Increased microclimatic variation in artificial nests does not create ecological traps for a secondary cavity breeder

Abstract

Artificial devices are increasingly used in conservation measures to mitigate the disappearance of natural habitats. However, few studies have demonstrated their benefits for the target species, and they may pose a risk of creating ecological traps. This occurs when lower individual fitness is found in artificial habitats that are more attractive than their natural equivalents. In this study, we tested the ecological trap hypothesis on a dense population of European rollers Coracias garrulus breeding in both natural cavities and nest-boxes. Our initial hypothesis was that the more stressful microclimatic conditions of nest-boxes would lead to reduced fitness of rollers, thus creating an ecological trap. The results showed that nest-boxes were preferred over natural cavities. Despite significantly more extreme microclimatic conditions in nest-boxes, we found similar breeding parameters between artificial and natural nest types. Our results also suggest that rollers selected the nest-boxes which best buffered the temperature, thus avoiding potential ecological traps. Overall our results lead to the conclusion that nest-boxes do not create ecological traps for rollers in this study site. However, other species may be more sensitive to microclimatic variations or less able to avoid the least favourable nest-boxes. These findings could help to inform the placement of nest-boxes in order to reduce extreme temperatures and variation in humidity rates. Future studies could compare nest types for other fitness parameters, such as juvenile body condition or survival. We also recommend the ecological trap hypothesis as a useful framework to evaluate the outcomes of artificial devices used for conservation.