Horsfield's Bronze-Cuckoo (Chalcites basalis) are found throughout Australia. These birds are brood parasites- that is they parasite the nest of another species of bird in order for the host species too raise their young. Horsefields Bronze-Cuckoo's favor the nests of  Fairy Wrens and Thornbills (Brooker, Brooker 1989). The Cuckoo's have evolved many strategies to aid them in their deceptions. The eggs of Cuckoo's superficially resemble the eggs of their host species making it difficult for hosts to detect the intruder.


Female Cuckoo's lay their eggs late in the developmental stage so that their chick is the first too hatch. Once hatched the young set about evicting the other eggs from the nest so that they can receive the sole attention of the host parents. Research by Langmore, Maurer, Adcock and Kilner (2008) found that  Horsfield's Bronze-Cuckoo chicks are born with the ability to mimic two species. Initially they will sing the begging cry of the Fairy-Wren. Langmore et. al. (2008) believe that the chick will change song due to environmental cue's and hypothesized that hunger was the driving factor. They found that  the chicks would switch form singing the Superb Fairy-Wren cry to a melody of cries, eventually whittling away notes and sounds that did not elicit a response form the host until they match the appropriate cry, in this case the Buff-Rumped Thornbill.This ability to mimic not only the hosts eggs superficially but also the cry of their young has led too the success of Cuckoo's globally.

On a side note the Cuckoo's do not have it all their own way. The relationship between the Horsfield's Bronze-Cuckoo and the Superb Fairy Wren is great example of the evolutionary arms race of species. Research by Langmore, Hunt and Kilner (2003) found that Super Fairy-Wrens abandoned a cuckoo chick 38% of the time. They discovered that some female Superb fairy-Wrens sing a special song too their developing eggs which contains a hidden 'key' note. This key note is incorporated into the begging cry of the chicks. The Cuckoo chicks not having heard the song during development miss out on this key note and as such are recognized by the parents as an intruder and are subsequently abandoned.

References:

Brooker, M Brooker, L Rowley, I 1988, 'Egg deposition by the bronze-cuckoos Chrysococcyx basalis and Ch. ludicus' Emu 88, pp. 107-109.

Langmore, N Hunt, S Kilner, R 2003, 'Escalation of coevolutionary arms race through host rejection of brood parasitic young', Nature 422, 157-160.

Langmore, N Golo, M Adcock, G Kilner, R 2008,'Socially Acquired Host-Specific mimicry and the Evolution of Host Races in Horsefield's Bronze-Cuckoo Chalcites basalis', Evolution  62, pp. 1689-1699.

Artist unknown, 'Egg comparisons', Photograph, BBC, viewed 10th May 2014, <http://news.bbc.co.uk/earth/hi/earth_news/newsid_8645000/8645158.stm>