Under the weather: Corticosterone levels in wild nestlings are associated with ambient temperature and wind

Abstract

Animals time reprocluctive events to overlap with periocls of favorable environmental conditions. However, weathet conditions can be unpredictable. Young animals may be particularly susceptible to extreme weather during sensitive developmental periods. Here, we investigated the effects of adverse weather conditions on corticosterone levels {a hormone linked to the avian stress resp0nse) and body condition of wild nestling zebra finches (Taeniopygia guttata). We sowght to tease apart the direct versus indirect (i.e. parental) effects of weather on nestling physiology and condition by increasing parental work load with a clutch manipulation experiment. We Found that high temperatures were associated with lower levels of restraint-induced corticosterone and high wind speeds were associated with higher levels of baseline corticosterone. We found no associations between weathet and nestling bocly condition. However, clutch manipulation did affect body condition, with nestlings from experimentally enlarged clutches in worse condition compared to nestlings from experimentally reduced clutches. Our findings suggest that weather can dircctly affect wild nestlings via changes in corticostetonc Ievels. Further research is nceded to understand how changes in corticosterone Ievels affect phenotype and survival in wild nestlings. Understanding how developing animals respond to changes in environmental predictability and extreme weather is vital for unders~anding the p0tential for rapid adaptation in the face of changing climatic conditions. Animals are undcr sclcetion to brecd when cnvironmcntal mnditions are optimal (Visser and Both, 2005). However, weather can be unpredictable and have significant consequences on reproductive outcomes (e.g. Breuner and Hahn, 2003; Martin and Wiehe, 2004). In birds, rainfall, wind, and high or low temperatures can affect nestling development, morphology, body condition, and survival (Conrey et al., 2016; Oberg et al" 2015). Developing animals can be particularly sensitive to perturbations in their environment and developmental effects can have sustained effects on phenotype and fitness across Jifehistory stages and even generations (reviewed in Crino and Breuner, 2015; Monaghan and Haussmann, 2015; Schoech et al" 2011). Consequently, exposure to extreme weather conditions during development could have profound and potentia!Jy long-lasting effects on nestlings via direct and/or indirect mechanisms (i.e. parental effects). Understanding how developing birds respond to extreme weather conditions is of relevance for predicting how they wiJJ cope with rapidly changing global conditions. Although the effects of weather on nestling condition and survival have been we!J described (e.g. Christensen-Dalsgaard et al., 2018; Geiser et al., 2008; Sicurella et al., 2015), the physiological mechanisms that modulate such changes in wild birds are less well-known. The glucocorticoid hormone corticosterone (CORD is an important modulator of the physiological stress response (Romero, 2004) and is thought to be ...

High temperatures drive offspring mortality in a cooperatively breeding bird

“…89 Study site and system 90 Fieldwork was conducted at the Kuruman River Reserve (33 km 2 , KRR; 26°58'S, 91 21°49'E) in the southern Kalahari. Mean summer daily maximum temperatures at the study site, 92 from 1995-2015, averaged 34.7 ± 9.7°C and mean annual precipitation averaged 186.2 ± 93 87.5mm [49].…”

Egg size is unrelated to ambient temperature in the opportunistically breeding zebra finch

“…For example, a recent study has found that in the hottest parts of Australia, the most significant climatic constraint on avian reproduction is ambient temperature during the late spring and summer ). Furthermore, nestlings reared in hot conditions were found to attain a smaller adult body size than those raised in more moderate ambient temperatures, both observationally and experimentally (Andrew et al 2017), and have a lower stress response at high temperatures (Crino et al 2020). Adults, are likely to be physiologically challenged by temperatures that are close to, or exceed, around 35°C (Smit et al 2013, Funghi et al 2019, and so we might expect that egg size is negatively related to the ambient temperature during the laying period.…”

Direct and indirect effects of high temperatures on fledging success in a cooperatively breeding bird

“…Adverse weather conditions impair nestling development Imlay et al 2018) by causing a trade-off between devoting energy to thermoregulation or to growth (Dawson et al 2005). High temperatures constrain nestling growth (Cunningham et al 2013;Andreasson et al 2018), result in smaller nestlings overall (Salaberria et al 2014;Wada et al 2015;Rodriguez and Barba 2016), alter corticosterone levels (Newberry and Swanson 2018;Crino et al 2020) and reduce survival probabilities (Greño et al 2008;Zuckerberg et al 2018;Bourne, Cunningham, et al 2020a). Higher rainfall often has a positive effect on nestling development (Wiley and Ridley 2016) and survival (Skagen and Yackel Adams 2012;Mares et al 2017), at least in arid and semi-arid ecosystems (Cumming and Bernard 1997;Hidalgo Aranzamendi et al 2019), although see Morganti et al (2017) and Cox et al (2019) for effects of rainy weather in temperate environments.…”