Why do Horsfield’s bronze-cuckoo Chalcites basalis eggs mimic those of their hosts?

@article{Langmore2009WhyDH,
  title={Why do Horsfield’s bronze-cuckoo Chalcites basalis eggs mimic those of their hosts?},
  author={Naomi E. Langmore and Rebecca M. Kilner},
  journal={Behavioral Ecology and Sociobiology},
  year={2009},
  volume={63},
  pages={1127-1131}
}
The Horsfield’s bronze-cuckoo (Chalcites basalis) egg closely matches the appearance of its host fairy-wren (Malurus spp.) eggs. Mimicry of host eggs by cuckoos is usually attributed to coevolution between cuckoos and hosts, with host discrimination against odd-looking eggs selecting for ever better mimicry by cuckoos. However, this process cannot explain Horsfield’s bronze-cuckoo egg mimicry because fairy-wren hosts rarely reject odd-looking eggs from their nest. An alternative hypothesis is… 
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