The Impact of Avian Insectivory on Arthropods and Leaf Damage in Some Guatemalan Coffee Plantations

Abstract

Experimental work has established that vertebrates can have a large impact on the abundance of arthropods in temperate forest and grasslands, as well as on tropical islands. The importance of vertebrate insectivory has only rarely been evaluated for mainland tropical ecosystems. In this study, we used exclosures to measure the impact of birds on arthropods in Guatemalan coffee plantations. Variation in shade management on coffee farms provides a gradient of similar habitats that vary in the complexity of vegetative structure and floristics. We hypothesized that shaded coffee plantations, which support a higher abundance of insectivorous birds, would experience relatively greater levels of predation than would the sun coffee farms. We found a reduction (64–80%) in the number of large (> 5 mm in length) but not small arthropods in both coffee types which was consistent across most taxonomic groups and ecological guilds. We also found a small but significant increase in the frequency of herbivore damage on leaves in the exclosures. This level of predation suggests that birds may help in reducing herbivore numbers and is also consistent with food limitation for birds in coffee agroecosystems. However, the presence of shade did not have an effect on levels of insectivory.

Ecological and Economic Services Provided by Birds on Jamaican Blue Mountain Coffee Farms

“…5, 2008 and control plants throughout the study period and farms. Invertebrate samples from all 30 exclosures contained taxa ranging in size from 1 mm (e.g., Formicidae) to >5 cm (e.g., Orthoptera, M.J. & J.K., unpublished data) in length, which is consistent with other exclosure studies (Greenberg et al 2000;Borkhataria et al 2006). Therefore, it is unlikely that 3-mm parasitoid wasps that attack berry borer (Damon 2000) and hymenopteran pollinators that can affect the fruit set of coffee (Ricketts et al 2004) were restricted by 58-mm mesh.…”

“…Exclosures were pyramidal pole frames of cut saplings over individual coffee plants wrapped in transparent nylon gill netting (N163A 58 mm mesh, Nylon Net Company, Memphis, Tennessee) and staked down to prevent entry of ground-foraging birds. Our design is typical for other experiments in the tropics that have successfully prevented access by small birds without restricting access by aerial and sessile invertebrates (Greenberg et al 2000;Perfecto et al 2004;Borkhataria et al 2006) or by Anolis lizards common on Jamaica and other Caribbean islands (Pacala & Roughgarden 1984;Borkhataria et al 2006).…”

“…A variety of biological controls for berry borers have been examined (e.g., parasitoid wasps; Chavez & Riley 2001), but they have not achieved widespread implementation and economic success (Batchelor et al 2005). Birds effectively control agricultural insect pests in temperate regions (Tremblay et al 2001;Mols & Visser 2002); reduce arthropods of several taxonomic groups in Guatemalan (Greenberg et al 2000), Mexican , and Puerto Rican coffee farms (Borkhataria et al 2006); and suppress simulated outbreaks of lepidopteran caterpillars in Mexican coffee farms . Nevertheless, no one has yet provided direct evidence of reduction of borers by birds or that these effects benefit crop production or farm income.…”

“…Nevertheless, no one has yet provided direct evidence of reduction of borers by birds or that these effects benefit crop production or farm income. Linking increases of saleable coffee berries with reductions in borers by insectivorous birds could provide a strong economic incentive to coffee farmers to promote vegetation complexity because birds and their services increase with vegetation complexity in coffee farms (Wunderle & Latta 1998;Greenberg et al 2000;Perfecto et al 2004).…”

Benefits of Studies of Overwintering Birds for Understanding Resident Bird Ecology and Promoting Development of Conservation Capacity

“…Migratory-bird research on the wintering grounds must focus on identifying sites that support high annual survival of both sexes in as high abundance as possible, and management of wintering habitat must focus on maintenance of these sites (Faaborg et al 2009b), such that we avoid problems associated with low habitat quality that delay initiation of spring migration and potentially reduce reproductive success on the breeding grounds . Numerous studies are needed on the ecology of wintering migrants that equal the quality of those of Holmes et al (1989) and Marra and colleagues (Marra & Holberton 1998;Marra & Holmes 2001) on the American Redstart, Latta and Faaborg on Cape May Warbler (Dendroica tigrina) and Prairie Warbler (D. discolor) (Latta & Faaborg 2001, Wunderle (Wunderle 1995;Wunderle & Latta 2000) on Black-throated Blue Warbler, and Greenberg et al (1997Greenberg et al ( , 2000 on bird use of coffee plantations, but they need to cover a broad range of species, habitats, and geography.…”