Sitella
Encyclopedia
The sittellas are a family, Neosittidae, of small passerine
bird
s found only in Australasia
. They resemble nuthatch
es, but whilst they were considered to be in that family for many years they are now afforded their own family. They do not migrate
other than for local movements.
The sittellas are small woodland birds with thin pointed down-curved bills, which they use to extricate insects from bark. Nests are open cups in forked branches.
They were formerly classified in two separate genera
with the Black Sittella in Daphoenositta and the Varied and Papuan Sittellas in Neositta. The two genera are now usually merged with Daphoenositta having priority.
es. As late as 1967 the sittellas were retained in that family by some authorities, although doubts about that placement had been voiced in the previous decades. Both their climbing technique and overall morphology are extremely similar; however they differ both in their sociality and their nesting behaviour, as sittellas create nests on branches whereas nuthatches nest in cavities in trees. In addition the specifics of the morphology of the leg differed, with sittellas having leg muscles more similar to those of the honeyeater
s. Their placement was then moved to various families, including the Old World babbler
s (an infamous wastebin taxon), the true treecreeper
s (Certhiidae, which range across the Holarctic
and Africa
) and the Australian treecreepers (Climacteridae). Their relationship with the Australian radiation of passerines was suggested by S.A. Parker on the basis of egg colour, nest structure and nestling plumage, and their position in this radiation was vindicated by Sibley
and Ahlquist
's DNA-DNA hybridization studies. These researchers placed the sittellas in a monotypic tribe within the superfamily Corvidae
. Today they are afforded their own family in a clade close to the berrypeckers and longbills (Melanocharitidae
) and the whistlers (Pachycephalidae
).
The sittellas comprise a single genus
, Daphoenositta, which contains two species. The two species were once considered to be two genera, but when the two were lumped the genus name of the less well known Black Sittella
was adopted (due to priority), while the family retained the family name based on the junior synonym (Neositta). The most common species, the Varied Sittella
, was once thought to represent several separate species, including five species in Australia, but in spite of considerable variation in plumage there are extensive zones of hybridization where the forms overlap (including an area of Queensland
where all five Australian subspecies exist), and are now thought to be a single species with eleven subspecies. The Black Sittella has three recognized subspecies.
s which resemble nuthatch
es in appearance. The wings are long and broad, and when spread have clearly fingered tips. The family has a generally weak flight
, which may explain their inability to colonize suitable habitat on islands like Tasmania
. The legs are short but they have long toes, but in spite of their lifestyle they show little adaptation towards climbing. They have short tails and are between 10–14 cm in length and 8-20 g in weight, with the Black Sittella tending to be slightly larger and heavier. The bill
is dagger shaped in the case of the Black Sittella and slightly upturned in the Varied Sittella. The plumage
of the Black Sittella is mostly black with a red face; that of the Varied Sittella is more complex, with the numerous subspecies having many variations on the theme. The sexes of some subspecies have entirely black heads, other white, and others dark crowns and paler throats. The backs of most subspecies are grey with darker wings, and the undersides are generally streaked or white. All sittellas exhibit some sexual dimorphism
in plumage.
females.
suggest that they live in clans of eight to twelve individuals and defend mutual territories
against other groups. Within the groups, mutual preening is common, and in the evening the groups roost communally as well. Birds traveling to the evening roosts do so at slightly different times, timing their arrival at 30-60 second intervals, presumably so as not to attract the attention of potential predators. Roost sites are usually high in trees on slightly inclined dead branches. All the birds in the group roost next to each other, touching, and facing the same direction. Amongst Australian birds Varied Sittellas are usually the first to arrive at roost sites in the evening and the last to leave in the morning, although they are not necessarily the first to sleep or last to wake. At the roost site the position occupied along the branch is generally not random; instead males generally adopt positions at the edges of the group whilst young birds tend to be found in the centre.
s and other arthropod
s. In one study in new South Wales adult beetle
s were the most common component of the Varied Sittella's diet, around 36%; particularly favoured were weevil
s, ladybirds, leaf beetles Chrysomelidae) and click beetles (Elateridae). A further quarter of the diet was composed of spider
s and true bugs. Also taken were beetle and moth larvae, grasshoppers, termites, wasps and bees. Ant
s were taken relatively infrequently compared to other Australasian birds in similar niches. The proportion of any one item in the diet apparently varies geographically and seasonally, for example another study found that beetle larvae composed 87% of the diet. The diet of the Black Sittella has, like other aspects of its biology, been little studied, although the stomach contents of one that were examined contained caterpillars and spiders.
