Data Zone
Justification of Red List category
This rarely seen species is classified as Vulnerable because it has a small, severely fragmented range and population, which are suspected to be undergoing a continuing decline owing to the loss and degradation of suitable habitat. In 1992, it was reported to be extremely numerous and under no threat, but recent information indicates otherwise.
Population justification
The paucity of atlas records strongly suggests that it is far rarer than previously thought, and probably numbers c.2,500 individuals. Some of the atlas data may, however, be misleading as the area between Durban and East London in the former Transkei was not well covered, giving the impression of a discontinuous distribution (N. Smith in litt. 2007, Taylor 2015), thus it is probably best placed in the band 2,500-9,999 mature individuals. This estimate equates to 3,750-14,999 individuals in total, rounded here to 3,500-15,000 individuals.
Trend justification
This species's population is suspected to be declining in line with habitat loss and degradation within its range. The likely rate of decline, however, has not been estimated.
Bradypterus sylvaticus is endemic to South Africa, being restricted to remnant forest patches in coastal regions of the Eastern and Western Cape. The population is highly fragmented, with four main isolated subpopulations. These are concentrated upon: 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. It also formerly occurred around Durban. Estimates of a population of hundreds of thousands in 1992 have been revised by the paucity of atlas records, which strongly suggest that it is far rarer, and probably numbers c.2,500 individuals. Some of the atlas data may, however, be misleading as the area between Durban and East London in the former Transkei was not well covered, giving the impression of a discontinuous distribution (N. Smith in litt. 2007, Taylor 2015). The small and most westerly population, located on the Cape Peninsula and now isolated by urbanisation, is believed to have halved in size since the late 1980s and may now number as few as 25-30 pairs (Pryke et al. 2010).
It typically occurs in thick, tangled vegetation along the banks of watercourses, or covering drainage lines in fynbos forest patches, or on the edges of afromontane forest. It occurs at the base of vegetation, and appears to frequently forage on the ground. It has adapted well to thickets of non-native brambles Rubus, and on the Cape Peninsula has retreated from natural, protected forests and colonised narrow belts of suburban riverine woodland, which may provide the dense understorey vegetation which appears critical for nesting (Pryke et al. 2010). Despite this, there are absolutely no records of range extension, suggesting that it either has very poor dispersal ability or very poor reproductive capacity. It is insectivorous (Visser and Hockey 2002); and it breeds between August and December when local invertebrate abundance is highest (Smith 2005, Pryke and Samways 2008).
Habitat loss, which resulted in the demise of the Durban population, is the primary threat and is largely a result of clearance of coastal forests. Burning of fire-breaks adjacent to forests is also causing habitat loss, and may prevent uncontrollable wildfires - like those recently on the Cape Peninsula - which could burn substantial areas of habitat. Conversely, the lack of a natural fire regime may also prove detrimental, as fynbos vegetaion may eventually become replaced by forest and the understorey vegetation required for nesting may become more sparse (Pryke et al. 2010). Removal of non-native brambles, the subject of several eradication campaigns, may ironically have negative impacts. Inbreeding depression may become a problem, particularly in the tiny, fragmented Eastern Cape subpopulation. Climate change may also affect this species (Şekercioğlu et al. 2012).
Conservation Actions Underway
The Table Mountain subpopulation falls within the boundaries of the Cape Peninsula Protected Natural Environment, but a large proportion occurs in suburbia. It is also frequently recorded in the Tsitsikamma National Park, and the scarce Eastern Cape population probably occurs at Dwesa and Cwebe Nature Reserves.
14-15 cm. Medium-sized, drab, brown warbler. Paler brown underparts. Pinkish-brown bill. Olive-brown legs. Similar spp. Difficult to separate from African Scrub-warbler B. barratti, which has spotted throat and longer tail. Voice Song is an accelerating trill.
Text account compilers
Ekstrom, J., Pilgrim, J., Symes, A. & Taylor, J.
Contributors
Smith, N.
Recommended citation
BirdLife International (2024) Species factsheet: Knysna Warbler Bradypterus sylvaticus. Downloaded from
https://datazone.birdlife.org/species/factsheet/knysna-warbler-bradypterus-sylvaticus on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.