| Abstrakt: |
Although the cuckoo Cuculus canorus parasitizes a variety of hosts, individual females are thought to favour just one species and they lay eggs coloured to match, more or less accurately, those of their particular host1–3. The mechanisms underlying this division of females into strains, or gentes, specializing on different hosts are unknown. From a study of museum collections we show that the eggs of British cuckoo gentes are statistically different and, using model eggs, we show by experiment that host discrimination against badly matching eggs is a selective force in gens maintenance and that cuckoos lay a better mimetic egg where the host species is apparently more discriminating. |
