Map of background radiation (µSv/h) in the Chernobyl region and location of the study sites.

<p>Adapted from European Union <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0100296#pone.0100296-European1" target="_blank">[77]</a>.</p

Box plots of background radiation level (µSv/h) for birds without and with sperm.

<p>Values are medians, quartiles, 5- and 95-percentiles and extreme values.</p

Observed age ratio (proportion of all birds that were yearlings) of birds captured in mist nets in relation to level of background radiation (µSv/h) during 2010–2011. Error bars represent standard errors.

<p>Observed age ratio (proportion of all birds that were yearlings) of birds captured in mist nets in relation to level of background radiation (µSv/h) during 2010–2011. Error bars represent standard errors.</p

Absence of sperm in relation to level of background radiation (model 1) and level of background radiation, keel length and body mass (model 2).

<p>The models had the statistics χ² = 68.74, d.f. = 2, <i>r</i>² = 0.15, <i>P</i><0.0001 and χ² = 81.44, d.f. = 4, <i>r</i>² = 0.18, <i>P</i><0.0001.</p

Observed adult tertiary sex ratio (proportion of all adult birds that were males) of birds captured in mist nets in relation to level of background radiation (µSv/h) during 2010–2011. Error bars represent standard errors.

<p>Observed adult tertiary sex ratio (proportion of all adult birds that were males) of birds captured in mist nets in relation to level of background radiation (µSv/h) during 2010–2011. Error bars represent standard errors.</p

Age ratio (% yearlings), sample size and difference between adult survival rate and adult survival rate estimate based on age ratio (100 - % yearlings) for areas with normal (< 0.05 µSv/h) and higher levels of background radiation ((≥ 0.05 µSv/h) during 2010–2011.

<p>Northern Ukraine has low levels of background radiation around 0.01–0.05 µSv/h in areas that are unaffected by contamination from Chernobyl <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035223#pone.0035223-Shestopalov1" target="_blank">[25]</a>. The null expectation for difference in survival rate is zero, while the predicted difference is expected to be zero for normal background radiation, but a significantly lower difference survival rate at higher levels of background radiation.</p

Proportion of birds with sperm in relation to background radiation level (µSv/h).

<p>Proportion of birds with sperm in relation to background radiation level (µSv/h).</p

Generalized linear mixed models of the relationship between three principal components of sperm behavior and radiation, species×radiation and year.

<p>The random species effects were as follows: PC1: variance component 0.585, 95% CI = 0.1081, 1.0612, accounting for 21% of the variance. PC2: variance component 0.360, 95% CI = 0.0694, 0.6501, accounting for 24% of the variance. PC3: variance component 0.095, 95% CI = −0.0631, 0.2533, accounting for 7% of the variance.</p

Variation in the global antagonistic index of female (left) and male barn swallows (right) under different background radiation levels.

<p>Variation in the global antagonistic index of female (left) and male barn swallows (right) under different background radiation levels.</p

Results of multiple regression analyses in which the radiation level was the independent variable, and inhibition capacity (i.e., halo size) was the dependent variable.

<p><i>Q</i> is the statistical probability after adjustment for number of tests. The asterisk (*) denote significant values.</p