Toes 3 and 4 fused at the base, e.g. kingfishers and hornbills (three toes forward, one backwards). In the case of trogons, toes 3 and 4 are forward and fused at the base, and toes 1 and 2 face backwards. (See Zygodactyl). Found on https://www.encyclo.co.uk/local/22222