Bachman's sparrow

Bachman's sparrow
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Emberizidae
Genus: Peucaea
Species: P. aestivalis
Binomial name
Peucaea aestivalis
Subspecies

Peucaea aestivalis aestivalis
Peucaea aestivalis bachmani
Peucaea aestivalis illinoensis

Synonyms[2]

Aimophila aestivalis

Bachman's sparrow (Peucaea aestivalis), is a small American sparrow that is endemic to the southeastern United States. This species was named in honor of Reverend John Bachman.

Adults have rufous brown upperparts and crown with gray and black streaking on the nape, back and primaries. The face is gray with a rufous brown eyestripe. It has a buff colored breast and whitish belly. These are mid-sized New World sparrows, measuring 12.2–16.2 cm (4.8–6.4 in) and weighing 18.4–23 g (0.65–0.81 oz).[3]

Their breeding habitat is open pine forests. The domed nest is usually built on the ground near a clump of grass or a bush. Females lay three to five eggs.

Bachman's sparrow is primarily a non-migratory resident, but it may retreat from some of the most northerly territories. The species is mainly a granivore, but it will also take some insects.

This bird is considered near threatened by the IUCN, with habitat loss one of the major factors often cited in its decline. Habitat degradation due to later stages of forest succession has also been attributed to the decline of this species. Prescribed forest burns may assist in recovery.

The song begins as a clear whistle, followed by a short trill.

Distribution

Bachman's sparrows occur primarily in the southeastern United States from the central region of peninsular Florida north to limited areas of extreme southern Virginia and west through portions of Tennessee, Kentucky and Missouri to eastern Oklahoma and eastern Texas.[4][5] Bachman's sparrows may rarely occur in more northerly areas that were part of their historic breeding range, including most of Illinois, Indiana, Ohio, West Virginia and parts of Pennsylvania and Maryland.[4][6][7]

Among the three subspecies of Bachman's sparrow, Peucaea aestivalis aestivalis breeds furthest east, from southeast South Carolina to peninsular Florida. Peucaea a. bachmanii occurs west of P. a. aestivalis to Mississippi and north to Kentucky. P. a. illinoensis occurs in the westernmost region of the species' range.[4][5][7]

Timing of major life events

Migration

Reviews and a field guide summarize the limited information available on Bachman's sparrow migration.[4][5][6][7] Bachman's sparrows in the southern portion of the range are resident, while those in Missouri, Arkansas, eastern Oklahoma, Tennessee, Virginia, parts of North Carolina, and extreme northern Mississippi and Alabama migrate south during winter.[5] Because of their secretive nature in winter, determining the presence of Bachman's sparrows is difficult. However, records of Bachman's sparrow occurrence on breeding grounds and specimens of subspecies collected outside their normal breeding range suggest that spring migration occurs from mid-March to May and fall migration occurs from late August through to late October.[4][6][7]

Breeding

Bachman's sparrows' breeding season typically begins in April and continues through August. The earliest date for Bachman's sparrow eggs in Florida is 14 April and the latest date is 4 August.[7] The earliest Bachman's sparrow nest found during a study in longleaf pine habitat of South Carolina was 10 April, while the latest nest found was early in the incubation stage on 5 August.[8] In a study of Bachman's sparrow reproduction in shortleaf and loblolly pine plantations of Arkansas, egg laying started as early as 17 April and continued until 26 August. However, 85% of clutches were started in May, June, or July.[4][9]

Bachman's sparrows typically raise 2 broods per breeding season and will renest after failed attempts.[9] In shortleaf and loblolly pine plantations of Arkansas, the average time between fledging of the 1st brood and starting the second brood was 12.3 days. This was not significantly (p=0.39) different from the 9.7-day average period between a failed nest and a subsequent nest attempt. On average, females attempted 3.1 nests per season. The maximum number of attempts per season was five.[9] The maximum number of nests attempted in longleaf pine habitat of South Carolina was also five. After two successful nests, a female attempted three times to raise a third brood.[8] Limited evidence suggests that three broods per season may occur occasionally.[4][7]

