Understory bird taxonomic and functional diversity during secondary forest succession in the tropical Andes

Abstract

Abstract Understanding understory bird taxonomic and functional diversity patterns across successional stages can be an essential criterion for conservation and ecological restoration strategies in the humid forests of the tropical Andes. We evaluated understory bird taxonomic and functional diversity in the secondary successional forests of the tropical Andes. Three successional stages were analyzed: young secondary forest (10–15 years old), mid-successional forest (25–30 years old), and mature forest (~100 years old). Birds were captured using mist nets across these successional stages. We defined functional traits for the captured species, including morphological, life history, and behavioral characteristics. The results showed that the alpha taxonomic diversity of understory bird species was similar across the three stages, with a total of 126 species recorded. However, alpha functional diversity varied, being lower in the mature forest. Beta taxonomic and functional diversity revealed that species turnover was the principal cause of the differences between successional stages. Specifically, species turnover between young and mid-secondary forests resulted from the colonization of mid-successional bird species and the local extinction of shrubland species. Functionally, generalist understory birds dominated young forests, while mid-secondary forests exhibited a greater variety of birds with foraging adaptations to different vegetation strata. In mature forests, the presence of understory insectivores, such as ant followers, was characteristic of this stage. These bird functional patterns reflect the environmental filter imposed by vegetation structure and resource availability at each successional stage. The functional diversity of the communities associated with each successional stage would have differential effects on the functioning of tropical Andean ecosystems. Conservation efforts should emphasize functional diversity and the protection of mature forests to maintain ecosystem resilience and support specialized bird species.