Реферат: Management Techniques For The RedCocked Woodpecke Essay
Management Techniques For The Red-Cocked Woodpecke Essay, Research Paper
Management techniques for the red-cocked woodpeckerABSTRACTThe red-cockaded woodpecker (Picoides borealis) has been listed as an endangered species since October, 1970. This species inhabits pine forests in the southeastern United States where the majority of prime timberland is privately owned. Private ownership of preferred habitat and historically destructive silvicultural practices create unique problems for federal wildlife managers. This report analyzes three management techniques being used to assess and augment red-cockaded woodpecker populations on federal lands in the region, primarily military installations. Seeking cooperation between diverse government agencies, wildlife managers attempt to accurately assess species abundance, alter woodpecker nesting cavities, and construct nest sites in an effort to enhance red-cockaded woodpecker habitat on limited federal holdings in the American southeast. Key words: Picoides borealis, Global Positioning System, Geographic Information System, cavity trees, cavity restrictorsThe red-cockaded woodpecker (Picoides borealis) is an endangered species that inhabits pine forests in an historical range from Texas to the Atlantic coast (Jackson, 1986; Reed et al., 1988). Picoides borealis nest in clans or family groups that usually consist of one breeding pair and 2 non-breeding male helpers (Jackson, 1986 ). This group establishes and defends a territory that includes foraging habitat and nesting “cavity trees” (Copeyon et al., 1991; Jackson et al., 1986; Rossell and Gorsira, 1996). Red-cockaded woodpecker clans excavate cavities in living pines, and have established a living and foraging routine in conjunction with the southeastern pine forests and the historical occurrence of fire, which reduces hardwood understory while sparing fire-resistant pines (Jackson, 1986). Much of the prime nesting and foraging habitat for this species has been systematically eliminated due to development, timber harvest and intensive fire suppression (Jackson, 1986). The emergence of dense hardwood understory and midstory as a result of fire suppression in red-cockaded woodpecker habitat has resulted in the abandonment of many otherwise undisturbed areas (Jackson, 1986; Kelly et al., 1993). The red-cockaded woodpecker has been listed as endangered since 1970 (Federal Register, 1970 as cited by Ertep and Lee, 1994). Four requirements for sustained red-cockaded woodpecker populations that are lacking in the species historical range are identified as critical to species stabilization and recovery: 1.) Open pine forests with shade tolerant understory controlled by cyclical fire seasons; 2.) Old growth Pinus palustrus aged > 95 years and Pinus taeda aged > 75 years; 3.) Approximately 200 acres for nesting group or clan; 4.) Multiple clans per area to maintain genetic stability and variability (Jackson, 1986). The opportunity to establish or preserve these habitat qualities on private timberland is largely lost due to historical harvest practices and development, and research on expanding populations on federal holdings is the most vital component in red-cockaded woodpecker stabilization and recovery (Jackson et al., 1979a; Jackson, 1986).Exacerbating the problem of habitat loss due to encroachment and fire-suppression are natural hazards such as hurricanes, pine-beetle infestations and usurpation of red-cockaded woodpecker cavities by other species (Carter et al., 1989; Rossell and Gorsira, 1996). Effects of historically natural hazards are multiplied in the context of a diminished species abundance (Carter et al., 1989; Jackson, 1986). Land management for wildlife is subject to unique difficulties in the Southeast, as the majority of forested land is privately owned (Jackson, 1986). In western states, approximately 2/3 of undeveloped land is federally administered, making the enactment of widespread management policies feasible, and controversies are apt to center around questions of access and use, rather than the more difficult problems concerned with private property rights. MATERIALS AND METHODSThis report will focus on the current techniques being explored and enacted to stabilize and increase red-cockaded woodpecker populations on federal lands throughout its previous range. Three areas of concern regarding the red-cockaded woodpecker populations on federal lands interact to define current management practices (Jackson, 1986). Wildlife biologists, foresters, and the military have tested and combined specific techniques involving habitat assessment and identification, cavity alteration, and cavity construction to manage limited habitat for the red-cockaded woodpecker on federally administered land (Carter et al., 1989; Copeyon, 1990; Ertep and Lee, 1994). Analysis of specific studies and practices in these three areas serve as a description of the technique for managing limited federal lands for the enhancement and stabilization of red-cockaded woodpecker populations.DISCUSSIONHABITAT ASSESSMENT AND IDENTIFICATIONA significant problem associated with the management of red-cockaded woodpecker populations is obtaining an accurate assessment of habitat availability and home range estimates (Ertep and Lee, 