see the orange on the map below, same shapes). Hummingbirds visit sapsucker trees all summer long, and they've been known to "shadow" the sapsuckers too!
Sapsucker trees (and spawells) are also important for other types of animals which use their trees as "nature's convenience store." Nocturnal moths feed on the sugary sap, and bats and other nighttime dwellers eat the moths and insects. Nocturnal flying squirrels aren't against lapping up some sugar water either. Many other diurnal (day time) species also rely on sapsucker wells too. This includes birds such as different species of woodpeckers, warblers, kinglets, nuthatches, and chickadees. Mammals such as grey squirrels, American martens (a type of weasel), and porcupines also like the sweet sap. Insects from a wide variety of families also join in at the 7-11 tree. This includes bees, wasps, hornets, butterflies, and more. Some lizards even get in on the sapwell action, including anoles, and skinks.
Are you convinced yet about how neat yellow-bellied sapsuckers are? Scientists call them a "keystone" species, because they are so important to many other species of birds and insects. They open up resources, and a food source, that would otherwise be unavailable to the critters in their ecosystems.
The last fun fact I'll share about yellow-bellied sapsuckers is their annoying habit of pounding their beak on metal and other objects. Yes, these are the ones that pound out a staccato Morse Code of noise on metal street signs, tin roofs, and metal siding. It doesn't appear to hurt them, and they seem to really like the loud sounds. He's are great video of one drumming on a metal BBQ.