“Cu-ckoo!” — A distinctive two-tone call by the male Common Cuckoo. Common Cuckoo (Cuculus canorus), is a member of the cuckoo order of birds, Cuculiformes and a summer migrant to Europe and Asia. The cuckoos have an interesting behavior not commonly found in other bird species. That is, brood parasitism – a behavior in which female cuckoos lay their eggs only in the nests of other species of birds (Davies & Brooke, 1988).

Unlike most mother birds, the cuckoos choose not to be involve in the parenting by laying their eggs under the care of another bird species, otherwise called the ‘foster parents’. Interestingly, the cuckoos are wise enough to select suitable host so that the foster parents do not realise they are rearing a cuckoo egg! This is done by selecting host whose eggs look like the cuckoos egg and also by mimicking the colour and pattern of the host eggs. The ‘cruel’ young cuckoo, once hatched, will dispose of any other eggs by heaving them out of the nest, leaving itself as the sole occupant (Davies & Brooke, 1988).

Over the years, the parasitic interaction of the cuckoos and its host has resulted in co-evolutionary arms races, a competition between the host evolving new unique egg patterns and the parasite developing new forgeries. In particular, the Tawny-flanked Prinia have developed defense against the cuckoo’s mimicry by varying their egg colours and patterns (Spottiswoode & Stevens, 2012). The photo below illustrates the variations in the appearance of the eggs laid by the cuckoos (top row) and their host (bottom row) as a result of the evolutionary arms race.

“Cuckoo in egg pattern ‘arms race’” by Emma Brennand, 24 March 2011.
URL: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9418000/9418131.stm (accessed on 5 April 2013)

However, brood parasitism has its cost. It is likely to be the reason for the rapidly declining cuckoo’s population and its approaching extinction. With the shrinking natural habitat and declining number of host nests (Ward, 2008), it is no wonder that the cuckoo’s spring song is in danger of dying out.

References:

1)    Journal article

Davies, N. B. & Brooke, M. DE L., 1988. An Experimental Study of Co-Evolution Between the Cuckoo, Cuculus canorus, and its Hosts. The Journal of Animal Ecology, 58(1): 207-224

2)    Journal article

Spottiswoode, C. N.& Steven, M., 2012. Host-Parasite Arms Races and Rapid
Changes in Bird Egg Appearance. The American Naturalist, 179(5): 633-648

3)   News article
Ward, J., 2008. “The Clock Is Ticking: Germany’s Cuckoos Are Struggling to Survive.” SPIEGEL Online, 13 March 2008.
URL: http://www.spiegel.de/international/germany/the-clock-is-ticking-germany-s-cuckoos-are-stuggling-to-survive-a-541323.html  (accessed on 9 Apr 2013)