Abstract
We used a distance-sampling survey method and multivariate statistics to obtain a unique estimate of bird species density and seasonal variation in shade-coffee plantations. Our aim was to determine which cultivation practices among plantations contribute most to bird abundance. We conducted avian species counts at 200 points distributed across 10 shade-coffee plantations bordering the lower slopes of the Mombacho Volcano Natural Reserve, in western Nicaragua. We measured vegetation structure (coffee plants and overstory). We used principal components analysis (PCA) among 14 habitat variables to derive a single phyto-geoclimate summary measure (PGSM). We also used PCA to derive an avian abundance summary measure (AASM) from three bird survey variables, which proved to be a good predictor of bird density. We found higher bird species densities (AASM) in organic and traditional polyculture shade coffee plantations whose structurally complex and diverse overstory could be verified by PGSM. However, this finding was true only for birds that were habitat specialists. Our results provide further evidence for promoting organic coffee cultivation practices that maintain a structurally diverse overstory and help retain avian species richness and abundance in coffee plantations.
Highlights
Elevated species richness, abundance and spatiotemporal use of traditional and diverse shade-coffee plantations by resident and migratory birds have been reported throughout the Neotropics [1]-[11]
We found higher bird species densities (AASM) in organic and traditional polyculture shade coffee plantations whose structurally complex and diverse overstory could be verified by phyto-geoclimate summary measure (PGSM)
We have shown by the methods of principal components analysis (PCA) and discriminant function analysis (DFA), that diverse vegetation and complex native canopy structure in organic shade-coffee plantations result in greater avian species diversity, richness, abundance, and composition as reported in previous studies [15] [18] [47]
Summary
Abundance and spatiotemporal use of traditional and diverse shade-coffee plantations by resident and migratory birds have been reported throughout the Neotropics [1]-[11]. Basal area and diversity of overstory trees in shade coffee and cacao plantations affect avian diversity and abundance and are often significantly correlated with numbers of forest specialist species [8] [19] [20]. Shade-coffee plantations often harbor more forest and overwintering generalists, especially insectivores and nectarivores, owing to flowering overstory trees such as Inga spp. with their extrafloral nectaries and their ancillary insects, as well as species of open habitats such as pastures and grasslands [4] [20] [30] [32] [33]
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