The avian default of 3 forward and 1 back is #anisodactyl, i.e., "digits not the same". The 2X2 pattern is #zygodactyl, i.e. "digits yoked". BUT, *which toes* point where matters.

Toes are numbered, with #1 (our "big toe") in opposition for birds; they've lost #5 (our "pinkie toe")...