Woodpeckers and the Southern Pine Beetle

James C. Kroll - Associate Professor of Forest Wildlife, Stephen F. Austin State University, Nacogdoches, Tex.
Richard N. Connor - Research Wildlife Biologist, Forest Service, U.S. Department of Agriculture, Southern Forest Experiment Station, Wildlife Habitat and Silviculture Labratory, Nacogdoches.
Robert R. Fleet - Research Associate in Forest Wildlife, Stephen F. Austin State University.

U.S.D.A. Combined Forest Pest Research and Development Program Agriculture Handbook No. 564

In 1974 the U.S. Department of Agriculture initiated the Combined Forest Pest Research and Development Program, an interagency effort that concentrated on the Douglas-fir tussock moth in the West, on the southern pine beetle in the South, and on the gypsy moth in the Northeast. The work reported in this publication was funded in part by the Program. This handbook is one in a series on the southern pine beetle.

Considerations for Forest Managers

Outbreaks of SPB probably result from environmental imbalances favoring the beetle over its host pine trees and lessening natural mortality of the insect. In integrated forest pest management programs, populations of natural enemies should be maintained and enhanced whenever possible. Management practices that favor higher populations of SPB predators and parasites should increase their capability to buffer SPB population interruptions. If forest managers want to favor woodpeckers known to feed on SPB, certain management options are available. Some options, however, may not be compatible with all management situations and economic considerations.

Limit Size of Clearcuts

Certain timber management practices may reduce the abundance of woodpeckers that feed on SPB. Clearcutting large tracts of land is detrimental; it takes large areas out of "woodpecker production" for 20-30 years. If beetle epidemics occur in such areas when trees mature, few woodpeckers would be present to help stop beetle increases. Clearcuts of 20-40 acres in size would have a smaller negative effect on woodpecker abundances.

Long, narrow clearcuts with and irregular shape might be preferred to square clearcuts. Using narrow cuts, a larger area could be harvested but the impact on woodpeckers would not be as great as in a similar-sized square cuts.

Consider Site Preparation Alternatives

Site preparation after clearcutting also influences woodpecker abundance. During all seasons, but mainly in summer and fall, woodpeckers supplement their insect diet with fruits, nuts and berries of native wild plants. Chopping and using K-G blades to prepare sites for seedlings greatly decrease the abundance of deciduous plants producing these fruits in East Texas. If site preparation is necessary, winter burning is the preferred treatment, and certainly less expensive.

Not preparing a site after harvesting favors woodpeckers. Fruit-producing plants then remain relatively undisturbed and branch slash left on the ground provides foraging sites for downy and hairy woodpeckers for several years. However, such an approach would discourage tree establishment and survival on many sites.

Manage for Snags Any trees remaining in clearcuts after site preparation should be left standing. They are valuable to woodpeckers as foraging sites and potential nest trees. If it is necessary to prevent competition with growing seedlings, live deciduous trees can be killed but left standing (Fig. 10). They could be girdled or injected with a silvicide not harmful to non target life forms. In pine forest management, Timber Stands Improvement (TSI) generally results in removal of deciduous trees and trees with any signs of damage or decay. Removal of all deciduous vegetation is unfavorable to woodpeckers, since pure stands lack insects normally associated with deciduous vegetation. Selective killing of hardwoods in mixed pine-hardwood stands, however, can enhance the quality of woodpecker habitat (Fig. 11). These trees could be killed and left standing as foraging sites and potential nest cavity sites. Woodpeckers need trees with fungal heartrots for nest sites. The fungal decay softens the heartwood and facilities nest cavity excavation. Removal of trees with existing holes, dead branches, or some other sign of decay can reduce availability of woodpecker nesting sites and seriously impair woodpecker reproduction. Remember, too, that many woodpecker nest trees have their tops broken off, so such trees should not be removed. Timber stand improvement for woodpeckers can be accomplished by providing a certain number of snags per acre for each species. Varying the number and size of snags can maintain woodpecker populations at desired population levels (Table 3). Thus, it may be possible to influence woodpecker abundance within a managed area by regulating the number of snags.
	Figure 10. - Snag containing a pileated woodpecker nest cavity.
	Figure 11. - Selective killing of hardwoods of varying sizes to provide nesting and feeding sites for woodpeckers.

Table 3. - Recommended sizes and numbers of snags to maintain selected densities of woodpecker populations (Evans and Conner 1979).

Species	Probable optimum d.b.h. ranges of nest trees in inches	Optimum ranges of nest tree heights in feet	Range in number of snags needed per 100 acres
			Good	Fair	Poor
Downy woodpecker	6-10	10-30	400-320	240-160	80
Hairy woodpecker	10-14	20-45	200-160	120-80	40
Pileated woodpecker	18-26	40-70	24-19	14-10	5
Red-bellied woodpecker	14-22	40-60	270-220	160-110	55

Lengthen Timber Rotation Ages

Short rotations can reduce woodpecker abundance. a rotation age of 70 years is a minimum for downy and hairy woodpeckers. In this time trees grow to sizes suitable for both nesting and foraging. In addition, fungi would have enough time to create suitable nest site conditions in some trees. Pileated woodpeckers require larger trees and more dead wood for foraging sites than do the smaller woodpeckers. Rotations that favor pileateds should exceed 80 years in pine forests. Optimum rotation ages should probably exceed 120 years. Rotation ages should be based on tree species, site, and management regime.

Leave Some Mature Forest

Even small areas of mature forest provide valuable habitat for woodpeckers. If 1/4 acre of each 5 acres cut was allowed to reach maturity and be maintained as such, this would help the smaller woodpecker species during early stages of timber regeneration. This method would not necessarily work for pileated woodpeckers, which require larger areas of mature forest. While the arrangement of these uncut areas could be somewhat flexible, maintaining winding but manageable corridors should be favored over small, unmanageable clumps. Such corridors (at least 150 ft wide) would provide opportunities for limited foraging and nesting sites immediately following clearcutting and would also be of value for longer periods of time.

On tracts of timber having prominent drainage patterns or inaccessible areas, corridors could be left and subsequently tied in with other uncut areas. An uncut area 20 times the width of streams, not to exceed a total width of 200 ft, could be left on both sides of water courses as a buffer strip. This uncut area would have the additional benefits of reducing erosion and siltation, as well as providing a forest canopy over streams where warming could harm fish populations and habitat.

Cutting Technique and Beetle-Killed Trees During cutting operations trees are cut as close to the ground as possible. The value of cut areas to pileated woodpeckers can be enhanced greatly by "high stumping" a few of the trees (Fig. 12). The resulting 3-ft-high stumps would soon be invaded by termites or carpenter ants, both of which are eaten by pileated woodpeckers. However, in many situations, regulations, economics, and equipment limitations prevent the implementation of high stumping for large numbers of trees. Beetle-killed pines can also be important to woodpeckers after the beetles are gone. A few of these trees should be left standing as nesting sites for woodpeckers. If an infested stand is to be salvaged, some trees should be left unharvested.

Figure 12. - "High stumping" to provide excellent foraging for pileated woodpeckers.

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