Sittellas forage on horizontal branches and the trunks of trees. Their foraging techniques has been described as hopping rapidly along the length of a horizontal branch, pausing briefly to peer for prey, occasionally hanging underneath the branch but usually on top of it. Most of the time is spent on branches rather than on the trunks. Birds on the trunks may travel upwards or downwards. Within the forest sittellas usually forage in the canopy. There are sexual differences in foraging, with males and females choosing to forage in slightly different microhabitats within the tree. Prey items are usually gleaned
directly from the bark, although in a few instances sittellas will sally
from the branch in order to snatch aerial prey. Having obtained prey sittellas will use their feet to hold it while they eat it, in a similar manner to parrot
s, and will also use their feet in order to hold back strips of bark in order to pry underneath it. There have even been isolated reports of tool use in some populations of sittellas. Sticks were used to pry boring beetle larvae out of cavities, in a similar fashion to that of tool using Woodpecker Finch
es of the Galapagos.
95% of the nests found in a study in New South Wales were in stringybarks, particularly the species Eucalyptus macrorhycha. The nests were almost always located high in the tree. Nest construction took around 7 days, but lining and decorating the nest added a few days to this. Nest building duties were shared amongst the group, and the speed of construction depended on how many birds were involved. Nests are usually placed in the prong of two branches, and is a deep cup decorated in the bark of the tree it is built in, thereby camouflaging
it. Around 2-3 eggs are laid and incubated
by the breeding female (or females if two are sharing the nest) for 19–20 days. Whilst incubating the breeding female is fed by the breeding male and helpers. After hatching the female broods the young for a few days, and for up to two weeks at night. The chicks are fed for 19–20 days in the nest. After fledging
the chicks have a protracted period of parental care lasting up to 80 days, although 60 days is more usual.
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s found only in Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
. They resemble nuthatch
Nuthatch
The nuthatches are a genus, Sitta, of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs...
es, but whilst they were considered to be in that family for many years they are now afforded their own family. They do not migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
other than for local movements.
The sittellas are small woodland birds with thin pointed down-curved bills, which they use to extricate insects from bark. Nests are open cups in forked branches.
They were formerly classified in two separate genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
with the Black Sittella in Daphoenositta and the Varied and Papuan Sittellas in Neositta. The two genera are now usually merged with Daphoenositta having priority.
Evolution and taxonomy
The true evolutionary affinities of the sittellas have long been clouded by their close resemblance to the Northern Hemisphere nuthatchNuthatch
The nuthatches are a genus, Sitta, of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs...
es. As late as 1967 the sittellas were retained in that family by some authorities, although doubts about that placement had been voiced in the previous decades. Both their climbing technique and overall morphology are extremely similar; however they differ both in their sociality and their nesting behaviour, as sittellas create nests on branches whereas nuthatches nest in cavities in trees. In addition the specifics of the morphology of the leg differed, with sittellas having leg muscles more similar to those of the honeyeater
Honeyeater
The honeyeaters are a large and diverse family of small to medium sized birds most common in Australia and New Guinea, but also found in New Zealand, the Pacific islands as far east as Samoa and Tonga, and the islands to the north and west of New Guinea known as Wallacea...
s. Their placement was then moved to various families, including the Old World babbler
Old World babbler
The Old World babblers or timaliids are a large family of mostly Old World passerine birds. They are rather diverse in size and coloration, but are characterised by soft fluffy plumage. These are birds of tropical areas, with the greatest variety in Southeast Asia and the Indian Subcontinent...
s (an infamous wastebin taxon), the true treecreeper
Treecreeper
The treecreepers are a family, Certhiidae, of small passerine birds, widespread in wooded regions of the Northern Hemisphere and sub-Saharan Africa. The family contains ten species in two genera, Certhia and Salpornis...
s (Certhiidae, which range across the Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
) and the Australian treecreepers (Climacteridae). Their relationship with the Australian radiation of passerines was suggested by S.A. Parker on the basis of egg colour, nest structure and nestling plumage, and their position in this radiation was vindicated by Sibley
Charles Sibley
Charles Gald Sibley was an American ornithologist and molecular biologist. He had an immense influence on the scientific classification of birds, and the work that Sibley initiated has substantially altered our understanding of the evolutionary history of modern birds.Sibley's taxonomy has been a...
and Ahlquist
Jon Edward Ahlquist
Jon Edward Ahlquist is an American molecular biologist and ornithologist who has specialized in molecular phylogenetics. He has collaborated extensively with Charles Sibley, primarily at Yale University.By 1987, both Ahlquist and Sibley had left Yale....
