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Aspects of the Breeding Biology and Productivity of Bachman's Sparrow in Central Arkansas
Thomas M. Haggerty
The Wilson Bulletin
Vol. 100, No. 2 (Jun., 1988), pp. 247-255
Published by: Wilson Ornithological Society
Stable URL: http://www.jstor.org/stable/4162564
Page Count: 9
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Breeding Bachman's Sparrows (Aimophila aestivalis) were studied in central Arkansas from 1983-85. Although one case of polygyny was observed, Bachman's Sparrows were primarily double-brooded and monogamous, breeding from 17 April-26 August. All nests were built on the ground. Clutches (mode = 4) laid during the first half of the breeding season were significantly larger than those laid during the second half. Females incubated eggs for 13-14 days, and both synchronous and asynchronous hatching were observed. The average nestling and fledgling periods were 9.0 ± 0.3 [SE] and 25.0 ± 1.2 days, respectively. Both parents cared for nestlings and fledglings. Females started second broods 12.3 ± 2.3 days after first-brood nestlings fledged, while males continued to care for first-brood fledglings. When nests failed, renesting attempts were made, and some pairs attempted 5 nests in one season. The average number of nests per season was 3.1 ± 0.2, and the average time interval between failed nests and repeat layings was 9.7 ± 1.6 days. The probability that an egg would produce a fledgling was 0.25. Predation was the major cause of nest failure. Nest success was not influenced by year, time of season, degree of nest concealment, habitat, or clutch size. On average, Bachman's Sparrow pairs produced 3.0 fledglings per year.
The Wilson Bulletin © 1988 Wilson Ornithological Society