Cuckoo Host Interactions in Norwegian Mountain Areas

Abstract

The host interactions of the European Cuckoo Cuculus canorus were studied in highland regions of Central Norway. Over a 12-year period, 17 potential host species were investigated for evidence of nest parasitism by the Cuckoo. Only three species were actually parasitized (Meadow Pipit Anthus pratensis, Reed Bunting Emberiza schoeniclus, and Lapland Bunting Calcarius lapponicus). These species have similar eggs and also had similar parasitism rates, viz. about 6% in the higher lying areas, and 25% (only Meadow Pipits) in the lower areas. This indicates that individual female Cuckoos have the opportunity to use several species as hosts, depending on the colour and shape of the host''s eggs. Breeding success for the Cuckoo was 56%. Deserted host nests contained significantly more eggs than undeserted nests, a fact which may indicate that one mechanism for the host to detect parasitism is to assess the number of eggs. It is therefore important for the Cuckoo to remove at least one of the host eggs when laying its own. This study shows that a mean of 1.5 eggs were probably removed per parasitized host nest.