Browsing by Author "Dr. Christopher E. Moorman, Committee Chair"

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    Considerations for Conservation of Shrubland Birds in Early Successional Forest Habitat
    (2009-12-07) Shake, Corey Scott; Dr. Christopher E. Moorman, Committee Chair
    Populations of many bird species associated with shrubland habitats are declining in the eastern United States, but incentive programs that restore shrubland or early-successional forest habitat on privately-owned land may help to ameliorate these declines. The habitat patches created by these programs are highly variable in size, shape, and surrounding habitat matrix, and it is unclear how these characteristics affect patch occupancy and nest survival of shrubland passerines. Our first objective was to determine how patch area, patch shape, and extent of forest cover in the surrounding landscape affect shrubland bird species’ occupancy of early-successional forest habitat patches and, for species that were area-sensitive, we sought to identify minimum area requirements. Our second objective was to determine if nest predation was higher at habitat edges, and whether patch vegetation structure or the landscape surrounding a patch influenced nest predation rates. To study patch occupancy, we surveyed 35 individual habitat patches in 2007 and 43 in 2008 for the presence of nine shrubland birds in North Carolina, USA. We then modeled individual patch occupancy probability of five of these species relative to patch area, patch shape, and % forest cover within 1 km of the patch. We documented evidence of area-sensitivity for yellow-breasted chat (Icteria virens) and prairie warbler (Dendroica discolor), and estimated minimum area requirements of 2.3 and 1.1 ha, respectively. Blue grosbeaks (Passerina caerulea) also were area-sensitive in irregularly-shaped patches. Predicted individual patch occupancy probability was >0.9 in patches ≥5.5 ha for all area-sensitive species. Shape index alone and proportion of forest cover were not important predictors of occupancy for shrubland birds. Restored shrubland and early-successional forest in agricultural landscapes can provide habitat for many shrubland birds, but patches should be >5 ha to maximize shrubland bird diversity. To study nest predation, we collected data on nests of five shrubland passerine species during the 2007 and 2008 breeding seasons in 12 early successional forest patches in North Carolina, USA. We used model selection methods to assess the effect of distance to cropland and mature forest edge on nest predation rates and accounted for other sources of variation, including temporal trends, nest stage, vegetation structure, and landscape context. For nests of all species combined, nest predation decreased with increasing distance to cropland edge, by nearly 50% at 250 m from the cropland edge. Nest predation of all species combined also was higher in patches with taller saplings and less understory vegetation, especially in the second year of our study when trees were 4-6 m tall. Predation of field sparrow (Spizella pusilla) nests was lower in landscapes with higher agricultural landcover. Nest predation risk for shrubland birds appears to be greater near agricultural edges than mature forest edges, and natural forest succession may drive patterns of local extinction of shrubland birds in regenerating forest patches. Thus, we suggest that habitat patches managed for shrubland bird populations should be considerably large or wide (>250 m) when adjacent to crop fields and maintained in structurally-diverse early seral stages.
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    Long-term Response of Herpetofauna and Soricids to Prescribed Fire and Fuel Reduction Treatments in the Southern Appalachian Mountains
    (2008-12-03) Matthews, Charlotte Esther; Dr. Christopher E. Moorman, Committee Chair; Dr. Cathryn H. Greenberg, Committee Member; Dr. Kenneth H. Pollock, Committee Member
    Recent use of prescribed fire and fire surrogates to reduce fuel hazards has spurred interest in their effects on wildlife. Some studies of fire in the southern Appalachian Mountains have documented few effects on reptiles and amphibians. However, these studies were conducted after only one fire and for only a short time period (1 to 3 years) after the fire. From mid-May to mid-August 2006 and 2007, we used drift fences with pitfall traps to trap reptiles, amphibians, and shrews in western North Carolina and to asses their response to 3 fuel reduction treatments: 1) twice-burned (2003 and 2006), 2) mechanical understory cut (2002), and 3) mechanical understory cut (2002) followed by 2 burns (2003 and 2006), and a control. We captured significantly fewer salamanders in the mechanical + twice-burned treatment than in twice-burned and control treatments, but more lizards in the mechanical + twice-burned treatment. Higher lizard captures in mechanical + twice-burned treatments was likely due to increased ground temperatures and greater thermoregulatory opportunities. Higher and more variable ground temperatures and faster drying of the remaining litter and duff in mechanical + twice-burned treatments may have led to fewer salamander captures in these treatments. We captured significantly fewer southeastern shrews (Sorex longirostris) in the mechanical + twice-burned treatment than in the mechanical treatment in 2006, but southeastern shrew captures did not differ among treatments in 2007. Total shrew captures did not differ among treatments in either year. Decreases in leaf litter and canopy cover in the mechanical + twice-burned treatment may have led to decreases in moisture and therefore decreases in southeastern shrew captures. Our long-term results, after 2 prescribed burns, differ from results after 1 prescribed burn, after which eastern fence lizard (Sceloporus undulatus) captures were greater in mechanical + burn treatments but salamander captures did not differ among treatments. Low-intensity fuel reduction treatments in the southern Appalachian Mountains do not appear to greatly affect reptile, amphibian, or shrew populations. However, multiple (>2) high intensity burns may benefit lizards but negatively affect salamanders and some shrew species, at least temporarily.