Pineywoods Wildlife Management
Red-Cockaded Woodpecker Life History
An eight inch long woodpecker with a solid black cap and nape, and prominent white cheek patches. The male has a tiny red streak behind the eye and near the ear (the cockade). The cockade is seldom visible in the field, making it difficult to distinguish males from females. The Red-cockaded Woodpecker is similar to the Downy and Hairy Woodpeckers in general appearance, except that it has a barred back, spotted breast, and the male has red on either side of the head rather than on the nape.
The Red-cockaded Woodpecker is found in mature pine forest of east Texas and the southeastern United States. It is the only species of woodpecker that excavates its cavity exclusively in living pines. In Texas, cavities have been found in longleaf, loblolly, shortleaf, and slash pines. Most cavities are found in trees 60 to 70 years old or older. The tree must have enough heart-wood (older, non-living, inner portion of wood) to contain the roosting chamber, since a chamber in sapwood (younger, living portion of wood) would fill with resin. Since heartwood is very hard, a large percentage of cavities is found in pines infected with a heart rot fungus called red heart. This fungus weakens the heartwood and makes cavity excavation easier.
A cluster site is a stand of trees containing and surrounding the cavity trees in which a group of woodpeckers nest and roost. In most clusters, all the cavity trees are located within a circle about 1500 feet in diameter. Preferred cluster sited are mature, park-like pine stands with 50-80 square feet of basal area per acre (about 90-145 trees averaging 10 inches in diameter). Ideally cluster sites should have a grassy understory with few or no hardwood or pine trees above 6 feet in height. Controlling midstory growth is especially critical within 50 feet of all cavity trees. Once the midstory grows to the levels of the cavities (20 to 50 feet above the ground) a high rate of cavity abandonment occurs. A few widely scattered hardwood trees and shrubs do not harm the woodpeckers and are beneficial to other wildlife. However, control of dense midstory vegetation is essential to maintain the cluster site.
An important function of the cluster site is to provide a source of new cavity trees. Cavity trees are generally used for several years, but an average of 5 percent of loblolly and shortleaf, and 1 percent of longleaf pines die each year. Causes of mortality include bark beetles, wind snap, and fire. Also, cavity enlargement by Pileated Woodpeckers often makes cavities unusable by the Red-cockaded Woodpecker. The cluster site should be at least 10 acres in size, with 10-30 mature pines, to ensure cavity trees for the future.
The best cluster site will not be used if the foraging or food gathering habitat is not suitable. Red-cockaded Woodpeckers exhibit a distinct preference for large living pines as foraging sites. Good foraging habitat consist of pine stands with 10 inches and larger in diameter measured at 4.5 feet above the ground. These birds also forage in pole stands, consisting of pines 4 - 10 inches in diameter. However, little use is made of sapling stands, which contains pines less than 4 inches in diameter. Also, Red-cockaded Woodpeckers are known to actively seek and forage extensively on pines infested by southern pine beetles (bark beetles).
The quality of the foraging habitat determines the amount needed to support a group of woodpeckers. While 125 acres of well stocked (100-140, 10 inch diameter trees per acre), mature pine is sufficient for some groups; whereas habitat conditions are less ideal, groups may require several hundred acres to meet their foraging needs.
The Red-cockaded Woodpecker has a complex social system. These birds live in groups, which usually have two to six birds, although as many as nine birds have been observed. The group may consist of only a mated pair; a mated pair with their current years' offspring; or a mated pair, their current years' offspring and helpers. These helpers are one to three year old adult birds, typically sons of one or both of the breeders. Helpers assist in incubating the eggs, feeding young, constructing new cavities, and defending the group's territory. Although Red-cockaded Woodpecker groups may consist of a number of adult birds during the nesting season, there is only one mated pair. A breeding male may live for several years; and when he dies, one of his helper sons generally becomes the breeding male.
A woodpecker group usually roost and nest in a cluster of cavity trees. The cluster may include one to 30 cavity trees. Most clusters have some cavities under construction, some completed and in use, and some abandoned, often occupied by competitors.
Generally, each member of a woodpecker group has its own cavity for roosting. Red-cockaded Woodpeckers defend their cavities from members of other groups and from other animals. Major competitors for nest cavities include other woodpeckers (Red-headed, Red-bellied, and Pileated) and Flying squirrels.
Red-cockaded Woodpeckers nest from April through July. Group members assist with incubating the eggs during the day, and the breeding male stays with the eggs at night. The eggs hatch in 10-12 days. Young birds leave the nest in about 26 days, but remain with the group. Studies have shown higher nestling survival at nests attended by helpers.
The diet of the Red-cockaded Woodpecker consists mainly of insects (85%), but also includes small fruits and seeds (15%). The birds concentrate their search for food on the trunks and limbs of live pine trees. They scale the bark and dig into dead limbs for insects and larvae.
Compared to decayed wood, the sapwood and heartwood of a living pine is very hard and difficult to excavate. The average time required to excavate a cavity is 1 to 3 years for loblolly and shortleaf pine, and 4 to 7 years for longleaf. Once the sapwood is penetrated, the abundant resin flow that occurs creates another barrier. Most of the work on cavities occurs in summer after the young leave the nest. Cavity excavation occurs primarily in the morning, but can occur any time during the day. Once completed, a cavity is used for several years. Cavities in longleaf pine are sometimes used for 20 and even 30 years.
Cavities are constructed by tunneling at an upward slope through the sapwood so that the resin pitch will drain from the hole. Once the birds have tunneled into the heartwood a sufficient distance, they excavate downward, forming a gourd-shaped chamber about 6 to 10 inches deep and 3 to 5 inches wide. Near the cavity entrance, numerous small holes called resin wells are chipped through the bark. The birds regularly peck at resin wells to keep resin flowing.
Red-cockaded Woodpeckers maintain open cavity holes by removing the growing tissue from around the holes. Eventually, the birds expose the sapwood for several inches around the entrance. This exposed area is called the plate. Pitch from the plate and resin wells coats the trunk of the cavity tree. The continuos flow of resin deters predators, especially snakes. Actively used trees have clear, sticky pitch, and freshly chipped, reddish bark around the resin wells and plate.