Meeting Abstract

P1.92  Sunday, Jan. 4   Perceptual modeling of egg color mimicry in cuckoo-host coevolutionary arms races IGIC, B*; GRIM, T; CASSEY, P; MOSKAT, C; RUTILA, J; HAUBER, ME; University of Auckland, New Zealand; Palacky University, Czech Republic; University of Birmingham, UK; Hungarian Academy of Sciences, Budapest; University of Joensuu, Finland; University of Auckland, New Zealand bigi001@ec.auckland.ac.nz

Coevolution between the common cuckoo Cuculus canorus and its passerine hosts has resulted in a female parasite laying eggs in nests of other birds, matching the eggshell coloration of the host that she most often parasitizes. This apparent visual mimicry reduces the chance that hosts recognize and reject foreign eggs. Past research used the human visual system or instrumentational measures of light reflectance to assess the extent of color-mimicry by cuckoo eggshells. Here we used sensory modelling of the avian visual system to test if color matching by cuckoos is representative of coevolved perceptual mimicry. We studied eggs from three cuckoo host-races, from Hungary, the Czech Republic and Finland, together with Finnish non-host species. We tested the alternative hypotheses that egg color matching between cuckoos and hosts is due to (i) shared habitat or (ii) shared eggshell structure, rather than owing to (iii) coevolutionary selection on mimetic coloration. The avian-perceived match between cuckoo egg colors was closer between the parasites and respective hosts compared to non-host species. In contrast, eggshell structure, as measured by shell thickness, was consistently similar amongst cuckoos compared to hosts and, thus, independent of cuckoo-host evolutionary interactions. These results strongly support the (iii) coevolutionary arms-race hypothesis.