Effects of X-irradiation on the Breeding Biology of Eastern Bluebirds
R. A. Norris
1956 several aspects of the reproductive biology of Eastern Bluebirds
were studied in the Savannah River Plant area of South Carolina.
The birds bred in nest-boxes throughout the spring and summer.
In April and May some of the adult females and nestlings were exposed
to X-irradiation, color-banded, and returned to their nests. The
dosage rate was high, 23.5 r per minute, and most of the individuals
received from 200 to 600 r. Several eggs were also exposed.
The breeding biology of irradiated and non-irradiated females was essentially
the same in the following respects: size of sets of eggs, length of
incubation, hatchability of eggs, nestling period, and general reproductive
success. In both irradiated birds and controls there were records
of second and third broods. Developing embryos were rather vulnerable
to radiation. Among nine irradiated bluebird eggs (mean dosage
about 420 r) the embryos died in three instances and the nestling hatching
from the other three eggs succeeded in fledging. Four nestlings
given 400 to 1200 r developed normally and fledged successfully.
It is suspected that week-old songbirds might have greater radioresistance
than laboratory chicks and ducklings of the same age. Limited
data obtained from other box-nesting species, the Great Crested Flycatcher
and Tufted Titmouse, suggested that the titmouse, at least, was similar
to the bluebird in its resistance to radiation sickness.
R.A. 1958. Some effects of X-irradiation on the breeding biology of
eastern bluebirds. Auk 75:444-455.
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