insessores

from The Century Dictionary.

• In ornithology: The perchers; in Vigors's system of classification, adopted by Swainson and many others, an extensive order of birds, of arboreal habits, having the feet fitted for perching, with 3 toes in front and 1 behind, and not raptorial.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) An order of birds, formerly established to include the perching birds, but now generally regarded as an artificial group.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a bird with feet adapted for perching (as on tree branches); this order is now generally abandoned by taxonomists