Hosts of interspecific brood parasites often evolve antiparasitic defences, like the recognition and rejection of parasite's eggs. Most hosts use differences in coloration and maculation to discriminate between their own and parasitic eggs, but there are a few cases of hosts using the size of eggs as a cue. To recognise parasite eggs, hosts may require the presence of their own eggs and use a discordancy rule or may use a mental template of their own eggs. Females are responsible for egg rejection in hosts in which they incubate alone, but if incubation is shared, males can also reject parasitic eggs. The rufous hornero, Furnarius rufus, a host of the shiny cowbird Molothrus bonariensis, ejects parasite eggs using egg size as a cue. We studied the cognitive mechanism underlying the recognition and ejection of parasitic eggs by this host. We experimentally parasitized hornero nests with eggs of different size, with and without the presence of host eggs and determined which sex was responsible for the ejection. We found that horneros ejected parasitic eggs using the size of the egg as a cue and did not need to compare parasitic eggs with their own eggs, which is consistent with the hypothesis of a mental template. Females and males ejected eggs at similar frequencies. We also found that cowbird eggs laid in hornero nests were longer and wider than those laid in nests of other host in the same area, which is consistent with the hypothesis of host-specific female cowbird lineages evolving larger eggs to deceit horneros from recognizing and ejecting their eggs.

中文翻译：

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雌性和雄性红褐色的 horneros 使用它们自己的鸡蛋大小的心理模板喷射闪亮的牛鸟蛋

种间繁殖寄生虫的宿主通常会进化出抗寄生虫防御，例如识别和拒绝寄生虫卵。大多数宿主使用颜色和黄斑形成的差异来区分自己的卵和寄生卵，但也有少数宿主使用卵的大小作为线索。为了识别寄生虫卵，宿主可能需要存在自己的卵并使用不一致规则或可能使用自己卵的心理模板。雌性负责单独孵化的宿主中的卵排斥，但如果共享孵化，雄性也可以拒绝寄生卵。红褐色的 hornero Furnarius rufus 是闪亮的牛鸟 Molothrus bonariensis 的宿主，它会根据鸡蛋大小作为线索排出寄生虫卵。我们研究了该宿主识别和排出寄生卵的认知机制。我们实验性地用不同大小的卵寄生 hornero 巢，无论是否存在寄主卵，并确定哪种性别负责排出。我们发现 horneros 以卵的大小为线索排出寄生卵，不需要将寄生卵与自己的卵进行比较，这与心理模板的假设是一致的。雌性和雄性以相似的频率排出卵子。我们还发现，在 hornero 巢中产下的牛鸟蛋比在同一地区其他宿主的巢中产下的蛋更长更宽，这与宿主特定的雌性牛鸟谱系进化出更大的蛋以欺骗 horneros 识别和排出的假设一致。他们的鸡蛋。有和没有宿主卵的存在，并确定哪种性别负责排出。我们发现 horneros 以卵的大小为线索排出寄生卵，不需要将寄生卵与自己的卵进行比较，这与心理模板的假设是一致的。雌性和雄性以相似的频率排出卵子。我们还发现，在 hornero 巢中产下的牛鸟蛋比在同一地区其他宿主的巢中产下的蛋更长、更宽，这与宿主特定的雌性牛鸟谱系进化出更大的蛋以欺骗 horneros 识别和排出的假设一致他们的鸡蛋。有和没有宿主卵的存在，并确定哪种性别负责排出。我们发现 horneros 以卵的大小为线索排出寄生卵，不需要将寄生卵与自己的卵进行比较，这与心理模板的假设是一致的。雌性和雄性以相似的频率排出卵子。我们还发现，在 hornero 巢中产下的牛鸟蛋比在同一地区其他宿主的巢中产下的蛋更长更宽，这与宿主特定的雌性牛鸟谱系进化出更大的蛋以欺骗 horneros 识别和排出的假设一致。他们的鸡蛋。这与心理模板的假设一致。雌性和雄性以相似的频率排出卵子。我们还发现，在 hornero 巢中产下的牛鸟蛋比在同一地区其他宿主的巢中产下的蛋更长更宽，这与宿主特定的雌性牛鸟谱系进化出更大的蛋以欺骗 horneros 识别和排出的假设一致。他们的鸡蛋。这与心理模板的假设一致。雌性和雄性以相似的频率排出卵子。我们还发现，在 hornero 巢中产下的牛鸟蛋比在同一地区其他宿主的巢中产下的蛋更长更宽，这与宿主特定的雌性牛鸟谱系进化出更大的蛋以欺骗 horneros 识别和排出的假设一致。他们的鸡蛋。