Hiroshi Nakamura

Nakamura, H. 1998. Dynamic relationships between the Common Cuckoo and a new host, the Azure-winged Magpie. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 3097. Johannesburg: BirdLife South Africa.

It is thought that the intricate relation between parasite and host has evolved through adaptation and counter-adaptations. Cuckoo Cuculus canorus parasitism on the Azure-winged Magpies Cyanopica cyana started about 30 years ago in central Japan and spread rapidly throughout the breeding areas of the magpie. I have been studying the parasitic relations in six regions for more than ten years. In some regions, parasitism rate increased rapidly and 80% of magpie nests were parasitised. The reason for this quick spread and heavy parasitism is that the magpie has no counter adaptations towards cuckoo parasitism. However, the magpie developed counter-adaptations over a short time (within 10 years); aggressiveness to the cuckoos and rejection of the cuckoo eggs increased with the progress of the cuckoo parasitism. The density of the magpie decreased after the start of cuckoo parasitism. In one region, a magpie population was wiped out. After the decrease of the magpie density, the cuckoos’ density decreased in some regions. In two regions, magpie populations increased after the decrease of cuckoo density. It was clear that the parasitic relations between the cuckoo and the new host changed dynamically over a short time in different manners in different regions.