Egg laying behavior of the common cuckoo (Cuculus canorus): data based on field video-recordings

The egg laying behavior of brood parasites is at the heart of studies on their co-evolution with hosts. Updating and reporting more egg laying behavior can improve our perception and insight on the brood parasitism process. During a 7 years’ study period, we monitored 455 Oriental reed warbler (Acrocephalus orientalis) nests during the egg laying period, of which 250 were parasitized by common cuckoos (Cuculus canorus). We randomly recorded 53 clear videos of cuckoo parasitism, analyzed and recorded all parasitic behavior of cuckoo in details, summarized the process of brood parasitism displayed by the common cuckoo. Based on analyses of these field video-recordings, we proposed a new explanation for the egg removal behavior, namely the delivery hypothesis, i.e. the egg pecking and biting may help parasitic cuckoos lay eggs faster, thereby avoiding the host’s attention and reducing host attacks, whilst egg removal is the side effect of egg pecking and biting. We concluded that common cuckoos do not care whether the host is around the nest, as they have a set of methods to deal with host attacks and can complete parasitism boldly and smoothly at any time.