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 prediction was that the more stressful microclimatic conditions of nest boxes would lead to reduced fitness of European 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 European rollers selected the nest boxes which best buffered the temperature, thus avoiding potential ecological traps. Overall our results led to the conclusion that nest boxes do not create ecological traps for European rollers in this study area. However, other species may be more sensitive to microclimatic variations or less able to avoid the least favorable 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.
Highlights
The rapid changes affecting biodiversity in recent decades have led to an expansion of habitat restoration and biodiversity offsetting programs (Dobson, 1997; Maron et al, 2015)
The higher occupation rates of nest boxes and similar egg-laying dates showed that artificial devices were preferred or selected by European rollers compared with natural cavities, but we did not find any significant differences in European roller breeding success between the two nest types
While we found that European rollers appear to avoid the least favorable nest boxes among those available, this choice was only possible because these were located in different settings, under tree canopy, which created a variety of microclimates
Summary
The rapid changes affecting biodiversity in recent decades have led to an expansion of habitat restoration and biodiversity offsetting programs (Dobson, 1997; Maron et al, 2015). Shelters for reptiles are positioned to replace disappearing stone walls and hedges (Grillet et al, 2010), bat boxes to compensate for felled cavity trees or restored buildings (Flaquer et al, 2006), and nest boxes to provide additional breeding places for birds and mammals (Goldingay & Stevens, 2009) Despite their extensive use in conservation and offsetting programs, robust evaluations of the benefit of artificial devices in terms of the population viability of the target species are rare (Wesołowski, 2011, but see Bourgeois et al, 2015; Bragin et al, 2017; Libois et al, 2012; Sutherland et al.., 2014). Based on these two predictions, we expected nest boxes to act as an ecological trap for the European roller
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