Thick-billed Weaver

The thick-billed weaver (Amblyospiza albifrons) is the only species in the genus Amblyospiza and one of the African weavers with the heaviest bills. Adults are about 18 cm long; females weigh around 36 g and males around 45 g. Adult males have a massive black bill, a white forehead and conspicuous white patches in the wings, while the rest of the plumage varies geographically from chestnut-brown to almost black. Females are brown above, heavily streaked below and have a yellowish bill.

Habitat use changes through the year. During breeding, thick-billed weavers are strongly associated with wetlands containing reeds, bulrushes, papyrus, sedges or rank grass, usually around standing or slow-moving water. Upright wetland stems are important not only as cover but as supports for the characteristic suspended nests.

Outside breeding the species is less tightly tied to marsh vegetation and also uses forest edges and clearings, plantations, cultivated areas and suburban wetlands. Local movements between these habitats allow birds to follow seasonal food and breeding conditions.

Despite its massive seed-cracking bill, the thick-billed weaver has an unusually broad diet. It eats hard-shelled seeds, including cultivated sunflower seeds, but also berries and other fruit, insects such as termites and a variety of other small invertebrates. Small frogs and aquatic snails have also been recorded.

Birds forage both on the ground and in vegetation and switch readily between feeding sites as local food availability changes. The powerful bill is used for hard seeds as well as softer fruit and animal prey and therefore does not restrict the species to one specialised feeding technique.

Thick-billed weavers are polygynous. A male may have as many as six females within his territory, and as many as three may nest there simultaneously. Apparently monogamous pairs nevertheless occur where breeding density is low. Colonies are often small, but one South African colony has held more than 100 nests. Breeding timing follows local rainfall and wetland conditions; in KwaZulu-Natal the egg-laying season lasts about 4.4 months and is centred on December.

The nest is distinctive: a compact globe woven from thin strips of reed and suspended between upright stems, usually 1–3 m above ground or water. The entrance is positioned near the top and is narrowed as construction progresses. The male builds the main outer structure, while the female completes and lines the nest cup.

Clutches average about three eggs. The female incubates alone for roughly 14–16 days and also performs most chick feeding by regurgitation, although males occasionally help. The young remain in the nest for about 18–20 days. Nest predators include white-browed coucals (Centropus superciliosus), introduced house crows (Corvus splendens) and Nile monitors (Varanus niloticus).

The thick-billed weaver is classified as least concern on the IUCN Red List. It has a very large sub-Saharan African range and remains locally common in suitable wetland and forest-edge habitat.

Drainage, clearing or degradation of reedbeds and other wetlands can remove local breeding sites, but no severe threat is known across the species' entire range. The species also uses some artificial and modified wetlands, which can provide additional breeding habitat where dense emergent vegetation is retained.