Bachman's sparrow nests are constructed on the ground by females and are primarily made of grasses. All nests (n=71) found in a study in shortleaf and loblolly pine plantations of Arkansas were built on the ground. Most nests (70%) were built at the base of bluestem clumps, although nests were found at the base of small trees, forbs, and other grass species.[9] On the same study site, only 7% of nests were not either partially or completely domed. Most nest entrances were oriented to the north.[4][6][7][10]

Clutch size varies from three to five.[6][7] Average clutch size on a site in Arkansas was 3.9,[9] while in a longleaf pine community in South Carolina mean clutch size was 3.6.[8] Both of these studies found significant (p≤0.02) decreases in clutch size as the breeding season progressed.[8][9] On a dry prairie site in Florida (n=9) average clutch size was 3.44 and on another (n=5) it was 3.6.[11] In shortleaf and loblolly pine plantations of Arkansas, females laid an average of 11.6 eggs (n=20) over the course of the breeding season.[9]

In shortleaf and loblolly pine plantations in Arkansas, females incubated eggs for 13 to 14 days. The average nestling period was 9 days, and the average period between fledging and independence was 25 days. Both parents care for the young during these periods.[9] A review suggests that Bachman's sparrows probably breed the year after hatching.[4]

Bachman's sparrows exhibit some fidelity to breeding sites. Over a two-year period in shortleaf and loblolly pine plantations of central Arkansas, 6 of 34 adults returned to areas where they had a territory in a previous year. This varied across years, with a 29% return rate of adult birds banded in 1983 and none of the adults banded in 1984 returning to the site in 1985. No juveniles (n=60) returned to the site.[9]

Nesting success

Values of nest success reported for Bachman's sparrows vary. Daily nest survival rate of Bachman's sparrow ranged from 0.89 to 0.96 across sites and years in the dry prairie of central Florida. On average 3.13 birds were fledged per successful Bachman's sparrow nest. Estimates of productivity ranged from 1.21 to 4.16 offspring per pair per year across sites and years.[11] In a South Carolina longleaf pine community, daily survival rate of Bachman's sparrow nests in 1995 was 0.952, which was significantly (p=0.04) higher than the 1996 daily nest survival rate of 0.889. Earlier nesting attempts (before June 15, n=15) had significantly (p=0.05) higher survival rates than those started later in the year (n=11). Daily nest survival rate was 0.922 during incubation and 0.973 during the nestling stage.[8] In central Arkansas, daily success rate during the incubation period was 0.965, while in the nestling period it was 0.919.[9] In the glades of south-central Missouri, 8 female Bachman's sparrows fledged an average of 1.5 young per season over 2 years.[12] Predation accounted for 80% of egg loss on study sites in Arkansas[9] and 94% of nest failures on sites in central Florida.[11] Information on Bachman sparrow nest predators can be found in the Predators section of this summary. Cowbirds[9] and nest abandonment [11] were the other known causes of nest failure.

Survival

Survival of Bachman's sparrows during the breeding season has been investigated in a South Carolina study area dominated by longleaf pine.[8][13] Recapture of banded birds resulted in a monthly survival rate during the breeding season of 0.94.[13] Using radio telemetry, average survival of Bachman's sparrows from 20 April to 26 July was 80.0%. In another radio telemetry study, four mortalities out of 38 Bachman's sparrows were documented over two years. The overall breeding season survival rate was estimated as 0.893.[8] According to a literature review, Bachman's sparrows have been captured that were at least three years old.[4]

Preferred habitat

Bachman's sparrows inhabit areas with a dense layer of ground vegetation and open mid-stories with scattered shrubs and saplings, including young clearcuts and open pine (Pinus spp.) forests.[12][14][15][16][17]

