Functional Responses of Bird Assemblages to Land-Use Change in the Colombian Llanos Region

Abstract

Land-use change in the Colombian Llanos due to agro-industrial expansion affects biodiversity. This change alters species occurrence probability, consequently impacting species’ composition. For some species, the occurence probability increases with land-use changes, while it stays unchanged or decreases for others. This interspecific variation in the response to land-use change may be mediated by functional traits, among other factors. We investigated response functional traits to land-use changes and their influence on the occurrence probability of bird species in the Colombian Orinoquia region. We compiled data for 13 morphological and life-history traits of 364 species recorded in forests, savannas, rice fields, palm oil crops, and livestock pastures in the piedmont and flooded savanna landscapes. We used a novel framework to identify response functional traits (i.e., traits with a significant effect on occurrence probability) through multiple statistical tests. We used random forest models to identify response functional traits to land-use change for pairwise comparisons of natural vs. agricultural land use types. For the functional traits, we estimated the influence of their states as trait attributes on species’ responses to land-use changes. We identified functional groups based on hierarchical clustering analysis. Functional groups corresponded to different levels of response, that is, different changes in probability occurrence. Land-use changes altered the multidimensional space of bird traits (i.e., functional diversity), implying modifications in species' composition, functional redundancy, and functional group turnover. Functional traits were similar for random forest classifications of the same natural cover but differed among landscapes. In the piedmont forests, social behavior—migratory status—was a functional trait combination common to all classifications, while foraging behavior-nest location trait combination was common to all forests scenarios in flooded savannas landscape classifications. Migratory status was a functional trait for all savanna classifications. Functional groups described the impacts of land-use changes on bird assemblages. Identification and characterization of these groups using trait attributes can help predict species' responses to land-use changes and guide conservation efforts toward groups with decreased occurrence probability, including recommendations for agricultural practices that can reduce impacts on the Orinoquia biodiversity.