Sapsuckers are "Keystone" Species
by Ro Wauer
One of our most interesting wintertime birds is the yellow-bellied sapsucker, a member of the woodpecker family that occurs in Texas only from about October to March. Most of the year it resides on its nesting ground in the far northern portion of North America, in a broad belt from Alaska eastward across Canada to the Maritime Provinces and barely reaching the northeastern corner of the United States. Breeding birds utilize the northern deciduous forests.
Although sapsuckers are only a middle-sized bird, about 8.5 inches in length, they are far more influential than their size might suggest. It is their interrelationship with other birds and additional animal species that gives them a centerpiece or "keystone" status within the wildlife communities. While woodpeckers also have considerable influence on other birds, because so many other cavity nesting birds are able to use their deserted nest cavities when they move on to another cavity, sapsucker activity affects a much wider range of wildlife.
All members of the woodpecker family "drill" into woody plants to extract food. In the cases of woodpeckers, they extract insects, such as beetle larvae and ants. Sapsuckers make only shallow holes, known as sap wells, in woody plants that allow the sap to flow. They then lick up the sap, their principal source of nutrients. Flowing sap in turn attracts other birds as well as numerous insects. The numerous insects then attract several other birds that feed on the insects, although they never utilize the sap per se. Some wildlife communities become dependent upon the sap wells that are maintained by the sapsuckers. This situation occurs on both their breeding grounds as well as on their wintering grounds, such as those in South Texas.
Sapsucker activity is reasonable easy to locate. They usually drill a series of tiny holes in parallel rows, eight to twenty feet above the ground, when searching for a good sap well. Once they locate a good well, they will return time and again, and year after year, to keep it flowing. And it isn't long before adjacent wildlife begins to take advantage of the fresh source of food. Warblers, kinglets, and wrens are some of the South Texas birds that take advantage of the flowing sap wells by licking sap, while warblers, flycatchers, and hummingbirds are most attracted by the insects that are attracted to the wells. Numerous butterflies, including some of our larger species, including question mark, red admiral, and the hackberry butterflies, frequent sap wells. Some species, both birds and butterflies, develop a trap-line and fly from one well to the next as part of their daily routine. In a sense, sapsucker sap wells become the center of an active community.
Yellow-bellied sapsucker, a name that may sound like it was invented by a cartoonist, is therefore most appropriate. Our wintering yellow-bellied sapsuckers can readily be distinguished from other woodpeckers by their medium size, red forehead and throat, black-and-white face, black chest, and yellow belly. The somewhat smaller downy woodpecker, a year-round resident of riparian areas, is black-and-white, except for the male's red nape. The slightly larger ladder-backed woodpecker, also a year-round resident with a black-and-white streaked, ladderlike back, has a black chest; males possess a red cap. The larger red-bellied woodpecker is fairly common in the northern half of the South Texas region, while the similar golden-fronted woodpecker occurs only in the southern portion of our region. Both of these larger woodpeckers have a barred back and grayish underparts. In addition, the northern flicker is also fairly common in winter; it is easily identified by its yellow flight feathers and spotted breast. The much larger pileolated woodpecker is a bird primarily limited to riparian areas, and the red-headed woodpecker, with an all-red head, is only rarely found in South Texas. In addition, there are three additional North American sapsuckers: red-breasted, found only on the West Coast; red-naped, found throughout most of Western North America; and Williamson's sapsucker that occurs only in the mountainous West.
Woodpeckers include a variety of fascinating birds that have significant influence in our natural habitats. But none are as important to our South Texas wintertime communities as our little yellow-bellied sapsucker.