Mixed clutches in Montagu's harrier Circus pygargus nests: a maladaptive brood parasitism by galliform birds

Abstract

Cases of mixed clutches in raptor nests are very scarce in the literature. Among 279 harrier nests monitored between 1991–1996 and 2010–2011 in two different areas of central Spain, quail eggs were found in one harrier nest, and 13 others contained partridge eggs. Harrier eggs were smaller in nests which contained galliformeggs, and therefore more similar in size and appearance to the foreign eggs, which may suggest a maladaptative behaviour on the part of the galliforms.