Blunt egg pole holds cues for alien egg discrimination: experimental evidence

• Published in: Journal of avian biology Vol. 41; no. 2; pp. 111 - 116
• Main Authors: Polačiková, L., Grim, T.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.03.2010; Blackwell Publishing Ltd; Blackwell Publishing; John Wiley & Sons, Inc
• Subjects: Acrocephalus; Acrocephalus arundinaceus; Animal nesting; Bird nesting; Birds; Brood parasitism; coevolution; color; egg shell; Eggs; Eggshells; Embryogenesis; Letter; Parasite hosts; Parasites; Parasitism; Turdus; Turdus philomelos; Warblers
• ISSN: 0908-8857; 1600-048X
• DOI: 10.1111/j.1600-048x.2010.04983.x

Eggshell colour patterns play a crucial role in avian host-parasite coevolution. In contrast to many experiments investigating general host egg discrimination abilities, studies testing where specific recognition cues are located on the eggshells (on blunt, sharp or both egg poles) are lacking. Previous studies suggested that discrimination cues might be located at the blunt egg pole, where the shell patterning is typically concentrated. We tested this hypothesis experimentally in species subject to interspecific (great reed warblers Acrocephalus arundinaceus, reed warblers A. scirpaceus), and also intraspecific parasitism (song thrushes Turdus philomelos, blackbirds T. merula). We examined host responses towards two types of intraspecific eggs painted non-mimetic immaculate blue either at blunt or sharp poles. All four species rejected eggs manipulated at the blunt pole at significantly higher rates, indicating that they perceive the critical recognition cues in the same egg part. Thus, the presence of egg recognition cues at the blunt egg pole may be a general phenomenon in birds parasitized by both intraspecific and interspecific parasites.