Pileated Woodpecker Damage to Red-Cockaded Woodpecker Cavity Trees in Eastern Texas

Wilson Bull., 110(3), 1998, pp. 362-367

PILEATED WOODPECKER DAMAGE TO RED-COCKADED WOODPECKER CAVITY TREES IN EASTERN TEXAS

DANIEL SAENZ,v3‘ RICHARD N. CONNER, ’ CLIFFORD E. SHACKELFORD? AND D. CRAIG RUDOLPH ’

ABSTRACT.-We surveyed all known Red-cockaded Woodpecker (Picoides borealis) cavity trees (n = 514) in the Angelina National Forest in eastern Texas for Pileated Woodpecker (Dryocopus pileatus) damage. We compared the frequency of Pileated Woodpecker damage to Red-cockaded Woodpecker cavity trees in longleaf pine (Pinus palustris) habitat to damage in loblolly (P. faeda)-shortleaf (P. echinata) pine habitat. We also examined the effectiveness of restrictor plates in deterring Pileated Woodpecker enlargement of Red-cockaded Woodpecker cavities. Pileated Woodpecker damage was significantly greater in longleaf pine habitat than in the loblolly-shortleaf pine habitat in spite of census results showing similar abundance levels of Pileated Wood- peckers in the two forest types. We suggest that limited numbers of snags in the longleaf habitat may focus Pileated Woodpecker excavation on Red-cockaded Woodpecker cavity trees, whereas a greater amount of midstory vegetation in the loblolly-shortleaf pine habitat may serve to reduce visibility, thereby lowering Pileated Woodpecker detection and destruction of Red-cockaded Woodpecker cavities. Restrictor plates were very effec- tive in preventing Pileated Woodpecker enlargement of cavities. While restrictor plates are useful for protecting Red-cockaded Woodpecker cavities, they should be used only in small populations when cavities are in short supply. The Pileated Woodpecker plays an important role, especially in the longleaf ecosystem which is a relatively cavity-barren environment, by providing nesting sites for larger secondary cavity users, such as Amer- ican Kestrels (Falco snarverius). Eastern Screech-Owls (Otus ash), and fox squirrels (Sciurus n&r). Received 7 Jan. 1998, accepted 20 April ’ 1998.

The federally listed endangered Red-cock- the frequently burned pine savannas where aded Woodpecker (Picoides borealis; USDI snags (standing dead trees that are used for 1970) is endemic to the southeastern United nesting by most primary cavity nesters such States (Jackson 1971), and is unique because as woodpeckers) are short-lived and hardwood of its dependence on living pine trees in which midstory is infrequent or absent as a result of it excavates roost and nest cavities (Steirly frequent fires. It can take several years for 1957). The pines used as cavity trees are gen- Red-cockaded Woodpeckers to fully excavate erally mature, because the woodpeckers need cavities in living pines but these cavities often heartwood (non-living xylem) large enough in last for decades (Conner and Rudolph 1995). diameter to house a cavity and sufficient time Upon cavity completion, the Red-cockaded for fungus (Phellinus pini) to decay the heart- Woodpecker excavates shallow holes into the wood for excavation (Jackson and Jackson xylem, termed resin wells, which are worked 1986, Conner and OHalloran’ 1987, DeLotelle regularly to stimulate copious resin flow (Li- and Epting 1988, Rudolph and Conner 1991). gon 1970, Dermis 1971). Resin flow may Young trees usually have thicker sapwood serve to protect cavities from predators and (living xylem that surrounds the heartwood some cavity competitors (Dennis 1968, 1971; and actively conducts resin) which means a Ligon 1970; Jackson 1978; Rudolph et al. proportionally smaller diameter heartwood 1990). The Red-cockaded Woodpecker can be (Conner et al. 1994). viewed as a keystone species in the southern The ability to excavate cavities in living pine ecosystem because of its ability to pro- pines was likely an evolutionary advantage in duce cavities in a relatively cavity-barren environment (Conner et al. 1997b). This has a ’ ’ Wildlife Habitat and Silviculture Laboratory (main- positive impact on faunal diversity by provid- tained in cooperation with the College of Forestry, Ste- ing cavities for secondary cavity users (Ru- phen E Austin State Univ.), Southern Research Station, dolph et al. 1990, Conner 1995, Conner et al. USDA Forest Service, Nacogdoches, TX 75962. 1997a). 2 Texas Partners In Flight, Texas Parks and Wildlife Dept., 4200 Smith School Rd., Austin, TX, 78744. The old living pines and frequently burned 3 Corresponding author; ecosystem devoid of midstory that once gave E-mail: [email protected]. the Red-cockaded Woodpecker an ecological

