from The American Heritage® Dictionary of the English Language, 5th Edition.
- adjective Having two toes projecting forward and two projecting backward, as certain climbing birds.
- noun A zygodactyl bird, such as a parrot.
from The Century Dictionary.
- In ornithology, yoke-toed: noting those birds, or the feet of those birds, which have the toes disposed in pairs, two before and two behind.
- noun A yoke-toed bird; a bird having the toes arranged in pairs.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Zoöl.) Any zygodactylous bird.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- adjective Having two
toespointing forward, and two pointing backward; zygodactylous.
- noun ornithology Any such
bird(such as the parrot.)
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adjective (of bird feet) having the first and fourth toes directed backward the second and third forward
from Wiktionary, Creative Commons Attribution/Share-Alike License
According to Britannica.com this arrangement is called zygodactyl and is typical of parrots, woodpeckers, cuckoos and a few other kinds.
Wood peckers and other birds that climb tree trunks often have these zygodactyl toes.
He suggested that it evolved semi-zygodactyl feet from an anisodactyl ancestral roller because its large size and specialisation for arboreal life required improved perching abilities.
It's superficially similar to true rollers (Coraciidae) and ground-rollers (Brachypteraciidae) but, unlike them, has semi-zygodactyl feet (though it has frequently very depicted inaccurately by artists who, in the absence of better information, have assumed that it's anisodactyl, like true rollers).
Like all parrots, they are zygodactyl, having 4 toes on each foot - two front and two back.
Given the strong sexual dimorphism and barred, brown female plumage of the Courol, its semi-zygodactyl feet, strong, reinforced jaws, and habit of eating caterpillars, this proposed link - which, ironically, puts the Coural back where it started in 1783 - is intriguing (cuckoos have really interesting jaws, as do the possibly related turacos and hoatzins) [sexual dimorphism in the cuckoo