Geology topics

S.G. Somershoe

Publications and source records attributed to S.G. Somershoe.

4 recordsLinked to original sources

USGS2008

Bird response to silviculture induced change in forest structure within bottomland hardwood forests

Silvicultural treatments prescribed to encourage development of desired stand structure (i.e., wildlife-forestry) should result in increased abundance of many bird species of management concern, especially species using dense understory habitat. Desired forest conditions within bottomland vary among sites, but average 60-70% overstory canopy that is heterogeneously distributed with >5 dominant trees/ha retained, and a basal area of 14-16 m2/ha. Desired mid-story and understory cover are between 25-40%. Cavity trees (small and large) as well as dead and/or stressed trees should be retained, ultimately providing >14 m3/ha coarse woody debris, and shade-intolerant tree regeneration should be present on 30-40% of the area. We assessed avian response to prescribed wildlife-forestry silviculture treatments via distance-adjusted point counts and constant effort mist-netting within forest stands on Tensas River National Wildlife Refuge in northeastern Louisiana. More species and individuals were detected within stands 1-13 years post-treatment than within untreated stands. Most species, especially species benefiting from disturbance, increased in density after treatment. A few species decreased in density, yet remained fairly relatively abundant post-treatment. Captures from netting suggested three generalized responses to wildlife-forestry silviculture: (1) species with rapid, short-duration positive response, (2) species with slower but more prolonged positive response, and (3) species which initially declined but had long-term positive population response. We recommend increased use of prescribed wildlife-forestry silvicultural prescriptions to enhance bottomland forest habitat for priority bird species.

Book chapter↗

USGS2006

Combining Breeding Bird Survey and distance sampling to estimate density of migrant and breeding birds

We combined Breeding Bird Survey point count protocol and distance sampling to survey spring migrant and breeding birds in Vicksburg National Military Park on 33 days between March and June of 2003 and 2004. For 26 of 106 detected species, we used program DISTANCE to estimate detection probabilities and densities from 660 3-min point counts in which detections were recorded within four distance annuli. For most species, estimates of detection probability, and thereby density estimates, were improved through incorporation of the proportion of forest cover at point count locations as a covariate. Our results suggest Breeding Bird Surveys would benefit from the use of distance sampling and a quantitative characterization of habitat at point count locations. During spring migration, we estimated that the most common migrant species accounted for a population of 5000-9000 birds in Vicksburg National Military Park (636 ha). Species with average populations of 300 individuals during migration were: Blue-gray Gnatcatcher (Polioptila caerulea), Cedar Waxwing (Bombycilla cedrorum), White-eyed Vireo (Vireo griseus), Indigo Bunting (Passerina cyanea), and Ruby-crowned Kinglet (Regulus calendula). Of 56 species that bred in Vicksburg National Military Park, we estimated that the most common 18 species accounted for 8150 individuals. The six most abundant breeding species, Blue-gray Gnatcatcher, White-eyed Vireo, Summer Tanager (Piranga rubra), Northern Cardinal (Cardinalis cardinalis), Carolina Wren (Thryothorus ludovicianus), and Brown-headed Cowbird (Molothrus ater), accounted for 5800 individuals.

Condor↗

USGS2005

Winter status of White-eyed Vireos in northeastern Louisiana

In December 2004, February 2005, and June 2005, we recaptured a White-eyed Vireo (Vireo griseus) that was banded on 19 May 2004 at the same location on the Tensas River National Wildlife Refuge, Madison Parish, LA. This is the first documented permanent resident White-eyed Vireo outside of resident populations known from Florida and southern Texas. This individual appears to be resident near the northern limit of the winter range for the species. Although White-eyed Vireos are uncommon in northeastern Louisiana during winter, we detected other White-eyed Vireos during line transect surveys and banding during winters 2003-2004 and 2004-2005. The lack of research and observation of winter birds in northern Louisiana and the secretive and inconspicuous behavior of White-eyed Vireos in winter may have led to an underestimation of abundance at the northern limits of their winter range.

North American Bird Bander↗

USGS2003

Habitat use by Swainson's Warblers in a managed bottomland forest

The Swainson's Warbler ( Limnothlypis swainsonii ) is a locally distributed and relatively uncommon Neotropical migrant songbird that breeds in the bottomland forests of the southeastern United States and spends the nonbreeding season in the Caribbean Basin. Populations of Swainson's Warblers have declined during recent decades as bottomland forests have come under increasingly intensive management and large areas have been converted to other land uses. We examined the habitat around song perches used by male Swainson's Warblers at Big Hammock Wildlife Management Area, a managed bottomland forest along the Altamaha River in Tattnall County, Georgia. We quantified 20 features of habitat structure in areas occupied by Swainson's Warblers (occupied plots) and two sets of controls: unoccupied plots adjacent to occupied plots (adjacent control plots) and unoccupied plots throughout the management area (general control plots). Occupied plots and adjacent control plots both differed in structure from the general control plots. We detected no significant differences, however, in vegetation structure between occupied plots and adjacent control plots. General control plots tended to have a greater number of trees, greater basal area, and a complete canopy, whereas occupied and adjacent control plots had high densities of small stems, cane, herbaceous ground cover, and leaf litter; this latter pattern is typical of documented Swainson's Warbler breeding habitat. Lack of significant differences in vegetation structure may be due to great variation in habitat structure around song perches, small sample size, or scarcity of Swainson's Warblers. Future research should focus on quantifying habitat characteristics around nest sites, song perches, and feeding areas. Our results suggest that management of bottomland habitats by thinning forests and encouraging regeneration of canebrakes is needed for successful conservation of Swainson's Warblers.

The Wilson Bulletin↗