The invasive pest fruit fly Drosophila suzukii is thought to be a specialist on healthy, i.e. unwounded, non-fermenting fruits. Morphological (sharp ovipositor) and neurophysiological/behavioural adaptations have been suggested to contribute to distinct adult feeding (wounded/microbe-laden fruits) and reproductive (healthy fruits) sites. We tested whether (1) variation in the overall availability of fruits, (2) variation in fruit type (healthy, wounded, fermenting), and (3) the relative abundance of different fruit types are ecological determinants of D. suzukii egg-laying decisions. even though individual flies reduced their reproductive output when resource availability (blueberries) was low, a significantly higher proportion of eggs was allocated to healthy fruits, relative to wounded and fermenting fruits. However, the preference for healthy over wounded fruits declined continuously with a decrease in the relative abundance of healthy fruits and the overall reproductive output did not change. Under laboratory conditions, D. suzukii larvae achieved a higher developmental success on wounded than on healthy blueberries, but suffered less from density-dependent competition in healthy fruits. these data suggest that D. suzukii, despite showing an egg-laying preference for healthy fruits, also uses wounded/fermenting fruits as egg-laying sites, and that it may thrive well in windfall fruits.Drosophila suzukii, a devastating invasive insect in European and American fruit plantations, has been described as being '…extremely fond of otherwise undamaged, ripening fruits…' 1 . Indeed, unlike most other drosophilid fruit fly species that are able to use only fruits with cracked skins for egg-laying, a serrated ovipositor enables D. suzukii to pierce the intact skin of many cultured and wild fruits and to insert their eggs into the fresh fruit flesh 2 . The subsequent larval development and microbial growth cause a rapid fruit decay that renders cherries, blue-, straw-, and blackberries etc. unmarketable. Recently, Karageorgi et al. 3 showed that an egg-laying preference of D. suzukii for intact ripening over rotting strawberries is mediated by a combination of chemo-and mechanosensation. This apparent preference has been suggested to have resulted in distinct adult feeding and breeding sites 4 . Studies designed for describing neurophysiologically 'hard-wired' preferences, however, often overlook the impact of variation in experience and internal status, i.e. optimal foraging decisions 5 , as well as neural limitations in detecting the preferred host in naturally complex ecological settings 6 .Conclusions regarding such 'hard-wired' preferences are particularly problematic for polyphagous insects 7like D. suzukii -where individuals are confronted with hosts that vary widely in suitability and availability. For example, the extent to which a particular host is used for oviposition may be affected by the type and density of alternative hosts in the vicinity, resulting in apparently suboptimal host use 8 . Suboptimal host u...

Predation and brood parasitism are common reasons for nesting failure in passerine species and the additive impact by invasive species is a major conservation concern, particularly on tropical islands. Recognising the relative contribution of the different components of nesting failure rates is important to understand co‐evolutionary interactions within brood parasite–host systems. In the remote archipelago of New Caledonia, the fan‐tailed gerygone Gerygone flavolateralis is the exclusive host of the brood‐parasitic shining bronze‐cuckoo Chalcites lucidus. Additionally, invasive rodents also possibly have an impact on breeding success. To estimate the impact of potential nest predators, we 1) video monitored nests to identify predators, 2) estimated the probability of predation based on nest visibility and predator abundance and 3) tested the possibility that the location of experimental nests and lack of odour cues decrease the predation by rodents. In addition, we estimated nest survival rates using data collected in different habitats over the course of eight breeding seasons. Nesting success of fan‐tailed gerygones was relatively low and predation was the main cause of nesting failure. We recorded mainly predation by native birds, including the shining bronze‐cuckoo, whereas predation by rats was rare. In open habitats predation by cuckoos was much lower than predation by other avian predators. Neither predator activity around nests nor nest visibility influenced the probability of predation. Experimental nests in more accessible locations and containing an odorous bait were more exposed to rodent predation. Apparently, the fan‐tailed gerygone has either never been specifically vulnerable to predation by rats or has developed anti‐predator adaptations.

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