The ibises are long-legged, long-necked wading birds that look superficially like herons. Their feeding styles, however, are very different. They are mostly tactile feeders, and use their long, often decurved bills to probe in shallow water or mud for invertebrates or small vertebrates. They generally inhabit wetlands, but some forage in upland fields or along densely forested rivers. They are sociable in all seasons, feeding in flocks, and nesting in colonies. They fly with their necks fully extended, and flocks often congregate in lines or V-formations and may flap and glide in unison. They begin breeding at two to four years and are monogamous, but pair bonds last a single season. Both members of the pair help build bulky platform nests, incubate two to four eggs, and feed the young, which stick their heads into the adults' mouths and feed on partly digested food. Some species in this group are migratory, and others are resident.