364 THE WILSON BULLETIN . Vol. 110, No. 3, September 1998

2 400 IJ NO PILEATED DAMAGE q PILEATED DAMAGE 2 I- 300

z 6 a 200 0

is g 100

i a 0 LOB-SHORT LONGLEAF FIG. 1. The number of Red-cockaded Woodpecker cavity trees on the Angelina National Forest damaged by Pileated Woodpeckers (cavity enlargement or other excavations) in loblolly-shortleaf pine habitat compared to longleaf pine habitat (x2 = 41.2, P < 0.001). sapling (5-16 cm DBH) and pole (17-32 cm DBH) cavity trees showed signs of woodpecker ex- hardwoods and pines in each plot. Two-tailed t-tests cavations in the loblolly-shortleaf pine habitat. were used to compare snag availability and midstory About 4.8% of all cavity trees in the longleaf openness between the loblolly-shortleaf pine and the longleaf pine forest types. All analyses were calculated pine habitat were damaged annually by Pile- using PC-SAS (SAS Institute, Inc. 1988). ated Woodpeckers compared to 1.3% in the loblolly-shortleaf pine habitat. RESULTS Two hundred nineteen natural cavity trees Pileated Woodpeckers regularly excavated contained 276 cavities without restrictor into Red-cockaded Woodpecker cavity trees plates. Cavity enlargement occurred in 41.3% and enlarged cavity entrances; 27.2% (140 of (114 of 276) of all unrestricted cavities. Pile- 514 cavity trees, both habitat types combined) ated Woodpeckers enlarged Red-cockaded showed some evidence of Pileated Woodpeck- Woodpecker cavities at a significantly greater er damage. Pileated Woodpecker damage to rate in longleaf pine habitat than loblolly- Red-cockaded Woodpecker cavity trees was shortleaf pine habitat (x2 = 31.5, P < 0.001; significantly greater in longleaf pine habitat Fig 2). In longleaf pine habitat 50.7% (106 of than in loblolly-shortleaf pine habitat (x2 = 209) of the unrestricted cavities were enlarged 41.2, P < 0.001; Fig 1). In the longleaf pine whereas only 11.9% (8 of 67) were enlarged habitat type 35.8% (126 of 352) of the cavity in loblolly-shortleaf pine habitat. Approxi- trees showed signs of Pileated Woodpecker mately 2.8% of the cavity trees in the longleaf excavation whereas 8.6% (14 of 162) of the pine habitat were enlarged by Pileated Wood-

300 - IJ NO ENLARGEMENT z . q ENLARGEMENT F

5 200 -

LOB-SHORT LONGLEAF FIG. 2. The number of natural Red-cockaded Woodpecker cavities without restrictor plates on the Angelina National Forest enlarged by Pileated Woodpeckers in loblolly-shortleaf pine habitat compared to longleaf pine habitat (x2 = 31.47, P < 0.001). Saenz et al. l DAMAGE TO RED-COCKADED CAVITY TREES 365

