“…Here we experimentally tested whether the catabolic actions of high glucocorticoid concentrations can be counteracted by the effects of high nucleotide availability on telomere dynamics during growth using a wild avian model ( Parus major , great tit) with known effects of glucocorticoids on telomere length during a phase of rapid growth (Casagrande et al, 2020). The great tit is a common passerine found throughout Europe and Asia that has become a popular model species for ecological studies in a variety of research areas (Hau et al, 2022; Laine et al, 2016; Ouyang et al, 2012; Regan & Sheldon, 2023; Verhagen et al, 2020), including telomere length (Atema et al, 2021; Casagrande et al, 2020; Stier et al, 2016, 2021), mitochondrial (Casagrande et al, 2020; Nord et al, 2021) and gene expression studies (Lindner et al, 2021). Great tits have been found to exhibit substantial variation in telomere length (Atema et al, 2019), which has been linked to various life history traits and environmental factors (Casagrande et al, 2020; Stier et al, 2016, 2021).…”