<b>Nest defense </b><b>by </b><b>incubating female birds: same threat, different strategies</b>

This study was conducted in the Miao minority villages of Leishan County (26°02′-34′ N, 107°55′-108°22′ E), Guizhou Province, southwestern China. It has a total area of 1218.5 km² and a humid mid-subtropical monsoon climate with an average annual temperature between 14 °C and 15 °C in most areas, an average maximum temperature of 35.6℃, and an average minimum temperature of -8.9℃. Leishan County is rich in forestry resources, with a forest coverage rate of 72.8% (Zhang <i>et al</i>. 2023).The experimental period of this study was performed in the months of March–July during the years 2021–2023. The study was conducted by hanging artificial nesting boxes to recruit birds for breeding; the two main species of birds utilizing these nesting boxes were Japanese tits and russet sparrows.This study investigated the nest defense strategies of two sympatric cavity-nesting bird species in response to predation risk, brood parasitism risk, and non-lethal human interference. The nest defense behavior of incubating females of Japanese tits (<i>Parus minor</i>) and russet sparrows (<i>Passer cinnamomeus</i>) were tested in response to three types of risk. Both species could eavesdrop on heterospecific alarm calls and effectively distinguish between the territorial calls and alarm calls of Japanese tits. However, the two sympatric cavity-nesting bird species adopted completely different strategies for nest defense. Japanese tits ensure current breeding success by remaining quietly inside the nest without revealing their locations when confronted with threats. In contrast, russet sparrows prioritize their own survival and promptly fly out of the nest when danger approaches. Our study revealed a trade-offs between bird parents’ own survival and reproduction and showed that sympatric cavity-nesting bird species adopt different nest defense strategies when faced with the same threats.