Ecological studies on mountain bird communities

Lodge Kodkod, situated in the Villarrica catchment of the Araucanía Region near Pucón, Chile, has served as a base for an ongoing program of ecological research spanning more than 15 years. The lodge sits within the temperate rainforests of the southern Andes — part of a globally recognized biodiversity hotspot characterized by high endemism — and has hosted a series of coordinated studies examining how bird communities are structured across the mountain landscape, from disturbed lowland forests up through old-growth stands to the subalpine and alpine zones.

Study Area and Long-Term Monitoring

The research has been conducted across a network of sites in the Araucanía and Los Ríos regions, spanning an elevational gradient from roughly 200 to nearly 1,800 meters above sea level. Field surveys over 15 years have generated more than 2,185 point counts in temperate rainforests of the southern Andes. The broader mountain bird study added a further 2,202 point-counts across four mountain habitat types — successional montane forest, old-growth montane forest, subalpine, and alpine — detecting 74 bird species in total. Together, these surveys constitute one of the most sustained long-term avian monitoring programs anywhere in southern South America, a region where such data are critically scarce.

How Bird Communities Change with Elevation and Habitat

The overarching finding across these studies is that the mountain landscape around Lodge Kodkod supports strikingly different bird communities at different elevations and habitat types, and that the treeline is the single most important ecological boundary organizing this variation.

Below treeline, 58 bird species were detected, occupying a mean elevational range of 1,081 meters — reflecting wide habitat tolerance and generalist behavior. By contrast, above treeline, 16 species (22% of all species detected) were found exclusively in alpine habitats, with a mean elevational range of only 298 meters. These alpine specialists live in a highly compressed altitudinal band and, unlike their forest counterparts, are almost completely dependent on a narrow set of resources.

The treeline functioned as an inflection line above which species composition changed by 91%, and functional trait turnover was two to three times greater than in communities below treeline. This is not simply a thinning of the same community at higher elevations — it is a near-complete reorganization of which birds are present and how they make their living.

The subalpine zone emerged as a particularly important transition. A combined influence of habitat type and elevation produced a hump-shaped pattern of diversity along the elevational gradient, with species richness peaking at 1,200–1,400 meters in old-growth montane forest and subalpine habitats before declining in the alpine. The highest functional richness — the greatest variety of ecological roles represented in a bird community — was found in subalpine habitats, followed closely by old-growth montane forest.

The Role of Forest Structure and Microclimate

Within the forested zone, a master's thesis study (Hartong, 2026) drew on the full 15-year dataset to examine how forest structure and short-term microclimatic conditions shape bird diversity in old-growth versus second-growth stands. Species richness showed no consistent differences between old-growth and successional forest types overall, but forest type effects were evident at the species level, with pronounced heterogeneity and directionally contrasting responses among species within the same functional guild diluting emergent patterns at the guild level.

Detectability was primarily influenced by wind, highlighting the strong role of microclimatic variability in shaping survey-level detections. Practically, this means that ignoring wind conditions when designing surveys leads to serious underestimates of bird diversity, particularly in exposed mountain habitats.

Significant differences between forest types were restricted to vertical-profile generalists and non-cavity nesters, both occurring at lower densities in old-growth stands. Other guilds showed weak, directionally consistent trends suggesting an advanced structural recovery in the secondary forests examined. The overall picture is one of complementarity: old-growth and second-growth forests each contribute something distinct to the regional bird diversity of the landscape.

Alpine Birds: Specialists with Distinctive Life Histories

The alpine community above the treeline stands out not only for its different species composition but for its unusual ecological traits. Alpine birds in the south temperate Andes were almost exclusively migratory, inhabiting a restricted elevational range and nesting in rock cavities — a breeding strategy that is effectively the norm at high elevation in this system.

