Villagers are very skiddish when introduced in desert biomes.

Valid homes can be created, villagers either spawned using Villager Eggs or cured from Zombie Villagers, will recognize and establish a village--however, they will run in and out of their homes frantically and group together day and night, as if there's always danger lurking nearby. As far as I know, this only occurs in Desert/DesertHills/Savannah biomes. Once set to Beach or similar dry biome, they behave normally.