Sociable weaver

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Sociable weaver
Sociable weaver (Philetairus socius).jpg
At Tswalu Kalahari Reserve, South Africa
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Ploceidae
Genus: Philetairus
A. Smith, 1837
Species:
P. socius
Binomial name
Philetairus socius
(Latham, 1790)
Philetairus socius distribution map.png
  range centred on the Kalahari, Namib and northern Karoo regions
An adult and juvenile bird in the Kgalagadi Transfrontier Park Philetairus socius (45062827395).jpg
An adult and juvenile bird in the Kgalagadi Transfrontier Park

The sociable weaver (Philetairus socius) is a species of bird in the weaver family, endemic to Southern Africa. [2] It is the only species in its genus Philetairus. It is found in South Africa, Namibia, and Botswana, [1] but its range is centered within the Northern Cape Province of South Africa. [3] The species builds large, compound, community nests, a rarity among birds. These nests are perhaps the most spectacular structure built by any bird. [4]

Contents

Taxonomy and systematics

The sociable weaver was first described by ornithologist John Latham in 1790. Alternative names include the common social weaver, common social-weaver, and social weaver. [5] Formerly, four subspecies were recognised, but the species is now considered monotypic. The sociable weaver is the only extant species in the genus Philetairus. [6]

Phylogeny

Based on a 2017 DNA-analysis, P. socius belongs to the group of sparrow weavers (subfamily Plocepasserinae) and is most related to the genus Pseudonigrita . These two genera are the sister group of the genus Plocepasser . The most basic genus of the subfamily is Sporopipes . [7] Provided that genera are correct clades, the following tree expresses current insights.

Ploceidae
Amblyospizinae

Amblyospiza albifrons

Plocepasserinae

Sporopipes

Plocepasser

Philetairus socius

Pseudonigrita

Bubalornithinae
Ploceinae

all other weaverbirds

Description

Measuring around 14 cm (5+12 in) in length, the sociable weaver has a black chin, black, barred flanks, and a scalloped back. [8] It typically weighs 26–32 g (15161+18 oz), and sexes are indistinguishable. [2]

Distribution and habitat

The species ranges across northwestern South Africa and southwest Botswana, and extending northwards across Namibia. [8] It is strongly associated with the arid savannas characteristic of the southern Kalahari region. [2] The presence of stiff grasses such as Stipagrostis ciliata (syn. Aristida ciliata) – an important nesting material – is an important determinant of its distribution. [3] The taller grasses and the fire-prone nature of the Northern and Central Kalahari regions may be a factor for the absence of the bird in those regions. [3] The area is semiarid with low and unpredictable rainfall occurring mostly in the summer. The population has not been quantified, but the birds are described as "common to abundant". [1]

Behaviour and ecology

Breeding

In the southern range of the weaver's habitat, breeding may occur any time of the year and is closely linked to rainfall. In the northern range, a discrete breeding season between December and August has been noted. [3] They may skip breeding during years when rainfall is low and a substantial number (sometimes over half) of birds in the colony may never breed in a given season. [2] Under typical conditions, weavers raise up to four broods per breeding cycle. Sociable weavers are known to assist in the care of younger siblings and unrelated hatchlings, and nearly all pairs are assisted by helpers. [2] A mating pair has been recorded as producing nine broods in a single season in response to repeated predation of its young. Unlike northern temperate passerine birds, which commence breeding within the first year of life, sociable weavers exhibit delayed-onset breeding, at sometimes up to two years of age. [2]

Nesting

Webervogelnst Auoblodge.JPG
The nesting colonies of the sociable weaver are amongst the largest bird-created structures.
Camel Thorn (Vachellia erioloba) with Sociable Weavers (Philetairus socius) collective nests ... (50981196923).jpg
Camel thorn with Sociable weavers' nests.

