According to Britannica.com this arrangement is called zygodactyl and is typical of parrots, woodpeckers, cuckoos and a few other kinds.    From Wordnik.com.  [New Archaeopteryx fossil provides further insight into bird, dinosaur evolution - The Panda's Thumb] Reference

Wood peckers and other birds that climb tree trunks often have these zygodactyl toes.    From Wordnik.com.  [CNN Transcript May 16, 2007] Reference

Like all parrots, they are zygodactyl, having 4 toes on each foot - two front and two back.    From Wordnik.com.  [Norwich Bulletin Home RSS] Reference

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.    From Wordnik.com.  [ScienceBlogs Channel : Life Science]

This is -- zygodactyl.    From Wordnik.com.  [CNN Transcript May 16, 2007] Reference

zygodactyl -- zygodactyl.    From Wordnik.com.  [CNN Transcript May 16, 2007] Reference