Susceptibility of Red-Cockaded Woodpecker Colony Areas to Southern Pine Beetle Infestation in East Texas

Seven red-cockaded woodpecker (Picoides borealis) colonies and stands within a one-quarter mile radius were hazard-rated for susceptibility to the southern pine beetle (Dendroctonus frontalis Zimm.). Individual colonies generally were ranked low to moderate hazard using the Texas Hazard system and moderate hazard using the National Forest Risk system. Within one-quarter mile of the colonies, 28% of the stands were low hazard, 25% moderate, 0.3% high and 7.5% extreme with Texas Hazard. Four percent were low hazard, 52% moderate, and 6% high with National Forest Risk. Moderate to extreme hazard stands within one-quarter mile of the colonies could increase the probability of beetle infestation i these areas, thus threatening foraging areas and individual colony trees. Documented bark beetle activity within colonies did not correspond directly with hazard ratings, suggesting that development of a different model may be needed for these • This work was supported by a cooperative agreement between the Southern Forest Experiment Station and Stephen F. Austin State University, Nacogdoches, TX. Appreciation is extended to Steve Cannel and Glenn Donnahoe (Angelina Ranger District) and Mack Little (National Forests in Texas) for providing CISC data, compartment maps, and aerial photographs. We also thank Ronald F. Billings, Peter L. Lorio, Jr., Ray R. Hicks, Jr., Roger P. Belanger, Timothy D. Schowalter, Wesley A. Nettleton and William M. Lannan for crit h ical comments on an earlier draft of this manuscript. Current address for J.H. Mitchell: Department of Entomology, Oregon State University, Corvallis, OR 97331. 158 SjAg 15(1991) RCW colonies to incorporate stand characteristics, disturbances, cavity tree condition, and other bark beetle species. South. J. Appl. For. 15(3):158-162. The red-cockaded woodpecker (RCW) (Picoides borealis) is an endangered species endemic to mature loblolly (Pinus taeda), shortleaf (P. echinata), and longleaf (P. palustris) pine forests of the southern United States. A major threat to RCW populations is the loss of old growth southern pines for nesting habitat (U.S. Fish and Wildlife Service 1985). Only 2.5% (1.6 million acres of commercial forestland in the South is currently considered acceptable nesting habitat, a decline of 13% over the past 25 years (Lennartz et al. 1983). RCW populations have declined severely on National Forests in Texas (Conner and Rudolph 1989) and southwide (Ligon et al. 1986). The number of active colonies on the Angelina National Forest, TX, has decreased from 38 in 1983 to 22 in 1987 to 19 in 1988, a 42% decline in four years. Similar trends have been observed on the Davy Crockett and Sabine National Forests (Conner and Rudolph 1989). One of the major threats to currently active colonies is the loss of cavity trees from southern pine beetle (SPB) (Dendroctonus frontahs Zimm.) infestations (Kulhavy et al 1990, USDA Forest Service 1987). In the Four Notch Further Planning Area, TX, 5 of 12 known RCW colonies were infested by SPBs and abandoned in an outbreak covering 3750 ac (55% of the area) in 1983 (Billings and Varner 1986). In the Kisatch•e Hills Wilderness in 1986, all cavity trees in one active colony were destroyed by SPBs, and two colonies were abandoned after subsequent control activities (Kulhavy et al. 1991). In addition to direct cavity tree mortality, reduction in the acreage of potential cavity trees and foraging habitat can also occur due to SPBs (Billings and Varner 1986, Kulhavy et al. 1991, USDA Forest Service 1987). Red-cockaded woodpeckers most commonly select mature living pines for cavity excavation and are the only North American woodpeckers to nest in living pines exclusively. Excavation of a single cavity in a tree may reqmre less than four months if the heart rot fungus (Phellinus pini) •s present, and up to 2 years or longer if no decay is present (Conner and O'Halloran 1987). Cavity trees used by a RCW clan are commonly clustered in a colony containing from 1 to 30 cavity trees spaced up to 2400 ft apart (Jackson and Thompson 1971). Cavity trees are classified as active (used for nesting and roosting) or inactive (abandoned) (Jackson 1977, 1978). Of the active trees within a colony, only one is used as the nest tree. Barring death of the tree or loss of the cavity to competing woodpeckers, the RCWs will use the same cavity tree for years or even decades (U.S. Fish and Wildlife Service 1985). A unique behavior of the RCW is to peck numerous resin wells above and below the entrance of a cavity and along the tree bole (Jackson 1978). Th•s pecking activity presumably stimulates the flow of pine oleoresin that acts as a barrier against rat snake predation. Protection of these trees is crucial to the survival of existing populations of RCWs, particularly in areas such as the Angelina National Forest where populations are declining. Some of the most useful forest management tools developed from SPB research are techniques to rank forest stand susceptibility to SPB infestation (Billings et al. 1985, Hicks et al. 1980, 1981, 1987, Lorio and Mason 1982). These techniques are referred to as hazardor risk-rating systems. Researchers have developed different definitions for hazard and risk. For our purposes, hazard indIcates the relative susceptibility of an area, based solely on site and stand factors and host abundance. Risk is defined as the probability of bark beetle infestations becoming established within a given time span and results from the interaction of hazard and existing SPB populations (Paine et al. 1984). Applications of hazardand risk-rating techniques have been used to determine susceptibility of active RCW colonies to SPB infestation in loblolly and shortleaf pine types (Belanger et al. 1988, Kulhavy et al. 1988, Mitchell 1987). Belanger et al. (1988) found that hazard and risk of RCW colony stands to SPB infestation in Georgia were very low. However, that study did not evaluate the potential of infestation from stands adjacent to RCW col-