The present state of fragmentation and degradation in tropical agricultural landscapes could cause avian insectivore community disassembly and lead to increased arthropod pest populations. A greater understanding of the role played by opportunistic insectivores, such as hummingbirds, in mediating arthropod community dynamics is thus critical to our reliance on conservation biological control. Hummingbird abundance and diversity is largely unaffected by forest fragmentation and the taxa is often more abundant in secondary forest. In this study, we aimed to increase the breadth of our understanding of bird-insect interactions in agricultural landscapes, by considering the role of hummingbirds in mediating arthropod communities in a coffee agroecosystem. Across a gradient of agricultural intensification, we conducted foraging observations, bird and arthropod community surveys and collected hummingbird fecal samples. Total DNA was extracted from fecal samples and a metabarcoding approach was used to identify consumed arthropods and pollen. We combined these methods to specifically answer: (1) how does coffee management affect hummingbird communities? and (2) what types and at what rate do hummingbirds consume arthropods in this system? Work was conducted in the Soconusco region of Chiapas, Mexico in a landscape dominated by coffee production.
Results/Conclusions
Hummingbird abundance was significantly higher in shade-grown coffee (6.27 birds per hectare) than in more intensively-grown sun coffee (0.41 birds per hectare). Yet, hummingbirds were still present on sun coffee farms when floral resources were locally abundant. Canopy cover and floral abundance were the most important micro-habitat characteristics that accounted for differences in bird abundance between sites. Observations revealed that hummingbirds forage for arthropods within the coffee layer and gleaned insects from coffee plants, though this took up a proportionally low amount of their time. We extracted DNA from sixty hummingbird fecal samples from four species. Barcodes identified from feces were from a great diversity of arthropods, including herbivores, predators and parasitoids. The abundance of hummingbirds in shade-grown coffee suggests that these opportunistic insectivores could be consuming a significant amount of arthropods with both direct and indirect effects on herbivorous pests of coffee.