Pest reduction services by birds in shade and sun coffee in Jamaica. 2010. Johnson, M. D., J. L. Kellermann, and A. M. Stercho. Animal Conservation 13:140-147.
Matt Johnson’s team from Humboldt State University (CA) continues its excellent research on birds and ecosystem services on coffee farms in Jamaica. This study, similar to others, looked at pest reduction on a 18 ha farm, Kew Park Coffee. This farm is about 70% shaded; the other 30% has shade trees too young to provide shade yet. The farm also has one side bordered by dense second growth forest.
Exclosures were placed on some coffee trees to prevent birds (but not insects) from accessing them, and the number of insects on these and control trees were examined. The authors found that on trees where birds had access, there was a 40 to 58% reduction in the coffee berry borer (CBB), or broca (Hypothenemus hampei), the world’s most serious coffee pest.
The most common means of controlling CBB are the nasty pesticide endosulfan (although some are developing resistance), or scent traps. Traps are most effective when female CBBs leave coffee cherries to lay eggs in other cherries; the birds in these studies usually attacked the CBBs as they were entering new cherries. Thus, the birds can provide an extra layer of control even on farms that use traps. The authors determined that the pest reduction by the birds on this small farm amounted to 12% of the value of the crop.
This study did not find that birds were more effective at controlling pests in shade than in sun, but it may have been due to the small size of the farm and the proximity of adjacent forested area. A previous study on four different Jamaican farms by some of the same researchers found that the birds consuming CBBs declined dramatically in abundance as distance from forest patches increased. Birds may have made use of the unshaded portions of the farm in the current study because of the amount of forest and shaded coffee surrounding it. I saw a presentation by another member of this research team at a recent ornithological conference that indicated some of the bird species in question foraged in coffee during the day, but retreated to forest patches to roost at night.
Bird species found in the shaded portion of the farm in good numbers, but not at all in the sun portions, included the national bird of Jamaica, the Red-billed Streamertail (Trochilus polytmus), a hummingbird also known as “Doctorbird”, shown above); another resident hummingbird, the Jamaican Mango (Anthracothorax mango); and the North American migrants the Black-and-white Warbler (Mniotilta varia) and Prairie Warbler (Dendroica discolor), which winter on the island.
Johnson, M., Kellermann, J., & Stercho, A. (2010). Pest reduction services by birds in shade and sun coffee in Jamaica Animal Conservation, 13 (2), 140-147 DOI: 10.1111/j.1469-1795.2009.00310.x