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A Mandarin Duck Egg Hatched in a Scaly-sided Merganser Nest

Male mandarin duck swimming in Yuanmingyuan Wetland, Beijing
Research · Reproduction & development

A mandarin duck (Aix galericulata) egg hatched successfully in a nest of the scaly-sided merganser (Mergus squamatus) in the Changbai Mountains of northeastern China. The 2026 study provides direct evidence that interspecific brood parasitism between the two cavity-nesting ducks can result in a successfully hatched mandarin duckling.

The researchers monitored an artificial nest box beside the Manjiang River during the 2024 breeding season. A scaly-sided merganser pair occupied the box, where eight eggs were recorded before incubation. Six were similar in size, while two were distinctly smaller and resembled mandarin duck eggs. On 7 June the first duckling hatched and showed the short, broad bill and yellowish-brown plumage of a mandarin duck. It remained in the nest for one day before leaving; scaly-sided merganser ducklings hatched on 9 and 10 June.

After hatching, the researchers compared the eggshells and analysed mitochondrial DNA from the shell membranes. One hatched shell and one unhatched egg matched the smaller, yellowish-cream appearance of Mandarin Duck eggs, while five hatched shells and one unhatched egg matched the host species. The 12S rRNA sequence from the membrane of the hatched parasitic egg matched the Mandarin Duck reference sequence. Additional mitochondrial and microsatellite analyses showed that all Scaly-sided Merganser ducklings were full siblings from the same parental pair, with no evidence of intraspecific brood parasitism in this nest. The authors suggest that competition for limited nest cavities or reproductive pressure on an individual female may help explain the Mandarin Duck’s behaviour, but these causes were not tested directly.

Sources and image credit

  1. Liu, S., Li, D., Zhang, S., Yi, G., & Zhao, Y. (2026). A case of successful brood parasitism by Mandarin Duck (Aix galericulata) on Scaly-sided Merganser (Mergus squamatus). BMC Zoology, 11, 21. https://doi.org/10.1186/s40850-026-00271-5Primary peer-reviewed article published 28 May 2026. Field monitoring in the Changbai Mountains during the 2024 breeding season documented a Mandarin Duck egg successfully hatching in a Scaly-sided Merganser nest; morphology and mitochondrial 12S rRNA confirmed the parasitic duckling as Mandarin Duck.

Image: FlyingBatt / Wikimedia Commons — male Mandarin Duck photographed in the Yuanmingyuan Wetland, Beijing, China, in March 2024; representative species image, not a bird from the Changbai Mountains study · CC BY-SA 4.0 · Source

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