's DNA-DNA hybridization studies. These researchers placed the sittellas in a monotypic tribe within the superfamily Corvidae
Corvidae
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs and nutcrackers. The common English names used are corvids or the crow family , and there are over 120 species...
. Today they are afforded their own family in a clade close to the berrypeckers and longbills (Melanocharitidae
Melanocharitidae
The Melanocharitidae, the berrypeckers and longbills, is a small bird family restricted to the forests of New Guinea. The family contains ten species in four genera...
) and the whistlers (Pachycephalidae
Pachycephalidae
The family Pachycephalidae, collectively the whistlers, includes the whistlers, shrike-thrushes, shrike-tits, pitohuis and Crested Bellbird, and is part of the ancient Australo-Papuan radiation of songbirds. Its members range from small to medium in size, and occupy most of Australasia...
).
The sittellas comprise a single genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Daphoenositta, which contains two species. The two species were once considered to be two genera, but when the two were lumped the genus name of the less well known Black Sittella
Black Sittella
The Black Sittella is a species of bird in the Neosittidae family.It is found in Indonesia and Papua New Guinea.-References:* BirdLife International 2004. . Downloaded on 25 July 2007....
was adopted (due to priority), while the family retained the family name based on the junior synonym (Neositta). The most common species, the Varied Sittella
Varied Sittella
The Varied Sittella, Daphoenositta chrysoptera is a small, around 10–11 cm long, songbird native to Australia and New Guinea. It is also known as the Australian Nuthatch, Orange-winged Sittella and the Barkpecker. Its crown and head can be white, grey or black, and its body is either whitish...
, was once thought to represent several separate species, including five species in Australia, but in spite of considerable variation in plumage there are extensive zones of hybridization where the forms overlap (including an area of Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
where all five Australian subspecies exist), and are now thought to be a single species with eleven subspecies. The Black Sittella has three recognized subspecies.
Morphology
The two species of sittella are small passerinePasserine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
s which resemble nuthatch
Nuthatch
The nuthatches are a genus, Sitta, of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs...
es in appearance. The wings are long and broad, and when spread have clearly fingered tips. The family has a generally weak flight
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
, which may explain their inability to colonize suitable habitat on islands like Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
. The legs are short but they have long toes, but in spite of their lifestyle they show little adaptation towards climbing. They have short tails and are between 10–14 cm in length and 8-20 g in weight, with the Black Sittella tending to be slightly larger and heavier. The bill
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
is dagger shaped in the case of the Black Sittella and slightly upturned in the Varied Sittella. The plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
of the Black Sittella is mostly black with a red face; that of the Varied Sittella is more complex, with the numerous subspecies having many variations on the theme. The sexes of some subspecies have entirely black heads, other white, and others dark crowns and paler throats. The backs of most subspecies are grey with darker wings, and the undersides are generally streaked or white. All sittellas exhibit some sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in plumage.
Vocalizations
The calls of sittellas are generally simple and uncomplicated. Apparently the family has no need for long distance territorial calls, and the majority of calls are simple contact calls utilized to retain flock cohesion. The most commonly heard call is the chip contact call, although there also exists a rallying call (to call together the group), as well as begging calls issued by incubatingAvian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
females.
Habitat and behaviour
The sittellas are social and generally restless birds of scrub, forests and woodlands. In Australia they generally avoid only the dense rainforest, whereas in New Guinea this is the only habitat they inhabit, avoiding only lowland forest. They generally live at low densities, between 0.1 to 0.6 birds per hectare, and are sedentary. The sittellas are generally highly social, usually being found in groups of five or more individuals and only more rarely in pairs. Studies of Varied Sittellas in New South WalesNew South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
suggest that they live in clans of eight to twelve individuals and defend mutual territories
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
against other groups. Within the groups, mutual preening is common, and in the evening the groups roost communally as well. Birds traveling to the evening roosts do so at slightly different times, timing their arrival at 30-60 second intervals, presumably so as not to attract the attention of potential predators. Roost sites are usually high in trees on slightly inclined dead branches. All the birds in the group roost next to each other, touching, and facing the same direction. Amongst Australian birds Varied Sittellas are usually the first to arrive at roost sites in the evening and the last to leave in the morning, although they are not necessarily the first to sleep or last to wake. At the roost site the position occupied along the branch is generally not random; instead males generally adopt positions at the edges of the group whilst young birds tend to be found in the centre.
