Increasing temperatures increase the risk of reproductive failure in a near threatened alpine ground‐nesting bird, the Cape Rockjumper Chaetops frenatus

Abstract

A major cause of reproductive failure in birds is nest predation. Predation risk depends on predator type, as predators vary in their ecology and sensory modalities (e.g. visual vs. olfactory). Snakes (generally olfactory predators) are a major nest predator for small birds, with predation strongly associated with higher temperatures. We investigated nest survival in a ground‐nesting alpine species, the Cape Rockjumper Chaetops frenatus, endemic to alpine fynbos in southwestern South Africa. We collected 3 years of nest data, testing whether nest survival was related to (1) habitat stage (early post‐fire vs. late post‐fire habitat, ≤ 3 and > 3 years since fire respectively), (2) nest concealment and (3) temperature. We found that nests had better survival at lower temperatures, with snake predation (our main source of predation) increasing in higher temperatures.

Disentangling climatic and nest predator impact on reproductive output reveals adverse high‐temperature effects regardless of helper number in an arid‐region cooperative bird

“…This finding is consistent with negative effects of high temperatures on reproduction found in other arid-region vertebrates (e.g. common fiscals Lanius collaris [Cunningham et al 2013] predator-prey interactions as found here requires further scrutiny in other species (Oswald et al 2020).…”

Baked eggs: catastrophic heatwave‐induced reproductive failure in the desert‐adapted Zebra Finch (Taeniopygia guttata)

“…Therefore, the combination of the heart rate monitoring and continued presence of adults in many nests gives us confidence that the mortality of embryos was a direct effect of the heat, rather than an indirect effect caused first by parental desertion. An alternative reason for greater mortality with increasing temperature is higher levels of predation, as suggested by a recent study of a ground-nesting species in Africa, which found that reproductive failure was greater at higher ambient temperatures due to predation by snakes (Oswald et al 2020). We found little evidence of predation of the nests in our study.…”

Nest concealment is associated with reproductive traits across sympatric bird species

“…We present and compare the results of both phylogenetically controlled and conventional analyses in line with recommendations from the literature (Oswald et al, 2020;Schluter, 2000;Swanson & Bozinovic, 2011). We first used conventional analysis, fitting general linear models to response variables (e.g., clutch size, incubation period, nestling period, and nest success) as predicted by nest concealment, with body mass as a potential confounding effect.…”

“…often have no relation between nest concealment and nest success when their nests are accessible (Conover et al, 2010;Oswald et al, 2020).…”