The broader comparative study (Martin et al., 2021) placed these findings in a hemispheric context by comparing the Chilean mountains to equivalent systems in British Columbia, Canada. South temperate mountains supported a greater proportion of the regional species pool (63% versus 44% in north temperate mountains), and the highest species richness in south temperate mountains occurred at and above treeline, with 41 species detected there. Strikingly, south temperate bird communities contained greater functional redundancy and more evolutionarily isolated species, consistent with convergent evolution in challenging, high elevation habitats, while north temperate communities exhibited lower functional redundancy and higher total phylogenetic diversity.

One important conservation finding: only 18% of the 63 species observed in the south temperate Andes, and only 5% of alpine species, have had a formal conservation status assessment — meaning that the communities documented at Lodge Kodkod and surrounding mountains are largely invisible to global conservation assessments, despite being ecologically distinctive and potentially vulnerable to climate change.

Owls as Indicators of Forest Quality

An earlier study (Ibarra et al., 2012) used the same mountain landscape to examine how two owl species respond to the gradient of forest disturbance and age, from lowland disturbed forests to protected old-growth Andean stands. Rufous-legged Owls were found principally in old-growth Araucaria–Nothofagus stands, while Austral Pygmy Owls favored old-growth evergreen stands; both species showed a seasonal decline in calling activity in autumn and winter. Habitat modeling revealed that Rufous-legged Owls selected stands with tall trees, relatively low tree density, and high bamboo density — a more specific set of habitat requirements than the Pygmy Owl — and that there was no evidence that the presence of one species negatively influenced the other's use of a territory. The results underlined the dependence of forest-specialist birds on structural attributes of old-growth forests that are lost or degraded under logging and land conversion.

Survey Methodology

A methodological paper (Drake, de Zwaan, Altamirano et al., 2021) used the Chilean study mountains as one of two continental test cases to compare the performance of traditional point counts against autonomous recording units (ARUs) for monitoring bird diversity at high elevation. ARUs could capture approximately 93% of species present in British Columbia but only about 58% in Chile, despite Chilean mountain communities being less species-rich overall — a difference driven by the Chilean avifauna containing a higher proportion of less-vocal species that acoustic recorders miss. The study concluded that combining both methods offers the best balance of accuracy and efficiency, and that the Chilean mountain context in particular requires human observers to reliably characterize bird communities.

Broader Significance

Together, the studies conducted at and around Lodge Kodkod paint a coherent picture of how avian communities in the south temperate Andes are organized across the mountain landscape. Forest birds below the treeline are diverse, wide-ranging, and respond primarily to the structural attributes of vegetation — forest age, canopy structure, and microclimate. The treeline marks a sharp ecological boundary above which the community is reconstituted almost entirely: fewer species, narrower ranges, almost exclusively migratory, and nesting in rock cavities. In between, the subalpine ecotone supports the greatest concentration of functional diversity in the landscape. This program of research, rooted in over 15 years of field surveys based at Lodge Kodkod, represents a rare example of sustained, long-term ecological monitoring in the Global South and provides the baseline needed to track the effects of climate change and habitat loss on a biogeographically unique avifauna.

References

Ibarra et al. (2012). Rufous-legged Owl and Austral Pygmy Owl stand use in a gradient of disrupted and old growth Andean temperate forests, Chile. Studies on Neotropical Fauna and Environment, 47(1), 33–40.

Altamirano, de Zwaan, Ibarra, Wilson & Martin (2020). Treeline ecotones shape the distribution of avian species richness and functional diversity in south temperate mountains. Scientific Reports, 10, 18428.

Drake, de Zwaan, Altamirano et al. (2021). Combining point counts and autonomous recording units improves avian survey efficacy across elevational gradients on two continents. Ecology and Evolution, 11, 8654–8682.

Martin, Altamirano, de Zwaan, Hick, Vanderpas & Wilson (2021). Avian ecology and community structure across elevation gradients: The importance of high latitude temperate mountain habitats for conserving biodiversity in the Americas. Global Ecology and Conservation, 30, e01799.

Hartong (2026). How forest structure and microclimate influence long-term avian diversity in temperate rainforests of the southern Andes. MSc thesis, Pontificia Universidad Católica de Chile.

To see more results of studies undertaken in Lodge Kodkod, go to our Publications page