Data from: Persistent organic pollution in a high-Arctic top predator: sex-dependent thresholds in adult survival

In long-lived species, any negative effect of pollution on adult survival
may pose serious hazards to breeding populations. In the present study we
measured concentrations of various organochlorines (OCs: PCB and
organochlorine pesticides) in the blood of a large number of adult
glaucous gulls (Larus hyperboreus) breeding on Bjørnøya (Bear Island) in
the Norwegian Arctic, and modelled their local survival using
capture–recapture analysis. Survival was negatively associated with
concentrations of OCs in the blood. The effect of OCs was nonlinear and
evident only among birds with the highest concentrations (the uppermost
deciles of contamination). The threshold for depressed survival differed
between the sexes, with females being more sensitive to contamination. For
birds with lower OC concentration, survival was very high, i.e. at the
upper range of survival rates reported from glaucous and other large gull
species in other, presumably less contaminated populations. We propose two
non-exclusive explanations. Firstly, at some threshold of OC
concentration, parents (especially males) may abandon reproduction to
maximise their own survival. Secondly, high contamination of OC may
eliminate the most sensitive individuals from the population (especially
among females), inducing a strong selection towards high-quality and less
sensitive phenotypes.