1994; Reed et al., 1988). Differences in habitat quality and availability throughout the range of the red-cockaded woodpecker affect population density and the range of foraging and nesting activities within colonies, making general application of population estimators difficult (Reed et al., 1988). This issue was addressed in 1988 during a study to evaluate red-cockaded woodpecker population indices. Reed et al. (1988) set out to evaluate studies concerning red-cockaded woodpecker population indices and, if necessary, develop a new techniques to more accurately estimate adult population size. Reed at al. (1988) researched the circular scale technique (CST) as described by Harlow et al. (1983) and found that application of this method of population estimation is limited. CST utilizes aerial identification of active cavity tree groups, and encompasses said groups in a 460-m diameter circle that contains as many of the active cavity trees as possible (Harlow et al., 1983 as cited by Reed et al., 1988). While Harlow et al. (1983) and Lennartz and Matteaur (1986) used CST with great accuracy in their study areas, estimating population sizes to between 92 and 95% of the true number, the 1988 study by Reed et al. determined that the technique cannot be used throughout the red-cockaded woodpecker range. Using CST in the Sandhills region of North Carolina underestimated the number of groups in the Reed et al. study population (Reed et al., 1988). In the Reed et al. (1988) study area, red-cockaded woodpecker population density and the spatial arrangement of colonies was frequently influenced by habitat fragmentation which led to the violation of assumptions held necessary in the CST method of population estimation (Reed et al., 1988). Conclusions in the Reed et al. (1988) study indicate that CST may be generally used as an index, but further research is necessary to establish a universal technique to estimate red-cockaded woodpecker populations. The development of sophisticated computer programs and topographical analysis techniques may make assessment of red-cockaded woodpecker habitat and species abundance more accurate and less time consuming (Ertep and Lee, 1994; Reed et al., 1988). These advancements in geographic analysis and terrain assessment technology have provided for an unlikely union between wildlife managers and natural resource agencies on US military installations throughout the southeast (Ertep and Lee, 1994; USMC, 1995). The coordination of Geographic Information System programs (GIS) and Digital Multispectral Videography (DMSV) at Fort Benning, Georgia adds a new technological advantage in the search for red-cockaded woodpecker colonies and habitat by accurately identifying longleaf pine stands (USACE, 1996). Image analysis and confirming Global Positioning System information has been validated in initial tests by the confirmation of three GIS and DMSV-identified red-cockaded woodpecker sites through direct ground observation in the areas (USACE, 1996). Research is ongoing to examine the initial findings associated with these new and highly technical habitat assessment techniques (Ertep and Lee, 1996).
CAVITY ALTERATIONA significant problem in the recovery of red-cockaded woodpecker populations involves the usurpation of nesting cavities by other species, primarily southern flying squirrels (Gloucomys volans), northern flickers (Colaptes auratus), European starlings (Sturnus vulgaris), and other species of woodpeckers (Carter et al., 1989; Rossell and Gorsira, 1996). Invasive species occupy or significantly alter cavities, preventing their continued use by red-cockaded woodpeckers (Carter et al., 1989). Many nesting locations take months or years to construct, and adequate old-growth pines are now less frequent in the red-cockaded woodpecker range (Walters, 1986). Wildlife managers and foresters have experimented with altering or reinforcing red-cockaded woodpecker nesting cavities to discourage these invaders. Carter et al. (1989) describe specific techniques for cavity alteration. Three types of cavity restrictors alter the character of the cavity entranceway, acting as a deterrent to enlargement or access by other species (Figure 1). Cavity restrictors generally consist of a camouflaged metal plate fastened over the cavity entrance (Carter et al., 1989). A study by Rossell and Gorsira (1996) demonstrates the importance of specific cavity parameters in assessing the availability of nesting and roosting cavities for red-cockaded woodpeckers. The results of their study showed that red cockaded woodpeckers nested only in cavities with normal entrances (Rossell and Gorsira, 1996). Even if cavities with enlarged entrances contained normal chambers and were not occupied by competing species, red-cockaded woodpeckers avoided them (Table 1). TABLE 1+Diurnal occupants versus entrance (ent.) and chamber (ch.) characteristics of active red-cockaded woodpecker (Picoides borealis) cavities in the Northeast Management Area, Fort Bragg, North Carolina, May, 1993. (Rossell and Gorsira, 1996)Use among entrance and chamber categoriesNormal ent.Enlarged ent. Occupant or ContentsNorm. ch.Enlarged ch.Norm ch.Enlarged ch. Red cockaded-woodpecker21000Southern flying squirrel7417Red-bellied woodpecker0010Red-headed woodpecker2000Screech owl0002Northern flicker0002Nest