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Arnold Air Force Base

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Sinking Pond Photos
Typical grassland habitat at Arnold Air Force Base.

Photo by John W. Lamb

A typical summer grassland field at AAFB.

Location:  Approximately 70 southeast of Nashville, near the towns of Manchester, Tullahoma, and Winchester in the counties of Coffee and Franklin, Tennessee.
Physiographic Province:  PIF 14 (Interior Low Plateaus [Eastern Highland Rim]); BCR 27 (Southeastern Coastal Plain)
Tennessee IBA Site Map - AAFB.bmp (80006 bytes)
Geographical Coordinates: 
    Woods Reservoir--Lat. 351754W  Long. 0860549W
Elevation Range:
    961' Woods Reservoir   
Size:  39,081acres (including 3,632-acre Woods Reservoir)
USGS 7.5' quad:  Capitol Hill

The site is predominately upland and swamp oak forest. Of the forested areas, 23,492 acres are in native hardwoods and 5,785 acres are in planted, non-native pines. Forested areas are most frequently characterized by closed canopies dominated by various oaks. Dry sites are dominated by post oak, blackjack oak, scarlet oak, southern red oak, and black oak. Wet sites are dominated by white oak, willow oak, water oak, and overcup oak. Understories include a wide variety of species including dogwoods, maples, sassafras, sourwood, and blueberries. Numerous wetlands occur across the base, with prevailing vegetation ranging from grassland to closed-canopy forest. Several hundred acres of open, prairie-like barrens occur primarily in the airfield and along powerline and railroad rights-of-way.
    The 3,632-acre Woods Reservoir is an impoundment on the Elk River built in 1952 to supply cooling water to Arnold Engineering Development Center. Major tributaries include Bradley, Brumalow, and Rollins creeks. Drainage area above the dam covers 263 square miles. The Tennessee Wildlife Resources Agency leases 1,900 acres for a waterfowl refuge.
    Lying in the heart of the barrens region of the Eastern Highland Rim, the term "barrens" was used by early travelers and settlers of the region to refer to grassy openings that were barren of trees. Barrens most often refers to grasslands similar to the Midwestern tallgrass prairie but also may be used to describe openings with scattered trees that may resemble savanna or shrubland. Access to the site is restricted.

IBA Criteria:  2, 3, 4a, 4b, 5

Ornithological Importance:  The area contains significant acreage of barren grasslands, a rare habitat in Tennessee, along with the complement of species that such a habitat attracts; a large heronry; and waterfowl concentrations. The Bald Eagle, a Tennessee In Need of Management species, occurs during the winter in small numbers. From 1988-2005, there have been an average of 1.8 birds per year (1.67 adults and 0.17 immatures) with a high count of 3 individuals in 1991-1992 and 2004-2005. The species does not nest. One to two breeding pairs of Bachman's Sparrow, a Tennessee Endangered species, used the site 1994-1997, but the species has not been detected since (summer 2005).
    Note 1. During the breeding season, there are generally 20-30 breeding pairs of Henslow's Sparrows, a Tennessee In Need of Management species. In the period 1999-2005, a total of 135 individuals were banded. See the table below for a breakdown of numbers banded and recaptures in this period.

Henslow's Sparrow graph.

Table by John W. Lamb

This table graphs the total number of Henslow's Sparrows banded and recaptured in the period 1999-2005.

   Note 2. AAFB lies in the heart of the barrens grassland region of the Eastern Highland Rim. Several hundred acres of open, prairie-like barrens occur primarily in the airfield and along powerline and railroad rights-of-way. The suite of breeding species associated with grassland occurs including Common Yellowthroat, Grasshopper Sparrow, Henslow's Sparrow (see Note 1 above), and occasionally Dickcissel.  An estimated 40 breeding pairs of Grasshopper Sparrows have been documented in the area 1994-2005. The Prairie Warbler is widespread in shrubland and savannah habitats and is the most abundant species at MAPS (see Note 6 below). The winter suite of species associated with the grassland includes Northern Harrier, Savannah Sparrow, and Vesper Sparrow (mainly migrant).
    Note 3. Waterfowl
(ducks, geese, and swan) numbers on the "Tennessee Mid-Winter Waterfowl Survey, 2001-2004, averaged 5,374 birds. Yearly totals were 2001 (18,052), 2002 (1,491), 2003 (1.037), and 2004 (917). There was no survey recorded for 2005. Migrant Blue-winged Teal numbers include: September 6, 2003 (100). Common Loons regularly number 100. Some records include: January 13, 2004 (30), November 13, 2004 (26), December 5, 2005 (100+), and January 15, 2006 (100+). Around 100 Horned Grebes
regularly winter on the lake. Examples: November 9, 2003 (150+) and January 28, 2006 (100).
    Note 4.
Sinking Pond, a National Landmark located on AAFB, Lat. 352504N  Long. 0860332W, is a 400-acre seasonally flooded, forested wetland and site to one of the largest Great Blue Heron heronries in Tennessee. It has been in continuous use since at least 1965. Numbers peaked in 2000 with 743 nests. In 2004, there were 117 nests. No reason is known for the decrease. The table below chart's the number of nests from 1965 to 2005. The site also contains the only example on AAFB of the "critically imperiled globally" overcup oak/river birch/resurrection fern forest community type (Pyne et al. 1998). The Sinking Pond colony enjoys protection from human disturbance and habitat destruction, two major causes of the species declines in the late 1960's and early 1970's (Short and Cooper, 1985).
        In addition to the Sinking Pond heronry, there is a small heronry on Elder Island in Woods Reservoir. This island is northwest of the Morris Ferry Bridge on Highway 127 and is visible from the bridge. Recent heronry activity on or near the island includes: September 6, 2003--Roost of Great Blue Heron (1), Great Egret (8), Cattle Egret (50, some observed nesting, young heard), Green Heron, and Black-crowned Night-Heron (10, some observed nesting, young heard); May 23, 2004--Cattle Egret, Green Heron, and Black-crowned Night-Heron on island with Great Blue Heron in area; August 2, 2004--Cattle Egret (8-10 young) and Green Heron (4 young), with Great Blue Heron on island and Black-crowned Night-Heron nearby but no young seen.; August 23, 2004--Great Egret (2), Little Blue Heron (1 adult), Green Heron, and Black-crowned Night-Heron (1 adult, 1 immature).

