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Common Cuckoos Were Filmed Destroying Parrotbill Clutches During Egg-Laying

Common cuckoo in flight
Research · Behaviour

Common cuckoos (Cuculus canorus) were filmed destroying eggs in nests of vinous-throated parrotbills (Sinosuthora webbiana) while the hosts were still laying, documenting a destructive behaviour at a stage normally considered ideal for brood parasitism. The five cases, each involving a different and independent host nest, were analysed in a South Korean study first published on 17 April 2026.

The recordings came from nests monitored from construction onward. The five attacks took place between 4 and 16 June 2007, during the first five days of the host laying period.

Eggs were swallowed, broken or carried away

The attacks were brief, lasting only 2–74 seconds. During them, cuckoos swallowed eggs whole, broke eggs and consumed their contents, or removed eggs in the bill. Each event caused the loss of one to four eggs. Three attacks resulted in complete clutch destruction and two in partial clutch predation, but every affected nest was subsequently deserted and no additional eggs were laid.

The authors distinguish this behaviour from the more familiar removal of one or two host eggs that often accompanies cuckoo egg-laying. In these cases, the birds were clearly consuming or destroying host eggs, making the events egg predation rather than routine egg removal during parasitism.

Why destroy a nest at the best time to parasitise it?

The timing makes the behaviour unusual. Cuckoos normally benefit from laying during the host’s laying period because this helps their chick hatch early. The authors therefore discuss several possible functions rather than presenting one explanation as established.

One possibility is that destroying a clutch can reset the host’s breeding attempt when the cuckoo is not yet ready to lay. Another is that, in a semi-colonial host such as the vinous-throated parrotbill, synchronous breeding provides many nests at once, allowing a cuckoo to eliminate a nest that is unsuitable while retaining other opportunities. Egg recognition is especially relevant in this host: parrotbills in the study population lay either white or turquoise-blue eggs, cuckoo eggs closely mimic the blue type, and parrotbills can reject poorly matching cuckoo eggs. The authors therefore also suggest that clutch destruction may reduce the host’s opportunity to reinforce its recognition of its own egg appearance, potentially affecting later defences against parasitic eggs.

Sources and image credit

  1. Lee, Y., & Jang, W. (2026). Clutch destruction by Common Cuckoos (Cuculus canorus) during the laying stage of Vinous-throated Parrotbills (Sinosuthora webbiana): First video evidence. Ecology and Evolution, 16(4), e73387. https://doi.org/10.1002/ece3.73387Primary open-access Nature Note first published 17 April 2026 under CC BY 4.0. Fieldwork was conducted at Puyong-ri, Yangpyeong-gun, Gyeonggi-do, South Korea. Five video-documented events during host laying showed Common Cuckoos swallowing, breaking or carrying away eggs; all affected nests were subsequently deserted.

Image: Mildeep / Wikimedia Commons — Common Cuckoo in flight, photographed in Nepal on 25 September 2021; representative species image, not one of the South Korean cuckoos in the study; cropped to 16:9. · CC BY-SA 4.0 · Source

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