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Colorado College

Publication Date

Fall 2022

Program Name

Panama: Tropical Ecology, Marine Ecosystems, and Biodiversity Conservation

Abstract

(Trochilidae) are a large Neotropical bird family of nectar-feeders that have evolved as pollinators of many Neotropical plants. Interactions between hummingbirds and plants form mutualistic networks that may change in structure over environmental and anthropogenic gradients. While the unique dynamics of hummingbird diversity and floral interactions have been studied throughout the Neotropics, differing drivers between locations emphasizes the need for further local research. This deficit is especially crucial in biodiverse and understudied locations like the Western Highlands of Panamá. In this study, I investigated how hummingbird diversity, abundance, and floral interactions differed between Cloud Forest, Garden, and Oak Forest on Mount Totumas, Chiriquí Highlands, Panamá. I quantified and compared hummingbird richness, Shannon diversity, abundance, floral density, and floral visitation during three days of replicate point counts in each site. Additionally, I constructed quantitative hummingbird-plant networks, computed standard network indices, and compared hummingbird specialization at a species-level. Across study sites, I made 548 observations of 14 hummingbird species, and observed 4533 hummingbird visits to 35 plant species. Hummingbird richness was highest in the Garden, while Shannon diversity was slightly higher in the Cloud Forest. Hummingbird relative abundance, floral density, and visitation rates were significantly higher in the Garden site, and decreased in Cloud Forest and Oak Forest. Linear models suggest that floral density predicts hummingbird abundance and richness, suggesting that high floral density in the Garden likely attracts hummingbirds. While not representative of a complete elevational gradient, hummingbird diversity decreased at the higher elevation Oak Forest site. The study area hummingbird-plant network was speciose, with the Garden contributing more species and interactions than the forest sites. Across sites, nestedness (wNODF) and connectance (C) were lower than expected by null models, while network-level specialization (H2’) and modularity (Q) were higher. Network-level specialization was higher in the forest sites than in the Garden, possibly indicating hummingbird foraging flexibility in human-impacted landscapes. Hummingbird species specialization (d’) varied on a species-specific level between sites, and was not significantly predicted by hummingbird body length, bill length, or bill curvature. While there are clearly structural differences in hummingbird-plant interactions between sites, further study over the entire year is essential to fully describe hummingbird dynamics at Mount Totumas.

Disciplines

Biodiversity | Botany | Environmental Monitoring | Latin American Studies | Ornithology | Research Methods in Life Sciences

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