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Argentine ants harm nestlings of the blue tit

The consequences of ant invasions on ecosystems may only become apparent after long periods. In addition, predicting how sensitive native fauna will respond is only possible if the underlying proximate mechanisms of their impact are identified. The attraction of the native and invasive ant community to artificial bird nests was studied, together with reproduction of a wild native songbird over five consecutive breeding seasons in relation to the presence of an invasive ant species. Biometric, reproductive and individual blood parameters of great tits Parus major breeding in invaded as compared to uninvaded sites by Argentine ants Linepithema humile were analysed. Great tits bred preferably in uninvaded territories by the Argentine ant. Moreover, Argentine ants were more abundant at nests in invaded sites, than any native ant species were at uninvaded sites. Further, Argentine ants recruited at the artificial nests more intensively and responded to a larger variety of nest (intact eggs, cracked eggs, faeces, and cracked eggs plus faeces) contents than native species. Although breeding success and adult condition did not vary in relation to invasion status, offspring quality was negatively affected by the presence of Argentine ants. Nestlings reared in invaded sites were lighter, with lower wing/tarsus length ratio and had a reduced nutritional condition and altered oxidative stress balance as measured from several blood parameters. The interspersed distribution and small distance between invaded versus uninvaded territories suggest that ant presence affects nestling condition through direct interference at the nest. These results highlight the importance of evaluating the proximate effects like physiological parameters of the native fauna, when studying invasive ant-native bird interactions. informacion[at]ebd.csic.es: Álvarez et al (2020) Breeding consequences for a songbird nesting in Argentine ant' invaded land. Biol Invasions https://doi.org/10.1007/s10530-020-02297-3


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Population differentiation between natural and human-managed areas

Population differentiation between natural and human-managed areas

Landscape change induced by humans can alter the environmental conditions and thus promote unusually rapid evolutionary changes and/or at remarkably small spatial scales. In a managed property and a natural reserve situated less than 10 km apart, we tested for morphological differentiation of a migratory insectivorous bird, the red-necked nightjar (Caprimulgus ruficollis). At both sites, we also estimated site fidelity and quantified the potential foraging opportunities for nightjars, as measured by food supply and the availability of foraging sites. Breeding birds in the managed habitat were significantly larger in skeletal size than those in the natural one. However, there were no significant differences in wing or tail length. No individual (out of 1130 captures overall over 5 years) exchanged areas between years and immigration from neighboring areas was almost negligible, suggesting strong site fidelity. Food supply for nightjars was similar in both areas, but the availability of foraging sites was remarkably higher in the managed property as a result of human activity. Hence, nightjars in the latter habitat benefited from increased foraging opportunities in relation to those in the natural site. It seems likely that the fine-scale variation in nightjar morphology reflects a phenotypic response to unequal local conditions, since non-random dispersal or differential mortality had been determined not to be influential. High site fidelity appears to contribute to the maintenance of body-size differences between the two habitats. Results from this nightjar population highlight the potential of human-induced changes in landscape configuration to promote population-level responses at exceedingly small geographic scales. información[at]ebd.csic.es Camacho et al (2015) The road to opportunities: Landscape change promotes body size divergence in a highly mobile species Curr Zool 62:00?00