Cape Rockjumper Chaetops frenatus Scientific name definitions
Version: 2.0 — Published May 17, 2021
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Demography and Populations
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Measures of Breeding Activity
Age at First Breeding
Birds can breed as early as 3-6 months of age (15), but generally thought to be at least one year old before breeding.
Intervals Between Breeding
Annual breeder, with main breeding season August-December. Birds may have less than 6 months between breeding seasons, as nests may still be active into January and new nest activity may begin in July (see Breeding: Phenology) (5 ; 15).
Clutch Size and Number of Clutches per Season
Clutches are usually 2, but can be 3 (see Breeding: Eggs) (5). It is difficult to determine the total number of clutches they may attempt in a single season due to the difficulty in finding nests (as may be inferred from the lack of re-nesting observed in the earlier study; 15). Timing would suggest a few nest attempts were not located in 2017 and 2018 (5). However, there were two territories where timing between nest attempts assured researchers they had not missed any attempts (less than 10 days between nest attempts): for these two territories, 5 nest attempts were recorded in a single season — in one territory the first nest attempt was successful (fledging in mid-September) and followed by 4 failed attempts, and in the other territory all 5 nest attempts were not successful (with their longest-lasting nest failing when nestlings were 12 days old) (5).
Number of Broods Normally Reared per Season
There is no evidence that birds re-nest after 2 successful broods in a single season, but birds sometimes continue nest attempts after a single successful brood (see above and Breeding: Phenology) (5).
Annual and Lifetime Reproductive Success
No published information on lifetime reproductive success.
Occasionally only one egg in a brood will hatch (see Breeding: Hatching). Hatch success varies among years, as does fledge success: 63% of eggs hatched in 1998 (n = 8 nests) with 44% of those eggs resulting in fledged young, 61%of eggs hatched in 1999 (n = 10 nests) with 19% of those resulting in fledged young, and 72% of all eggs laid hatched in 2000 (n = 12 nests) with 67% resulted in fledged young (15).
Experiences roughly 25% nest success (see Behavior: Predation and Demography: Causes of Mortality below). Rates of breeding success depend on several factors. There is no evidence for whether breeding success is related to nest attempt. Birds have greater breeding success associated with lower temperatures, and in territories that have more recently burned (5). With one exception (see Breeding: Parental Care: Nest Sanitation) the only reason for nestlings failing to fledge was nest predation (5).
Life Span and Survivorship
There is no information on lifespan. The oldest bird on record (a male) was banded at Blue Hill Nature Reserve as an adult in 2013, and was last observed in 2019 (although no attempts to re-sight this individual have been made since 2019), so at last observation was >7 years old (unpublished banding data).
Disease and Body Parasites
No mites or ticks have been recorded on any banded birds, despite being recorded on other birds caught nearby (such as Protea mites common on the Cape Sugarbird Promerops cafer; unpublished banding data).
Causes of Mortality
The only known instances of mortality due to exposure are from when nests with eggs were covered by snow (see Breeding: Incubation: Hardiness of Eggs).
Predation is the most common cause of nest failure: for known causes of predation, 64.3% were from snakes, and 22.2% were from mongooses (5; see Behavior: Predation for a full list of nest predators). Avian predators have not been recorded accessing nests. The chacma baboon (Papio ursinus) is likely to opportunistically depredate nests, but this has yet to be observed — in one instance baboons explored a nest, but this nest had 3 hours previously been depredated by a Boomslang (KNO, personal observations).
Direct Human Impacts
There is currently no information on human impacts on the Cape Rockjumper. Potential threats of human impact include mainly land-transformation for agriculture and land-use for recreation (see Conservation: Effects of Human Activity).
Population Spatial Metrics
Individuals within a specific group remain fairly close, maintaining distances of about 5–20 m (see Behavior: Social and Interspecific Behavior).
Territories are 10-20 hectares (25-50 acres) near Cape Town (15), although further east territories seem to be larger than 20 hectares (Movements and Migration: Dispersal and Site Fidelity). Territory size possibly is related to habitat conditions and population density.
For details on territorial behavior, see Behavior: Agonistic Behavior: Territorial Behavior.
Original population estimates suggested 90,000 individuals, but this was extrapolated using the entire Fynbos biome and not specifically mountain Fynbos. Birds occur at densities of 0.56–1.02 individuals/km2 within mountain Fynbos habitat (31). Their area of occupancy (specific to mountain Fynbos) was calculated to be 5,913 km2 and overall population 32,551–59,289 birds (31). Core habitats of Fynbos are well protected within a large network of provincial nature reserves (31).
The species is thought to be undergoing a moderately rapid decline, as implied by range and reporting rate reductions between Southern African Bird Atlas Projects 1 & 2 (SABAP). 2015 analysis found the range reduction between SABAPs was found to be 32% (SABAP1 1987-1992; SABAP2 2007-ongoing), with a reporting rate decline of 31% (31). In 2017 the range decline was reassessed at 25%, but with a reporting rate decline of 53.4% (12). The time between SABAPs also is greater than the three generation period for this species (ca 13 years), and so the rate of decline is assessed as being <30% over three generations, but it is suspected to approach this rate. Given that climate change may be having a particular impact on this species, this decline is suspected to continue into the future. The species is listed as Near Threatened (see Conservation and Management: Conservation Status).
There currently are no regulations in place specifically to protect the Cape Rockjumper. However, the uniqueness of its mountain Fynbos habitat has led to habitat protection throughout its distribution. Most notably, much of its habitat falls under the protection of CapeNature (for example, Anysberg Nature Reserve), the provincial nature authority for the Western Cape of South Africa, either directly or through stewardship programs (for example, Blue Hill Nature Reserve). Areas of mountain Fynbos are also protected under the Eastern Cape Parks and Tourism Association (for example, the Baviaanskloof World Heritage Site).
See Habitat for more information on mountain Fynbos.