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How and why do cloud forest bird communities respond to forest fragmentation in an Andean biodiversity hotspot?

Presented by IBP's Southwest Avian Ecologist Dr. Harry Jones
Wednesday, February 15, 2023 at 2pm Eastern/1pm Central/12pm Mountain/11am Pacific Time
This webinar is FREE but registration is required. Register Here
The cloud forests of the Tropical Andes of South America are home to a high diversity of endemic and restricted range bird species, but increasingly at risk from habitat loss. Forest clearance for cattle farming and crop cultivation, particularly coffee, has led to the loss of 1-4% of Andean cloud forests over the last twenty years, and in Colombia only ~30% of the historical coverage of these forests remains. Forest loss often results in forest fragmentation, or division of remaining habitat into isolated patches of varying sizes and shapes. To better understand how cloud forest bird communities respond to fragmentation, we surveyed bird communities across a gradient of fragment patch sizes in the Western Andes of Colombia. Species richness declined with decreasing habitat amount, increasing edge density, and increasing disturbance through selective logging. These effects were driven by the loss of forest-dependent species, which were also area sensitive. Small forest fragments may mimic the structure and composition of early-successional Andean forests, driving spatial turnover patterns favoring disturbance-adapted species at the expense of primary-forest specialists. Large forest reserves are therefore required to conserve forest-dependent Andean birds.
Next, we asked which mechanisms might be driving extirpation of species from cloud forest fragments by relating avian functional traits to area sensitivity. We found that species with more specialized diets, which use the canopy and subcanopy, that have larger relative eye sizes, and that have larger clutch sizes were significantly more area sensitive. Insectivores with more pointed wing shapes, and more aerial lifestyles, were also more significantly area sensitive. These results suggest that reduced vegetation structure, loss of late-successional plant species, and loss of epiphytic plants may reduce food availability in fragments. Similarly, the ability to tolerate higher light intensity near fragment edges, or when traversing matrix habitat, may be important for persistence in fragments and suggests that habitat configuration may be of special importance in fragmented Andean landscapes. Overall, a lack of information on foraging, movement, and breeding ecology complicates avian conservation in the Andes.