White-faced Ibis

FUN AND INTERESTING FACTS ABOUTWHITE-FACED IBIS

 

The White-faced Ibis is a long-legged wading bird with reddish eyes and a long, slender, decurved bill. Plumage is chestnut colored with green and purple iridescence. During the breeding season, a white feather border can be seen around the base of the bill along with red lores and legs. Juveniles lack the white on the face and the red legs.They stand about 19 inches tall, and have a 3-foot wingspan. Males have the same coloring as females but males are generally bigger than females, and males have longer bills than females. Bill length is between 6 and 7 inches long. Parts of the face, as well as the legs and feet are red or purple because bare skin is exposed.

 

These ibis are wary and shy, making getting close to them difficult. White-faced Ibis patterns at Pixley NWR:

Each August, the Pixley NWR staff floods 307 acres of refuge land to provide night roosting habitat for the Sandhill Cranes that are about to arrive from their summer breeding grounds in Alaska; most of these flooded basins are shallow, usually just 5 to 8 inches deep, which is the preferred depth for both the night roosting cranes and ibis. This shallow water is enough to prevent mammalian predators like coyotes from catching an ibis or crane as they rest in the marsh during the night; any splashing by the coyote would surely alert the entire flock to the danger.

 

Each evening between September and April, thousands of ibis silently fly into the Pixley NWR marsh about 30 minutes before sunset. This dramatic fly-in lasts merely 12 to 15 minutes, until all of these 15,000 ibis are densely packed together in a black mass about a block long in the middle of the marsh; probably this tightly huddled behavior helps them to conserve heat as they stand together in the cold marsh for about 8 hours. Just before sunset, after all of these ibis have settled down in the marsh, the horizon fills with the sights and sounds of waves of thousands of cranes as they descend towards this same marsh. It seems amazing how Mother Nature has arranged both species to take turns flying in to this marsh at different times to prevent collisions and traffic jams! Also interesting, both species fly out of this marsh in a similar fashion, with the ibis leaving first about 30 minutes before sunrise, and the cranes flying away near sunrise!

 

At first, the small ibis groups form messy wide arches as they fly towards the Pixley NWR marsh. These different lines of ibis join together as they approach the marsh. They then morph into a dense, black, amoeba-like swarm (much like starlings) that folds and gyrates in a wonderful nature ballet as they descend downward into the marsh. Possibly, this interesting swarming behavior by White-faced Ibis might only occur at the Pixley NWR! It is believed that this swarming behavior confuses avian predators like Peregrine Falcons and Red-tailed Hawks that been known to RARELY prey on adult White-faced Ibis; however, at Pixley NWR, White-faced Ibis predation by large falcons and Red-tailed Hawks may not be such a rare event. Both Peregrine and Prairie Falcons regularly are seen near this marsh, and several Red-tailed Hawks are perched each evening on nearly every snag surrounding this marsh.

 

Most interestingly, at the BIRDS OF PREY DISPLAY just past the sharp right hand turn off of the gravel trail to the platform, there is clear evidence that indeed some birds of prey species apparently can read! Several raptors have been regularly using this display as their primary feeding spot. Below this sign are numerous pellets filled with bones, hairs, and feathers. Also, there are numerous White-faced Ibis feathers below this display, plus an orange tail feather from a Red-tailed Hawk. Apparently, a Red-tailed Hawk snagged a White-faced Ibis during their fly-in, carried it to this display, plucked away its feathers, and ate the ibis!

 

Life span: The longest known lifespan of this species in the wild is 14 years and 6 months. However, in the wild, White-faced Ibis typically don’t live longer than 9 years. In captivity they have lived to 14 years. Both males and females become sexually mature after 2 years.

