Pitta
Pittas are a family, Pittidae, of passerine birds found in Asia, Australasia and Africa. There are 44 species of pittas, all similar in general appearance and habits. The pittas are Old World suboscines, and their closest relatives among other birds are in the genera Smithornis and Calyptomena. Initially placed in a single genus, as of 2009 they have been split into three genera: Pitta, Erythropitta and Hydrornis. Pittas are medium-sized by passerine standards, at in length, and stocky, with strong, longish legs and long feet. They have very short tails and stout, slightly decurved bills. Many have brightly coloured plumage.
Most pitta species are tropical; a few species can be found in temperate climates. They are mostly found in forests, but some live in scrub and mangroves. They are highly terrestrial and mostly solitary, and usually forage on wet forest floors in areas with good ground cover. They eat earthworms, snails, insects and similar invertebrate prey, as well as small vertebrates. Pittas are monogamous and females lay up to six eggs in a large domed nest in a tree or shrub, or sometimes on the ground. Both parents care for the young. Four species of pittas are fully migratory, and several more are partially so, though their migrations are poorly understood.
Four species of pitta are listed as endangered by the International Union for Conservation of Nature; a further nine species are listed as vulnerable and several more are near-threatened. The main threat to pittas is habitat loss in the form of rapid deforestation, but they are also targeted by the cage-bird trade. They are popular with birdwatchers because of their bright plumage and the difficulty in seeing them.
Taxonomy and systematics
The first pitta to be described scientifically was the Indian pitta, which was described and illustrated by George Edwards in 1764. Carl Linnaeus included the species in his revised 12th edition of the Systema Naturae based on Edwards' descriptions and illustrations as well as other accounts, placing it with the Corvidae as Corvus brachyurus. Ten years later Statius Müller moved it and three other pittas to the thrush family Turdidae and the genus Turdus, due to similarities of morphology and behaviour. In 1816 Louis Pierre Vieillot moved it to the new genus Pitta. The name is derived from the word pitta in the Telugu language of South India meaning "small bird".The family's closest relatives have for a long time been assumed to be the other suboscine birds, and particularly the Old World suboscines; the broadbills, asities and the New World sapayoa. These arboreal relatives were formerly treated as two families, and are now either combined into a single taxon or split into four. A 2006 study confirmed that these were indeed the closest relatives of the pittas. The clade they form, the Eurylaimides, is one of the two infraorders of suboscines, which is one of three suborders of the passerine birds. With regards to their relationship within the Eurylaimides, another 2006 study placed the pittas as a sister clade to two clades of broadbills and asities. This same study postulated an Asian origin for the Eurylaimides and therefore the pittas.
Two DNA studies, from 2015 and 2016, came to a different conclusion, finding that the Eurylaimides were divided into two clades and that the pittas formed a clade with the broadbills of the genera Smithornis and Calyptomena, with the remaining broadbills and asities in the other clade. The 2016 study also disputed the earlier claims about the origin of the group, and concluded that the most likely ancestral home of the pittas and the Eurylaimides was Africa. The study found that the pittas diverged from the Smithornis and Calyptomena broadbills 24 to 30 million years ago, during the Oligocene. The pittas diverged and spread through Asia before the oscines reached the Old World from Australia.
The number of pitta genera has varied considerably since Vieillot, ranging from one to as many as nine. In his 1863 work A Monograph of the Pittidae, Daniel Elliot split the pittas into two genera, Pitta for the species with comparatively long tails and Brachyurus for the shorter-tailed species. Barely two decades later, in 1880/81, John Gould split the family into nine genera, in which he also included the lesser melampitta of New Guinea, where it was kept until 1931 when Ernst Mayr demonstrated that it had the syrinx of an oscine bird. Philip Sclater's Catalogue of the Birds of the British Museum brought the number back down to four – Anthocincla, Pitta, Eucichla, and Coracopitta. Elliot's 1895 Monograph of the Pittidae included three genera split into subgenera Anthocincla, Pitta, and Eucichla.
