Mental health is a well-established and economically significant ecosystem service provided by nature, protected areas, and biodiversity; but detailed mechanisms, and differences between individuals and ecosystem components are less well understood (Arola et al., 2023; Buckley & Chauvenet, 2022; Buckley & Cooper, 2022; Buckley et al., 2019; Irvine et al., 2023; Moll et al., 2022; Samus et al., 2022). In particular, mental health is improved by birdsong, with greater gains from more diverse bird assemblages (Echeverri et al., 2021; Ferraro et al., 2020; Hammoud et al., 2022; Stobbe et al., 2022; Zhu et al., 2020); but we do not know whether different bird species have different effects for different people, and if so, why.