Sinking Pond heronry graph.

Table by John W. Lamb

Great Blue Heron heronry at Sinking Pond 1965-2004.

    Note 5. The initially sampling design assigned points counts was to habitats in proportion to their abundance in the region. Eighty-one diurnal and twenty-one nocturnal survey points in portions of AAFB in Coffee County were monitored in 1994 and 1995. Six diurnal survey points and one nocturnal survey point were added in 1996 in order to include a native Barrens grassland. Sixteen diurnal and eight nocturnal survey points were added in 1998 to include Franklin County for a total of 103 diurnal and 30 nocturnal survey points.Point locations were subjectively chosen, limiting possibilities for analyzing and interpreting data. This sampling design provided limited feedback for ecosystem management at AAFB because it was not integrated with other monitoring efforts. The sampling design was altered in 2003 as part of an ongoing effort to develop an Integrated Ecological Monitoring (IEMon) program for the installation. Point counts in 2004-2005 have focused on a Henslow's Sparrow habitat study.
        In the period 1994-2000, there were 615 diurnal point counts representing 84 species of 8,352 individuals. Breakdown of counts are 1994 (81), 1995 (81), 1996 (95), 1007 (82), 1009 (72), 1999 (102), and 2000 (102). Of the top 20 species, 10 are neotropical (50%). The top 20 species are summarized in the table below.

Top 20 Species On Counts at AAFB
By Relative Abundance of Individuals 1994-2000


Indigo Bunting*612
Great Blue Heron531
Yellow-breasted Chat*488
Tufted Titmouse422
Northern Cardinal420
American Crow363
Eastern Towhee337
Field Sparrow327
Common Yellowthroat*305
Yellow-billed Cuckoo*263
Red-eyed Vireo*252
Blue Jay238
Northern Bobwhite235
Red-bellied Woodpecker226
American Goldfinch223
Wood Thrush*200
Prairie Warbler*192
Carolina Wren183
Blue-gray Gnatcatcher*181
White-eyed Vireo*167
Summer Tanager*154
* = neotropical 

        Survey points for nocturnal counts monitoring Whip-poor-will and Chuck-will's-widow populations are located near historical diurnal survey points and spaced at least 0.8-km apart. Each survey point is visited once per year in June. Regression analysis has found no significant trends over time for the percent of points on which Whip-poor-wills occur (i.e. distribution on the base) or in the number of individuals encountered at each stop. While Whip-poor-will is more common than Chuck-will's-widow at AAFB, regression analysis results for Chuck-will's-widow indicate that there have been increases in both the distribution (percent of stops) and number (average number per stops) of Chuck-will's-widows. These species are on the USFWS (20202) species of concern list and appear to be stable or increasing within the bounds of AAFB.
    Note 6. A MAPS site has been conducted 1999-2005. In this 7-year period, 41 species and 974 individuals were banded with 497 recaptures. The most common species were Prairie Warbler (126), Yellow-breasted Chat (117), Indigo Bunting (112), and Common Yellowthroat (107).

Site Criteria



Avg. No Season

Max. No. Season

Years of Data



Henslow's Sparrow (NOM) (See Note 1 above.)



3Habitat: Grassland (See Note 2 above.)     
4aWaterfowl (See Note 3 above.)W   5

Wading Birds (See Note 4 above.)







Monitoring: Point Counts (See Note 5 above.)







Monitoring: MAPS (See Note 6 above.)






Season1   B = Breeding, W = Wintering, SM = Spring Migration, FM = Fall Migration
Source 2  1-Atlas Breeding Birds of Tennessee 2-Breeding Bird Surveys 3-Christmas Bird Counts
4-Point Counts 5-Refuge Counts 6-Personal observations (John Lamb) 7-Other (specify)

Ownership:  US Air Force, Department of Defense
    Contact:  John W. Lamb
, Conservation Biologist, ATA Conservation,1103 Avenue B, Arnold Air Force Base, TN 37389-1800, 931-454-5378 (office), 931-454-5126 (fax), john.lamb@arnold.af.mil

Conservation Concerns:  Potential concerns are forest fragmentation and limited barrens habitat.

Management Program:  A large-scale barrens restoration plan is in place using prescribed fire and select harvest to restore the barrens. Also, the reduction of forest fragmentation is being achieved by stopping the practice of day-lighting roads in interior forest and allowing openings to regenerate naturally.

Submitted by:  John W. Lamb
, Conservation Biologist, ATA Conservation,1103 Avenue B, Arnold Air Force Base, TN 37389-1800, 931-454-5378 (office), 931-454-5126 (fax), john.lamb@arnold.af.mil

Additional Contributors:  

B. D. Carver, J. W. Lamb, L. Jennings, R. Moore, and G. West. 1998. Great Blue Heron colony status and nest site characteristics at Sinking Pond, Tennessee. Migrant 69:176-178.

This page was last updated on 02/19/06.