Florida Grasshopper Sparrow
Florida Grasshopper Sparrow
Ammodramus savannarum floridanus
|Listed||July 31, 1986|
|Description||Short-tailed sparrow, mostly gray and black, streaked with brown.|
|Habitat||Poorly drained, frequently burned-over scrub land.|
|Food||Insects, seeds, berries.|
|Reproduction||Clutch of three to five eggs.|
The Ammodramus savannarum floridanus (Florida grasshopper sparrow) is a short-tailed bird, about 5 in (13 cm) long. Darker in color than related sub-species, it is mostly black and gray, streaked with brown on the nape and upper back. Adults have whitish, unstreaked front parts with some buff on the throat and breast. In juveniles the breast is streaked. The stripe over the eye tends to be ochre, and the bend of the wing is yellow; the feet are flesh colored. There are no marked sexual differences. The Florida grasshopper sparrow gets its common name from its weak song, which resembles the buzz made by grasshoppers.
Like other grasshopper sparrows this species probably produces a clutch of three to five eggs. The incubation period is about 12 days; young fledge in nine days. The grasshopper sparrow forages on the ground for insects, seeds, and berries. It is nonmigratory.
The Florida grasshopper sparrow inhabits stunted, scrubby growths of saw palmetto, dwarf oaks, bluestems, and wiregrass, which are maintained by periodic fires. Areas of low, sparse growth, rather than sod-forming grasses, are needed for nesting. Common shrubs of the habitat include pawpaw, dwarf oak, gopher apple, and St. John's wort. Common grasses and herbs include pineland threeawn, bluestems, flat-topped goldenrod, beak rushes, pipewort, and yellow-eyed grass.
Grasshopper sparrows are found throughout much of temperate North America. The Florida subspecies, though, is limited in range and is geographically isolated from other subspecies. It is adapted to scrub habitat in Florida's south-central prairie region. Of the nine sparrow locations known at the time of listing, the bird remains at only three.
Although some historical populations have disappeared, the sparrow has been found at four previously unreported locations since it was listed, resulting in a total of seven known colonies by 1994. Fortunately, the largest known populations are on public lands—the Commission's Three Lakes Wildlife Management Area (Osceola County) and the Air Force's Avon Park Range (Highlands and Polk counties)—and have remained stable. An early 1990s survey of singing birds also detected 14 males on the National Audubon Society's Kissimmee Prairie Sanctuary in Okeechobee County. Assuming an equal sex ratio, the 150 males counted during surveys at the time represent a minimum total population of 300 adults. Other colonies may exist on some private ranches where access to researchers is denied. Surveys conducted between 1980 and 1984 estimated an adult population of less than 250 birds at nine widely scattered Florida sites—in southern Osceola, southern Polk, northern Highlands, western Okeechobee, and western Glades counties.
The prairie region of south-central Florida has increasingly been converted to pasture to the detriment of the grasshopper sparrow. This sparrow will nest in improved pastures where some native vegetation remains. But when pastureland is stripped of shrubs and saw palmetto, the bird is driven out.
Conservation and Recovery
Much of the land within the range of the Florida grasshopper sparrow is contained in a few large, private ranches, and many landowners are unaware of the sparrow's existence. Recovery of the bird could be helped if ranchers adapted their pasture management practices to the sparrow's nesting cycle. For example, the sparrows currently occupy several pastures that are managed by periodic winter burns. By avoiding the nesting season, winter burns do not adversely affect sparrow populations. Rather, they improve the habitat by maintaining the prairie scrub community at an early successional stage.
The Air Force's Avon Park Bombing Range is one of the more valuable pieces of real estate in Florida in terms of wildlife management. The Range contains over 100,000 acres (40,000 hectares) with an estimated 5,000 acres (2,000 hectares) of increasingly rare scrub habitat, rich in native wildlife. The land not only shelters the grasshopper sparrow, but other Endangered and Threatened species as well. The Air Force is working with the U.S. Fish and Wildlife Service to determine a productive management plan for scrubland under its authority.
According to the 1988 Florida Grasshopper Sparrow Recovery Plan, the sparrow can be reclassified to the less critical category of Threatened if 50-100 breeding pairs become established at each of 10 secure, discrete sites throughout its former range, and can be delisted if established at 25 such sites. Results from singing male surveys conducted by the Florida Game and Fresh Water Fish Commission, U.S. Air Force, volunteers, and a private consultant, however, did not, by 1994, indicate that a change in the bird's classification was warranted. Abandoned locations on private lands have been plowed and planted with non-native grasses to improve cattle grazing or for use in sod production.
Personnel from the Florida Game and Fresh Water Fish Commission, Air Force, National Audubon Society, and Archbold Biological Station conducted a banding study of the bird from 1989-1992. Seventy-three Florida grasshopper sparrows on the Avon Park Range were captured with mist nets and color-banded for the study. Sightings and recaptures of marked individuals provided some much needed information. Territory size during the breeding season averaged 4.37 acres (1.77 hectares), and population density was 0.02 territory/acre (0.05 territory/hectares). Thus, the recovery plan objective of a minimum viable colony of 50 breeding pairs would require over 2,470 acres (1,000 hectares) of contiguous habitat.
Recovery of the Florida grasshopper sparrow will be possible only if the bird can increase in numbers and range. Although most known populations of this subspecies are on protected lands, most of the available prairie habitat for future populations is on private lands that are vulnerable to conversion. Land use trends indicate continued habitat loss for the sparrow. Data gathered during recent studies, however, will be used to develop strategies for recovery and will enable property owners to make informed resource management choices. State and Federal agencies and conservation organizations have banded together, literally and figuratively, in a partnership to recover the Florida grasshopper sparrow. Information gathered through banding studies and surveys of singing birds is providing information land managers can use to prevent extinction of this rare bird.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
Delany, M. F., and J. A. Cox. 1985. "Florida Grass-hopper Sparrow Status Survey." Report, U.S. Fish and Wildlife Service, Jacksonville, Florida.
Kale, H. W., II. 1978. Rare and Endangered Biota of Florida ; Vol. 2, Birds. University Presses of Florida, Gainesville.
U.S. Fish and Wildlife Service. 1988. "Recovery Plan for Florida Grasshopper Sparrow." U. S. Fish and Wildlife Service, Atlanta, Georgia.