Modern treatments of taxa within the family vary as well. A 1975 checklist included six genera, whereas the 2003 volume of the Handbook of the Birds of the World, which covered the family, placed all the pittas in a single genus. Writing in 1998, Johannes Erritzoe stated that most contemporary authors considered the family to contain a single genus. Before 2006 the family was not well studied using modern anatomical or phylogenetic techniques; two studies, in 1987 and 1990, each used only four species, and comparisons amongst the family as a whole had relied mostly on external features and appearances.
A 2006 study of the nuclear DNA of the pittas was the first to examine most representatives of the family, and found evidence of three major clades of pitta. Based on the study the pittas were split into three genera. The first clade, using the genus name Erythropitta, included six species that had previously been considered closely related based on external features. They are all generally small species with small tails, extensive amounts of crimson or red on the underparts, and greenish or blueish backs. The second genus, Hydrornis, includes variable Asian species. These species are unified morphologically in exhibiting sexual dimorphism in their plumage, as well as in possessing cryptic juvenile plumage. This genus includes the eared pitta, which had often been placed into its own genus, Anthocincla, on account of its apparently primitive characteristics. The third genus, Pitta, is the most widespread. Most species in this genus have green upperparts with a blue wing-patch, dark upperparts and cinnamon-buff underparts. This clade contains all the migratory pitta species, and it is thought that many of the pitta species from islands are derived from migratory species. This division of the pittas into three genera has been adopted by the International Ornithological Congress' Birds of the World: Recommended English Names, the Handbook of the Birds of the World's HBW Alive checklist, and the International Union for Conservation of Nature.
As with genera, there has been considerable variation in the number of accepted pitta species. The checklists of Sclater and Elliot at the end of the 19th century contained 48 and 47 species respectively. More recent checklists have had fewer than this, one from 1975 listing just 24 species. Since the 1990s, the figure has been between 30 and 32 species; the 2003 Handbook of the Birds of the World recognised 30. One species not recognised by the handbook is the black-crowned pitta, which it treated as a subspecies of either the garnet pitta or the graceful pitta. Since the publication of the handbook, further splits to pitta species have been made; in 2010 the banded pitta was split into three species, one endemic to Java and Bali, one endemic to Borneo and one found in Sumatra and the Thai-Malay Peninsula. A 2013 study found that the red-bellied pitta, a widespread species found from Sulawesi to Australia, was actually a species complex. The study divided it into 17 new species; some authorities have recognised fewer, for example the IOC have recognised only 10.
Description
The pittas are small to medium-sized passerines, ranging in size from the blue-banded pitta at to the giant pitta, which can be up to in length. In weight they range from. Pittas are stout-bodied birds with long, strong tarsi and long feet. The colour of the legs and feet can vary dramatically even within a species. This may be a characteristic used by females in judging the quality of a prospective mate. The wings have ten primaries that are generally rounded and short; those of the four migratory species are more pointed. There are nine secondaries with the tenth being vestigial. Anatomically, pittas have large temporal fossae in the skull unlike typical perching birds. The syrinx is tracheo-bronchial and lacks a pessulus or intrinsic muscles. Pittas are behaviourally reluctant to fly, but are capable and even strong fliers. The tails range from being short to very short, and are composed of twelve feathers.Unlike most other forest-floor bird species, the plumage of pittas is often bright and colourful. Only one species, the eared pitta, has entirely cryptic colours in the adults of both sexes. In the same genus, Hydrornis, are three further species with drabber than average plumage, the blue-naped pitta, blue-rumped pitta and rusty-naped pitta. Like the other Hydrornis pittas they are sexually dimorphic in their plumage, the females tending towards being drabber and more cryptic than the males. In general the sexes in the family tend to be very similar if not identical. Across most of the family the brighter colours tend to be on the undersides, with patches or areas of bright colours on the rump, wings and uppertail coverts being concealable. Being able to conceal bright colours from above is important as most predators approach from above; four species have brighter upperparts.