Sociality and morphology differentiate niches of 13 sympatric Amazonian woodcreepers (Dendrocolaptinae)

• Published in: Ornithology 2022-04, Vol.139 (2), p.1
• Main Authors: Powell, Luke L, Rutt, Cameron L, Mokross, Karl, Wolfe, Jared D, Johnson, Erik I, Rodrigues, Patricia F, Stouffer, Philip C
• Format: Article
• Language: English
• Subjects: Coexistence; Dendrexetastes rufigula; Dendrocincla merula; Dominance hierarchies; Forage; Foraging; Hierarchies; Hylexetastes perrotii; Lepidocolaptes albolineatus; Maneuvers; Mass; Morphology; Myrmecophily; Niche overlap; Niches; Plant cover; Prey; Species; Strata; Swarming behavior; Swarms; Sympatric populations
• ISSN: 0004-8038; 2732-4613
• DOI: 10.1093/ornithology/ukac002

Abstract 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. Lay Summary • A remarkable 13 woodcreeper species coexist in the Amazon Rainforest north of Manaus, Brazil. • All are small- to medium-sized, uniformly drab brownish birds that hitch up tree trunks. • Theory states that species cannot coexist if they occupy the same niche, so what distinguishes each of these similar species? • We used a combination of behavioral (e.g., social structure, foraging style, vertical stratum, and propensity to follow army ants) and physical traits (e.g., mass, bill size) to measure the niches of these species. • Social structure separated many species, as did their preferred height in the forest. • Mass and bill length furthe