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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] Álvarez et al (2020) Breeding consequences for a songbird nesting in Argentine ant' invaded land. Biol Invasions
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Lifelong effects of trapping experience

Lifelong effects of trapping experience

Long-term monitoring of individually marked animals is usually required for reliable estimation of numerous life history parameters. However, capture, marking and manipulation can dramatically alter the animals' behaviour after capture, and thus affect subsequent recapture success. Here, a pied flycatcher population was used as an example to illustrate the sampling bias resulting from the repeated capture of free-ranging individuals. By using repeated measures of the same individuals obtained during our long-term survey, the interannual response of breeding adults to capture-related stress was specifically evaluated, measured as latency to enter nestboxes equipped with a swing-trap. Moreover, the changes in the mean and variance of bird age with varying trapping effort were examined using subsamples of the data set. Birds without any previous trapping experience entered nests more quickly than experienced ones, after controlling for other factors affecting latency, such as the sex, offspring quality and the order of capture relative to the other pair member. Birds' reluctance to enter the nest furthermore increased as the number of captures in previous years accumulated, implying that individual pied flycatchers became progressively more difficult to capture over the course of the study. These results indicate that repeated exposure to capture stress over an animal's lifetime may induce long-lasting behavioural modifications that may influence trappability of the older segments of the population. This may ultimately lead to sampling bias towards younger ages, especially when effort is limited. The study concludes that systematic age bias due to trapping experience can have important implications for the estimation of variation in a range of traits and should therefore be carefully checked in longitudinal studies. informacion[at] Camacho et al (2017) Lifelong effects of trapping experience lead to age-biased sampling: lessons from a wild bird population.