0.3 q LOB/SHORT q LONGLEAF 1

SPRING WINTER

FIG. 3. The mean number of Pileated Woodpeckers detected at each site in loblolly-shortleaf pine habitat compared to longleaf pine habitat during spring (t = 1.31, P > 0.05) and winter (t = 0.36, P > 0.05) surveys. peckers annually compared to only 0.8% en- The mid-story components (sapling and pole- largement in the loblolly-shortleaf pine habi- size pine and hardwood trees) were also sig- tat. nificantly more abundant in loblolly-shortleaf Restrictor plates (n = 54) were very effec- pine habitat than longleaf pine habitat (P -=c tive in preventing enlargement by Pileated 0.001; Table 1). Woodpeckers as compared to unprotected cavities (x2 = 31.0, P < 0.001). In only one in- DISCUSSION stance were Pileated Woodpeckers able to de- Many Red-cockaded Woodpecker cavity stroy a cavity fitted with a restrictor plate. The trees in the Angelina National Forest were Pileated Woodpecker excavated a second en- damaged by Pileated Woodpeckers. Because a trance above the restrictor plate exposing the large population of Pileated Woodpeckers is cavity above the original cavity entrance. present across the forest, the difference in the Abundance estimates from point counts re- amount of Pileated Woodpecker damage be- vealed that Pileated Woodpeckers were simi- tween the longleaf pine habitat and the lob- larly abundant in the two pine habitat types lolly-shortleaf pine habitat is surprising. (Fig 3). We failed to detect differences be- At least two factors may account for the tween habitat types in Pileated Woodpecker differences in Pileated Woodpecker damage to abundance during both winter (t = 0.355, P Red-cockaded Woodpecker cavity trees be- > 0.05) and spring (t = 1.310, P > 0.05). tween the two habitat types. We suggest that There were significantly more and larger the relatively low number of snags in the snags in loblolly-shortleaf pine habitat than in longleaf habitat as a result of frequent burning longleaf pine habitat (P < 0.001; Table 1). and longer lived longleaf pine trees may focus

TABLE 1. Habitat comparisons between longleaf habitat and loblolly-shortleaf habitat.

Lob-Shoe Longleafa Habit&’ Cottlpo”e”ts x (SD) x (SD) f P TOTSNAG 1.95 1.97 0.25 0.55 10.539

a Data collected from 160 0.04 ha plots in each habitat. b The habltat components sampled are as follows, (TOTSNAG = the total number of snags in the plot, LRGSNAG = the number of large snags in the plot, SAPLHWD = the number of saphng hardwoods in the plot, POLEHWD = the number of pole-sized hardwoods in the plot, SAPLPIN = the number of saplq pines m the plot, and POLEPIN = the number of pole-sired pines in the plot). 366 THE WILSON BULLETIN l Vol. 110, No. 3, September 1998 more of the attention of Pileated Woodpeckers Woodpeckers should be allowed to enlarge on Red-cockaded Woodpecker cavity trees cavities for larger secondary cavity nesters in than in the loblolly-shortleaf pine habitat areas where Red-cockaded Woodpecker pop- where snags are more abundant. Pileated ulations are stable, as a way to maintain nat- Woodpeckers are known to use snags exten- ural fauna1 diversity. sively for foraging and excavating roost and ACKNOWLEDGMENTS nest cavities (Conner et al. 1975, Kilham 1976, Bull and Meslow 1977, Conner 1980, We thank J. H. Carter III, R. G. Hooper, L. A. Fitz- Bull 1987). We also suggest that the openness gerald, E C. James, J. D. Ligon, D. M. Brooks, D. J. Ingold, R. H. Doster, and J. R. Walters for constructive of the frequently burned longleaf pine habitat comments on the manuscript. may allow Red-cockaded Woodpecker trees to be more easily detected by Pileated Wood- LITERATURE CITED peckers than trees in the infrequently burned ALLEN, D. H. 1991. An insert technique for construct- loblolly-shortleaf pine habitat. ing artificial cavities for Red-cockaded Wood- The reasons why Pileated Woodpeckers ex- peckers. U.S. For. Serv. Gen. Tech. Rep. SE-73: cavate holes in Red-cockaded Woodpecker l-19. cavity trees and enlarge cavities still are poor- BULL, E. L. 1987. Ecology of the Pileated Woodpeck- er in northeastern Oregon. J. Wildl. Manage. 