Breeding ground diet of the common cuckoo Cuculus canorus

Breeding ground food availability is critical to the survival and productivity of adult birds. Furthermore, many migrant birds rely on breeding ground food resources to achieve breeding condition following migration. The common cuckoo Cuculus canorus (cuckoo) is a brood-parasitic, Afro-Palearctic migrant bird that on arrival to its breeding grounds exhibits behaviours of delayed egg-laying and voracious feeding to achieve breeding condition. It is a species in long-term decline in many European countries, and variation in trend between regions and habitats suggests breeding ground causes, including adult food supply. However, cuckoo diet has not been studied in detail since before the most significant population declines in Europe began in the mid-1980s. Largely anecdotal field observations suggest that cuckoos feed predominantly on large moth and butterfly (Lepidoptera) larvae. Here we use high-throughput DNA sequencing of arthropod prey in faeces to determine adult cuckoo diet.