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Tami Lau Spatial overlap of turkeys and quail May 8, 2006p. 1Spatial and Habitat Overlap of Wild Turkeys and California Quail at Annadel State Park,CaliforniaTami LauAbstract Wild turkeys (Meleagris gallopavo) were introduced to California in the earlytwentieth century for hunting. Their range has increased rapidly since then and they arebecoming a concern due to conflict and competition with native species. The purpose of thisstudy is to assess the potential for competition between wild turkeys and California Quail(Callipepla californica), a native game bird with similar habitat requirements, at Annadel StatePark (Santa Rosa, California). Using a modified distance sampling technique, I determinedhabitat type use and spatial overlap of the two species for October 2005 through April 2006. Iused Gower's Similarity Coefficient and a contingency table with a chi-square goodness of fittest to show that turkey and quail use different geographic areas of the park and different habitattypes, suggesting the possibility of spatial separation and differentiation. These results have adirect impact on the management of wild turkeys, particularly on government lands. Theeradication of wild turkey populations would be time-consuming and costly, as turkeys areextremely resilient. If they are not causing any negative impacts on local species such asCalifornia Quail, as appears to be the case, perhaps they can be simply monitored for the timebeing and attention directed to other areas of concern in the park.Tami Lau Spatial overlap of turkeys and quail May 8, 2006p. 2IntroductionHumans have introduced thousands of plant and animal species into various ecosystems inthe past few centuries (Brown and Sax 2004). Introductions occur for a variety of reasons –some species are introduced for food, some are introduced for sport or amusement, some areintroduced through the accidental release of pets or laboratory subjects, and some are introducedthrough the unintentional transport of species to exotic locales. While only approximately oneout of every 100 introduced species becomes established (Krebs 2001), the ones that do canbecome a problem. Introduced species often have no natural predators in their newenvironments, and those that become invasive grow unchecked and become pests or threats tohumans and other species around them (Krebs 2001). In 1999, it was estimated that the costsassociated with introduced invasive species in the United States were approximately $138 billion(Swauger et al. 2003). In addition to economic losses, there can also be substantial ecologicalchanges (Brown and Sax 2004). Invasive species currently have a negative impact on 42 percentof federally listed threatened or endangered species (Swauger et al. 2003) through competitiveexclusion, niche displacement, hybridization, introgression, and predation (Mooney and Cleland2001). Historically, introduced species are responsible for about 40 percent of extinctions,mostly in mammals and birds (Krebs 2001).The wild turkey (Meleagris gallopavo) is one such problematic introduced species. Wildturkeys were introduced in California in the late nineteenth century (CDFG 2004). An extinctspecies of wild turkey (Meleagris californica) was native to southern California, including SantaBarbara, Orange, and Los Angeles Counties (CDFG 2005), but was absent from California at thetime of European settlement (Burger 1954). The first introduction of Meleagris gallipavooccurred on Santa Cruz Island in 1877 by a private rancher, but the State Department of Fish andGame began efforts to introduce wild turkeys for hunting in 1908 (CDFG 2004). Between thattime and 1951, 3,063 turkeys were introduced in 23 counties; the program was ultimatelyterminated because of the poor breeding and survival rates of the released birds (Burger 1954).In the 1960’s, the department began experimenting with the release of wild-caught turkeys fromother states; the program’s success led to the release of 2,924 birds between 1959 and 1988.After 1988, the program focused on releasing birds in higher elevation public lands, and 943turkeys were released between 1989 and 1999 (CDFG 2004). The department currently managesthem as resident game birds.Tami Lau Spatial overlap of turkeys and quail May 8, 2006p. 3However, problems arise when turkeys spread out from the areas they were intended toreside in and occupy other areas, such as parks and wildlife reserves. Their range has expandedsignificantly since their introduction, and like other invasive species, wild turkeys may poseproblems in these new environments. Turkeys are prolific and can increase their population sizerapidly given suitable conditions (Barrett and Kucera 2005). One area of potential conflict isspatial competition with other similar native species. Wild turkeys exhibit low selectivity withregards to habitat selection (Miller et al. 2000), but are generally found in woodlands (Dickson1992, York 2003). California Quail (Callipepla californica), another species of omnivorousgame bird, tend to live in areas that a mix of open feeding areas and brushy covered areas(Leopold 1977). Both species prefer to roost off the ground at night (Dickson 1992, Leopold1977). Because these habitat requirements are somewhat similar, the possibility for competitionis high. And because turkeys are less selective than quail, the possibilities of a negative stress onquail are higher than on turkeys. Alternatively, the two species could be coexisting throughspatial differentiation or niche differentiation. Effects on quail are important because CaliforniaQuail, in addition to being a similar native bird species, is the state bird of California and iscurrently in decline across its range (Calkins et al. 1999).The idea of spatial competition or overlap and its consequences is not new. Several modelshave attempted to separate the factors that influence the outcome of spatial competition (Hofer etal. 2004, Tilman 2004, Carrete et al. 2005, Crowley et al. 2005). A study on the caribou-moosesystem in Alberta, Canada, for example, found that these two species were spatially separated,resulting in different predation rates by wolves (James et al. 2004). The impact of introducedspecies on their new environments has also been studied. For


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