Abstract Niche partitioning is often considered an important mechanism promoting species co‐occurrence in species‐rich communities. As species richness increases, niche partitioning may lead to different niche structures, including increased packing of species niches when the community niche space remains unchanged, or expansion of the community niche spaces as additional species are incorporated. In hummingbird assemblages, competitive interactions can strongly influence niche partitioning, and competition often is influenced by resource availability and bill morphology. However, it remains unclear whether resource availability and morphological traits influence hummingbird co‐occurrence through niche expansion or packing. Here, we used the interaction niche—which quantifies hummingbird resource niches in terms of plant traits on which the birds forage—to evaluate whether interaction niche packing or expansion characterizes hummingbird co‐occurrence in a high‐Andean montane forest in southern Ecuador. We found that when hummingbird species richness was high, interaction niche packing and not expansion predominated and was characterized by greater niche overlap among species. However, niche overlap was greater when flower resource availability was low and lower when co‐occurring hummingbirds had divergent bill lengths. These results highlight the importance of morphological traits and floral resource availability on interaction niche overlap in Andean hummingbird species, and how this, in turn, defines patterns of species co‐occurrence. Further, these findings reveal that the interaction niche offers a powerful tool to explore the ecological processes potentially leading to species co‐occurrence. Read the free Plain Language Summary for this article on the Journal blog.
Rojas et al. (Wed,) studied this question.