Showing papers by "William J. McShea published in 2000"

The influence of acorn crops on annual variation in rodent and bird populations

Abstract: I recorded mast production by oaks (Quercus sp.) at 12 forested sites in western Virginia for 6–12 yr and measured its impact on the abundance of small mammals, understory vegetation, and artificial-nest predation. White-tailed deer (Odocoileus virginianus) were excluded from half the 4-ha sites after at least one season of data collection. My hypothesis was that annual variation in acorn crops affected multiple species and that the strength of those interactions is mediated by white-tailed deer. The acorn crop was variable across sites and year, with some of the between-site variability explained by differences in elevation. All sites experienced at least one mast failure, and mast failure years were generally consistent across sites. White-footed mouse (Peromyscus leucopus), eastern chipmunk (Tamias striatus), and gray squirrel (Sciurus carolinensis) populations were significantly correlated with annual fluctuations in the acorn crop. The exclusion of deer had a significant impact on P. leucopus and T. striatus populations by increasing the number of animals captured following low acorn mast years. Annual fluctuations in the acorn crop, but not in rodent densities, were significantly correlated with the rates of predation on artificial nests the next summer. There was no significant interaction between predation rates and the exclusion of deer. An index from the Breeding Bird Survey (BBS) for Virginia was used to measure regional numbers for 11 common species captured at the sites. The index for two understory species was significantly negatively correlated with the mean acorn crop measured 2 yr previously. The effect of white-tailed deer on the forest community was not consistent across all conditions, as sites with large acorn crops were not strongly influenced by deer. These data are consistent with the hypothesis that mast crops from oaks serve as important determinants of community function within Appalachian forests.

Managing the Abundance and Diversity of Breeding Bird Populations through Manipulation of Deer Populations

Abstract: Deer densities in forests of eastern North America are thought to have significant effects on the abundance and diversity of forest birds through the role deer play in structuring forest understories. We tested the ability of deer to affect forest bird populations by monitoring the density and diversity of vegetation and birds for 9 years at eight 4-ha sites in northern Virginia, four of which were fenced to exclude deer. Both the density and diversity of understory woody plants increased following deer exclosure. The numerical response of the shrubs to deer exclosure was significantly predicted by the soil quality (ratio of organic carbon to nitrogen) at the sites. Bird populations as a whole increased following exclosure of deer, particularly for ground and intermediate canopy species. The diversity of birds did not increase significantly following exclosure of deer, however, primarily because of replacement of species as understory vegetation proceeded through successional processes. Changes in understory vegetation accounted for most of the variability seen in the abundance and diversity of bird populations. Populations of deer in protected areas are capable of causing significant shifts in the composition and abundance of bird communities. These shifts can be reversed by increasing the density and diversity of understory vegetation, which can be brought about by reducing deer density.

Predicting presence and abundance of a small mammal species: the effect of scale and resolution

Abstract: Management of small mammal communities in forest ecosystems requires a working knowledge of the scales at which species presence and abundance can best be predicted. Habitat-based models were developed to characterize the distribution of a boreal relict, the southern red-backed vole, Clethrionomys gapperi, in the southern Appalachian Mountains, USA, at three hierarchical scales of analysis. Vole presence and abundance were most evident at the high-resolution (macrohabitat) scale, followed by the intermediate-resolution scale. The low-resolution model was the least effective for predicting presence or abundance and reflects the need for more resolute landscape classification systems if small mammal populations are to be accounted for in an ecologically relevant manner. Tree and shrub communities indicative of suitable vole habitat included Fraxinus pennsylvanica and Tsuga canadensis in the canopy and Carpinus caroliniana in the understory. Vole abundance increased with incidence of tree species such as Bet...

Anesthesia in female white-tailed deer using Telazol and xylazine

Abstract: Thirty two free-ranging female white-tailed deer (Odocoileus virginianus) were anesthesized with varying Telazol® and xylazine HCl combinations in Front Royal (Virginia, USA) between August 1992 and September 1992. All animals were caught in baited box traps, manually restrained, and hand injected with a combination of Telazol and xylazine administered intramuscularly. Deer received mean ± SE dosages of 2.53 ± 0.16 mg/kg Telazol and 0.69 ± 0.05 mg/kg of xylazine. These dosages achieved a rapid and effective anesthetic plane for short-term procedures such as weighing, blood collection, and translocation. Eight of 32 deer (25%) required an intravenous (i.v.) supplement of ketamine HCl (100 mg) to maintain a safe plane of anesthesia. Ketamine supplementation provided an average of 11.8 ± 2.0 min additional safe handling. Satisfactory reversals were achieved in all deer by administering yohimbine HCl 16 mg i.v. (dose range, 0.22 to 0.48 mg/kg) to all animals.

Parental care of fledgling wood thrushes

Abstract: We report the study of parental care of Wood Thrush (Hylocichla mustelina) fledglings from nest-leaving to independence. From 1993 to 1995, we captured, radio-tagged, and monitored the movements and behavior of 23 fledglings and their parents from 12 broods at the U.S. Marine Corps Base, Quantico, Virginia. For pairs that subsequently renested (n = 5), the family group of male, female, and fledglings, remained within 62 (±5 SE) m of the first nest after fledging. During the period of post-fledging parental care, mean maximum distance between parents was 70 (±14) m. Females attended the young 13 (±1.3) days before initiating the incubation of a second clutch. Males continued attending the fledglings for 6 (±0.7) more days until the young achieved independence and dispersed (28–36 days post-hatching). In final clutches (n = 7), brood care was divided between the parents, and the position of the fledglings relative to the nest depended on the parents' choice of molting site (in the nesting area or e...