High sensitivity of tropical forest birds to deforestation at lower altitudes

Abstract

Habitat conversion is a major driver of tropical biodiversity loss, but its effects are poorly understood in montane environments. While community-level responses to habitat loss display strong elevational dependencies, it is unclear whether these arise via elevational turnover in community composition and interspecific differences in sensitivity or elevational variation in environmental conditions and proximity to thermal thresholds. Here we assess the relative importance of inter-and intraspecific variation across the elevational gradient by quantifying how 243 forest-dependent bird species vary in sensitivity to landscape-scale forest loss across a 3000-m elevational gradient in the Colombian Andes. We find that species that live at lower elevations are strongly affected by loss of forest in the nearby landscape, while those at higher elevations appear relatively unperturbed, an effect that is independent of phylogeny. Conversely, we find limited evidence of intraspecific elevational gradients in sensitivity, with populations displaying similar sensitivities to forest loss, regardless of where they exist in a species' elevational range.Gradients in biodiversity response to habitat loss thus appear to arise via interspecific gradients in sensitivity rather than proximity to climatically limiting conditions.

Checklist of the Birds of the Municipality of Salamina (Caldas), Central Andes of Colombia: New Records and Taxonomic Updates

“…We surveyed birds using point-counts (Ralph et al, 1996). The pointcounts method is frequently used to survey birds in the tropical Andean region (e.g., Mills et al, 2023). For each location, we used a total of six point-counts (one point x two days x three sampling events).…”

Building a mechanistic understanding of climate-driven elevational shifts in birds

“…Tree species diversity is thought to promote food availability, particularly for frugivores [144,145], and has been found to predict species richness in Cameroon [146], Papua New Guinea [143], and Peru [135]. Though the majority of these studies have investigated gradients in bird diversity rather than distributional limits, it seems likely that both structural diversity and plant composition would play a role in determining elevational range limits [147], as well as species' ability to adapt to change [148]. Indeed, habitat has been linked to elevational shifts in temperate regions [32,35,37,40], while in the tropics, lagged shifts in birds indicate a slow, incremental response to shifts in habitat [17,67,149].…”

“…Studies investigating the interaction between habitat loss and elevational shifts are scant, although there is evidence that habitat loss is more of an issue for species at lower elevations [68,148,213,218,219], and projections suggest an important role for habitat availability in limiting range shifts [200,219]. In the Usambara Mountains of Tanzania, a 40-yr resurvey of 29 bird species along a fragmented elevational gradient suggested an important role for fragmentation in mediating elevational shifts [65].…”

“…However, this study was restricted to fragmented forest and did not include a control system of continuous forest. For example, in a spatial study of occupancy in Colombia, Mills et al [148] suggested that high elevation bird species (~2700 m in elevation) can tolerate greater levels of habitat loss due to the naturally patchier configuration of montane forest. Perhaps habitat loss is less of an impediment to range shifts at high elevations.…”

Effects of Deforestation on Foraging Behavior, Ectoparasites, and Adult Survival in the Vulnerable La Selle Thrush, Turdus swalesi, in Haiti

“…Of the 1227 bird species worldwide that are currently considered threatened with extinction, 79% occur in lowland and mountain tropical forests [1]. Deforestation, overexploitation, pollution, invasive species, and diseases have been identified as major threats for Neotropical forest bird species [1][2][3], and recent evidence [4] further indicates that their decline can take place in relatively large and protected areas. Knowledge about the ecology, behavior, and key demographic parameters is therefore of crucial importance for their conservation [5][6][7].…”