First recorded evidence of ejection of a cuckoo egg in a fairy-wren species

Brood-parasitic cuckoos lay their eggs in the nests of other birds, abandoning parental care to their hosts. Many host species have evolved defences to escape or reduce the costs associated with cuckoo parasitism. Superb Fairy-wrens Malurus cyaneus, which are a host to several cuckoo species in Australia, can distinguish cuckoo eggs based on their size or shape, or by using indirect cues such as the timing of egg laying or the presence of an adult cuckoo near the nest. They have previously been shown to reject cuckoo eggs by methods of egg burial or abandonment. These methods are likely to be costlier than ejecting the cuckoo egg from the nest (as seen in some other host species), because of the complete failure of the reproductive attempt, in addition to the costs associated with renesting. In this study, we document with photograph and video footage an incident of a Fan-tailed Cuckoo Cacomantis flabelliformis parasitising a nest of a Superb Fairy-wren in the Australian National Botanic Gardens, Canberra. Shortly after the parasitism event occurred, we recorded the female Fairywren returning to the nest and ejecting the single Cuckoo egg. To our knowledge, this footage represents the first evidence of ejection of a cuckoo egg in this species.