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Species interactions in recently established mixed colonies : Implications for conservation
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Resumo(s)
Human-induced changes in the environment dramatically shape the distribution of many species by restricting their access to resources such as food or nest-sites. Ongoing biodiversity loss has prompted conservation projects and large-scale nest-site provisioning to halt species declines. While successful at recovering endangered populations, artificial nests may turn into ecological traps by attracting animals to sites that end up reducing their fitness, or into conservation traps by making populations fully reliant on continuous conservation actions. Particularly, these new artificial nesting landscapes may alter the structure and functioning of communities, and modify or promote new species interactions, with unknown consequences for the conservation of target species.
In Europe, large-scale nest-site provisioning aimed at recovering lesser kestrel (Falco naumanni) populations attracted several other bird species forming mixed colonies. The main objective of this thesis was to investigate the consequences of these breeding assemblages for the conservation of the lesser kestrel and the European roller (Coracias garrulus) in Portugal. Using long-term monitoring data and a wide range of field techniques, this thesis first addresses the challenges and opportunities of artificial nests for the successful persistence of populations. Then, it investigates how costs and benefits typically associated with group living, such as increased transmission of parasites, competition for resources, and protection from predators, may affect the conservation of lesser kestrels and rollers.
Overall, this thesis demonstrates that artificial nesting landscapes may cause target species to become fully reliant on conservation actions and could concentrate species with similar niches in supra-optimal breeding densities. Ectoparasite burden was influenced by the relative abundance of each host species, most species highly overlapped in their trophic niche, and rollers acquired clear anti-predatory benefits from nesting near lesser kestrels. Understanding the impacts of nest-provisioning beyond the recovery of target populations, by considering how they attract other species and shape the interactions between them and their resources, will help researchers and conservation managers to draw and adapt conservation actions that guarantee the long-term persistence of wildlife populations.
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Palavras-chave
conservação colónias multiespecíficas francelho ninhos artificiais rolieiro artificial nests conservation lesser kestrels mixed-species groups rollers