Woodcreepers (Dendrocolaptinae) represent a remarkably uniform group of brownish birds that move by hitching up tree trunks as they forage for arthropod prey. Despite these superficial similarities, we were able to uniquely differentiate the niches of all 13 species north of Manaus by integrating morphological traits (e.g., mass and bill size) with behavioral traits (e.g., sociality, stratum use, and foraging maneuvers). The 5 ant-following (myrmecophilous) species, with their larger bodies and heavier bills, were morphologically distinct from the 7 species that join mixed-species flocks. A combination of vertical stratum, mass, and bill length further distinguished among mixed-flocking species. Two canopy species— the solitary Dendrexetastes rufigula and the mixed-flocking Lepidocolaptes albolineatus—consistently foraged at higher strata than other species. For the remaining mixed-flocking species, the largest 3 species differed significantly by mass, whereas the smallest 3 species, which overlapped broadly in mass, were uniquely distinguished by bill length. The 5 ant-following species differed in their degree of specialization on ant swarms, from facultative (Hylexetastes perrotii) to obligate (Dendrocincla merula). The ant-followers also showed nearly discrete mass distributions that essentially differed by Hutchinsonian 1:1.3 ratios, which likely allows them to maintain interspecific dominance hierarchies at the front of raiding army ant swarms. The behaviors we quantified (sociality, vertical strata, and myrmecophily), together with morphology (mass and bill size), separated all 13 species. We speculate that niche partitioning and competitive exclusion allow each woodcreeper to uniquely access invertebrate prey, permitting coexistence and contributing to high alpha diversity at our study site.

See methods section of paper.

Coauthors: Cameron L. Rutt,1,2,d, Karl Mokross,1,2,e Jared D. Wolfe,1,2,3,f, Erik I. Johnson,1,2,g Patricia F. Rodrigues,1,2,3,*, and Philip C Stouffer1,2

1 School of Renewable Natural Resources, Louisiana State University AgCenter and Louisiana State University, Baton Rouge, Louisiana, USA 1.65 2 Biological Dynamics of Forest Fragments Project, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil

3 Biodiversity Initiative, Houghton, Michigan, USA

a Current address: Institute of Animal Health and Comparative Medicine, Graham Kerr Building, University of Glasgow, Glasgow, UK

b Current address: CIBIO-InBIO, Research Centre in Biodiversity and Genetic Resources, University of Porto, Campus de Vairão, Vairão, Portugal

c Current address: BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, 4485-661 Vairão, Portugal

d Current address: American Bird Conservancy, The Plains, Virginia, USA 1.70 e Current address: Sci-Comms Comunicação Visual, R. José Manoel Serpa, São Carlos, Brazil

f Current address: Michigan Technological University, College of Forest Resources and Environmental Science, Houghton, Michigan, USA

g Current address: National Audubon Society, Baton Rouge, Louisiana, USA