Habitat characteristics

Bachman's sparrows' need of a dense layer of herbaceous vegetation is widely documented. Vegetation density was greater below 3 feet (0.9 m) than above 3 feet (0.9 m) and percent ground cover and percent grass cover were consistently higher (>58%) on sites occupied by Bachman's sparrow than unoccupied sites in Arkansas, Alabama, Florida, South Carolina and North Carolina.[18] In 17- to 28-year- old slash pine plantations of northwestern Florida that had been burned within 4 years, Bachman's sparrow abundance was significantly (p=0.043) correlated (r=0.46) with relative volume of grass.[17] In longleaf and loblolly pine stands of varying ages and under different management in South Carolina, areas occupied by Bachman's sparrows consistently had high vegetation volumes ≤3 feet (1 m) above ground.[14] Sites occupied by Bachman's sparrows in longleaf pine woodlands of Florida managed for the red-cockaded woodpecker (Picoides borealis) had significantly (p=0.007) higher vegetation densities ≤ 2 feet (0.5 m) than unoccupied sites in the study area. Grass density, primarily bluestems (Andropogon spp. and Schizachyrium spp.) ≤ 2 feet (0.5 m) above ground, was also significantly (p=0.004) greater on occupied compared to unoccupied sites.[16] Bachman's sparrows were significantly (p≤0.01) more abundant in mixed pine-grassland restoration stands in Mississippi, which had greater understory, grass, and forb cover, than traditionally managed stands.[19] In 1- to 6-year-old loblolly pine stands of eastern Texas, herbaceous ground cover (p=0.003) was greater in study areas occupied by Bachman's sparrows.[20] In south-central Missouri, glades occupied by Bachman's sparrows had significantly more grass (p=0.03) and forb cover (p=0.0005) than unoccupied glades.[12] However, vegetation densities below 3 feet (0.9 m) and percent ground and grass cover in areas occupied by Bachman's sparrow did not differ significantly (p>0.05) from unoccupied areas of loblolly and shortleaf pine plantations in Arkansas.[15]

Factors such as the patchiness of vegetation and species composition of the ground layer may affect habitat suitability by influencing foraging success and the availability of food and nesting material. In Georgia, Bachman's sparrows did not occur in open areas with uniformly dense herbaceous vegetation, despite these sites having a similar volume of vegetation ≤3 feet (1 m) above ground as recently burned pineland sites that were occupied by Bachman's sparrow.[21] Although measurements were not taken, observations of Bachman's sparrow in clearcuts in eastern Texas suggest they may favor tall grass in clumpy rather that uniform distribution.[20] In loblolly and shortleaf pine plantations of Arkansas, explanations suggested for a lack of evidence of ground layer features influencing selection of breeding territories included importance of habitat characteristics that were not measured, such as patchiness of the herbaceous layer and species composition.[15] In a predominantly longleaf pine forest in Georgia, Bachman's sparrows were significantly (p=0.04) more abundant in areas where ground cover was primarily Beyrich threeawn (Aristida beyrichiana), compared to relatively disturbed communities of bluestems (Andropogon spp.) and silkgrass (Pityopsis spp.).[22]

Amount of litter and debris on a site may influence Bachman's sparrow habitat selection. Percent litter cover was consistently high (>58%) on sites occupied by Bachman's sparrow in Arkansas, Alabama, Florida, South Carolina and North Carolina.[18] Although statistical significance was not tested due to small sample size, Bachman's sparrows occurred at higher densities in control plots (1.5 territories/40 ha) than plots that had downed coarse woody debris >4 inches (10 cm) in diameter removed (0.4 territories/40 ha) in a loblolly pine forest of South Carolina. Haggerty[18] suggests that litter may provide habitat for Bachman's sparrow prey, but that too much litter could interfere with foraging. In loblolly and shortleaf pine plantations of Arkansas, litter cover (78%) and depth (0.5 inches (1.2 cm) on sites occupied by Bachman's sparrows were significantly (p≤0.01) lower than litter cover (88.9%) and depth (1.6 inches (4.2 cm)) on unoccupied sites.[15]

