Seasonal metabolic adjustments in an avian evolutionary relict restricted to mountain habitat

Seasonal variation in thermoregulatory capacity of three closely related Afrotropical Estrildid finches introduced to Europe

“…Instead, the downregulation of metabolic rates we observed fits with Lovegrove's (2000;2003) suggestion that, because of the generally less severe winters compared to the northern hemisphere, energy conservation would be the primary seasonal metabolic response in Afrotropical species, as lower maintenance energy requirements may increase winter survival (Maddocks and Geiser, 2000;Sharbaugh, 2001). Lower winter metabolic rates have been observed in multiple studies (e.g., Lindsay et al, 2009;Oswald et al, 2021;Smit and McKechnie, 2010). Similar findings have been published for captive-bred birds, such as rock kestrels (Falco rupicolus, Bush et al, 2008) and ring-necked parakeets (Thabethe et al, 2013).…”

Two independent approaches to assessing the constancy of evaporative water loss for birds under varying evaporative conditions

“…We observed increases in Cdry and consequently Cwet and VO2 in helox compared to air below the TNZ, occurring as a consequence of maintaining Tb constant under conditions of greater conductive heat loss in helium, as is typically observed for endotherms (e.g. Leon and Cook, 1960;Rosenmann and Morrison, 1974;Maddocks and Geiser, 1999;Oswald et al, 2021). Helox:air ratios for Cwet and VO2…”

“…To our knowledge helox has not been used to modify the evaporative environment for a bird, although it is routinely used to modify their thermal environment (e.g. Rosenmann and Morrison, 1974;Maddocks and Geiser, 1999;Oswald et al, 2021). Here we manipulate two components of Fick's law, the Δwvp and the diffusion coefficient to examine avian physiological control of EWL, using the mesic-habitat red-capped parrot (Purpureicephalus spurius) as a model.…”

Variable choice affects estimations of vulnerability to climate change

“…We used the Cape Rockjumper Chaetops frenatus ('Rockjumper') as a case study, a South African mountain-endemic with multiple life-history traits associated with vulnerability to climate change (see review in Pacifici et al 2015). These life-history traits include specialized habitat (restricted to the rare Mountain Fynbos biome) and restricted distribution (Lee & Barnard 2016), in addition to limited thermal tolerance (Oswald et al 2018b(Oswald et al , 2020b. Further, multiple studies have indicated additional aspects of Rockjumper ecology (specifically aspects of their nesting ecology) that make them vulnerable to high T air .…”

“…These life‐history traits include specialized habitat (restricted to the rare Mountain Fynbos biome) and restricted distribution (Lee & Barnard 2016), in addition to limited thermal tolerance (Oswald et al . 2018b, 2020b). Further, multiple studies have indicated additional aspects of Rockjumper ecology (specifically aspects of their nesting ecology) that make them vulnerable to high T air .…”