Habitat And Behavior
Ibises are found on shores and marshes worldwide, mainly in tropical habitats, but some are found in south-temperate regions. Ibises feed in flood plains, marshes, and swamps, and along streams, ponds, and lakes. Their diet is varied, consisting of aquatic invertebrates, insects, snails, fish, reptiles, amphibians, and even small mammals. Generally, ibises feed in large groups of up to 100 birds, and the flock may include other species of waders. Ibises usually feed by wading through shallow water and grabbing available prey with their beak.
Some species of ibis are solitary in their nesting habits within a prescribed territory, but most nest in large colonies of up to 10,000 pairs. Within the colony there may be several different species of ibis. These birds tend to be monogamous (faithful to a single mate) during a breeding season, but observers have also noted promiscuous mating within the large colonies.
Both male and female ibises build the nest, protect it from intruders, incubate the eggs (from two to six at a time), feed the fledglings, and care for them for about a month after they are hatched. Before mating, there is a courtship period, involving displays and the enhancement of the color of the face, legs, bill, and exposed parts of the bird's skin.
The series of courtship behaviors that ibises display (preening, shaking, and bill popping) are ritualized, beginning when the birds gather near secluded nesting areas. The male birds display, the females are attracted to them, and mating follows. Males may behave aggressively in defending their nesting site from other males, but they can also act aggressively towards females not selected as the mate.
Display preening involves pretending to preen the front or back feathers. Display shaking involves shaking loose wings up and down, and bill popping involves snapping the bill up and down with a popping sound. Ibises also have a sleeping display, in which they pretend to be asleep. The head rub during courtship is a sign for the female to enter the nesting area, where she performs a bowing display, keeping her head and body low as she comes near the male. The male may pretend to be aggressive before he finally allows the female to enter his nesting area. Head shaking is one of the displays ibises perform after mating as a greeting and acceptance. The intimacy of their relationship can be seen in mutual preening of one another, shaking, and the rubbing of their heads against each other.