Diet and foraging
The principal component of the diet of sittellas are insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and other arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s. In one study in new South Wales adult beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s were the most common component of the Varied Sittella's diet, around 36%; particularly favoured were weevil
Weevil
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
s, ladybirds, leaf beetles Chrysomelidae) and click beetles (Elateridae). A further quarter of the diet was composed of spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s and true bugs. Also taken were beetle and moth larvae, grasshoppers, termites, wasps and bees. Ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s were taken relatively infrequently compared to other Australasian birds in similar niches. The proportion of any one item in the diet apparently varies geographically and seasonally, for example another study found that beetle larvae composed 87% of the diet. The diet of the Black Sittella has, like other aspects of its biology, been little studied, although the stomach contents of one that were examined contained caterpillars and spiders.
Sittellas forage on horizontal branches and the trunks of trees. Their foraging techniques has been described as hopping rapidly along the length of a horizontal branch, pausing briefly to peer for prey, occasionally hanging underneath the branch but usually on top of it. Most of the time is spent on branches rather than on the trunks. Birds on the trunks may travel upwards or downwards. Within the forest sittellas usually forage in the canopy. There are sexual differences in foraging, with males and females choosing to forage in slightly different microhabitats within the tree. Prey items are usually gleaned
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
directly from the bark, although in a few instances sittellas will sally
Hawking (birds)
Hawking is a feeding strategy in birds involving catching flying insects in the air. The term usually refers to a technique of sallying out from a perch to snatch an insect and then returning to the same or a different perch...
from the branch in order to snatch aerial prey. Having obtained prey sittellas will use their feet to hold it while they eat it, in a similar manner to parrot
Parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...
s, and will also use their feet in order to hold back strips of bark in order to pry underneath it. There have even been isolated reports of tool use in some populations of sittellas. Sticks were used to pry boring beetle larvae out of cavities, in a similar fashion to that of tool using Woodpecker Finch
Woodpecker Finch
The Woodpecker Finch, Camarhynchus pallidus, is a species of bird in the Darwin's finch group of the tanager family Thraupidae. Woodpecker Finches occur widely in the Galapagos Islands, from sea level to high elevations....
es of the Galapagos.
Breeding
Very little is known about the breeding of either of the two species of sittella in New Guinea, although Black Sittellas in breeding condition have been observed August and May, suggesting that they may either be biannual breeders or year round breeders. The Varied Sittella populations in Australia are cooperative breeders (and the group composition of Black Sittellas suggest they are too), and possibly have to be in order to be successful. There is some evidence that not only to groups cooperate in raising the young, not an uncommon strategy in birds, but have a plural breeding system, where more than one pair inside the group nest, and the group help raise both broods. There have even been instances of two females sharing a nest.95% of the nests found in a study in New South Wales were in stringybarks, particularly the species Eucalyptus macrorhycha. The nests were almost always located high in the tree. Nest construction took around 7 days, but lining and decorating the nest added a few days to this. Nest building duties were shared amongst the group, and the speed of construction depended on how many birds were involved. Nests are usually placed in the prong of two branches, and is a deep cup decorated in the bark of the tree it is built in, thereby camouflaging
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
it. Around 2-3 eggs are laid and incubated
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
by the breeding female (or females if two are sharing the nest) for 19–20 days. Whilst incubating the breeding female is fed by the breeding male and helpers. After hatching the female broods the young for a few days, and for up to two weeks at night. The chicks are fed for 19–20 days in the nest. After fledging
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
the chicks have a protracted period of parental care lasting up to 80 days, although 60 days is more usual.
Species
- Black SittellaBlack SittellaThe Black Sittella is a species of bird in the Neosittidae family.It is found in Indonesia and Papua New Guinea.-References:* BirdLife International 2004. . Downloaded on 25 July 2007....
, Daphoenositta miranda - Varied SittellaVaried SittellaThe Varied Sittella, Daphoenositta chrysoptera is a small, around 10–11 cm long, songbird native to Australia and New Guinea. It is also known as the Australian Nuthatch, Orange-winged Sittella and the Barkpecker. Its crown and head can be white, grey or black, and its body is either whitish...
, Daphoenositta chrysoptera- Papuan Sittella, Daphoenositta (chrysoptera) papuensis
External links
- Sittella videos on the Internet Bird Collection