Herbaceous ground cover reduces nest predation in olive groves

Abstract

Capsule Bare ground increases artificial nest predation in olive groves.

Aims To assess the effect of different soil management regimes on nest predation rates in olive groves.

Methods We performed nest predation experiments with artificial nests during the breeding season in 2013, in two areas of southern Spain. Each artificial nest (n = 300) contained three quail Coturnix eggs, two of which were unmanipulated and the third one was emptied and injected with plaster. Predators were identified by marks on eggs filled with plaster.

Results Ground nests were significantly more depredated, irrespective of the presence of ground cover; tree nests were less depredated in fields with ground cover. There was a clear difference in nest predators of ground and tree nests. Rodents were the most frequent predators of tree nests.

Conclusion Lower predation rates of tree nests in orchards with ground cover are probably linked to a change in the foraging behaviour of rodents, which in these more complex habitats might be restricted by rodents' own risk of predation. This study underscores the important role of agricultural practices in preserving farmland bird communities, particularly tree-nesting species, suggesting that for this group, implementation of ground cover in olive groves might enhance breeding success by reducing nest predation rates.

Acknowledgements

We thank all the farmers who gave us permission to work in their fields. Special thanks go to Juanma and Stelle for their help in collecting data. We are also thankful to Isabel C. Barrio for her thorough review of this manuscript. The University of Córdoba and the Institute for Sustainable Agriculture of the Spanish National Research Council (CSIC) funded this project.

Supplemental Material

A supplementary online appendix giving predation rates by predator type, nest position and with/without herbaceous cover (Table S1) and showing examples of artificial nests, photo-trapped predation attempts and the marks left on artificial and real eggs by different predator species (Figs S1–S8) can be accessed at http://dx.doi.org/10.1080/00063657.2014.961894.