Feeding habits of Black-billed Magpie during the breeding season in Mediterranean Iberia: the role of birds and eggs

[Capsule]: Feeding habits of the Black-billed Magpie are of interest for researchers, conservationists and hunters since magpies are considered as predators of eggs and chicks of both songbirds and gamebirds. [Aims]: To characterize the feeding habits of magpies during their breeding season in agricultural environments of central Spain, and to assess the occurrence and incidence of birds and eggs in the magpie's diet. [Methods]: Diet was determined by the analysis of gizzard contents from 118 culled magpies. The diet was described as the frequency of occurrence (FO) and the percentage of volume (VOL) of a certain food item and for each gizzard. [Results]: Magpies presented a generalist diet, which included a wide range of foods. Arthropods and cereal seeds were the most frequently consumed food groups (FO > 60%). Eggs and birds were consumed only occasionally (FO < 6% and 17%, respectively; percentage of volume, VOL < 4%). [Conclusion]: Our findings suggest that other birds and their eggs do not represent an important food for magpies in Mediterranean agricultural environments under the conditions found during this study. Nevertheless, more complex studies in different scenarios (i.e. different population sizes of magpies and prey), and over longer temporal scales, are still necessary to clarify this controversial issue.
The study was funded by Consejería de Medio Ambiente of Junta de Comunidades de Castilla-La Mancha (Project PREG-05-23). F. Díaz-Ruiz holds a postdoctoral contract financed by the European Social Fund (ESF) and the Junta de Comunidades de Castilla-La Mancha (Operational Programme FSE 2007/2013). M. Delibes-Mateos is supported by the Talentia Postdoc Program launched by the Andalusian Knowledge Agency, co-funded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions (COFUND – Grant Agreement n° 267226) and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía.