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POPULATION DYNAMICS OF MEDITERRANEAN WATERBIRDS AND THEIR DEMOGRAPHIC AND BEHAVIOURAL RESPONSES TO GLOBAL CHANGE

Final Report Summary - MATERGLOBE (POPULATIOFinal Report Summary - MATERGLOBE (population dynamics of mediterranean waterbirds and their demographic and behavioural responses to global change)

Project context and objectives

Coastal, wetland, island and marine ecosystems have been largely modified during the last century making them especially vulnerable to global change threats. In the Mediterranean basin over the last few decades, major socio-economic changes have increased the negative impact of human activity, mainly along the coasts, pushing many endemic species to the edge of extinction. The study of how individuals in a population react to changes in their environment, taken in a broad sense (climate but also biotic relationships and changes resulting from socio-economic activities) is key to understanding how present threats impact now and will impact in the future the dynamics of a population. The IEF Marie Curie MATERGLOBE project aimed at providing advances in the understanding of ecological, demographical, evolutionary, behavioural and conservational aspects of Mediterranean waterbirds. It has succeeded in providing important advances in the understanding of the population dynamics of three waterbird species (flamingos, shearwaters and European storm petrels) as well as in the spur-thighed tortoise. From this understanding, we can build scenarios and make previsions on the dynamics of the species and envisage appropriate conservation measures for those which are deemed vulnerable.

Project work and results

We studied the wintering strategies of flamingos born on a large Mediterranean colony (Rhone delta, France) over 34 years. During their first winter, and especially during wet years, most young (80 %) leave France to go south; 34 % cross the Mediterranean to winter in Africa. This strategy appears costly as > 50 % of them will die (vs. 20 % of the others). Flamingos rapidly become very faithful to their wintering grounds. However, those that do change tend to winter nearer their birth colony. Their presence at proximity probably allows them to more easily secure a nesting site when the breeding season arrives. Yet, adults migrating long distances to winter have higher survival (97 % vs. 94 %), especially during cold spells (such as in 1985 and 2012 when French residents suffered extreme mortality). Given current frequency of cold spells, simulations indicate that resident, medium- and long-distance wintering strategies are probably equivalent in terms of fitness. The coexistence of different strategies within this population is an asset that should allow the population to persist through changing environmental conditions.

We analysed the impact of climate on the survival, reproductive skipping, nest dispersal and breeding success of the Cory’s shearwater, a trans-equatorial migratory long-lived seabird. Large-scale climatic indexes had a pronounced effect on survival (SOI), probably because the Atlantic hurricane season is modulated by the SOI and coincides with shearwater migration to their wintering areas, directly affecting survival probabilities. Breeding success was affected by another climatic factor, the NAO, probably as a result of its effect on the timing of peak abundance of squid and small pelagics, the main prey for shearwaters. No climatic effect was found either on reproductive skipping or on nest dispersal. The potential increase of hurricane frequency due to global warming may interact with other global change agents (such as incidental by-catch and predation by alien species) nowadays impacting shearwaters, affecting the future viability of these populations.

We assessed the impact of fire on survival rates, reproduction and movement patterns in an endangered terrestrial tortoise inhabiting the Mediterranean region, the Spur-thighed tortoise. Fire caused direct and delayed reductions in local survival, young individuals being the most affected. There were no differences in fecundity and movement patterns of tortoises between burned and unburned areas. Under fire frequencies similar to those occurring in the wild (<1 fire every 20-30 years) most tortoise populations can weather the fires. But, if fire frequency slightly increases, the probability of quasi-extinction increases dramatically. Except for very large populations, more recurrent fires may severely threaten the species. Our results have straightforward applications for fire management purposes in those areas of the Mediterranean region where this endangered species is present.

We studied evolvability of two life-history traits (timing of recruitment and laying date) in two adjacent colonies of the European storm petrel. We found significant heritability only in laying date in one colony. Interestingly, in this colony, positive selection of earlier breeding birds was detected. The evolutionary potential in timing of reproduction may be crucial to the ability of populations to bear environmental changes. Our results show that evolvability of a life-history trait may vary within a surprisingly small spatial scale, through diversifying natural selection and limited gene flow.

We investigated the effects of first reproduction on the subsequent survival of male and female European storm petrels. We found that survival of inexperienced females was lower than that of experienced females and males. The effort invested by inexperienced females in the production of a large egg (=25 % of adult body mass) may explain the observed differences in survival.

We evaluated the effectiveness of artificial nest boxes as a management measure for European storm-petrel conservation on Benidorm Island (Spain). Individuals breeding in artificial nests show higher survival rates and breeding success than birds breeding in natural sites, probably as a consequence of protection against gulls. Following the installation and successful occupation of nest boxes, breeding numbers of storm petrels greatly increased.

We demonstrated that European storm petrels are able to distinguish kin from non-kin odours. Birds preferred unrelated odours. This behaviour allows these highly philopatric birds to avoid inbreeding and tune their mate choice. Our result suggests that sophisticated olfactory communication is relevant in birds, and tunes important traits such as philopatry.

Finally, we developed a statistical method for estimating survival when animals tend to be captured several times in a row. We applied this method to Cory’s shearwater data and showed that survival is underestimated if the correction is not applied. We also developed a method to estimate demographic parameters of individuals that remain in clusters (families or pairs). We demonstrated that paired Cory's shearwaters tend to be captured together, but not to die together.

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