Integrating vision, audition and olfaction traits: a roadmap for contrasting sensory ecologies of birds and rodents

Sensory ecology seeks to understand how organisms detect and use information from their environment, yet comparative analyses across multiple sensory modalities remain rare. Here, we present a roadmap for contrasting the sensory ecologies of birds and rodents using surrogate morphological and acoustic traits associated with vision, audition, and olfaction. We focused on 277 breeding bird species from Québec, Canada, and 117 rodent species from two major families, combining published datasets with measurements taken from preserved museum specimens. We first evaluated the validity of surrogate traits by comparing them with standard measures of sensory performance. We then quantified body‐mass allometries for each trait and projected species into a sensory plane to identify poles of relative specialization and patterns of trait covariation. Most visual and auditory traits displayed negative allometry with body mass, indicating disproportionate investment in these systems among smaller‐bodied species, whereas olfactory traits were closer to isometry. Vision specialists are typically found among diurnal open‐habitat species or nocturnal closed‐habitat species. In birds, olfaction specialists are represented by species with an aquatic lifestyle and nests exposed to predation, whereas in rodents they are species active at night in structurally complex habitats. Hearing appears to be coupled with vocalization in birds, but with vision in mammals, suggesting a possible sensory‐axis contrast between target identification and broader environmental surveillance. Together, these results show that comparative sensory ecology can be structured around measurable surrogate traits, body‐size scaling, and multidimensional trait spaces, providing a general framework for investigating patterns of ecological clustering.