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NATURAL HISTORY

CAPE SABLE SEASIDE SPARROW }  Ammodramus maritimus mirabilis
FAMILY: Fringillidae

DESCRIPTION: The Cape Sable seaside sparrow is a small bird measuring about five inches in length. It has a dark, olive gray back; an olive brown tail and wings; light gray streaks on its breast and sides; yellow lores; and gray ear patches behind its eyes. There is a small patch of yellow on the edge of each of its wings. Male and female plumage looks similar.

HABITAT: The Cape Sable seaside sparrow inhabits interior southern Florida’s brushless, subtropical marshes, which are dry most of the year but are seasonally flooded with fresh to slightly brackish water. The sparrow avoids brushy or rocky marshlands, as well as dense stands of cordgrass, cattail, and shrubs.

RANGE: The Cape Sable seaside sparrow’s original range probably included all suitable habitat in south and southwestern Florida, extending from Cape Sable in the south to Ochopee in the northwest to Taylor Slough and the east Everglades in the east. Currently, the known distribution of the bird is restricted to two areas of marl prairies east an west of Shark River Slough, and flanking Taylor Slough.

MIGRATION: This bird is nonmigratory.

BREEDING: Nesting can occur from February through late August, though most occurs during April and May, with the time and length of the nesting period dependent on flooding — nesting activities decrease abruptly when marshes flood. The birds construct cupped nests in clumps of grass about six inches above the ground. Usually three or four eggs are laid. The female incubates the eggs for 12 days and young fledge at when they are between nine and 11 days old. These sparrows usually attempt to nest two or three times each season, with a success rate of 40 to 75 percent.

LIFE CYCLE: Sparrows are generally short-lived, with an average lifespan of two to three years.

FEEDING: Cape Sable seaside sparrows are dietary generalists, taking advantage of any food available as they forage low in the grass and on the ground. They feed on grasshoppers, caterpillars, beetles, spiders, and grass and sedge seeds.

THREATS: The principal reasons for the decline of the Cape Sable seaside sparrow and the greatest threats to its continued survival are hydrologic alteration, vegetation changes, fire, development, and pollution. Catastrophic storms, such as the hurricanes in 1935 and 1992, can lead to natural vegetation changes that make the environment unsuitable for Cape Sable seaside sparrows, thus causing local extirpations.

POPULATION TREND: There were an estimated 6,656 Cape Sable seaside sparrows in 1981. The population estimate in 1992 was 6,450 birds, but in 1993, they numbered 3,347 and in 1994 they totaled just 2,800 birds — a decrease likely due to the devastating effects of Hurricane Andrew in August 1992. These sparrows have declined by as much as 60 percent rangewide since 1992. The western subpopulation has declined by about 90 percent.

Cape Sable seaside sparrow photo courtesy Flickr/woodcreeper