material1111Unoccupied29334CAVITY CONSTRUCTIONTechniques to artificially create red-cockaded woodpecker cavities have been initially successful on federal holdings such as Fort Bragg, North Carolina, which holds one of the largest red-cockaded woodpecker populations on federally administered lands (Copeyon et al., 1991; Rossell and Gorsira, 1996). The technique and effectiveness of artificial cavity construction is best examined by analyzing the physical characteristics of artificial red-cockaded woodpecker cavities, and reviewing studies wherein the cavities are used as a management tool (Copeyon, 1990; Copeyon, et al., 1991; Rossell and Gorsira, 1996). Perhaps the most comprehensive study concerning artificial cavity construction for the benefit of the red-cockaded woodpecker was conducted by Copeyon, Walters and Carter as part of a ten year study of red-cockaded woodpecker populations in the Sandhills region of North Carolina (1991). Their work, Induction of Red-Cockaded Woodpecker Group Formation by Artificial Cavity Construction, (Copeyon et al., 1991) represents the most practical and valuable guide to red-cockaded woodpecker population enhancement techniques to date (Conner and Rudolph, 1995). In 1990, Carole Copeyon published an article describing a technique for constructing artificial cavities for red-cockaded woodpeckers. Explaining that excavation of suitable livingcavities takes a minimum of ten months and normally much longer to complete, Copeyon (1990) surmised that construction of artificial cavities may be an effective management tool that would encourage colonization of abandoned areas and reduce energy expenditure associated with nesting cavity construction. After making the decision to use artificial nesting cavities as a management tool, wildlife managers should attempt to select older trees in their respective areas of responsibility (Copeyon, 1990; Copeyon et al., 1991). Selection of older trees mimics the natural inclination of the red cockaded woodpecker and that older trees have sufficient heartwood development to support large nesting and roosting cavities without sustaining damage (Copeyon, 1990). As indicated previously, red-cockaded woodpeckers generally select trees between 80 and 100 years old depending on species availability. Copeyon (1990) reveals that an adequate artificial nesting cavity requires an entrance approximately 4.4cm.-6.4cm. in diameter placed at 1-24 meters above ground level. An entrance tunnel should be excavated into the heartwood with the nesting chamber extending down at a right angle to the entrance tunnel to a depth between 20.3 and 27.3cm. (Figure 2) (Copeyon, 1990). Small resin wells are drilled around the tree above and below the entrance site (Copeyon 1990; Rossell and Gorsira, 1996). Seepage from these wells act to discourage competitors and predators (Copeyon, 1990). The results of Copeyon s initial study concerning red-cockaded woodpecker cavity construction are contained in (Table 2). TABLE 1. +Use of artificial cavities by red-cockaded woodpeckers (Picoides borealis) in the Sandhills region of North Carolina (Copeyon, 1990). SpeciesAge #Constructed#ActiveLongleafOld2925Moderate74Young22Total3831LoblollyOld43Young21Total64Cavity construction for red-cockaded woodpecker management is an effective tool for inducing the formation of new colonies in the species historical range, and may prove to increase reproductive success in already established colonies (Copeyon et al., 1991). RESULTSFurther research is necessary to establish the impact of management for the red-cokaded woodpecker on other species (Masters et al., 1996). Initial studies indicate that management practices involving the clearance of hardwood understory and the initiation of prescribed burns in red-cockaded woodpecker habitat increase forage for white-tailed deer (Odocoileus virginianus) (Masters et al., 1996). Studies continue to examine concerns about possible negative effects of single species management practices in association with red-cockaded woodpecker recovery effort (Masters et al., 1996). In the 25 years since the identification of the red-cockaded woodpecker as an endangered species, establishing a unified recovery program among the diverse federal agencies responsible for the administration of lands within the species range has been difficult (Jackson, 1986). In the first 15 years of listing, no programs existed to effectively manage habitat for the red-cockaded woodpecker. Jackson (1986) described the situation as especially urgent, as the red-cockaded woodpecker was becoming dependent on widely dispersed islands of habitat, isolating colonies and creating the potential for catastrophic losses due to natural occurrences and inter-species competition for roosting and nesting sites. Since 1986, research into habitat requirements for successful red-cockaded woodpecker colonies have been identified (Copeyon et al., 1991; Jackson, 1986). Improvements in identifying suitable habitat, altering existing cavities to decrease competition for roosting and nesting sites, and initiating formation of red-cockaded woodpecker colonies through construction of artificial cavities have been synthesized into a specific technique of managing federal lands for the red-cockaded woodpecker (Copeyon et al., 1991; Ertep and Lee, 1994; Rossell and Gorsira, 1996).