The grey-capped social weaver (Pseudonigrita arnaudi) 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.

The French naturalist Charles Lucien Bonaparte described the grey-capped social weaver as Nigrita arnaudi in 1850.

In 1903, the German zoologist Anton Reichenow assigned the species to his newly erected genus Pseudonigrita, because he considered P. arnaudi and P. cabanisi related to weaverbirds (Ploceidae), while the other species Nigrita bicolor, N. canicapillus, N. fusconota and N. luteifrons are negrofinches assigned to the estrildid finches.

[4] Based on a molecular phylogenetic study published in 2017 (which did not include P. cabanisi), the genus Pseudonigrita belongs to the group of sparrow weavers (subfamily Plocepasserinae), and is most closely related to Philetairus socius.

[8][7] The birds make long series of seven to ten high-pitched piercing squeaks, sounding like tseeer-tseeer-tseeer-....[7][10] The grey-capped social weaver is monogamous and breeds in colonies.

[11][12] In studies conducted in Kenya, some individuals were observed to rest in their nests year round, even outside the breeding periods, with two to five together.

[11][12] The grey-capped social weaver feeds on both grass seeds and insects, such as grasshoppers, beetles, termites and caterpillars.

Breeding takes place throughout the year, but there is a peak that enables the birds to make use of periods that food is plenty, such as between August and December in South Sudan and between March and May in eastern Africa.

Aggregated nests, thick walls and communal sleeping are considered adaptations against the cold nights in the arid distribution area of P.

Due to its social structure, P. arnaudi only starts breeding when in larger established groups (at least about ten pairs).

A specialised website suggest a ground cover of sand beneath the nesting branches, and grass elsewhere, inter-planted with a few very resistant shrubs.