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Gamma Irradiation of Tree Swallow Embryos and Subsequent Growth and Survival

Reto Zach and Keith R. Mayoh
The Condor
Vol. 88, No. 1 (Feb., 1986), pp. 1-10
DOI: 10.2307/1367747
Stable URL: http://www.jstor.org/stable/1367747
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Gamma Irradiation of Tree Swallow Embryos and Subsequent Growth and Survival
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Abstract

Tree Swallow (Tachycineta bicolor) eggs from 35 nests, 7 to 8 days into incubation, were acutely exposed to gamma-radiation doses of about 0.4, 0.8, 1.6 or 3.2 Gy in the laboratory. The naturally incubated eggs were hatched in the laboratory and the young returned to the nests for raising by parents. Transport controls were treated identically, but not irradiated; box controls were left undisturbed in the nests. The overall mean hatching and fledging successes were 92.8% and 71.8%, respectively, and were unaffected by radiation exposure. Nestlings died from several causes including predation and harsh weather. Observed statistics and fitted parameters from the Richards model both indicated depressed growth in the 1.6-Gy and 3.2-Gy nestlings. Radiation exposure increased incubation time and depressed body mass and foot and primary-feather lengths at fledging. Box controls had shorter incubation times and greater hatching body masses than transport controls, suggesting experimental stress factors other than radiation exposure. Data from a few nests showed that chronic doses of about 1.0 Gy· d-1 reduces hatching, but not fledging, success. It also depresses growth far more severely than a 3.2-Gy acute dose. Since Tree Swallow embryos appear to be less sensitive to external gamma-radiation exposure than man, existing protective measures for man should be satisfactory for birds.

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