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Article History

Received: 5 December 2024

Revised: 10 July 2025

Accepted: 16 July 2025

First Online: 12 September 2025

Declarations

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: Fieldwork was carried out with permission from Yongji Forestry Bureau, Jilin, China. All experimental procedures were conducted under license from the Animal Management Committee at the College of Life Sciences, Beijing Normal University (permit no. CLS-EAW-2021–003). The use of animals adheres to the guidlines set forth by the Animal Behavior Society/Association for the Study of Animal Behaviour.

: Large brains confer cognitive advantages but incur substantial energetic costs. The arms race between avian brood parasites and their hosts could drive the evolution of host brain size, such that hosts with a larger brain might outperform in egg-rejection behavior. However, empirical studies testing this hypothesis are notably lacking. Firstly, we investigated the relationship between Daurian redstarts’ head size and egg-recognition ability. Furthermore, we examined the correlation between host head size and egg-ejection probability. Contrary to expectations, our results do not support a positive relationship between host head size and either egg-recognition ability or egg-ejection probability in Daurian redstarts, suggesting that the evolution of host brain size might be not driven by the cognitive demands of egg rejection in Daurian restarts.

: The authors declare no competing interests.