Videos of nest defense against cuckoo egg-laying from 2013 to 2022

As the first line of defense in avian brood parasitism, nest defense plays
an important role in reducing nest parasitism and increasing host fitness.
However, systematic studies on its effectiveness (i.e., on whether it
successfully prevents cuckoo parasitism) are lacking. Based on 214 video
recordings from 10 years of field observations, we evaluated the
effectiveness of nest defenses of the Oriental reed warbler (Acrocephalus
orientalis) in deterring common cuckoo (Cuculus canorus) parasitism. The
results revealed that, under a breeding pair situation (≤ 2 host
individuals), nest defenses of the warbler were hardly effective in
resisting the egg-laying behavior of the cuckoo, and many of the cuckoos
under attack were able to complete the parasitic process without being
harmed. However, when hosts were ≥ 3 host individuals, the trigger value
was reached, and the warbler was able to effectively thwart the
cuckoo's parasitism and cause lethal damage to the cuckoo. This
indicated that the host group was effective in resisting the cuckoo, which
fully demonstrates the importance of cooperation and socially transmitted
defenses among host neighbors in resisting cuckoo parasitism.