All parrots are zygodactyl, with two toes at the front of each foot and two at the back, and all parrot eggs are white in color. Parrots can be found in most warm regions of the world, including India, southeast Asia, Southern regions of North America, South America and west Africa. By far the greatest number of parrot species come from Australasia, South America, and Central America. No parrot's natural range currently extends into the United States, although the Carolina Parakeet and Thick-billed Parrot once ranged into southern states. The order is diverse and contains exceptions (notoriously the Eclectus for sexual dimorphism, and the kakapo for flightlessness, diet & digestion, and lek breeding). However, most parrots are cavity nesters, are minimally or not sexually dimorphic, and seem to be highly social. Along with the Corvidae, the Psittaciformes are generally considered the most intelligent of the birds. Parrots are altricial (their young are helpless at birth) and the larger species breed slowly (K-selection). Extant species range in size from the Buff-faced Pygmy-parrot, at under 10 g and 8 cm (3.2 inches), to the Hyacinth Macaw, at 1.6 kg (3.5 lbs) and 1 meter (3.3 feet).