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<p>Host defenses against brood parasitism typically focus on egg recognition, whereas nestling discrimination remains comparatively rare and is less well understood. We examined both stages of defense in the common myna (<i>Acridotheres tristis</i>), a host of the non-evicting Asian koel (<i>Eudynamys scolopaceus</i>), by experimentally introducing foreign eggs and nestlings of varying sizes into their nests. Egg rejection showed a size-dependent pattern: all large eggs, including quail, red-painted quail, and pigeon-sized model eggs, were accepted, whereas small eggs were rejected variably. Bulbul eggs were consistently ejected, shrike eggs were occasionally removed, and drongo eggs were always retained. Survival analyses confirmed that smaller eggs were rejected more rapidly and with a higher probability, and conspicuous coloration further accelerated rejection, as observed for bulbul eggs. Nestling experiments revealed an even sharper decision rule: all small nestlings (3–6&#xa0;g) were rejected, whereas all large nestlings (11–18&#xa0;g) were fully accepted and fledged successfully. These results indicate that common mynas integrate multiple cues, including egg size, color, maculation, and nestling body size, to identify foreign young. Our study reveals an integrated system of host recognition across both eggs and nestlings, highlighting the need to investigate defenses against non-evicting brood parasites to better understand the evolution of egg and nestling discrimination.</p>

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Discrimination and rejection of eggs and nestlings by common mynas (Acridotheres tristis)

  • 期刊论文

  • 发表日期：

    2026年5月29日

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  • Asif Sadam,
  • Huijian Hu,
  • Wei Liang

摘要

Host defenses against brood parasitism typically focus on egg recognition, whereas nestling discrimination remains comparatively rare and is less well understood. We examined both stages of defense in the common myna (Acridotheres tristis), a host of the non-evicting Asian koel (Eudynamys scolopaceus), by experimentally introducing foreign eggs and nestlings of varying sizes into their nests. Egg rejection showed a size-dependent pattern: all large eggs, including quail, red-painted quail, and pigeon-sized model eggs, were accepted, whereas small eggs were rejected variably. Bulbul eggs were consistently ejected, shrike eggs were occasionally removed, and drongo eggs were always retained. Survival analyses confirmed that smaller eggs were rejected more rapidly and with a higher probability, and conspicuous coloration further accelerated rejection, as observed for bulbul eggs. Nestling experiments revealed an even sharper decision rule: all small nestlings (3–6 g) were rejected, whereas all large nestlings (11–18 g) were fully accepted and fledged successfully. These results indicate that common mynas integrate multiple cues, including egg size, color, maculation, and nestling body size, to identify foreign young. Our study reveals an integrated system of host recognition across both eggs and nestlings, highlighting the need to investigate defenses against non-evicting brood parasites to better understand the evolution of egg and nestling discrimination.