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The global population of Cape Rockjumper Chaetops frenatus is suspected to be in decline, approaching but not attaining the 30% threshold, which would qualify it as Vulnerable.
The Cape Rockjumper is endemic to the region (Cohen and Frauenknecht 2005) and restricted to Mountain Fynbos of the Western Cape and Eastern Cape provinces of South Africa (Fraser 1997). Its westernmost distribution is the Piketberg and Cederberg mountains, Western Cape, extending southwards and eastwards to Uitenhage, Eastern Cape (Fraser 1997). The species is absent from the Cape Peninsula despite suitable habitat and climate. Typically sedentary, there is no evidence for earlier suspected seasonal or altitudinal migrations (see Hockey et al. 1989), as families are found in the same territories all year round (Oswald and Lee unpubl. data). The species is separated by 100-150 km from the southernmost Drakensberg Rockjumper populations. The Cape Rockjumper is well represented in the IBA network, being found in all Western Cape mountain IBAs including the Kouga-Baviaanskloof complex, Swartberg, Outeniqua, Cederberg, Boland and Langeberg. Local habitat preference is for Rocky Mountain Fynbos on high slopes and ridges from sea level-2 300 masl (Lee and Barnard 2015). Preference for low vegetation cover explains absence along the southern Fynbos mountain ranges at lower altitudes where vegetation recovers quickly after fires and is often replaced by Afromontane forest (Lee and Barnard 2015). The AoO is given as 5 913 km2 based on presence in SABAP2 pentads (Lee and Barnard 2015). However, it is likely that this AoO measure is an underestimate, as rugged mountaintops are likely to be under-surveyed by atlas contributors, and that the AoO lies between 7 671 and 12 692 km2 (Lee and Barnard 2015). The latter values were calculated from ideal climate space models. The range of the Cape Rockjumper is the most highly fragmented of all endemic bird species in the Fynbos Biome (Lee and Barnard 2015).
The global population was estimated at 32 550 - 59 290 mature individuals by Lee and Barnard (2015). This estimate was obtained from lower and upper 95% confidence limits of density estimates multiplied by the EoO estimate of 58 126 km2. Confidence in the population estimate is medium.
The population estimate provided by Lee and Barnard (2015) is a baseline for this species. Their examination of the atlas data indicates a decline of 32% in the number of QDSs that the species was recorded in SABAP2 (38) to SABAP1 (56) with a 31% decline in reporting rates. The gap between SABAP1 and SABAP2 is in the region of 25 years. While the decrease in reporting rates and population decrease is not always linear it is assumed that the Cape Rockjumper population is undergoing a decline approaching 30% over a three-generation period (12.9 years). Confidence in this population trend estimate is low.
Projected range modelling, based on occurrence data from SABAP, has suggested this species is vulnerable to climate change with conditions in the Fynbos Biome predicted to get drier and hotter (Klausmeyer and Shaw 2009). Tight overlap between observed distribution and climate models, with mean annual temperature identified as a limiting factor, suggest this species is in decline due to vulnerability to climate change. Milne (2014) demonstrated that this species had the lowest physiological tolerance to high temperature of 12 species tested from the Fynbos Biome, and climate has been documented to be warming in its range (van Wilgen et al. 2015). However, the increased fire frequency and extent in the region (Kraaij et al. 2012) should otherwise benefit this species through increased availability of low-growth habitat of medium fire ages that this species prefers. It is likely that the mechanisms causing declines are linked to decreased foraging windows, as this species seeks shade and is inactive at high temperatures, coupled with a lower chick survival rate in high temperatures (Oswald and Lee unpubl. data). While habitat loss is a concern, causes of declines in reported ranges for Cape Rockjumper over the relatively short period between atlas projects (c. 25 years) are unlikely to be due to direct landscape transformation through agriculture (Lee and Barnard 2015) as most arable land in the Fynbos Biome had already been converted well before the first atlas period (Cowling et al. 1986). Cape Rockjumpers are susceptible to the loss of eggs from natural predation (Holmes et al. 2002), with Chacma Baboon Papio ursinus and Small Grey Mongoose Galerella pulverulenta eliciting alarm calls (P Barnard unpubl. data). Additional potential predators include Yellow Mongoose Cynictis penicillata, Striped Polecat Ictonyx striatus and White-necked Raven Corvus albicollis, as well as snakes including Boomslang Dispholidus typhus and Cape Cobra Naja nivea (Holmes et al. 2002). The expansion of invasive alien vegetation in high altitude areas may also represent a threat to the species' habitat through transformation and loss of habitat. These areas are more difficult to access and clear of invasive alien vegetation.
No species-specific conservation efforts are underway.
If this species is losing range due to increasing temperatures, site-specific conservation measures will prove especially challenging given the global nature of the threat. In the meantime, special attention should be paid to those populations potentially most at risk: isolated populations on the edge of the species' range and isolated populations throughout the range. Protected area expansion tools, such as Biodiversity Stewardship, should be used to gain formal protection for sites in critical corridors linking populations and critical habitat for this species, particularly for the most at risk populations. Additional conservation actions targeting habitat rehabilitation and protection in these mountain ranges should include alien vegetation eradication programmes in core habitat areas, and appropriate fire management. Such actions should also target key lowland corridors critical for connectivity and dispersal for this species.
* The following key research questions should be addressed:
* Is there evidence that Cape Rockjumpers can adapt physiologically with increasing temperatures?
* Are Cape Rockjumpers capable of using behavioural mechanisms and microclimates to offset increasing temperature? Do these behavioural and site selection strategies involve fitness tradeoffs?
* Are Cape Rockjumpers fledging rates adversely impacted with periods of warm temperatures?
* Are Cape Rockjumpers losing range due to increased predator or competitor activity?
* Is there evidence of genetic isolation of populations on the Fynbos islands in the Klein Karoo region, and does this have repercussions for their survival?
* What is the degree of genetic interchange and connection between populations of Cape Rockjumpers on different mountain chains across their range?
* Which populations represent source or sink populations for this species, and which lowland areas represent important corridors connecting populations?