“Timing of breeding in an ecologically trapped bird”

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Franck A. Hollander, Nicolas Titeux, Marie-Jeanne Holveck, and Hans Van Dyck

A female red-backed shrike (Lanius collurio) on the nest in a young spruce tree of a forest plantation clearing. Although this habitat is preferred over farmland habitat, shrikes experience an ecological trap in this forest habitat.
(Credit: Franck Hollander)

Human-induced environmental change has the capacity to confuse the way organisms perceive their environment and ultimately respond to it. For instance, organisms may prefer to settle and reproduce in anthropogenic habitats of low quality even when higher-quality habitat is available. Such ecological traps lead to fitness loss and are of growing conservation concern worldwide. While the underlying mechanisms are still poorly understood, a recent study shows a functional explanation for ecological traps in seasonally changing environments.

Researchers from the Université Catholique de Louvain in Belgium studied the relationship between timing of breeding, reproductive performance, and food resources to explain the observed ecological trap in the red-backed shrike (Lanius collurio), a long-distant migratory bird breeding in seasonally changing habitats. Their previous work showed that this bird prefers to breed in newly colonized forest clearings, where its reproductive performance is significantly lower than in farmland, which is its original longtime breeding habitat. For three successive years, they sampled data in these two human-modified habitats.

The team found a stronger seasonal decrease in the food resources available for rearing nestlings in forest clearings compared to farmland habitat. This provides a functional explanation for why brood size and quality also gradually decreased more strongly in the preferred forest habitat over the course of the season. This is the first time that maladaptive timing of breeding has been found to explain fitness loss in an ecological trap.

The same mechanism possibly creates ecological traps for a wide range of organisms breeding in seasonal environments. There is now a need to study how trapped organisms will further cope with their situation and with further environmental change that might arise. The results of this study are also relevant for conservation strategies: Plantation forests may provide less valuable conservation opportunities than previously thought. Read the Article