Plocepasser mahali

Geographic Range

White-browed sparrow weavers Plocepasser mahali are widely distributed in semi-arid regions of Africa, primarily in dry acacia and mopane woodland areas. They range from north-eastern to southern Africa where they maintain year-round territories. They are a common resident in Zimbabwe and Zambia and are also found in Botswana, Ethiopia, Kenya, Mozambique, South Africa, Angola, Namibia, Tanzania, Somalia, Sudan, and Malawi.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

The habitat of Plocepasser mahali is commonly associated with Acacia thorn trees in which they nest and roost. Although Acacia trees occur across a range of habitats, P. mahali are found primarily in open, semi-arid regions where these trees occur. On the edge of their range, they are found near dense vegetation, but typically are found in areas with sparse ground cover. Mopane woodland, dry bush, and thornveld support populations of white-browed sparrow weavers. Populations also inhabit human-disturbed environments like open golf-courses or along transitional habitat edges.

• Habitat Regions
• tropical tropical

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• scrub forest scrub forest

Physical Description

White-browed sparrow weavers are approximately 17-19 cm in length. They are light brown above and have brown wings with white wing bars. The head fades from dark brown to light brown and has a broad white eyebrow stripe. All underparts are white and sometimes have dark markings near sides of the breast. A white rump and dark brown tail are visible in flight. Adult females and males are similar in appearance, but can be distinguished by beak color with males having black bills and females having horn-colored bills. Additionally, dominant males have larger wing length and body mass than dominant females. White-browed sparrow weavers plumage does not vary during the mating season.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

White-browed sparrow weavers form cooperatively breeding groups composed of 9-14 birds, in which there is one dominant breeding pair and subordinates. A single dominant female in a group lays and incubates eggs while a dominant male exhibits intense mate guarding against subordinate males that attempt copulation. Subordinate females show no signs of reproductive attempts, and have never been observed to lay eggs.Cooperative groups nest in thorn-trees and build both roost nests and breeding nests, the latter characterized by one entrance rather than two. Their nests are large, rounded structures compactly made of dry grass stems, with 3-32 nests built in a colony. All members of a colony contribute to building the nests. Nests are often concentrated onto one side of a nest tree. A number of hypotheses have been proposed to explain this phenomenon including the effects of sunshine heat loading, ultraviolet radiation, and wind exposure and direction. Ferguson and Siegfried (1989) found wind-direction to be the most important factor influencing nest placement, as strong winds caused rapid deterioration of nests when placed in direction of prevailing winds.

• Mating System
• cooperative breeder cooperative breeder

Clutch size is typically two eggs, but one to four egg clutches can occur. Eggs are cream-colored or pinkish white with pink-brown blotches. Incubation period is 14-19 days and hatching of chicks occurs typically within three days of each other.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Subordinate group members contribute to nest building, defense, and caring of young of a single dominant breeding pair, often helping rear the young of the dominant bird that reared them.

Lifespan/Longevity

The typical lifespan of P. mahali ranges from two to five years.

Behavior

White-browed sparrow weavers live year-round in territorial colonies and remain within close range of their nest tree. Groups typically forage together in flocks on the ground and engage in group defense of their colony. They roost together at night, but sleep one bird to a nest, unlike other weaver birds who sleep together in a nest. Dominant birds display more acts of aggressive behavior within their group, such as displacing or chasing other members.

• Key Behaviors
• arboreal arboreal
• motile motile
• sedentary sedentary
• territorial territorial
• social social

Communication and Perception

White-browed sparrow weavers have a unique vocalization and communication system within their small cooperative groups of a dominant breeding pair and non-breeding males and females. All males and females in a group participate in a chorus of chattering, chirping medleys which function as territorial calls. Group-living and chorus song also allow for increased vigilance behavior during foraging, using combinations of calls as warnings. While duet songs are mainly produced by the dominant pair, all subordinates can participate in duet songs. Males and females equally contribute to duet songs and have similar syllable repertoires. The dominant male in a cooperative group has an additional unique solo song consisting of 67.0 ± 4.0 syllables which functions as a mating call.