Bachman's sparrow inhabits areas with open overstories. In sites in eastern Texas of varying age since clearcutting, study areas occupied by Bachman's sparrows had significantly (p<0.01) fewer short (≤ 10 feet (3m)) and tall (>10 feet (3m)) trees than unoccupied study areas.[23] In longleaf and loblolly pine stands of varying ages and under different management in South Carolina, plots occupied by Bachman's sparrows consistently had low volumes of vegetation from 7 to 13 feet (2–4 m) above ground compared to unoccupied sites.[14] In middle-aged and mature forests of Georgia composed primarily of loblolly pine, Bachman sparrow densities were negatively associated with tree/shrub volume and vegetation volume from 7 to <16 feet (3 to <5 m).[21] In loblolly and shortleaf pine plantations of Arkansas, Bachman's sparrow breeding areas had significantly lower percent canopy cover (p<0.001), shorter woody vegetation (p≤0.01) and fewer trees (p<0.001) and shrubs (p≤0.05) than unoccupied sites.[15] In south-central Missouri, Bachman's sparrows occurred in glades with less than 30% woody cover, and occupied glades had significantly (p≤0.05) lower percentages of deciduous and coniferous saplings, deciduous and coniferous trees, and total woody vegetation.[12] Mid-story density was marginally (p=0.055) greater on unoccupied sites, and Bachman's sparrow abundance was significantly (p=0.043) negatively correlated (r= –0.446) with mid-story density in longleaf pine woodlands of northwestern Florida. However, relative abundance of Bachman's sparrows was not significantly (p=0.107) associated with canopy cover and there were no significant (p=0.133) differences in canopy cover between occupied and unoccupied sites.[16]

There is evidence that Bachman sparrow may prefer sites with some tall vegetation. In north-central Florida, densities of Bachman's sparrows in young (2–4 years) slash pine plantations with artificial snags added (n=3) was 31.4 pairs/km², while in similar vegetation without snags (n=3) Bachman's sparrow density was 22.3 pairs/km² [8]. In an area in South Carolina composed of longleaf and loblolly pine, Bachman's sparrow occurred at significantly (p=0.002) higher density in clearcuts than middle-aged (22–50 years) stands, while in another area clearcuts had relatively low densities of Bachman's sparrows. Vegetation differences between the 2 sites are likely to explain the difference. The site with relatively low densities of Bachman's sparrows had been drumchopped, which resulted in a lower volume of vegetation from 3 to 7 feet (1–2 m) above ground. The authors suggest that the lack of vegetation in this height range may have limited perches, resulting in fewer birds on the site.[14] An investigation of Bachman's sparrow habitat characteristics in 1- to 6-year-old loblolly pine stands of eastern Texas led to recommendations that 2 to 5 tall (>39 feet (12 m)) trees/100 ha remain on a clearcut for Bachman sparrow singing perches.[20] In Georgia, the lack of vegetation from 10 to <16 feet (3 to <5 m) was suggested as a possible reason for the absence of Bachman's sparrows from open field vegetation.[21] However, across the southeast, vegetation density from 3 to 6 feet (0.91–1.8 m) above ground varies widely on sites occupied by Bachman's sparrows, suggesting their requirements for the density of this vegetation layer are comparatively flexible.[18]

In the dry prairie of central Florida, Bachman's sparrows used clumps of saw-palmetto that had "natural" burrows significantly (p<0.001) more than would be expected based on availability. The authors suggest that Bachman's sparrows in prairie habitat use burrows as areas of refuge from predators.[24]

Landscape level effects

Several studies have investigated the importance of landscape attributes on Bachman's sparrows. For a discussion of the possible importance of patchiness of vegetation within a site see the habitat characteristics section.

