Cape Rockjumper Chaetops frenatus Scientific name definitions
Version: 2.0 — Published May 17, 2021
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Priorities for Future Research
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Priorities for Future Research
Sensitivity to Climate Change
While there is still no single reason for the link between declining populations and warming temperatures (13), there are multiple areas where the Cape Rockjumper faces potential vulnerability. Physiologically, it faced potentially unsustainable water requirements at high temperatures, with juveniles particularly susceptible (3; 2). In addition, at high temperatures it may have as yet undemonstrated negative knock-on effects due to changes in foraging behavior; birds began foraging more often in shade than sun, and when doing so showed decreased foraging effort (4). For nestlings, higher temperatures (>23°C) resulted in reduced daily mass gain, likely from an increase in nestling water and energy demands (9). As well, there was greater probability of nest predation by snakes (mainly by boomslang Dispholydus typus) increasing at temperatures ca 25 °C (5).
Under predictive future temperature scenarios, the risk of reduced daily body mass and snake predation increased in frequency, duration, and geographic extent (8). For example, from the number of consecutive days where the Cape Rockjumper nestlings were exposed to reduce daily mass gain increased from <5 consecutive days over 22.4°C in 2014 to ca 18–35 consecutive days over 23.4°C by 2076 across the species range. There was also an increase in the risk of snake predation from 20–40 days over 25 °C in 2014 to 40–60 by 2076. A combined predictive map for both the consecutive number of days >22.4°C and number of days >25°C revealed increased the total number of days where rockjumpers are vulnerable to negative temperature effects increase from ca 15–35 to ca 40–80 days by 2076 (8).
Areas for Future Research
Further work is needed to isolate the exact reason for population declines that are associated with warming temperatures. There is no information on fledgling survivorship post-fledging. As such, there is no information on whether decreased mass gain at high temperatures has negative effects on their long-term survival, recruitment, and breeding success (9). Long-term studies on population persistence in mountain birds remains a gap in current ecological research (11).
Further study is needed to examine the implications of foraging in the sun and the possibility of missed opportunity costs when birds are using shaded microsites at high temperatures. A supplementary study for its behavior, examining foraging success and energy acquisition from different prey types, would allow for a better understanding of whether there are negative costs associated with birds using shade to try and cope with high temperature (4).
There also is still a general lack of knowledge in regard to its life history. We currently do not have information on adult mortality (natural or from predation) and dispersal. We also do not have complete information on their social group dynamics and cooperative breeding, which will require a more long-term project involving banding of all nestlings and genetic testing. It would also be useful to have a genetic study identifying the relationships between adults in territories and paternity (and maybe even maternity) of eggs.
Due to the prevalence of boomslang as a nest predator there should be a study on the biology and abundance of boomslangs in the fynbos. It is likely they are a major nest predator of all avian species in the fynbos, and so increasing temperature may also place the other endemics and near-endemics at risk. However, their distribution and population abundance throughout the fynbos is as yet unknown.