Wednesday, 27 August 2014

Knysna warbler

Bradypterus sylvaticus

Photo by Trevor Hardaker (Trevor and Margaret Hardaker)

Common name:
Knysna warbler (en); felosa-de-Knysna (pt); bouscarle de Knysna (fr); zarzalero del Knysna (es); Kapbuschsänger (de)

Order Passeriformes
Family Sylviidae

This species is endemic to South Africa, being restricted to a few coastal patches in the Eastern and Western Cape regions, namely the coast between Port St. Johns and Dwesa Nature Reserve, the Southern Cape, from Tsitsikamma to Sedgefield, the south slopes of the Langeberg Mountains, near Swellendam, and the east slopes of Table Mountain.

These birds are 14-15 cm long and weigh 16-21 g.

The Knysna warbler is mostly found in dense undergrowth of moist temperate forests and native fynbos dry scrublands, particularly along watercourses and drainage lines, but also uses non-native bramble Rubus sp. thickets and suburban areas.

They feed mainly on the ground, taking grasshoppers, insect larvae, spiders, slugs, worms, woodlice, cockroaches, earwigs, stick insects and crane flies.

Knysna warblers breed in August-December. They are monogamous, solitary nesters, and the female builds the nest alone. The nest is a thick-walled cup made of dry grass and narrow-bladed leaves, constructed on a platform of dead and dying leaves and lined with finer plant material. The female lays 2-3 pinkish white eggs with reddish speckles and spots, which she incubates alone for 16-19 days. The chicks are fed by both parents and fledge 12-14 days after hatching.

IUCN status - VU (Vulnerable)
This species has a relatively small and fragmented breeding range and the global population is estimated at 2.500-10.000 individuals. The overall population is suspected to be declining, with a decrease of over 50% in the Cape peninsula, and the extirpation of the population in Durban due to habitat loss and degradation. Habitat loss is mainly caused by the clearance of coastal forests, while the lack of a natural fire regime may also prove detrimental, as fynbos vegetation may eventually become replaced by forest and the understorey vegetation required for nesting may become more sparse. Removal of non-native brambles, the subject of several eradication campaigns, may ironically have negative impacts, and inbreeding depression may become a problem, particularly in the tiny, fragmented Eastern Cape sub-population.

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