The family Threskiornithidae includes 35 extant species of large wading birds, and one more that became extinct in historical times. The family has been traditionally classified into two subfamilies, the ibises and the spoonbills; however, recent genetic studies have cast doubt on this arrangement, and have found the spoonbills to be nested within the Old World ibises, and the New World ibises as an early offshoot. These studies found two major clades within the family, a widespread clade that includes the type genus Threskiornis and seven other genera (including the spoonbills) occurring in both the Old and New Worlds, and a smaller group of entirely New World species, with five genera. In response to these findings, the International Ornithological Congress (IOC) reclassified Threskiornithidae and their sister taxa Ardeidae under the order Pelecaniformes, instead of the previous order of Ciconiiformes, in 2010.

A study of mitochondrial DNA of the spoonbills plus the sacred and scarlet ibises found that the spoonbills formed a clade with old world genus Threskiornis, with Nipponia nippon and Eudocimus as progressively earlier offshoots and more distant relatives, and hence casts doubt on the arrangement of the family into ibis and spoonbill subfamilies. Subsequent studies have supported these findings, the spoonbills forming a monophyletic clade within the "widespread" clade of ibises, including Plegadis and Threskiornis, while the "new World Endemic" clade is formed by the genera restricted to the Americas such as Eudocimus and Theristicus. and the southernmost is black-faced ibis, south to 55°S in Tierra del Fuego.

The Llanos are notable in that these wetland plains support seven species of ibis in the one region.

Ibises and spoonbills feed on a wide range of invertebrates and small vertebrates; ibises by probing in soft earth or mud, spoonbills by swinging the bill from side to side in shallow water. They roost in trees near water, or standing in shallow water. They are gregarious, feeding, roosting, and flying together, often in formation.

Nesting is colonial in large or small groups or occasionally singly, nearly always in trees overhanging water, but sometimes on islands or small islands in swamps. Generally, the female builds a large structure out of reeds and sticks brought by the male. The typical clutch size is two to five; hatching is asynchronic. Both sexes incubate in shifts, and after hatching feed the young by partial regurgitation. Two or three weeks after hatching, the young no longer need to be brooded continuously and may leave the nest, often forming creches but returning to be fed by the parents.

Species

There are 35 extant species of ibis and spoonbill, and one (Réunion ibis) that became extinct in historical times.

  • Actiornis (Late Eocene of England)
  • Apteribis. Several species of flightless ibises from Hawaii.
  • ?Dakotornis (Late Paleocene of North Dakota, US)
  • Gerandibis. Discovered in France. It is the sole species known for this genera.
  • ?Minggangia (Late Eocene of China)
  • Rhynchaeites (Early to Middle Eocene of England and Germany, potentially Denmark and Wyoming, US)
  • ?Vadaravis (Early Eocene of Wyoming, US)
  • Xenicibis. Discovered in Jamaica.

References

  • Threskiornithidae videos on the Internet Bird Collection