Mareike Kortmann and co-authors share a summary about their latest study which focusses on the ability of sample coverage to impact diversity measures of bird communities in tropical lowland forests.
Tropical old-growth forests are disappearing at an alarming rate, leading to concerning biodiversity loss. But amidst this global decline, some forest areas are also recovering. Second-growth forests—those that regenerate after agricultural use—may offer valuable contributions to restoring some of what’s been lost. In a new study from the Ecuadorian Chocó Forest, we explored how bird diversity develops in landscapes that blend agriculture, regenerating forests, and old-growth remnants. The study is part of the REASSEMBLY project, analysing the dynamics of natural forest recovery from agriculture. Our findings offer valuable insights for land managers and conservation practitioners seeking to achieve the best outcomes from recovering forest areas.
Listening to birds in a complex landscape
To understand how bird communities recover in second-growth forests, we used bioacoustic recorders to identify bird species. We sampled 66 plots that spanned a gradient: from actively used pastures and cacao plantations to forests regenerating after agriculture (1–38 years post-use), and finally to pristine old-growth forest. This gradient reflects the typical small-scale agricultural landscapes of the Ecuadorian Chocó Forest, where agricultural patches are characterized by remnant trees and, occasionally, small groups of trees
Our study area is part of the largest remaining patch of Chocó Forest in Ecuador (Canandé Reserve), spanning over 300,000 hectares. This expanse is sufficient to support viable populations of old-growth specialists, which were present in our recordings—including the Bicolored Antbird (Gymnopithys bicolor), Ocellated Antbird (Phaenostictus mcleannani), Banded Ground Cuckoo (Neomorphus radiolosus), and Lita Woodpecker (Piculus litae).
By analysing bird diversity in terms of species richness, function, and evolutionary relationships, we built a comprehensive picture of how bird communities change as forests recover.
Regrowth can bring recovery
The results revealed a clear trend: bird communities shifted noticeably along the recovery gradient. While old-growth forests harboured distinct bird assemblages, secondary forests were also highly diverse. In fact, regenerating forests within these smallholder agricultural mosaics supported impressive levels of bird diversity. Interestingly, some typical old-growth bird species, like the Banded Ground Cuckoo, frequently ventured into agricultural areas, possibly attracted by remnant trees.
However, the study also highlighted important nuances: while taxonomic and phylogenetic diversity (the number and evolutionary variety of species) remained stable along the gradient, functional diversity was higher in agricultural and second-growth areas. Because the open habitat patches in our study area result from logging and land use, the higher functional diversity observed in these patches represents an artificial increase compared to old-growth patches. This increase likely stems from the inclusion of additional open-land species from more southern areas of South America alongside forest species. These trends were also shown by another study within our project (Falconí-López 2024).
Practical takeaways for conservation and management
Our study underscores the importance of nuanced biodiversity monitoring. Traditional measures like species counts don’t tell the full story. Incorporating aspects like functional and phylogenetic diversity, as well as beta diversity, paints a more accurate picture of restoration success.
The findings also highlight actionable opportunities. Second-growth forests on small, abandoned agricultural sites demonstrated significant potential to support bird diversity, especially when integrated with remnant trees and embedded in an old-growth matrix. This reinforces the value of smallholder landscapes in conservation strategies. Supporting natural forest recovery in these contexts can be a practical and impactful strategy.
Read the full article “Sample coverage affects diversity measures of bird communities along a natural recovery gradient of abandoned agriculture in tropical lowland forests” in Journal of Applied Ecology.
