Foraging behavior of migrant warblers in mixed-species flocks in Venezuelan shade coffee: interspecific differences, tree species selection, and effects of drought

Abstract

ABSTRACT. Shade coffee has been identified as an important habitat for Nearctic-Neotropical migrants during the non-breeding season, including species of conservation concern such as Cerulean Warblers (Setophaga cerulea). To better understand habitat features important for migrants in shade coffee, we studied the foraging behavior of migrants in mixed-species flocks at six shade-coffee farms in the Cordillera de Merida, Venezuela, in 2008Venezuela, in -2009 and the El Niño drought year of 2009-2010. We examined interspecific differences in foraging behavior and tree species selection of three foliage-gleaning migrants, Blackburnian (Setophaga fusca), Cerulean, and Tennessee (Oreothlypis peregrina) warblers, and aerial-foraging American Redstarts (Setophaga ruticilla). For morphologically similar Blackburnian and Cerulean warblers, we also examined factors influencing foraging rates (attack and movement rates), capture of large prey, and maneuver/substrate type. We found that aerial-foraging American Redstarts foraged lower, used more aerial maneuvers, showed no tree species selection, and were less likely to forage in flocks than foliage-gleaners. Although foraging rates were similar for Blackburnian and Cerulean warblers, the three foliage-gleaners differed in foraging height and use of maneuvers. Cerulean Warblers foraged lower than the other two species, whereas Blackburnian Warblers used the greatest proportion of woody gleans. All three foliage-gleaners selected Inga spp. (a commonly planted shade tree in shade-coffee farms) for foraging, and Blackburnian and Cerulean warblers captured a greater proportion of large prey in Inga spp. than in other tree species. During the drought year, Blackburnian and Cerulean warblers captured half as many large prey and used a greater proportion of woody-gleans. We found that interactions among behavioral, floristic, and environmental drivers influenced the foraging behavior of migrants wintering in shade coffee. Our results support those of previous studies suggesting that migrants partition resources behaviorally during the non-breeding season, that foliagegleaners may benefit from the presence of shade trees, especially Inga spp., in agroforestry systems, and that drought may influence the foraging behavior of foliage-gleaning migrants, presumably due to reduced prey availability. RESUMEN. Comportamiento de forrajeo de reinitas migrantes en bandadas mixtas en café bajo sombra en Venezuela: diferencias inter-específicas, selección de especies de arboles y efectos de sequiasEl café bajo sombra ha sido identificado como un hábitat importante para especies migratorias nearticoneotropicales durante laépoca no reproductiva, incluyendo especies con importancia para la conservación como Setophaga cerulea. Con el fin de obtener un mejor entendimiento de las características del hábitat importantes para las especies migratorias en los cafés bajo sombra, estudiamos el comportamiento de forrajeo de migrantes en bandadas mixtas de especies, en seis fincas con café bajo sombra en l...

Foraging behavior of Cerulean Warblers during the breeding and non-breeding seasons: evidence for the breeding currency hypothesis

“…Three sites had recently been partially harvested to ∼50% stocking (Newell and Rodewald , ). During the non‐breeding season, we studied Cerulean Warblers at six shade coffee farms on the western slopes of the Cordillera de Merida in the Venezuelan Andes (Bakermans et al , , Newell et al ). Field work was conducted for seven weeks from 27 November 2008 to 28 January 2009 during a non‐drought year.…”

“…We observed foraging behavior from 27 April through 9 July at six sites in two state forests in Vinton and Jackson counties. Three sites had recently been partially harvested to ß50% stocking Rodewald 2011, 2012). During the non-breeding season, we studied Cerulean Warblers at six shade coffee J.…”

“…Field Ornithol. farms on the western slopes of the Cordillera de Merida in the Venezuelan Andes (Bakermans et al 2009, Newell et al 2014. Field work was conducted for seven weeks from 27 November 2008 to 28 January 2009 during a non-drought year.…”

Variation on species composition and richness in mixed bird flocks along an altitudinal gradient in the Central Andes of Colombia

“…However, a precise definition of nuclear species and their We observed that several migratory species such as Piranga rubra, Leiothlypis peregrina, Setophaga petechia, S. fusca, Geothlypis philadelphia, Cardellina canadensis, and M. varia joined MBF at Quindío, being some of them common or identified as potential nuclear species. Migratory species participate frequently in MBF in the tropical Andes, but those studies had been focused mainly in agroforestry ecosystems or secondary forests (Arbeláez-Cortés, Rodríguez-Correa et al 2011;McDermott & Rodewald 2014;Newell et al 2014). Here we document these migratory species in several forest fragments indicating that they do not only join MBF in different habitats, but also could have a role in their cohesion.…”

The evolution and ecology of individual specializations amongst a group of dietary generalists.

“…In many traditional studies on resource partitioning, researchers consider how environmental heterogeneity can enable species to differentially access resources. Species can feed in different habitats and microhabitats (Navarro et al 2009;Symes et al 2013;, on different items (Pulliam 1985;Beaulieu and Sockman 2012), at different times (Chesson 2000;Reum & Essington 2008), and by using different foraging methods (Toft 1980;Frere et al 2008;Knickle and Rose 2014;Newell et al 2014;O'Neill and Gibb 2014). While many of these studies demonstrate niche partitioning, they do not consider the role that individual and/or ontogenic trait variation may play in niche partitioning (Hirai andMatsui 2002, Lasky et al 2014).…”