Common Cuckoo

Climate change

The cuckoo has increased in abundance in Finland, but has declined sharply in many European countries. Climate change has a significant impact on the occurrence of the cuckoo through its host species, and the timing of nesting is particularly important for the nest parasite. Now, due to global warming, many of the cuckoo’s host species have brought forward their spring migration and the start of nesting. It is more difficult for the cuckoo to catch the early spring, as it is a long-distance migrant. The reasons for the increase in the cuckoo’s abundance in Finland have not been studied; perhaps the chicks are surviving better due to warming.

Situation abroad

In wintering areas and along migration routes, the cuckoo is threatened by habitat changes, such as the reduction of suitable feeding places due to changes in agriculture, for example, and the global loss of insects.

Nice to know

The cuckoo is the only nest parasite (in the Finnish birds). The cuckoo is known to host several dozen different species, including the common redstart (Phoenicurus phoenicurus), white wagtail (Motacilla alba) and dunnock (Prunella modularis). The female cuckoo always lays her eggs in the nest of the same species in whose care she herself grew up. Although its eggs are larger than those of its hosts, the eggs in each type of host nest resemble the host’s eggs. The adult mimics the sparrowhawk; since that species is a predator, the mimicry gives the female time to lay her eggs without being attacked.

So why do parents of another species feed the chicks of other species? The hatched cuckoo chick, guided by instinct, pushes the other eggs and chicks out of the nest. The cuckoo is the only chick in the nest, and its large red mouth begging for food tells the mothers: food here and now! The cuckoo chick eventually grows much larger than its foster parents, but the red mouth of the begging cuckoo tricks the parents into feeding the cuckoo until it is fully grown.