The ability of the Bachman's sparrow to detect and colonize areas before they are no longer suitable may depend on the size and isolation of the habitat. In south-central Missouri, only glades ≥ 29 acres (11.7 ha) were occupied by Bachman's sparrows.[12] The probability of Bachman's sparrow occupying pine-grassland restoration stands in Mississippi increased as size of areas with long burning rotations, short-harvest rotations, and no removal of hardwoods decreased (p=0.05) and as the perimeter to area ratio of these areas increased (p=0.02).[19] In South Carolina, distance from source populations significantly (p≤ 0.05) influenced the ability of Bachman's sparrows to colonize recent clearcuts in both years on one study area and in 1 of 2 years in another study area. The authors suggest that the presence of corridors in the latter study area may have resulted in distance being less influential.[25]

Bachman's sparrows' association with edge habitat is uncertain. In eastern Texas clearcuts with relatively abundant loblolly pine, sites with Bachman's sparrow territories were significantly (p<0.01) closer to the edge of the study area and the number of Bachman's sparrows was significantly (p<0.05) correlated (r=–0.22) with distance to edge.[23] However, in dry prairie of central Florida the difference in Bachman's sparrow densities in edge and core habitat was not significant (p≥0.36), and both edge and core habitat were considered population sinks.[11]

Territory and density

Territory size of Bachman's sparrows varies. In Missouri glades, reports of average Bachman's sparrow breeding territory range from 1.5 acres (0.62 ha, n=13) to 7 acres (2.9 ha, n=7).[12] In loblolly and shortleaf pine plantations of central Arkansas, mean home range size (n=25) during the breeding season was 6 acres (2.5 ha).[15] In on a south-central Florida site with saw palmetto and scrub palmetto (Sabal etonia) interspersed amongst threeawn (Aristida spp.), Bachman's sparrow territories (n=6) averaged 12.5 acres (5.1 ha). In winter (November–January), the average home range size of 8 Bachman's sparrows was 1.6 acres (0.65 ha) in the dry prairie of central Florida.[24]

Bachman's sparrow density during in the breeding season has been estimated in several habitats. On clearcuts of various ages with relatively abundant loblolly pine in eastern Texas, maximum Bachman sparrow density was 1.9/10 ha.[23] In South Carolina, Bachman's sparrow densities ranged from 0 to 0.48/ha across sites of different ages and management regimes.[14] In Georgia, Bachman sparrow densities ranged from 0 to 0.92 birds/ha on sites ranging from an open field to middle-aged and mature forests composed primarily of loblolly pine.[21] In a south-central Florida community composed of saw palmetto, scrub palmetto, and threeawn, Bachman's sparrow density averaged 1 male/33 ha. In dry prairie of central Florida, Bachman's sparrow densities varied from 0.92 to 3.24 territories/10 ha across sites and years.[11] Bachman's sparrow densities calculated from breeding bird censuses in longleaf pine forests was >15 territories/40 ha, while densities from winter bird population studies were from 6 to 10 individuals/40 ha.[26]

Food habits

Bachman's sparrows forage on the ground for plant seeds and arthropods. In a predominately loblolly and shortleaf pine habitat of eastern Texas, all Bachman's sparrow foraging observations were on the ground[27] and a literature review states that Bachman's sparrows rarely forage in shrubs.[4]

Reviews[4][7][28] and an investigation of the Bachman sparrow's diet in eastern Texas[27] summarize the species that comprise the Bachman's sparrow's diet. A variety of grass seeds such as panicgrasses, bristlegrasses (Setaria sp.), crowngrasses (Paspalum spp.), and threeawns are eaten by Bachman's sparrows as well as seeds of several other taxa, including blueberries (Vaccinium spp), pines, and sedges (Carex spp). Arthropods in the Bachman's sparrow's diet include grasshoppers and crickets (Orthoptera spp.), spiders (Araneae), beetles (Coleoptera spp.), caterpillars (Lepidoptera spp.), wasps (Hymenoptera), and leafhoppers (Cicadellidae).[4][7][27][28] Insects comprise more of the Bachman's sparrow diet in spring and fall than in winter.[4][7][28] Stomach contents of Bachman's sparrow collected in eastern Texas in summer (n=5) and fall (n=11) had a greater abundance of insects than those collected in winter (n=4).[27]

