Bachman's Sparrow


Photo Credit: Eric C. Soehren

 

OTHER NAMES: Pine Woods Sparrow (Dunning 1993).

DESCRIPTION: Total length about 15 centimeters (six inches). Brownish gray with reddish streaks on back; underparts unstreaked with buffy to gray breast and sides, and whitish belly. Crown reddish brown, and cheeks dull gray with a well-defined eyebrow and reddish brown eye line extending back from eye. Have a thin dark malar streak and a relatively large bill with dark upper mandible and paler lower mandible. Tail relatively long and rounded. Most easily identified by song, which can be variable but typically consists of a clear introductory whistle followed by a series of lower pitched trills that sounds like here, kitty, kitty, kitty, kitty (Dunning 1993). Three subspecies described: subspecies breeding in Alabama (A. a. bachmani) doubtfully distinct from the western subspecies (A. a. illinoensis) and intergrades with the eastern subspecies (A. a. aestivalis; Dunning 1993).

DISTRIBUTION: Southeastern United States (Dunning 1993). Most breeding populations occur in the Coastal Plain and Piedmont from southeastern Virginia to central Florida and west into Arkansas and eastern Texas, but small populations breed in south-central Missouri, Kentucky, and Tennessee. Found in most of Alabama where open-canopied pine forests exist. Species expanded its distribution northward in the late 1800s and early 1900s, coinciding with heavy destruction of longleaf pine forests in the south and abandonment of farmlands in the north. Distribution began contracting by 1930 and now similar to historical distribution, but many populations relatively small and isolated. Northern populations migratory and spend winter with resident populations in the Gulf states from eastern Texas to Florida and north along the Atlantic Coast into North Carolina. Nonbreeding winter populations very secretive, so status not precisely known (Dunning 1993).

HABITAT: Most frequently found in open pine forests that contain a diverse ground cover of herbaceous vegetation. Also may occur in clearcuts the first four to seven years after cutting, but clearcuts soon become unsuitable as they become dominated by trees and shrubs; furthermore, clearcuts unlikely to become colonized unless in close proximity to stands containing breeding birds (Dunning et al. 1995). A key component determining habitat suitability is a high percentage of ground cover composed of perennial grasses growing in distinctive clumps (Haggerty 2000). Pine forests with a relatively open canopy (more than 50 percent) and frequent burning (every two to three years) support the largest populations (Tucker 2002). Although most populations probably were found in longleaf pine forests during historic times, also do well in relatively young (at least 15-year-old) stands of other southern pines if stands are managed to maintain an open canopy and are frequently burned (Tucker et al. 1998). Frequent burning to prevent the understory from becoming dominated by woody vegetation (trees, shrubs, and vines) is key to maintaining diverse ground cover of herbaceous vegetation required.

LIFE HISTORY AND ECOLOGY: Appear to be socially monogamous, but bigamous males documented (Dunning 1993). Nesting begins in April, runs through September, and is mostly complete by August (Dunning 1993). Breeding territories used for both nesting and feeding, but adjacent territories often overlap. Agonistic interactions between adjacent territory holders primarily limited to bouts of counter singing and occasional chases. Nest building and incubation of eggs only by females. All nests built on ground, usually at base of a grass clump, and often with a dome overhead. Most nests largely constructed of fine grass stems and lined with moss setae or fine rootlets, but pine needles and stems of forbs also used. Most clutches contain four solid white eggs, but clutch sizes range from two to five eggs. Eggs incubated by female for 12 to 14 days and nestlings usually fledge on day nine post-hatching. Both sexes feed nestlings and fledglings, but male often takes responsibility of caring for fledglings while female begins another nesting attempt. Unsuccessful females will renest five or more times per season. Replacement clutches laid, if previous attempts fail; most pairs probably attempt two broods per season, but some will attempt three. Forage by slowly walking and gleaning food from ground or adjacent vegetation or jumping off ground to catch or glean prey. Eat a variety of arthropods (insects and spiders) and grass seeds. Foraging habitats probably primary factor limiting distribution. Herbaceous ground cover must be low and dense enough to support an abundance of arthropods at or near ground level, but must occur in clumps with bare spaces for birds to maneuver (Haggerty 2000).

BASIS FOR STATUS CLASSIFICATION: Threats in Alabama similar to threats throughout distribution; although common in many areas with suitable habitat, many areas with apparently suitable habitat unoccupied because of habitat fragmentation and isolation from breeding populations. Distribution-wide, more than 95 percent of primary habitat (i.e., longleaf pine forests) has been lost and much of the remaining habitat has been degraded by suppression of fire. This has resulted in declining populations, and many remaining populations being threatened by small population sizes, fire suppression, and direct loss to changing land uses. Partners In Flight (PIF) assessment scores indicate the Bachman’s Sparrow has restricted breeding and nonbreeding distributions. Also, severe deterioration in future suitability of breeding and nonbreeding conditions is expected (PIF 2002).

Author: James W. Tucker, Jr.

SCIENTIFIC NAME: Aimophila aestivalis (Lichtenstein)

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