Sex-biased survival of nestlings under unfavourable conditions drives secondary sex ratio in little owls (Athene noctua)

Identifying variation in key life history traits is crucial to predict population dynamics of endangered species. An increased bias in sex ratio as a result of low habitat quality can reinforce population decline and drive small populations to extinction. This is particularly true for monogamous bird species such as the little owl (Athene noctua). However, the underlying mechanisms driving biased sex ratios often remain elusive. Using a robust sample of molecular sex determination data recorded at two nest visits within each of 247 broods we examined the development in brood sex ratio, sexual size dimorphism and factors affecting the survival of little owl nestlings. Brood sex ratio in little owl broods was female-biased at fledging but not before the middle of the nestling period and it was female-biased at the end but not at the beginning of the breeding season. Female nestlings showed higher body mass than male nestlings of the same hatching rank. A survival analysis corroborated that late-hatched nestlings of low body mass showed reduced survival under adverse habitat conditions, resulting in a male-biased nestling mortality. Our conclusions therefore support theoretical predictions according to which the more sensitive sex will be disproportionally affected by unfavourable conditions that were previously identified by feeding experiments in the study system. This pattern of condition-dependent secondary brood sex ratio can severely affect the demographic parameters of endangered species and provides important implications for conservation.peerReviewe

Decision support tool for establishing an action plan aiming to decrease the discharge of micro pollutants into sewage system networks

The innovative decision support tool assists in ranking pollution sources and different urban watersheds, based on potential local emissions and the sensibility of the receiving water bodies. The potential local emissions are calculated by coupling characteristics of pollution sources to data bases containing potential emission coefficients of micro pollutants:, 1) Industrial/artisanal activities: APE (principal activity code) - emission (kg/year) by substance and by APE (mean values from national and local data bases): 2) Stormwater runoff: surface type (from national data bases and interpretation of satellite pictures) - emission (kg/year) by substance and by type of surface (literature data) and dependent on typical local rainfall: 3) Domestic: number of habitants - emission (kg/year) by substance and by habitant (literature data). The level of (eco) toxicity of each substance allows to transform potential emissions in potential pressures (PP). The hydraulic model of the sewage system network allows to affect parts of the local potential pressures to the water body. For each water body, a sensibility index (SI) is calculated based on its physico-chemical characteristics and its functions. The ratio PP/SI allows for ranking pollution sources. The coupling to a data base describing solutions for emission reduction for different pollution sources (substitution, treatment, education,..) will allow elaborating an action plan associated to a socio-economic evaluation