Predators

Data demonstrating which species prey on Bachman's sparrow are lacking. However short-tailed hawks (Buteo brachyurus) [48] and possibly American kestrels (Falco sparverius) [24] prey on adult Bachman's sparrows. Species responsible for nest predation are not generally known.[9][11] Evidence in two studies suggest mammalian predators.[8][9] and snakes eat Bachman's sparrow nestlings.[9]

Bachman's sparrow nests are occasionally parasitized by brown-headed cowbirds (Molothrus ater).[9] In shortleaf and loblolly pine plantations of central Arkansas, 5% of 38 nest failures were due to brown-headed cowbird parasitism.[9]

References

 This article incorporates public domain material from the United States Department of Agriculture document "Aimophila aestivalis".

  1. ↑ BirdLife International (2012). "Peucaea aestivalis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ "Peucaea aestivalis". Avibase.
  3. ↑ CRC Handbook of Avian Body Masses, John B. Dunning Jr. (ed.). CRC Press (1992), ISBN 978-0849342585.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Dunning, John B. 1993. Bachman's Sparrow. In: Poole, A.; Stettenheim, P.; Gill, F., eds. The Birds of North America. No. 38. Philadelphia, PA: The Academy of Natural Sciences; Washington, DC: The American Ornithologists' Union: 1–16
  5. 1 2 3 4 National Geographic Society. 1999. Field guide to the birds of North America. 3d ed. Washington, DC: The National Geographic Society
  6. 1 2 3 4 5 Mumford, Russell E.; Keller, Charles E. 1984. The birds of Indiana. Bloomington, IN: Indiana University Press ISBN 0253107369.
  7. 1 2 3 4 5 6 7 8 9 10 11 Stevenson, Henry M.; Anderson, Bruce H. (1994). The birdlife of Florida. Gainesville, FL: University of Florida Press ISBN 0813012880
  8. 1 2 3 4 5 6 7 8 Stober, Jonathan M.; Krementz, David G. 2000. Survival and reproductive biology of the Bachman's Sparrow. In: Proceedings of the annual conference of the Southeastern Association of Fish and Wildlife Agencies; 2000 October 28 – November 1; Baton Rouge, LA. 54. Tallahassee, FL: Southeastern Association of Fish and Wildlife Agencies: 383–390.
  9. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Haggerty, Thomas M. (1988). "Aspects of the breeding biology and productivity of Bachman's Sparrow in central Arkansas" (PDF). The Wilson Bulletin. 100 (2): 247–255. JSTOR 4162564.
  10. ↑ Haggerty, Thomas M. (1995). "Nest-site selection, nest design, and nest-entrance orientation in Bachman's Sparrow". The Southwestern Naturalist. 40 (1): 62–67. JSTOR 30054395.
  11. 1 2 3 4 5 6 7 Perkins, Dustin W.; Vickery, Peter D.; Shriver, W. Gregory (2003). "Spatial Dynamics of Source-Sink Habitats: Effects on Rare Grassland Birds". Journal of Wildlife Management. 67 (3): 588–599. doi:10.2307/3802716. JSTOR 3802716.
  12. 1 2 3 4 5 6 Chambers, Rachel J. 1994. Habitat relations of Bachman's sparrows and other birds on Missouri glades. Columbia, MO: University of Missouri-Columbia. Thesis
  13. 1 2 Krementz, David G.; Christie, Jeffrey S. (1999). "Scrub-Successional Bird Community Dynamics in Young and Mature Longleaf Pine-Wiregrass Savannahs". Journal of Wildlife Management. 63 (3): 803–814. doi:10.2307/3802793. JSTOR 3802793.
  14. 1 2 3 4 5 Dunning John B. Jr.; Watts, Bryan D. (1990). "Regional differences in habitat occupancy by Bachman's Sparrow". The Auk. 107 (3): 463–472. JSTOR 4087909.