51: ly understood. Pileated Woodpeckers only in- 472-48 1. frequently use such trees for roosts or nests BULL, E. L. AND E. C. MESLOW. 1977. Habitat require- (Conner et al. 1996). We suggest that Pileated ments of the Pileated Woodpecker in northeastern Woodpeckers are attracted by excavations of Oregon. J. For. 75:335-337. other woodpeckers, in this case Red-cockaded CARTER, J. A., J. R. WALTERS, S. H. EVERHART,AND l? Woodpecker cavities, and begin excavating D. DOERR. 1989. Restrictors for Red-cockaded Woodpecker cavities. Wildl. Sot. Bull. 17:69-72. possibly for either foraging or nesting. We CONNER, R. N. 1980. Foraging habitats of woodpeck- also suggest that the sapwood is likely exca- ers in southwestern Virginia. J. Field Ornithol. 51: vated in the process of enlarging the cavity 119-127. chamber causing copious amounts of sticky CONNER, R. N. 1983. Comparisons of woodpecker resin to flow at the excavation site or into the nesting and foraging habitats in Virginia. Raven cavity, and that this may discourage Pileated 54164-70. Woodpeckers from completely excavating a CONNER, R. N. 1995. Red-cockaded Woodpecker cavity trees: an introduction. Pp. 335-337 in Red- cavity. Although these enlarged cavities may cockaded Woodpecker: recovery, ecology and not be fully excavated by the Pileated Wood- management (D. L. Kulhavy, R. G. Hooper, and peckers, the amount of enlargement is usually R. Costa, Eds.). College of Forestry, Stephen E sufficient for other cavity nesters. Austin State Univ., Nacogdoches, Texas. Restrictor plates effectively prevented Pi- CONNER, R. N., R. G. HOOPER, H. S. CRAWFORD,AND leated Woodpecker enlargement of Red-cock- H. S. MOSBY. 1975. Woodpecker nesting habitat in cut and uncut woodlands in Virginia. J. Wildl. aded Woodpecker cavities. However, we cau- Manage. 39:144-150. tion against using restrictor plates on all Red- CONNER, R. N. AND K. A. OHALLORAN.’ 1987. Cavity cockaded Woodpecker cavities. Although the tree selection by Red-cockaded Woodpeckers as Red-cockaded Woodpecker plays an important related to growth dynamics of southern pines. role in longleaf pine ecosystems by providing Wilson Bull. 94:398-412. cavities for smaller secondary cavity nesters, CONNER, R. N. AND D. C. RUDOLPH. 1989. Red-cockaded Woodpecker colony status and trends on the the Pileated Woodpecker may play an equally Angelina, Davy Crockett, and Sabine National important role by enlarging Red-cockaded Forests. Res. Pap. SO-250. U.S. Department of Woodpecker cavities and providing nest sites Agriculture, Forest Service, Southern Forest Ex- for larger secondary cavity nesters, such as periment Station. New Orleans, Louisiana. American Kestrels (F&o sparverius), Eastern CONNER, R. N. AND D. C. RUDOLPH. 1995. Excavation Screech-Owls (Otus asio), and fox squirrels dynamics and use patterns of Red-cockaded (Sciurus niger; Conner et al. 1997a). While Woodpecker cavities: relationships with coopera- tive breeding. Pp. 343-352 in Red-cockaded we know that restrictor plates are a good man- Woodpecker: recovery, ecology and management agement tool that may potentially be useful in (D. L. Kulhavy, R. G. Hooper, and R. Costa, Eds). recovering smaller Red-cockaded Woodpeck- College of Forestry, Stephen E Austin State Univ., er populations, we also suggest that Pileated Nacogdoches, l‘ exas.‘ Saenz et al. . DAMAGE TO RED-COCKADED CAVITY TREES 367

