Effects of Anthropogenic Introduction of Substrates on Egg Camouflage and Nesting Success in Ground-Nesting Birds

Abstract

To make many sites accessible, humans have constructed roads. New layers of different materials (pipeclay, gravel, etc.) are added to the original soil for the construction of unpaved roads, which in marshy areas are readily used as nesting sites by ground- nesting waterbirds. On the other hand, the disposal of dredged materials has been used as a specific management strategy to facilitate the nesting of ground- nesting waterbirds in order to compensate for the loss of natural habitats. The introduced substrates may differ in their physical properties (e.g., colouration) from the original ones, which may affect the sensory ecology of animals. By modifying the original backgrounds, nest camouflage could be altered, and this could affect nest success, in which case this may be relevant in conservation biology. Here, we focused on whether the introduction of novel substrates may affect nest camouflage and whether this might eventually affect nesting success in a ground- nesting bird that is declining globally, the Kentish plover Anarhynchus alexandrinus. To this end, we analysed images of nests according to the visual systems of their predators. We found that the camouflage of eggs with respect to both microhabitats and nest materials was worse in introduced substrates than in natural ones. However, nesting success was not affected by egg camouflage, likely because in our study sites the community of nest predators was diverse and used a variety of sensory systems to locate nests (sight, smell), and also because our sample sizes may have been moderately small. As it has been previously shown that camouflage may affect nesting success in some cases, managers planning the construction of nesting sites using artificial substrates should be aware of this and perform prospective studies of the effects of the substrates on nest camouflage of the target species.