  15. 1 2 3 4 5 6 Haggerty, Thomas M. (1998). "Vegetation structure of Bachman's Sparrow breeding habitat and its relationship to home range" (PDF). Journal of Field Ornithology. 69 (1): 45–50. JSTOR 4514284.
  16. 1 2 3 Plentovich, Sheldon; Tucker, James W. Jr.; Holler, Nicholas R.; Hill, Geoffrey E. (1998). "Enhancing Bachman's Sparrow Habitat via Management of Red-Cockaded Woodpeckers" (PDF). Journal of Wildlife Management. 62 (1): 347–354. doi:10.2307/3802298. JSTOR 3802298.
  17. 1 2 Tucker, James W. Jr.; Hill, Geoffrey E.; Holler, Nicholas R. (1998). "Managing mid–rotation pine plantations to enhance Bachman's sparrow habitat" (PDF). Wildlife Society Bulletin. 26 (2): 342–348. JSTOR 3784060.
  18. 1 2 3 4 Haggerty, Thomas M. (2000). "A geographic study of the vegetation structure of Bachman's Sparrow (Aimophila aestivalis) breeding habitat". Journal of the Alabama Academy of Science. 71 (3): 120–129.
  19. 1 2 Wood, Douglas R.; Burger L. Wes Jr.; Bowman, Jacob L. & Hardy, Carol L. (2004). "Avian community response to pine—grassland restoration". Wildlife Society Bulletin. 32 (3): 819–829. doi:10.2193/0091-7648(2004)032[0819:ACRTPR]2.0.CO;2. JSTOR 3784806.
  20. 1 2 3 Wan Ramle, Wan A. Kadir. 1987. Vegetational characteristics of early successional sites utilized for breeding by the Bachman's Sparrow (Aimophila aestivalis) in eastern Texas. Nacogdoches, TX: Stephen F. Austin State University. Thesis
  21. 1 2 3 4 Gobris, Nancy M. 1992. Habitat occupancy during the breeding season by Bachman's Sparrow at Piedmont National Wildlife Refuge in central Georgia. Athens, GA: University of Georgia. Thesis
  22. ↑ Rutledge, Brandon T.; Conner, L. Mike (2002). "Potential effects of groundcover restoration on breeding bird communities in longleaf pine stands". Wildlife Society Bulletin. 30 (2): 354–360. JSTOR 3784491.
  23. 1 2 3 Brooks, Robert Alexander. 1987. Avifaunal populations of regenerating clearcut areas in eastern Texas, with emphasis on the Bachman's Sparrow and Prairie Warbler. Nacogdoches, TX: Stephen F. Austin State University. Thesis.
  24. 1 2 3 Dean, Tylan F.; Vickery, Peter D. (2003). "Bachman's Sparrows use burrows and palmetto clumps as escape refugia from predators". Journal of Field Ornithology. 74 (1): 26–30. doi:10.1648/0273-8570-74.1.26. JSTOR 4131084.
  25. ↑ Dunning, John B.; Borgella, Rene; Clements, Krista; Meffe, Gary K. (1995). "Patch Isolation, Corridor Effects, and Colonization by a Resident Sparrow in a Managed Pine Woodland". Conservation Biology. 9 (3): 542. doi:10.1046/j.1523-1739.1995.09030542.x.
  26. ↑ Engstrom, R. Todd. 1993. Characteristic mammals and birds of longleaf pine forests. In: Hermann, Sharon M., ed. The longleaf pine ecosystem: ecology, restoration and management: Proceedings, 18th Tall Timbers fire ecology conference; 1991 May 30 – June 2; Tallahassee, FL. Tallahassee, FL: Tall Timbers Research, Inc.: 127–138
  27. 1 2 3 4 Allaire, Pierre N.; Fisher, Charles D. (1975). "Feeding Ecology of Three Resident Sympatric Sparrows in Eastern Texas" (PDF). The Auk. 92 (2): 260–269. doi:10.2307/4084555. JSTOR 4084555.
  28. 1 2 3 Martin, Alexander C.; Zim, Herbert S.; Nelson, Arnold L. (1951). American wildlife and plants. New York: McGraw-Hill Book Company, Inc.

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