The Asian Koel (Eudynamys scolopaceus) is a member of the Cuculiformes. As a cuckoo, it is a brood parasite, and the female lays its eggs in the nests of a variety of birds (Goodwin, 1983), while the males distract the host to lure them away from the nest (Dewar, 1907). A female might get rid of a host egg before laying her own egg (Payne, 2005).
Figure 1 in: “Female (Nominate Race)”, Asian Koel – Wikipedia, 5th March 2010.
It is presently distributed all over Singapore, in all habitats excluding the primary and secondary rainforest, yet was not perpetually so widespread. It was in fact was deemed as a non-breeding visitor up to the late 1980s. From the late 1980s till now, the Asian koel has managed to gain a foothold in Singapore by being a parasite of the House crow. There is an exploitative relationship between the two birds as the koel enhances its fitness at the expense of decreased survivorship of the crow. The population structure, abundance and distribution of the crow changes as a result. If the population of the crow increases, perhaps a result of an abundance of food and a lack of predation, so does the rate of parasitism; this can be shown by the Lotka-Volterra model for parasite-host interactions. Reciprocal effects between the crow and the koel population growth rates culminate in oscillations in both populations. For example, widespread culling of the crows or the presence of a disease that decimates the crow population, will eventually lead to a decrease in the population of the koels. The koels provide a natural form of keeping the crow population in check and perhaps studies should be conducted to determine if the population control by the koels can take away the need for crow culling.
Figure 2: in “House Crow”, House Crow- Wikipedia, 14th April 2010
Dewar, D (1907). “An enquiry into the parasitic habits of the Indian koel.”. J. Bombay Nat. Hist. Soc. 17 (3): 765–782.
“Female (Nominate Race)” by Asian Koel – Wikipedia, 5th March 2010. URL: http://en.wikipedia.org/wiki/Asian_Koel
Goodwin D. (1983). Crows of the World. Queensland University Press, St Lucia, Qld.
“House Crow”, by House Crow- Wikipedia, 14th April 2010. URL: http://en.wikipedia.org/wiki/House_Crow
Payne, RB (2005). The Cuckoos. Oxford University Press.