Tree cavities are key habitat components that structure the diversity of cavity–nesting communities (Martin and Eadie 1999). Most cavity users cannot create their own cavities (i.e., secondary cavity nesters [SCN]). Therefore, their populations can be limited by the production and availability of both excavated and natural cavities (Aitken and Martin 2008, Newton 1998).
Knowledge about the breeding biology of most neotropical cavity–nesting Glaucidium species varies from ‘unknown’ to ‘poorly known’ (Deville and Ingels 2012). The Austral Pygmy–Owl (Glaucidium nana), the southernmost Glaucidium species, is widely distributed in Chile, inhabiting forests, forest–steppe ecotones, shrublands, and sometimes urban parks (Jiménez and Jaksic 1989, Figueroa et al. 2013). Ibarra et al. (2012) suggested that in Andean temperate forests the Austral Pygmy–Owl selects stands with large living trees, which provide thermally suitable roosting and breeding sites. However, breeding records of this owl...