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Compass issue 12
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Compass is a quarterly publication of the USDA Forest Service's Southern Research Station (SRS). As part of the Nation's largest forestry research organization -- USDA Forest Service Research and Development -- SRS serves 13 Southern States and beyond. The Station's 130 scienists work in more than 20 units located across the region at Federal laboratories, universites, and experimental forests.



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Issue 12

Red-cockaded Woodpeckers and Hurricanes

by Zoë Hoyle

Ecologists use the term “highly specialized” to describe redcockaded woodpeckers. Though the birds will excavate their nesting and roosting cavities in most pines, they prefer old longleaf pines—100 years old or more old. They’re also the only North American woodpeckers that dig their cavities into live trees, a process that can take up to 12 years to complete. If their habitat is removed or altered significantly, the birds disappear. By 1970, the red-cockaded woodpecker had become scarce enough to be added to the Federal list of endangered species.

The decline of red-cockaded woodpecker populations coincided with the disappearance of their primary habitat. By the 1920s, the longleaf pine forests that once covered an estimated 90 million acres across the Southeastern United States were reduced by logging and clearing to less than 3 million acres patched across a range that once stretched from Virginia to Texas. Fire suppression has also played a part; red-cockaded woodpeckers will typically abandon a cavity if other trees grow close to the cavity entrance. Without periodic fires, the historically open midstories of southern pine forests soon become choked with brush and small hardwoods.

 

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Since the 1970s, when natural resource agencies started restoring red-cockaded woodpecker habitat, the species has made a comeback, with population numbers growing slowly but steadily across its range. Many of the restoration areas—and the remaining stands of old longleaf pine—lie along the Atlantic and Gulf Coasts, areas susceptible to damaging weather. Strong winds, downbursts associated with thunderstorms, and tornadoes frequently uproot cavity trees or snap them at the weak points created by woodpecker nesting cavities, so the damage is usually localized. “The good news is that it’s rare for these weather events to happen more than once in many years to a particular patch of red-cockaded woodpecker habitat,” says Craig Rudolph, SRS research ecologist with the Nacogdoches, TX, team of the SRS Southern Pine Ecology and Management unit. “In general, wind events have a minimal impact on populations—as opposed to individual birds.”

Hugo’s Hard Wind

Hurricanes, however, have the potential to severely impact redcockaded woodpecker populations. In 1989, when Hurricane Hugo hit the Francis Marion National Forest in South Carolina, the storm’s category 5 winds devastated the second largest population of red-cockaded woodpeckers then in existence. Before the storm, 477 groups of birds had been counted on the forest. After Hugo came through, an estimated 65 percent of the birds were dead or missing.

The storm uprooted or snapped cavity trees; of 1,765 cavities, 87 percent were destroyed. Red-cockaded woodpeckers live in groups of two to nine birds, the groups made up of a breeding pair and several male helpers. Each group member roosts in a separate cavity; the group’s cavity trees are clustered together. Half of the red-cockaded woodpecker clusters on the Francis Marion were completely destroyed, as well as hundreds of acres of pine forest that served as foraging habitat for the species. The loss was stunning, both in its severity and extent.

Bob Hooper, now retired but at that time a scientist with the Southeastern Forest Experiment Station (SEFES) that preceded SRS, immediately got together with colleagues to start assessing the damage and come up with a plan to recover the population. Fortunately, a major technological innovation—the artificial cavity—had recently been developed by biologists Carol Copeyon (North Carolina State University) and David H. Allen, also an SEFES scientist, to help move along red-cockaded woodpecker restoration efforts.

Hooper and his colleagues realized that many of the remaining woodpeckers would not survive unless they were quickly provided with cavities. A massive effort was mounted. More than 300 cavities were artificially excavated on the Francis Marion; within a few short years, more than 60 percent of the inserts were being used for nesting or roosting, and by 1994, woodpecker populations were back to 75 percent of those before Hugo.

The experience with Hurricane Hugo led Hooper to look more closely at possible hurricane impacts on red-cockaded woodpecker populations throughout their range in the Southeastern United States. Using historical hurricane records, Hooper determined that most existing populations of the endangered species were located in areas vulnerable to catastrophic hurricanes. He suggested that management plans for redcockaded woodpeckers include accommodations for the massive hurricane impacts that were certain to occur in the future. The Red- Cockaded Woodpecker Recovery Plan developed under the direction of the U.S. Fish and Wildlife Service mandated additional populations to accommodate periodic losses due to hurricanes.

Rita’s Benefits

Fortunately, most hurricanes don’t directly hit red-cockaded woodpecker populations; the storms usually lose power by the time they make it inland to the piney woods. In 2005, Hurricane Rita’s path through Texas provided the opportunity to assess the “normal” impact of hurricanes on red-cockaded woodpeckers. By the time Rita hit the national forests the winds were fairly low, so there was less damage to trees and fewer birds lost.

In Texas, all four of the national forests—Sam Houston, Davy Crockett, Angelina, and Sabine—have redcockaded woodpecker clusters. After Hurricane Rita came through, Texas National Forests and Grasslands contacted Rudolph and SRS research wildlife biologist Dan Saenz to help inventory damage to red-cockaded woodpecker habitat. “Craig and I were provided funds to do an assessment of the damage similar to the one Hooper did in South Carolina,” says Saenz.

Though the eye of Hurricane Rita passed directly between the Angelina and Sabine National Forests, the impacts of the storm were much less than those of Hugo. Because the forests are much farther inland than the Francis Marion, Rita had lost much of its strength by the time it reached red-cockaded woodpecker habitat in Texas.

“The documented woodpecker mortality was less than 10 total birds, and less than 7 percent of cavity trees were destroyed,” says Rudolph. “In contrast to the situation following Hurricane Hugo, the foraging habitat was only minimally impacted, with the loss of approximately 5 percent of the pines.”

After Rita, Forest Service technicians installed 117 artificial cavities in trees in the Angelina and Sabine National Forests. “Loss of cavity trees is never a good thing,” says Saenz. “But we found that the damage caused by hurricanes can be absorbed if there are enough trees left standing to install artificial cavities and if action is taken quickly before the birds disperse.”

Results from installing the artificial cavities once again demonstrated the genius of a relatively simple technology when applied with the right ecological knowledge. “The populations of red-cockaded woodpeckers actually rose very sharply after Hurricane Rita,” says Saenz. “There were lots of funds available to install artificial cavities all over the forests. The birds responded to the improved habitat, and we’ve seen the sharpest increase in numbers in Texas, probably ever.”

For more information:
Craig Rudolph at 936–569–7981, x4005 or
crudolph01@fs.fed.us

Dan Saenz at 936–569–7981, x4006 or
dsaenz@fs.fed.us

 





The installation of artificial nesting cavities has significantly improved the survival of redcockaded
woodpecker populations in hurricane zones. Photo credit: Dean Elsen
The installation of artificial nesting cavities has significantly improved the survival of redcockaded woodpecker populations in hurricane zones. Photo credit: Dean Elsen

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