Are both notes of the common cuckoo's call necessary for familiarity recognition?

Common cuckoos (Cuculus canorus) are best known for their simple two-note calls ("cu-coo"), which are uttered only by males during the breeding season. A previous playback study revealed that territorial males were more tolerant toward playbacks of the calls of familiar, neighbouring individuals than toward unfamiliar, stranger simulated intruders, exhibiting the classical "dear-enemy" phenomenon. Here we experimentally assessed whether the acoustic cues for familiarity recognition are encoded in the first and/or second note of these simple calls.

Common cuckoos (Cuculus canorus) affect the bacterial diversity of the eggshells of their great reed warbler (Acrocephalus arundinaceus) hosts.

The common cuckoo (Cuculus canorus) is an avian brood parasite, laying its eggs in the nests of other bird species, where these hosts incubate the parasitic eggs, feed and rear the nestlings. The appearance of a cuckoo egg in a host nest may change the bacterial community in the nest. This may have consequences on the hatchability of host eggs, even when hosts reject the parasitic egg, typically within six days after parasitism.

Competition with a host nestling for parental provisioning imposes recoverable costs on parasitic cuckoo chick's growth.

Chicks of the brood parasitic common cuckoo (Cuculus canorus) typically monopolize host parental care by evicting all eggs and nestmates from the nest. To assess the benefits of parasitic eviction behaviour throughout the full nestling period, we generated mixed broods of one cuckoo and one great reed warbler (Acrocephalus arundinaceus) to study how hosts divide care between own and parasitic young. We also recorded parental provisioning behaviour at nests of singleton host nestlings or singleton cuckoo chicks.