1999/02/22 by M. de L. Brooke, Sylvanus Hanley, Simon B. Laughlin · 8 citations
Environmental Science · Agricultural and Biological Sciences · #Avian ecology and behavior #Animal Behavior and Reproduction #Physiological and biochemical adaptations
paper · doi:10.1098/rspb.1999.0652
openalex publication_date 1999/02/22 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We developed a simple method that uses skulls to estimate the diameter, and hence the mass, of birds' eyes. Allometric analysis demonstrated that, within five orders (parrots, pigeons, petrels, raptors and owls) and across 104 families of flying birds, eye mass is proportional to (body mass)0.68 over a range of body masses (6 g to 11.3 kg). As expected from their habits and visual ecology, raptors and owls have enlarged eyes, with masses 1.4 and 2.2 times greater than average birds of the same weight. Taking existing relationships for flight speed on body mass, we find that resolution increases close to (flight speed)1.333. Consequently, large birds resolve objects at a longer time to contact than small birds. Eye radius and skull size co–vary in strict proportion, suggesting common physiological, aerodynamic and mechanical constraints. Because eye mass scales close to brain mass, metabolic rate and information processing could also be limiting, but the precise factors determining the scaling of eye to body have not been identified.