Lateral eye width for 240 species of Andean cloud forest birds

We quantified eye size using two sources. For 80% of the species (N = 192) we passively captured birds using mist nets at sites located within cloud forest tracts and regenerating second growth. One observer (IJA) used calipers to measure lateral eye width to the nearest 1.1mm. We compared our field measurements to published measurements of traverse eye diameter from preserved specimens for a subset of species (N =78; Ritland 1982) and found the two metrics to be highly correlated (r = 0.92, P &lt; 0.001). Hence, our field measurements can be considered accurate measures of true eye size. For the remaining 48 species (20%) we downloaded six photos per species of individuals perched in the field. We scaled photos in ImageJ using measurements of mean bill height, the position of which is clearly identified by the nares in photos. We only selected photos of birds at eye level, with the beak and eye positioned on the same focal plane. We averaged eye size across the six photos for each species and compared photo measurements from 20 species for which we also had field data. The two methods were strongly correlated (beta = 0.97, P &lt; 0.001, R-squared= 0.96). Photo measurements were on average 3% smaller than field measurements, so we calibrated mean eye size for the 48 species by multiplying by 1.03. The attached data set follows the taxonomy of the 2019 Clements List and the global Bird Tree (Jetz et al. 2012) and includes raw measurements and residuals of eye size on body mass, trophic guild and foraging stratum as described in the Elton Traits database, and classification of foraging maneuvers based on Birds of the World species accounts as either myopic (short-sited/gleaning), hyperopic (far-sighted/aerial), or nectar (hummingbirds) . See associated publication for details on analysis of eye residuals. <br>