The impact of the coffee technification process on bird diversity, density, and guild structure in Finca Irlanda, Chiapas, Mexico

Background/Question/Methods Several studies have documented relationships between vegetation complexity and bird diversity and density in coffee agroforests. Generally, bird richness and abundance is lower in more simplified systems. However, few have specifically documented the impact of the technification process (e.g. shade tree thinning or removal) on birds. Recent low coffee prices motivated coffee producers, including of historically shade-grown coffee farms, to technify farms in attempts to augment production. We took advantage of pre-technification data (from 2001-2002) and the 2-year technification process examine the impacts of technification on birds shortly after tree removal. We surveyed birds during three wet seasons (June-July 2002, 2007, 2008) and three dry seasons (February 2001, 2008, 2009) with 25m-radius, 10 minute point counts each separated by 100m. Sample sizes varied with date because of continuing technification but ranged from 48-66 points in shade and 66-79 points in cut areas. We measured several vegetation characteristics (e.g. tree density, diversity, height). We compared richness and abundance of birds in shaded and cut areas to pre-technification data. Additionally, we classified observed birds into feeding guilds (insectivore, nectarivore, granivore) and migrant status (migrant or resident) to examine if the transition process had disproportionate effects depending on natural history. Results/Conclusions Generally, bird richness and abundance declined with the technification process; shaded areas had similar or slightly lower richness and abundance per point than bird communities pre-technification, but cut areas supported much lower richness and abundance. During the post-technification wet seasons, we found 58 species and 1934 individuals under shade but only 49 species and 911 individuals in cut areas. In the dry season, bird richness and abundance was higher in shaded (81, 1628) than cut areas (46, 321), respectively. Migratory species declined most with two times the species and >6 times more individuals in shaded areas. Omnivore richness was not affected by cutting but there were three times as many individuals in the shaded areas. In contrast, nectarivore richness was higher in cut (10) than in shaded (8) areas due to either increased flowering in cut areas or elevational migration. Nectarivore abundance, however, was three times greater in the shaded habitat. Insectivorous birds were most sensitive to technification with higher richness (46 vs. 32) and abundance (1317 vs. 531) in shaded vs. cut areas, respectively, likely because of loss of specialized insectivores. Ironically, this loss of insectivorous birds may negatively impact producers, as birds are pest regulators in coffee agroecosystems.