Yellow-bellied Sapsuckers Drill those Linear Holes in your Trees

Who is making these rows in the trees?

Those neat rows of holes in your trees aren’t caused by an insect invasion; they’re the work of the yellow-bellied sapsucker.  Sapsuckers are winter residents in South Carolina, and they subsist on the sap in the holes as well as the insects that are attracted to them.  

Winter residents of South Carolina

This range map from Cornell University shows us how far they travel in winter in search of the sap and insects they feed on. (The blue is their winter range: yellow is migration, and orange is the breeding zone.

It's not just dead trees

While other woodpeckers, like red-headed and red-bellied woodpeckers, prefer hammering away at dead trees, the sapsuckers are interested in LIVING trees.  They have developed this adaptation where they create a superficial wound on the surface of the tree and then ingest both the sap that arises and insects that are drawn to the sap or are sheltering in the bark.  According to the Cornell Lab of Ornithology, sapsuckers create sap wells in over a thousand species of trees!  In my informal observations, we’re likely to see these rows of sapwells on oaks and pines.  And here’s an interesting fact: where they breed, the sapwells look different because they don’t need to tap deep into the tree in the warmer seasons: they can do more superficial harvesting of sap when trees are in a growing phase.

It is not usually fatal to the tree

Most species of tree can tolerate this level of sap “harvesting” with no problem, but occasionally trees will be weakened by stress, and parasites can take advantage.

Males have red throats

The bird above is either a female or a juvenile bird: note the white throat.  Both genders have a black cap and white wing patches, but the male also has a bright red throat.

Other Species Use Sapwells

There is some evidence that several other species take advantage of these calorie-rich food sources.  Ruby throated Hummingbirds may even time their migrations north to follow sapsuckers, so that the recently tended wells provide nutrient rich food for the journey.  In the nesting areas, these hummingbirds are frequently found nesting nearby.