The spatial configuration and management of agricultural and other land-use practices can affect ecological assemblages. However, the differences in how resident and migratory birds respond to land use are not well understood, hindering our understanding of bird biodiversity responses to land use. In a tropical moist broadleaf forest landscape of southeastern Mexico, we assessed alpha, beta, and functional diversity as indicators of ecosystem functioning in resident and migratory birds across landscape- and habitat-level gradients, incorporating distance to a protected area, understory vegetation cover, and three land uses: 1) primary forest, 2) secondary forest, and 3) cattle pasture. Compositionally, resident and migratory bird assemblages exhibited similar gradual shifts across land uses. However, while resident bird richness steadily declined with increasing distance from a protected area and simplification of understory vegetation structure, migratory bird richness did not change. Relative to primary forest bird assemblages, we found that migratory bird abundances were greater in secondary forest and cattle pasture, and migratory insectivores compensated for 68% of the abundance losses of resident insectivores in secondary forest and cattle pasture. Among these insectivores in secondary forest and cattle pasture, increases in migratory birds compensated for the abundance declines of resident birds that utilize foliage gleaning and sallying foraging methods. Our findings emphasize the importance of evaluating and managing landscapes around protected areas, highlight the distinct responses of resident and migratory birds to land use, and reveal the mechanisms that sustain ecosystem functions in modified landscapes.

Functional traits can determine pairwise species interactions, such as those between plants and pollinators. However, the effects of biogeography and evolutionary history on trait-matching and trait-mediated resource specialization remain poorly understood. We compiled a database of 93 mutualistic hummingbird-plant networks (including 181 hummingbird and 1,256 plant species), complemented by morphological measures of hummingbird bill and floral corolla length. We divided the hummingbirds into their principal clades and used knowledge on hummingbird biogeography to divide the networks into four biogeographical regions: Lowland South America, Andes, North & Central America, and the Caribbean islands. We then tested: (i) whether hummingbird clades and biogeographical regions differ in hummingbird bill length, corolla length of visited flowers and resource specialization, and (ii) whether hummingbirds’ bill length correlates with the corolla length of their food plants and with their level of resource specialization. Hummingbird clades dominated by long-billed species generally visited longer flowers and were the most exclusive in their resource use. Bill and corolla length and the degree of resource specialization were similar across mainland regions, but the Caribbean islands had shorter flowers and hummingbirds with more generalized interaction niches. Bill and corolla length correlated in all regions and most clades, i.e. trait-matching was a recurrent phenomenon in hummingbird-plant associations. In contrast, bill length did not generally mediate resource specialization, as bill length was only weakly correlated with resource specialization within one hummingbird clade (Brilliants) and in the regions of Lowland South America and the Andes in which plants and hummingbirds have a long co-evolutionary history. Supplementary analyses including bill curvature confirmed that bill morphology (length and curvature) does not in general predict resource specialization. These results demonstrate how biogeographical and evolutionary histories can modulate the effects of functional traits on species interactions, and that traits better predict functional groups of interaction partners (i.e. trait-matching) than resource specialization. These findings reveal that functional traits have great potential, but also key limitations, as a tool for developing more mechanistic approaches in community ecology.