Sociable weavers construct permanent nests on trees and other tall objects. These nests are amongst the largest built by any bird, and are large enough to house over 100 pairs of birds, [9] containing several generations at a time. The nests are highly structured and provide birds with a more advantageous temperature relative to the outside. The central chambers retain heat and are used for nighttime roosting. The outer rooms are used for daytime shade, inside temperatures in occupied chambers have been found to vary over a range of only 7–8 °C (45–46 °F) while outside temperatures varied from 16 to 33.5 °C (60.8 to 92.3 °F). [10]

The nests consist of separate chambers, each of which is occupied by a pair (sometimes with offspring) and used to roost and breed. Nests are built around large and sturdy structures such as acacia trees or sometimes even telephone poles. The trees generally used for nest-building are Acacia erioloba , Boscia albitrunca , and Aloidendron dichotomum . The birds at Etosha National Park also use Colophospermum mopane trees for nesting. [3] Large nesting colonies can be active across many generations, sometimes over 199 years. [2] [11] The nest appears like a large haystack in the tree. If seen from below, entrances into the chambers may be seen, giving a honeycomb appearance. The entrances may be about 3 in (76 mm) wide and can be up to 10 in (250 mm) long. [11] Sharp sticks may be placed to deter predators from entering.[ citation needed ]

Sociable weaver nests form a habitat that is occupied by animals of many different taxa, including several other bird species, which use the nest in different ways, such as for breeding (as with the paradise finch and rosy-faced lovebird), roosting (as with the familiar chat and ashy tit), or as a platform for the nests of larger birds (such as owls, vultures, or falcons). [3] [11] Although most birds use sociable weaver nests commensally, cases of predation upon nestlings and animosity with the weavers has been reported of the pygmy falcon in some sites in Kimberley. [12]

Reptile species also use the nests. Snakes, especially Cape cobras and boomslangs, are the most common nest predators, often consuming all the eggs in all the chambers of a large nest. [10] Nest predation is often as high; in one study, 70% of the clutches laid were preyed upon. [2] In addition, Trachylepis spilogaster (Kalahari Tree Skink) associate with the nests. Trees with nests appear to host more skinks than trees without nests. [13] Additionally, these skinks have learned to eavesdrop on sociable weaver alarm calls to determine when a pygmy falcon, one of its main predators, is approaching. [14]

Nests built in electricity poles sometimes cause short circuits in the rainy season and can catch fire in the dry season. [15]

Some evidence indicates that cooperation in nest-building is driven by kin selection. [16] [17]

The bird droppings under the nesting colonies of the sociable weaver are used by scarab beetles. [18]


Diet

The sociable weaver is insectivorous, with insects comprising 80% of their diet. As an adaptation to living in the dry Kalahari Desert, where standing water is scarce, the sociable weaver obtains all of its water from its diet. It also feeds on seeds and other plant products. Foraging is predominantly on the ground, but also on bark and leaves of trees. [2]

Status

Populations of the sociable weavers increased during the 2010s, perhaps due to increased availability of nesting structures such as electricity pylons and other man-made structures. Most of its present distribution is unlikely to see any major man-made alteration and its future in these areas is secure. A gap seen in its distribution in the Northern Cape Province, north of the Ghaap Plateau is probably due to habitat alteration by clearance of Acacia. In other areas, encroachment due to overgrazing may also cause local extinction.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Ploceidae</span> Family of small passerine birds

Ploceidae is a family of small passerine birds, many of which are called weavers, weaverbirds, weaver finches, or bishops. These names come from the nests of intricately woven vegetation created by birds in this family. In most recent classifications, the Ploceidae are a clade that excludes some birds that have historically been placed in the family, such as some of the sparrows, but which includes the monotypic subfamily Amblyospizinae. The family is believed to have originated in the mid-Miocene. All birds of the Ploceidae are native to the Old World, most in Africa south of the Sahara, though a few live in tropical areas of Asia. A few species have been introduced outside their native range.

<span class="mw-page-title-main">Village weaver</span> Species of bird in the Ploceidae family

The village weaver , also known as the spotted-backed weaver or black-headed weaver, is a species of bird in the family Ploceidae found in much of sub-Saharan Africa. It has also been introduced to Portugal and Venezuela as well as to the islands of Hispaniola, Martinique, Puerto Rico, Mauritius and Réunion.