 

Food habits: White-faced ibis feed by probing the substrate with their long bill, in search of small animals. They forage in flocks, up to 1000 individuals, taking advantage of insects and other food items disturbed by the other nearby ibis. They feed mainly in moist areas around bodies of water, flooded fields, and also in shallow (less than 8 inches) water. They are primarily carnivorous, feeding on insects, spiders, crayfish, crustaceans, worms, leeches, snails, frogs, newts, and fish. Snails and slugs are the large prey group by volume, accounting for 55 to 90% of all food eaten. Prey taken varies with the season, with more insects in the spring and summer than in other seasons. Males tend to eat more snails and slugs and females tend to eat more insects.

 

Breeding: White-faced ibis are colonial breeders. Colony size ranges from a few to over 10,000 individuals. They tend to show strong fidelity to certain preferred breeding colony sites. Breeding is from April to June. Incredibly, nests are often only 6-feet away from each other in these large nesting colonies! Nests are usually found in dense cattail and tule marshes, but can also be in a low tree, or on floating vegetation. White-faced ibis parents take turns in making the nest and guarding it. The male starts guarding the nest while the female gathers materials and then the role reverses while the female builds the nest the male gathers materials.Eggs are laid at a one to two day interval. Three to four eggs are laid, with a range between two to seven eggs, and are incubated for 21 to 22 days. During the first week after hatching there is a 60% mortality rate for third and fourth eggs produced, compared with a 5% mortality rate for first and second eggs. Once the eggs have been laid, the parents take turns in caring for the eggs, normally the males during the day and the females at night. Both sexes will fiercely guard the nest and the area around the nest within 3-feet against intruders, and the average nest is merely 6-feet away from its neighbors. They shade or incubate the eggs to keep them at the correct temperature. This treatment continues for the first week following hatching and occurs to a lesser extent (left alone for up to three hours) during the second week and is absent in the third week.The parents are monogamous and both care for the young.

 

Both male and female adults will feed the young. This is done by regurgitating partially digested food. Parents will shade their young while they are in the nest from the sun when it is hot out as the young tend to die quickly of heat exposure. The parents will also take the young on both a short walk and a short flight around the colony. Young ibis fledge after five weeks and are independent after eight weeks. There is no evidence to believe there is an association between the parents and young after they have reached independence. Water level stability is important in nesting areas. Nest colonies must remain flooded throughout the nesting period to deter mammalian predators, but water levels must not rise high enough to flood nests. Either of these conditions leads to abandonment of nests and reproductive failure.

 

Predation: The eggs, nestlings, and fledglings of White-faced Ibises are taken by many different predators, including gulls, magpies, Black-crowned Night-herons, Common Ravens, raccoons, striped skunks, spotted skunks, coyotes, mink, and long-tailed weasels. Mammals are more likely to become predators when water levels around nests fall, making access to the nest easier. Peregrine Falcons and Red-tailed Hawks are able to prey on the adult white-faced ibis, but predation on adults is rare. Humans are major predators of White-faced Ibises, for food, feathers, and sport. Adult ibises are vigilant in protecting their eggs and young from predators, helping to avoid predation. Their flocking habits also help in alerting flock members to potential danger.

 

Behavior: White-faced Ibises are social and nomadic. If a foraging area becomes too dry they will leave in search of a more suitable location. White-faced Ibises fly relatively long distances to find food. They fly at a rate of about 30 to 33 miles per hour. These ibis fly in a rather messy modified V formation for efficiency, which resembles more of an arch or semi-circle, with several ibis also flying inside this arch. White-faced Ibis are gregarious, living in large groups. They are tolerant of other ibises outside of the breeding season. White-faced Ibises forage in flocks, taking advantage of insects and other food items disturbed by the other nearby ibis.

 

Communication: When a group of White-faced Ibises flies overhead, you will generally only hear their wing beats; they are typically silent outside of their breeding colonies, where they communicate through sounds and visual displays. There are multiple different sounds that these birds make which have different meanings. There are separate sounds for calling to their young, when a mate is returning to the nest, and a sound used as a feeding call. Single birds, pairs, and flocks often give an "oink oink" or "ka-onk ka-onk" sound. During nest building, they often give a guttural babbling sound. Vocalizations during interspecific aggression are long "gheeeeeee" sounds and the greeting call by the male to the female is a "geeeeek, geeeeek, geeeeek" sound.

