Causes of Mortality of Red-Cockaded Woodpecker Cavity Trees

Abstract

Over a 13-year period we examined the mortality of cavity trees (n = 453) used by red-cockaded woodpeckers (Picoides borealis) on national forests in eastern Texas. Bark beetles (53%), wind snap (30%), and fire (7%) were the major causes of cavity tree mortality. Bark beetles were the major cause of mortality in loblolly (Pinus taeda) and shortleaf (P. echinata) pines, whereas fire was the major cause in longleaf pines (P. palustris). Cavity trees on the Angelina National Forest (NF) were dying at a higher rate than new, complete cavities were being excavated. Cavity enlargement by pileated woodpeckers (Dryocopus pileatus) on the Angelina NF was substantial, with 20% (49/ 249) of the cavity trees being enlarged over 7 years. To reduce cavity tree mortality, site disturbances in cluster areas (e.g., midstory control, prescribed burning, thinning) should be minimized during years when southern pine beetle (Dendroctonus frontalis) populations are elevated. Careful planning of timber cutting to avoid funneling wind into cluster areas might reduce wind damage to cavity trees. The red-cockaded woodpecker has been legally defined as an endangered species since 1970 (35 Fed. Register 16047, 13 Oct 1970). A habitat feature that is essential for the survival 0~ this species is a constant supply of living, old Ptnes with decayed heartwood (Jackson 1977, Conner and Locke 1982) and large crowns and open boles that have had some suppression in their growth history (Conner and O'Halloran 1987). The woodpecker excavates nest and roost ~~ies. in these trees (U.S. Fish W ildl. Serv. S • Lrgon et al. 1986). In the southern United tates old · f h ' 1 . Cos ' pmes o t IS type are re atlvely rare. . ta and Escano (1989) indicated that suffictentl ld . sho Y 0 pmes for cavity excavation are in So ~supply on many national forests in the is ut and that the age structure of most forests lo~u~h that supply of old pines is likely to be lions ; >20 years. Recent declines in populaRudo~ ~ed-cockad.ed woodpeckers (Conner and lack r 1989) might be caused in part by a 0 old-growth pines in southern pine forests. J. WILDL. MANAGE. 55(3):531-537 Thus, to develop management options that reduce the loss of cavity trees, it is important to identify factors causing this loss. In our study, we evaluate mortality of cavity trees used by red-cockaded woodpeckers and suggest management options to reduce losses. We thankS. C. Loeb, P. Lorio, R. W. Mannan, F . L. Oliveria, and J. R. Walters for constructive comments on an early draft of the manuscript. Partial funding was provided by a Challenge Cost Share Agreement (#19-90-008) with the Resource Protection Division, Texas Parks and Wildlife Department.