• Communication Channels
• acoustic acoustic

• Other Communication Modes
• duets duets
• choruses choruses

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

White-browed sparrow weavers feed on the ground in small flocks, scattered pairs, or individually near their nesting tree. Plants and ground insects are important sources of food for white-browed sparrow weavers. Because they commonly live near disturbed habitats, cultivated plants are a large part of their diet, such as maize and wheat seeds. Wild seeds of signalgrass g. Urochloa , Stipagrostis uniplumis , Limeum fenestratum , and Celosia . were found to be the most common plants in their diet. Termites, weevils, and ants are the most common insects in their diet with termites eaten in the greatest abundance. Birds have been observed digging into tunnels on the ground to access termites.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
• herbivore herbivore
  • granivore granivore

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts

Predation

Known avian predators of the white-browed sparrow weaver include hawks, kites, owls, and ravens, and more specifically the gabar goshawk and African black kite . When a predator is present, adults will cease foraging and feeding, and voice alarm-chattering as a group. This can delay foraging and feeding for prolonged periods, as hawks will hide in nearby trees waiting up to an hour for an emergence of a bird from their nest. Hawks are also thought to tear open the roof of the nests to access birds. Snakes, vervet monkeys , and humans also induce alarm calling in a colony, but the birds do not take shelter like they do in the presence of a hawk. Nesting in thorn-trees is thought to serve as a deterrent to predators. Additionally, two entrances in their roost nests allows for greater escape access in a predator encounter.

Ecosystem Roles

White-browed sparrow weavers' nests are sometimes utilized by other species for breeding purposes, including pygmy falcons and rosy-faced lovebirds . Other species are known to use the nests as roost sites at night including grey tits , black-collared barbets , red-headed finches , scaly-feathered finches , and black-cheeked waxbills . White-browed sparrow weavers also serve as prey for certain birds, reptiles, and mammals.

Economic Importance for Humans: Positive

There are no reported positive effects of white-browed sparrow weavers on humans, except that they serve as a species for research on cooperative breeding birds.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

White-browed sparrow weavers can be agricultural pests in human disturbed habitats such as open, cultivated land where they feed heavily on crops of maize and wheat.

• Negative Impacts
• crop pest

Conservation Status

White-browed sparrow weavers have an extremely large range across southern Africa. Although their population has not been quantified, they are common and abundant within their range. White-browed sparrow weavers are able to utilize human disturbed habitats, it is therefore likely that human development will not negatively impact the species. The conservation status of the species is listed as least concern according to IUCN Red List.

Additional Links

Encyclopedia of Life

Contributors

Clare Fastiggi (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Collias, N., E. Collias. 1978. Cooperative Breeding Behavior in the White-Browed Sparrow Weaver. The Auk , 95/3: 472-484.

Collias, N., E. Collias. 1977. Weaverbird Nest Aggregation and Evolution of the Compound Nest. The Auk , 94/1: 50-64.

Ferguson, J., W. Siegfried. 1989. Environmental Factors Influencing Nest-Site Preference in White-Browed Sparrow-Weavers (Plocepasser mahali). The Condor , 91/1: 100-107.

Ferguson, J. 1986. Ecological factors affecting social behavior of white-browed sparrow weavers Plocepasser mahali . Johannesburg, South Africa: University of Witswaterland.

Ferguson, J. 1988. Geographic variation in social behaviour of white-browed sparrow-weavers, Plocepasser mahali. African Zoology , 23/1: 1-6.

Ferguson, J. 2010. Vigilance Behaviour in White-browed Sparrow-weavers Plocepasser mahali. Ethology , 76/3: 223-235.

Harrison, X., J. York, D. Cram, A. Young. 2013. Extra-group mating increases inbreeding risk in a cooperatively breeding bird. Molecular Ecology , 22/22: 5700-5715.

Leitner, S., P. Mundy, C. Voigt. 2009. Morphometrics of White-browed Sparrow-Weavers Plocepasser mahali in south-western Zimbabwe. Ostrich , 80/2: 99-102.

Lewis, D. 1982. Dispersal in a Population of White-Browed Sparrow Weavers. The Condor , 84/3: 306-312.

Mackworth-Praed, C., C. Grant. 1963. Harlow, United Kingdom: Longmans, Green and Co LTD.

Stevenson, T., J. Fanshawe. 2005. Birds of East Africa: Kenya, Tanzania, Uganda, Rwanda, and Burundi . Princeton, N.J: Princeton University Press.

Voigt, C., J. Eppel, P. Mundy. 2012. Living Near Human Settlement-Habitat Use By White-Browed Sparrow-Weavers On A Golf Course. Honeyguide , 58/1: 17-21.

Voigt, C., S. Leitner, M. Gahr. 2006. Repertoire and Structure of Duet and Solo Songs in Cooperatively Breeding White-Browed Sparrow Weavers. Behavoir , 143/2: 159-182.

York, J., A. Radford, T. Groothuis, A. Young. 2016. Dominant male song performance reflects current immune state in a cooperatively breeding songbird. Ecology and Evolution , 6/4: 1008-1015.

International Union for Conservation of Nature. 2016. "Plocepasser mahali: BirdLife International: The IUCN Red List of Threatened Species 2016: e.T22718690A94592396" (On-line). Accessed April 11, 2018 at http://www.iucnredlist.org/details/22718690/0 .