I’ve summarized several papers from Matt Johnson and his students at Humboldt State University (CA) who study how birds provide pest control on coffee farms in Jamaica by preying on coffee berry borers. Here’s a new paper on the same theme, with the research being done in Costa Rica.
These researchers looked at coffee berry borer (Hypothenemus hampei, CBB) predation by both bats and birds; since bats were not found to be significant predators on CBB in this study I won’t go into those findings. The farms examined were “sun coffee” with less than 25% canopy cover, as shade coffee is not common in Costa Rica. To determine what birds were eating CBBs, the authors used DNA analysis of bird droppings. This is a great way to determine if birds are feeding on the CBB, since the insects are extremely tiny they would be difficult to detect in droppings visually. Still, the bird would have had to have recently fed on CBBs, and the DNA would need to have passed through the digestive system without too much degradation to be detected by this method.
When birds were excluded from the coffee shrubs, the number of shrubs infested with CBB almost doubled, and the CBB drilled deeper into the coffee cherries. Birds were more common in farms that had some embedded or nearby forest cover…and the more forest cover the less severe the borer infestations on control plots. Perhaps surprisingly, very small (less than a hectare) forest patches weaving through the farms provided more of this pest-control benefit than having a large forest reserve nearby.
The authors also calculated the economic benefits the birds provided to farmers. For two farms that formed the core of their study, birds saved between 25 and 70 kg of coffee per hectare annually, for a cost savings of US$75-310 per hectare based on the prices being received. For the smaller farm the total economic benefit of birds preying on CBBs was between US$3500-$9400, and for the larger farm US$17,000-55,100. Since the CBB has only been present in Costa Rica since 2000 and in the vicinity of the study sites since 2005, cost savings provided by the birds may be even higher when CBBs are more-well established.
Bird species that were found to have preyed upon CBBs were:
- Buff-throated Foliage-Gleaner (Automolus ochrolaemus). A common and widespread resident bird in the tropics which feeds on insects in shady forest situations.
- Rufous-breasted Wren (Pheugopedius rutilus). A common wren resident wren in parts of Central America that feeds on insects in thickets and forest edges.
- Rufous-capped Warbler (Basileuterus rufifrons). A resident tropical warbler profiled here in our Know Your Coffee Birds series.
- White-tailed Emerald (Elvira chionura). A resident tropical hummingbird known for inhabiting shaded coffee farms.
- Yellow Warbler (Setophaga petechia). While there is a resident form of Yellow Warbler in Costa Rica, it inhabits coastal areas. The Yellow Warblers in this study were migrants that breed in North America.
It’s interesting to note that although CBB have not been in the area for very long, native and migratory birds are already using them as a food source.
These studies on the identification, ecology, and effectiveness of natural predators of CBB are critical, given the expected spread of this pest due to climate change and the fact that they are evolving resistance to the potent insecticides used to combat them.
- Research: migratory birds provide pest control, increase profit, in Jamaican coffee farms
- Research: Birds reduce coffee pests in Jamaica, take 2
- Research: Borer-eating warblers may need nearby forests
Photo of Buff-throated Foliage-Gleaner by Jerry Oldenettel; Rufous-breasted Wren by Francesco Veronesi; White-tailed Emerald by Michael and Ellen Cox; all under a Creative Commons license. Rufous-capped Warbler and Yellow Warbler by Julie Craves, all rights reserved.
D.S. Karp, C.D. Mendenhall, R. Figueroa Sandi, N. Chaumont, P.R. Ehrlich, E.A. Hadly, & G.C. Daily (2013). Forest bolsters bird abundance, pest control and coffee yield Ecology Letters DOI: 10.1111/ele.12173