 

Range: White-faced ibises are widespread, with two distinct ranges; one population is found in North and Middle America and a separate population is found in South America. Those found in North and Middle America cover most of the western and mid-western United States and most of Mexico. Breeding areas are as far north as southern Canada and as far east as Nebraska. Additionally they are found along the Gulf coast of Texas and Louisiana and in central Mexico. Northern populations are migratory, mainly wintering in Mexico and Central America, while southern populations do not migrate. The White-faced Ibis here in Tulare County are resident birds, and do not migrate, and will winter and breed in Tulare County.The South American population of White-faced Ibises do not migrate for the winter. They are found from southern Brazil and southeastern Bolivia to northern Argentina. White-faced Ibis found in South America tend to be smaller than those found in North America.

 

Status: White-faced Ibis was on the California Species of Special Concern Highest Priority list in 1978. This species was once a locally common breeder the length of California. The center of abundance was in the San Joaquin Valley, but numbers also bred in northeastern California and the southern coastal area. In 1978, White-faced Ibis was not known to breed regularly anywhere in California. The Los Banos area in Merced Co., once the stronghold of this species in California, no longer supported any breeding birds in 1978. During this time, the last known nesting attempt by any substantial numbers of ibis was in 1960 (100 pairs at the mouth of the Alamo River); as many as 1500 birds were reported in the summer at the Salton Sea as recently as 1962, whereas only a few dozen birds had been reported in 1974 and 1975. Grinnell and Miller (1944) had even noticed this declining trend for this ibis by the 1940's. The wintering population of ibis in California was also declining; in the winter of 1976-77, fewer than 200 birds were reported in California, and these were all from just three localities; Los Banos Wildlife Area, Merced Co. (only 60 remained, where as many as 190 wintered there just 5 years earlier); Imperial Valley recorded only about 100 ibis; and near Oceanside, San Diego Co. recorded just 35 ibis! White-faced Ibis was also again listed on the 2nd edition of the California Species of Special Concern List in July 1992. However, since 1992, White-faced Ibis has experienced a remarkable recovery in California, and it was not listed on the 3rd and most recent California Species of Special Concern List (2008). Reasons for the decline: Threats to the White-faced Ibis include alterations to habitat, disturbance during nesting, pesticide contamination, a limited number of breeding locations, and fluctuating water levels within their habitat. Destruction of marsh habitat, especially along the southern coast and in the San Joaquin Valley, was perhaps the main factor responsible for the decline. This species prefers shallow, grassy marshes, and this type of wetland has disappeared from most of California. Furthermore, many wetlands were allowed to go dry during spring and summer for mosquito and cattail control. White-faced ibis were affected by contamination from the pesticide DDT in the 1960’s and 1970’s before it was banned resulting in the thinning of eggshells and reduction in reproductive success. The Bear River, Utah, population experienced disastrous eggshell thinning in the late 1960's, and there is reason to suspect that California populations were also contaminated. Interestingly, this species has also vanished from remaining suitable breeding habitat in California, implying that factors other than habitat destruction are involved.

 

Management & conservation: Preservation of suitable wetland habitats and maintenance of preferred breeding sites are essential to conservation of the White-faced Ibis. Water level stability in breeding areas must be actively monitored and manipulated to prevent abandonment of nests by the ibis. Key areas like Pixley NWR need to be allowed to remain wet and become overgrown with marsh vegetation. Shallow flooding of additional grassy areas will greatly benefit this species and other Special Concern species such as Fulvous Whistling Duck, Northern Harrier, Least Bittern, Short-eared Owl, Sandhill Crane, and breeding waterbirds in general. Such areas are also important for birding ecotourism; it is important to provide the essential components needed for the healthy, wetland habitats in which they live.

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