<span class="mw-page-title-main">Bird nest</span> Place where a bird broods its eggs

A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the elaborately woven hanging nest of the Montezuma oropendola or the village weaver—that is too restrictive a definition. For some species, a nest is simply a shallow depression made in sand; for others, it is the knot-hole left by a broken branch, a burrow dug into the ground, a chamber drilled into a tree, an enormous rotting pile of vegetation and earth, a shelf made of dried saliva or a mud dome with an entrance tunnel. The smallest bird nests are those of some hummingbirds, tiny cups which can be a mere 2 cm (0.8 in) across and 2–3 cm (0.8–1.2 in) high. At the other extreme, some nest mounds built by the dusky scrubfowl measure more than 11 m (36 ft) in diameter and stand nearly 5 m (16 ft) tall. The study of birds' nests is known as caliology.

<i>Poicephalus</i> Genus of birds

The genus Poicephalus belongs to the subfamily Psittacinae of the true parrots (Psittacidae) and comprises ten species of parrots native to various regions of the Afrotropical realm, which encompasses Sub-Saharan Africa, ranging from Senegal in the west, Ethiopia in the east, and to South Africa in the south. Like lovebirds (Agapornis) and vasa parrots (Coracopsis), the latter being endemic to Madagascar, the Poicephalus parrots are typical specimens of Afrotropical zoogeography. Several of the species exist in slightly different forms, or subspecies.

<span class="mw-page-title-main">Red-billed quelea</span> Small, migratory weaver bird native to Sub-Saharan Africa

The red-billed quelea, also known as the red-billed weaver or red-billed dioch, is a small—approximately 12 cm (4.7 in) long and weighing 15–26 g (0.53–0.92 oz)—migratory, sparrow-like bird of the weaver family, Ploceidae, native to Sub-Saharan Africa.

<span class="mw-page-title-main">Martial eagle</span> Species of bird

The martial eagle is a large eagle native to sub-Saharan Africa. It is the only member of the genus Polemaetus. A species of the booted eagle subfamily (Aquilinae), it has feathers over its tarsus. One of the largest and most powerful species of booted eagle, it is a fairly opportunistic predator that varies its prey selection between mammals, birds and reptiles. It is one of few eagle species known to hunt primarily from a high soar, by stooping on its quarry. This species, an inhabitant of wooded belts of otherwise open savanna, has shown a precipitous decline in the last few centuries due to a variety of factors. The martial eagle is one of the most persecuted bird species in the world. Due to its habit of taking livestock and regionally valuable game, local farmers and game wardens frequently seek to eliminate martial eagles, although the effect of eagles on this prey is almost certainly considerably exaggerated. Currently, the martial eagle is classified with the status of Endangered by the IUCN.

<span class="mw-page-title-main">Cape sparrow</span> Species of bird from southern Africa

The Cape sparrow, or mossie, is a bird of the sparrow family Passeridae found in southern Africa. A medium-sized sparrow at 14–16 centimetres (5.5–6.3 in), it has distinctive plumage, including large pale head stripes in both sexes. Its plumage is mostly grey, brown, and chestnut, and the male has some bold black and white markings on its head and neck. The species inhabits semi-arid savannah, cultivated areas, and towns, and ranges from the central coast of Angola to eastern South Africa and Eswatini. Three subspecies are distinguished in different parts of its range.

<i>Vachellia erioloba</i> Species of tree native to southern Africa

Vachellia erioloba, the camel thorn, also known as the giraffe thorn, mokala tree, or Kameeldoring in Afrikaans, still more commonly known as Acacia erioloba, is a tree of southern Africa in the family Fabaceae. Its preferred habitat is the deep dry sandy soils in parts of South Africa, Botswana, the western areas of Zimbabwe and Namibia. It is also native to Angola, south-west Mozambique, Zambia and Eswatini. The tree was first described by Ernst Heinrich Friedrich Meyer and Johann Franz Drège in 1836. The camel thorn is a protected tree in South Africa.

<span class="mw-page-title-main">Pygmy falcon</span> Species of bird

The African pygmy falcon —or simply pygmy falcon—is a diminutive raptor native to eastern and southern Africa. It is the sole species in its monotypic genus, Polihierax. The pygmy falcon is the smallest bird of prey on the African continent, and among the smallest raptors on earth; only the Asian falconets are smaller, weighing roughly 30-40 grams less and measuring about 5 cm shorter from head-to-tail.

