and Weight Variations in Summer Birds from Georgia and South Carolina
R. A. and D. W. Johnston
Statistical data are presented on weights of 576 specimens representing
97 species of birds. All were collected in summer, from 1947 to
1956, in southern Georgia and adjacent parts of South Carolina.
The general procedure and manner of presentation of data are explained.
The data are broken down into three categories: species, sex,
and age (adults versus fully fledged immatures). For each category represented
by more than one weight, the mean value with the standard error is given
both for weight and for sub-seasonal period of collection. For
more or less fat specimens, semi-quantitative indications of fat condition
are provided; these aid in the interpretation of certain weight values.
Data for certain species are subjected to further analysis. In
four species, males are significantly heavier than females; in four
others there is no significant difference between the sexes. By
our criterion (the validity of which is discussed), the difference between
the means of compared samples, if it is to be regarded as significant,
must equal or exceed 7 per cent of the weight of the male, or the difference
must show a P-value that is no greater than .10. Among compared
samples, immatures in most instances average slightly heavier than adults.
The coefficients of variability of weight samples, if compared sex for
sex, are on the whole significantly higher (P=.10) for immatures than
for adults. This marked variability is due in part (heavily irradiated
one) hatched, and two days later both parents were watched as they fed
their young. It was clear that both cared for the young throughout
the nestling period. When I visited the box on June 8 in order
to band the nestlings, both the male and female came fairly close and
issued scolding notes. Three days later the young departed from
the nest. Like the bluebirds, the female titmouse showed no signs
of radiation sickness.
R.A. and D.W. Johnston. 1958. Weights and weight variations in summer
birds from Georgia and South Carolina. The Wilson Bulletin 70:114-129.