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In the world of birds, radiation is more damaging to females

the tertiary sex ratio (here defined as the proportion of males among adults) was skewed towards an excess of males across 48 different bird species. This finding is in accordance with lower adult survival rates in females compared to males previously reported for barn swallows in contaminated areas around Chernobyl …..

Female barn swallows suffer differentially from the mortality costs of radiation, with male adult survival being reduced by 24%, while female survival is reduced by 57% in contaminated areas compared to controls 

Elevated Mortality among Birds in Chernobyl as Judged from Skewed Age and Sex Ratios PLoS One 13 April 12, “….Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions.

Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in
male-skewed adult sex ratios.

Methodology/Principal Finding
We estimated the effects of low-dose radiation on adult survival rates
in birds by determining age ratios of adults captured in mist nets
during the breeding season in relation to background radiation levels
around Chernobyl and in nearby uncontaminated control areas. Age
ratios were skewed towards yearlings, especially in the most
contaminated areas, implying that adult survival rates were reduced in
contaminated areas, and that populations in such areas could only be
maintained through immigration from nearby uncontaminated areas.
Differential mortality in females resulted in a strongly male-skewed
sex ratio in the most contaminated areas. In addition, males sang
disproportionately commonly in the most contaminated areas where the
sex ratio was male skewed presumably because males had difficulty
finding and acquiring mates when females were rare. The results were
not caused by permanent emigration by females from the most
contaminated areas because none of the recaptured birds had changed
breeding site, and the proportion of individuals with morphological
abnormalities did not differ significantly between the sexes for areas
with normal and higher levels of contamination.

Conclusions/Significance
These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation.

Such skewed age ratios towards yearlings in
contaminated areas are consistent with the hypothesis that an area
exceeding 30,000 km2 in Chernobyl’s surroundings constitutes an
ecological trap that causes dramatic excess mortality……..

the tertiary sex ratio (here defined as the proportion of males among adults) was skewed towards an excess of males across 48 different bird species. This finding is in accordance with lower adult survival rates in females compared to males previously reported for barn swallows in contaminated areas around Chernobyl …..

Female barn swallows suffer differentially from the mortality costs of radiation, with male adult survival being reduced by 24%, while female survival is reduced by 57% in contaminated areas compared to controls
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0035223

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April 13, 2012 - Posted by | environment, Reference

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