<span class="mw-page-title-main">White-headed buffalo weaver</span> Species of bird

The white-headed buffalo weaver or white-faced buffalo-weaver is a species of passerine bird in the family Ploceidae native to East Africa. The buffalo part of its name derives from its habit of following the African buffalo, feeding on disturbed insects. Two subspecies are recognized.

<span class="mw-page-title-main">Cape weaver</span> Species of bird

The Cape weaver is a species of bird in the weaver family, Ploceidae, found in southern Africa.

<span class="mw-page-title-main">White-browed sparrow-weaver</span> Species of bird

The white-browed sparrow-weaver is a predominantly brown, sparrow-sized bird found throughout central and north-central southern Africa. It is found in groups of two to eleven individuals consisting of one breeding pair and other non-reproductive individuals.

<span class="mw-page-title-main">Bird colony</span> Large congregation of birds at a particular location

A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony. Colonial nesting birds include seabirds such as auks and albatrosses; wetland species such as herons; and a few passerines such as weaverbirds, certain blackbirds, and some swallows. A group of birds congregating for rest is called a communal roost. Evidence of colonial nesting has been found in non-neornithine birds (Enantiornithes), in sediments from the Late Cretaceous (Maastrichtian) of Romania.

<span class="mw-page-title-main">Wattled starling</span> Species of bird

The wattled starling is a nomadic resident bird in eastern and southern Africa. It is a species of grassland, open woodland, and cultivation.

<span class="mw-page-title-main">Cape starling</span> Species of bird

The Cape starling, also known as red-shouldered glossy-starling or Cape glossy starling, is a species of starling in the family Sturnidae. It is found in Southern Africa, where it lives in woodlands, bushveld and in suburbs.

<span class="mw-page-title-main">Grey-capped social weaver</span> Species of bird

The grey-capped social weaver is a sparrow-like liver-colored bird, with a pale grey crown, a dark grey bill, a whitish eye-ring, horn-colored legs, with some black in the wing and a light terminal band in the tail, that builds roofed nests made of straws, breeds in colonies in thorny Acacia trees, and feeds in groups gathering grass seeds and insects. Male and female have near identical plumage. DNA-analysis confirms it is part of the weaver family. It is found in Ethiopia, Kenya, Somalia, South Sudan, Sudan, Tanzania, and Uganda.

<i>Pseudonigrita</i> Genus of birds

Pseudonigrita is a genus of sparrow-like birds in the weaverbird family.

<span class="mw-page-title-main">Black-capped social weaver</span> Species of bird

The black-capped social weaver is a sparrow-like species of bird that has been assigned to the weaverbird family. It was originally described by Fisher and Reichenow, and later re-classified by the latter to the genus Pseudonigrita. Adults have a large black cap, ivory-colored bill, red eyes, brown back and wings, blackish-brown tail, white throat and underparts with a black midline, and dark horn-colored legs. It breeds in colonies and roofed nests with an entrance at the bottom in thorny trees such as acacias are constructed by the male from grass stems. It is found in parts of Ethiopia, Kenya, Somalia, and Tanzania. It is sometimes kept and bred in captivity.

Griffiniella heterogamia is a species of cockroach described by Heinrich Hugo Karny in 1908. Its known distribution is limited to the neighboring countries of Namibia and Botswana.

<i>Trachylepis spilogaster</i> Species of lizard

The Kalahari tree skink, or spiny mabuya, is a species of lizard in the skink family (Scincidae). The species is endemic to southern Africa, including Namibia, South Africa, western Botswana, and southern Angola.

References

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  14. Lowney, Anthony M; Flower, Tom P; Thomson, Robert L (Jun 2020). "Kalahari skinks eavesdrop on sociable weavers to manage predation by pygmy falcons and expand their realized niche presence". Behavioral Ecology. 31 (5): 1094–1102. doi: 10.1093/beheco/araa057 .
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  17. Leighton, Gavin M.; Echeverri, Sebastian; Heinrich, Dirk; Kolberg, Holger (2015-08-29). "Relatedness predicts multiple measures of investment in cooperative nest construction in sociable weavers". Behavioral Ecology and Sociobiology. 69 (11): 1835–1843. doi:10.1007/s00265-015-1996-8. ISSN   0340-5443. PMC   4693614 . PMID   26726282.
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