White-faced Ibis

INTRODUCTION:
The White-faced Ibis has a discontinuous distribution in the W United States, Mexico and South America.
It is very similar to the Glossy Ibis - Plegadis falcinellus, and it was formerly considered to be a subspecies of Plegadis falcinellus. But some authors say that a small population of Glossy Ibis dispersed to the Americas, becoming isolated and evolving into a separate full species. Recent molecular phylogenetic studies show that both the White-faced Ibis and the Glossy Ibis had a common ancestor.
The ranges of these species are generally distinctive, but where they do overlap, intermediates, and possibly hybrids, make nearly impossible their identification. But actually, hybrids would be mainly produced in captivity.

The White-faced Ibis frequents freshwater wetlands. It nests in emergent vegetation or in low trees or shrubs over shallow water. This species breeds in colonies, and the breeding sites are often reused over several years. Both parents build the nest, incubate the eggs and feed the chicks.
The White-faced Ibis feeds on aquatic insects, crustaceans and earthworms, but other prey such as frogs, small fish, leeches and spiders are also part of the diet. It forages in shallow water by probing in soft mud, or by picking prey from water surface.

The White-faced Ibis is affected by predation during the breeding cycle, as birds and mammals are known to prey on eggs, chicks and young birds. But humans are major predators of adults for food, feathers and sport.
However, the population is currently stable and the species is not globally threatened at the moment.

DESCRIPTION OF THE BIRD:
Biometrics:
Length: 46-56 cm
Wingspan: 90-93 cm
Weight: 450-525 g

The White-faced Ibis is a dark chestnut bird, with green or purple on head and upperparts but the tail is darker.
The adult in breeding plumage has chestnut head, long neck, upper back, wing-coverts and underparts. The flight feathers show metallic green and bronze tones in all seasons. The wings are broad and fairly rounded.

On the head, the facial skin is pink, extending from the front of the eye through the lores to the bill base. A white band contrasts with the dark head, extending from the rear of the eyes and all around the bare facial skin at the base of the bill.
This feature is less conspicuous or absent in the Glossy Ibis.

The long, down-curved bill varies between 15 and 18 cm long. It is greyish and washed pink to olive at the base. The eyes are red (but dark brown in Glossy Ibis). The long legs and the feet are red to purple.

The non-breeding adult lacks the white band on the face and the red legs. Head and neck are grey-brown with whitish streaks. The wings are duller, with no olive, pink and purple iridescent shades on feathers. Legs and feet become reddish-brown to greyish.

Male and female have similar plumage, but the male is larger, with longer bill.
At hatching, the chick has bare underside, whereas rest of body is sparsely covered with brown or black down.
Two weeks later, it starts the juvenile plumage with the loss of the down and growing green and purple coloured feathers. The juvenile is smaller than adults. The eyes are grey-brown.

RANGE:
The White-faced Ibis has two distinct ranges, with one population in North and Middle America, and a second population in South America.
The northern population breeds as far north as S Canada, and as far east as Nebraska. It also occurs along the Gulf coast of Texas and Louisiana, and in C Mexico.
However, the populations of California, Texas, Louisiana and C Mexico are resident, whereas the other part of the northern population migrates southwards after breeding, to spend the winter in Mexico. Others migrate to Guatemala, El Salvador and Honduras.
The South American population does not migrate. It is found from S Brazil and SE Bolivia to N Argentina. The boundaries are the Pacific and Atlantic Oceans.

BEHAVIOUR IN THE WILD:
The White-faced Ibis feeds primarily on insects, crustaceans and earthworms. Insects include aquatic species and their larvae, but also insects living in damp soil. It also takes leeches, snails, crayfish and also vertebrates such as fish and frogs. The main prey are snails and slugs, accounting for 55 to 90% of all food eaten.
The White-faced Ibis probes the substrate with its long bill while foraging by wading in shallow water. It also picks insects and other food items from water surface or soil, and also from emergent vegetation.
It forages in large groups of up to 1,000 individuals. They are observed feeding in moist areas in shallow water. The prey differ depending on the season, and more insects are taken in spring and summer than in other seasons.

The White-faced Ibis breeds in colonies established in dense marshy vegetation, or low shrubs and trees above water, and occasionally on the ground on islands. The nest is a bulky platform with a cup at the centre.
The species is monogamous. The male displays at several possible nesting sites, including nests of previous years. During the displays, the male performs a “ritualized bill probing” and gives a call. The interested females answer with another call.
The nesting site is chosen by the female but both adults share the nesting duties.
At the nest-site, both mates preen each other and offer nesting material during the nest-building. They defend the area around the nest, but aggressive interactions are rare.

Following the breeding season, the White-faced Ibis moves southwards to spend the winter. However, populations of California, Texas, Louisiana and C Mexico are resident, like the South American population.
The birds of all populations are known to wander, and strays have reached the Atlantic Coast in the recent decades.
The migrating populations move twice a year.

The White-faced Ibis flies with the head straight out forwards while legs and feet are straight backwards. This flat profile makes the long, curved bill very conspicuous.
The flight is fast and strong, with active wingbeats interspersed with glides. When they fly in groups, they are usually seen in V-shaped flocks.

REPRODUCTION OF THIS SPECIES:
The breeding period takes place from April to May-June in North America and in November-December in South America.
The White-faced Ibis breeds in large, dense colonies. The nest-site is chosen by the female from potential nest-sites offered by the male. It is usually placed in emergent vegetation, or in low tree or shrub above the water, and even on the ground on small islands.
Both mates build the nest, a flat, bulky platform made of bulrushes and other plant stems. There is a depression in the centre of the structure for the eggs. Some nests are less elaborate and are only a pile of reeds.
The nests built in trees over water include a base of sticks and a larger mass of reeds and rushes.

The female lays 3-4, sometimes 2-5 pale blue-green to dark turquoise eggs. They are laid at one or two days interval. Both adults share the incubation during 21-22 days.
The downy chicks are fed by regurgitation by both parents. Three weeks after hatching, the young may move about outside the nest. They fledge after five weeks and become independent after eight weeks. They are usually able to fly at 4-5 weeks.

Some hybrids between the White-faced Ibis and the Glossy Ibis were reported in Alfalfa County, Oklahoma, in 2002. Both species were breeding in the same area. Up to five hybrids were discovered at this period.
Both Glossy Ibis and White-faced Ibis are known to have produced hybrids in captivity. In the wild, this may be a local phenomenon induced by the relative rarity of Glossy Ibis. An adult of this species in Oklahoma would have had few choices other than a White-faced Ibis for a mate.
More observations and studies are required.

PROTECTION / THREATS / STATUS:
The White-faced Ibis is threatened by habitat destruction and pesticides. Wetlands and marshes for both feeding and nesting are degraded by changes to water systems, pollution and drainage of these wet areas by humans.
The DDT was banned in 1970, and the wetland nesting habitats are now protected. However, disturbance of breeding colonies by humans may cause partial or total desertion during the breeding cycle. Hunting continues in some parts of the range, especially on the wintering grounds in Mexico.
The population is estimated to number 1,200,000 individuals. The overall trend is currently increasing, or stable for some populations. In addition, this species has a very large range in which it is not considered globally threatened.
The White-faced Ibis is currently evaluated as Least Concern.