News Release

Conservation under the shade coffee canopy: ant-bird interactions in Panama croplands

Peer-Reviewed Publication

Ecological Society of America

Shade grown coffee has become increasingly fashionable among American consumers. The beans are produced and harvested under trees in Central and South America, and the product is generally believed to be more environmentally friendly than the process of growing coffee in open sunshine. Tropical birds, it has been assumed, are better able to make use of the altered landscape of a shade-grown coffee plantation than they are an open-sun coffee area. A new study compares the two styles of coffee plantations, and evaluates the efficacy of using shade grown coffee as a bird conservation measure.

Published in the ESA peer-reviewed journal Ecological Applications (October issue 10,5), the study was led by Dina L. Roberts from the University of Georgia. Roberts and her colleagues Robert Cooper (University of Georgia) and Lisa Petit (Smithsonian Migratory Bird Center) spent two years studying the birds which live in and around the coffee plantations and forests of western Panama. Specifically, the scientists examined mixed-species assemblages of birds that follow swarm raids of army ants. In a phenomenon unique to tropical regions, these birds feed not on the ants themselves, but on other insects which are flushed from the leaf litter by the raiding ants. The swarms provide a unique opportunity to assess how different levels of disturbance may affect different forest bird species, because a wide variety of species typically use the swarms to obtain food. During the course of this study, 126 bird species were observed attending swarms.

The researchers observed and quantified ant-bird interactions in several different landscapes: areas of intact forest; shade growing coffee lands which were adjacent to forests; shade growing areas which were some distance from forested areas; and areas where coffee was grown in full sun.

Ant swarms did not occur in the full sun areas. In all shade coffee and forest plots, however, the abundance of ant swarms was high enough to support numerous kinds of birds. Also, Nearctic migrants that winter in Panama or migrate through the area composed a greater percentage of the attendant species in shade coffee habitats than in forests. Areas of shade grown coffee which were distant from the intact forest did experience swarming ants, and the swarms were attended by birds. But the researchers also found that many species of forest-dependent resident birds were never detected in the shade coffee areas which were distant from areas of continuous forest.

The researchers say this finding may be the result of many factors. Many of the resident bird species observed in the study have nesting habits which make them vulnerable in disturbed habitats. Also, some of the species of forest birds have evolved large, bulbous eyes in order to forage in the dim light of the forest. These birds would be less likely to fly through bright open spaces in order to reach coffee areas which are often like isolated islands of shade in the middle of pastures and recently cleared fields. In addition, the drier and warmer characteristics of the open areas may prove stressful to some forest bird species.

In addition to the variation in success due to proximity of forested areas, some ant-following birds which were once considered common in western Panama were not observed at all during this study.

While it is clear that the open sun coffee plantations negatively affect army ants and their avian followers, there also appears to be a limit, say the scientists, to the value of these traditional shade-grown coffee plantations for many forest bird species that forage at army ant swarms.

"With increasing distance from large areas of continuous forest," says Roberts, "the value of traditional shade-coffee habitats is lessened for certain components of the bird community."

These results, she says, point to the importance of protecting canopy shade trees in these coffee plantations. And while some species may be able to use the shade coffee areas, some sensitive forest species still need forests in order to survive. The research team also suggests that the areas of shade grown coffee would be well-situated as buffer zones near large forests. Wildlife corridors formed to connect shade coffee to other forested areas may also prove beneficial, by increasing the conservation value of these agricultural lands.

The researchers point out that at many places along the Pacific slope from Mexico to Colombia, these shade coffee plantations are often the only type of land which is anything like forest.

"Shade coffee plantations provide critical habitat for army ants and the associated biodiversity," says Roberts. "But shade coffee alone should not be considered a panacea for conservation efforts to protect sensitive forest species."

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**Photos are available for this story. Please contact Alison Gillespie or visit http://esa.sdsc.edu/press.htm for more information.**

Ecological Applications is a journal published six times a year by the Ecological Society of America (ESA). Copies of the above articles are available free of charge to the press through the Society's Public Affairs Office. Members of the press may also obtain copies of ESA's entire family of publications, which includes Ecology, Ecological Applications, and Ecological Monographs. Others interested in copies of articles should contact the Reprint Department at the address in the masthead.

Founded in 1915, the Ecological Society of America (ESA) is a scientific, non-profit, organization with over 7000 members. Through ESA reports, journals, membership research, and expert testimony to Congress, ESA seeks to promote the responsible application of ecological data and principles to the solution of environmental problems. For more information about the Society and its activities, access ESA's web site at:http://esa.sdsc.edu .


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