DOI: 10.5061/dryad.kkwh70shq
title: Eye size across avian lineages covaries with participation in a specialized foraging behavior

description: Foraging ecology and visual ability are often strongly related across
 animal lineages, as many organisms identify food sources by sight. Birds
 particularly rely upon vision to seek out prey or other food items,
 leading to the correlated evolution of eye size and foraging behavior.
 Here, we focus on a specialized foraging tactic termed ‘disturbance
 foraging’, whereby a responding species exploits prey items flushed by a
 disturbing species. Using global databases of disturbance-responder
 species and eye size measurements from museum specimens, we tested the
 prediction that relative eye size accounting for body mass allometry (a
 proxy for visual acuity and sensitivity) would be larger in disturbance
 foragers that require enhanced visual performance to locate escaping prey
 (N = 463) compared to other species (N = 2840). As predicted, disturbance
 foragers possessed larger relative eye sizes. Residual eye size was
 correlated with a gradient in avian foraging behavior, such that species
 with the smallest and largest relative eye sizes were near-sighted and
 far-sighted non-disturbance foragers, respectively, while disturbance
 foragers had intermediate eye sizes. Birds appeared to invest similarly in
 acuity and sensitivity in relation to foraging behavior as measured by
 their respective anatomical proxies (residual axial length (AL) and cornea
 diameter (CD)), although there was partial evidence that some species
 groups invested more in acuity based upon the eye shape ratio (CD/AL).
 These patterns imply that even highly specialized behavioral tactics may
 evolve in concert with their respectively linked neurological and sensory
 systems.
description: # Eye size across avian lineages covaries with participation in a
 specialized foraging behavior Dataset DOI:
 [10.5061/dryad.kkwh70shq](https://doi.org/10.5061/dryad.kkwh70shq) ##
 Description of the data and file structure ### Files and variables ####
 File: Supplement.zip **Description:**  The archived folder includes: (1)
 Species x trait matrix including all variables informing the analysis
 ("traits_all.csv") using the Jetz et al. (2012) Nature taxonomy:
 * species_jetz: species name based on the Bird Tree from Jetz et al.
 (2012) Nature * family_jetz: family name based on the Bird Tree from Jetz
 et al. (2012) Nature * group: species is terrestrial, aquatic, or a raptor
 * hab.bin: species specializes in forests (1) or does not specialize in
 forests (0) * for.bin: stereotypic foraging behavior - near-sighted/myopic
 (0) vs. far-sighted/hyperopic (1) * dist.bin: displays disturbance
 foraging behavior (1) or does not (0) * Diet.Carn: From Elton Traits
 (Wilman et al. 2014). Sum of invertebrate and vertebrate foraging
 percentages. Equals the percent of diet composed of invertebrates and
 vertebrates (non-plant) * Trophic.Level: trophic group based on the Avonet
 database (Tobias et al. (2024) Ecology Letters) * Trophic.Niche: trophic
 niche based on the Avonet database (Tobias et al. (2024) Ecology Letters)
 (2) Phylogeny used for analyses (see manuscript for details)
 ("MCC_AllBirdsHackett1.tre") (3) R script for analyses
 ("distfor_FINAL.R") ## External Files The eye size data can be
 accessed here:
 [https://datadryad.org/dataset/doi:10.5061/dryad.3xsj3txq7](https://datadryad.org/dataset/doi:10.5061/dryad.3xsj3txq7). ## Code/software All analyses were done in R 4.4.2. All files required to run the code are referenced in this Read Me file.