CONNER, R. N., D. C. RUDOLPH, D. L. KULHAVY, AND cockaded Woodpeckers: predator-prey adapta- A. E. SNOW. 1991. Causes of mortality of Red- tions. Auk 911342-347. cockaded Woodpecker trees. J. Wildl. Manage. 5.5: JACKSON,J. A. 1978. Predation by a gray rat snake on 531-537. Red-cockaded Woodpecker nestlings. Bird-Band- CONNER, R. N., D. C. RUDOLPH, D. SAENZ, AND R. R. ing 49:187-188. SCHAEFER. 1994. Heartwood, sapwood, and fun- JACKSON,J. A. AND B. J. S. JACKSON. 1986. Why do gal decay associated with Red-cockaded Wood- Red-cockaded Woodpeckers need old trees? pecker cavity trees. J. Wildl. Manage. 58:728- Wildl. Sot. Bull. 14:318-322. 734. JAMES,E C. AND H. H. SHUGART. 1970. A quantitative CONNER, R. N., D. C. RUDOLPH, D. SAENZ, AND R. R. method of habitat description. Audubon Field SCHAEFER. 1996. Red-cockaded Woodpecker Notes 24:722-726. nesting success, forest structure, and southern fly- KILHAM, L. 1976. Winter foraging and associated be- ing squirrels in Texas. Wilson Bull. 108:697-711. havior of Pileated Woodpeckers in Georgia and Florida. Auk 93: 15-24. CONNER, R. N., D. C. RUDOLPH, D. SAENZ, AND R. R. LAVES, K. S. 1996. Effects of southern flying squir- SCHAEFER. 1997a. Species using Red-cockaded rels, Glaucomys volans, on Red-cockaded Wood- Woodpecker cavities in eastern Texas. Bull. Tex. pecker, P&ides borealis, reproductive success. Ornithol. Sot. 30:11-16. M.Sc. thesis, Clemson Univ., Clemson, South CONNER, R. N., D. C. RUDOLPH, D. SAENZ, AND R. N. Carolina. COULSON. 199713. The Red-cockaded Woodpeck- LIGON, J. D. 1970. Behavior and breeding biology of ers’ role in the southern pine ecosystem, popula- the Red-cockaded Woodpecker. Auk 87:255-278. tion trends and relationships with southern pine LOEB, S. C., W. D. PEPPER,AND A. T. DOYLE. 1992. beetles. Tex. J. Sci. 49:139-154. Habitat characteristics of active and abandoned COPEYON, K. C. 1990. A technique for construction Red-cockaded Woodpecker colonies. South. J. of cavities for the Red-cockaded Woodpecker. Appl. For. 16:120-125. Wildl. Sot. Bull. 18:303-311. RUDOLPH, D. C. AND R. N. CONNER. 1991. Cavity tree COSTA, R. AND R. E. E ESCANO. 1989. Red-cockaded selection by Red-cockaded Woodpeckers in rela- Woodpecker status and management in the south- tion to tree age. Wilson Bull. 103:458-467. em region in 1986. U.S. Dept. Agric., For. Serv. RUDOLPH, D. C., R. N. CONNER, AND J. TURNER. 1990. Tech. Publ. RS-TP-12:1-71. Competition for Red-cockaded Woodpecker (Pi- DELOTELLE, R. S. AND R. J. ERING. 1988. Selection coides borealis) roost and nest cavities: the effects of old trees for cavity excavation by Red-cock- of resin age and cavity entrance diameter. Wilson aded Woodpeckers. Wildl. Sot. Bull. 16:48-52. Bull. 102:23-36. DENNIS, J. V. 1968. Rare Red-cockaded Woodpecker RUDOLPH, D. C., H. KYLE, AND R. N. CONNER. 1990. under study at Hobcaw. Catalyst 2: 12-14. Red-cockaded Woodpeckers vs rat snakes: the ef- DENNIS, J. V. 1971. Utilization of pine resin by Red- fectiveness of the resin barrier. Wilson Bull. 102: cockaded Woodpecker and its effectiveness in 14-22. SAS INSTITUTE, INC. 1988. SAS/STAT users’ guide. protecting roosting and nest sites. Pp. 78-86 in Release 6.03 edition. SAS Institute, Inc., Cary, The ecology and management of the Red-cock- North Carolina. aded Woodpecker (R. L. Thompson, Ed.). Bureau STEIRLY, C. C. 1957. Nesting ecology of the Red- of Sport Fisheries and Wildlife, U.S. Dept. of In- cockaded Woodpecker in Virginia. Atl. Nat. 12: terior, and Tall Timbers Research Station, Talla- 280-292. hassee, Florida. TAYLOR, W. E. AND R. G. HOOPER. 1991. A modifi- JACKSON,J. A. 1971. The evolution, taxonomy, dis- cation of Copeyons’ technique for making artifi- tribution, past populations and current status of cial Red-cockaded Woodpecker cavities. U.S. For. the Red-cockaded Woodpecker. Pp. 4-29 in The Serv. Gen. Tech. Rep. SE-72:1-31. ecology and management of the Red-cockaded USDI FISH AND WILDLIFE SERVICE. 1970. Listing of Woodpecker (R. L. Thompson, Ed.). Bureau of Red-cockaded Woodpecker as endangered. Fed- Sport Fisheries and Wildlife, U.S. Dept. of Inte- eral Register 35: 16047. rior, and Tall Timbers Research Station, Tallahas- USDI FISH AND WILDLIFE SERVICE. 1985. Red-cock- see, Florida. aded Woodpecker recovery plan. U.S. Fish and JACKSON,J. A. 1974. Gray rat snakes versus Red- Wildlife Service, Atlanta, Georgia.