While seasonal trends in testosterone levels are known from cross-cohort studies, data on testosterone inter-annual individual repeatability in wild birds are rare. Also, our understanding of hormonal age-dependent changes in testosterone levels is limited. We assessed plasma testosterone levels in 105 samples originating from 49 repeatedly captured free-living great tits (Parus major) sampled during the nesting to investigate their relative long-term repeatability and within-individual changes. Furthermore, we examined the inter-annual repeatability of condition-related traits (carotenoid- and melanin-based plumage ornamentation, ptilochronological feather growth rate, body mass, and haematological heterophil/lymphocyte ratio) and their relationships to testosterone levels. We show that testosterone levels are inter-annually repeatable in females, with a non-significant pattern in males, both in absolute values and individual ranks (indicating the maintenance of relative status in a population). In males, we found a quadratic dependence of testosterone levels on age, with a peak in midlife. In contrast, female testosterone levels showed no age-dependent trends. The inter-annual repeatability of condition-related traits ranged from zero to moderate and was mostly unrelated to plasma testosterone concentrations. However, males with elevated testosterone had significantly higher carotenoid-pigmented yellow plumage brightness, a trait presumably involved in mating. Showing inter-annual repeatability in testosterone levels, this research opens the way to further understanding the causes of variation in condition-related traits. Based on a longitudinal dataset, this study demonstrates that male plasma testosterone undergoes age-related changes that may regulate resource allocation. Our results thus suggest that, unlike females, male birds undergo hormonal senescence similar to mammals.

• Klíčová slova
• Ageing, Condition-related traits, Immunity, Ontogeny, Passerine birds, Repeatability, Senescence, Testosterone,
• MeSH
• divoká zvířata MeSH
• lidé MeSH
• Passeriformes * MeSH
• peří * MeSH
• rozmnožování MeSH
• testosteron MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• testosteron MeSH

Individuals reared in captivity are exposed to distinct selection pressures and evolutionary processes causing genetic and phenotypic divergence from wild populations. Consequently, restocking with farmed individuals may represent a considerable risk for the fitness of free-living populations. Supportive breeding on a massive scale has been established in many European countries to increase hunting opportunities for the most common duck species, the mallard (Anas platyrhynchos). It has previously been shown that mallards from breeding facilities differ genetically from wild populations and there is some indication of morphological differences. Using a common-garden experiment, we tested for differences in growth parameters between free-living populations and individuals from breeding facilities during the first 20 days of post-hatching development, a critical phase for survival in free-living populations. In addition, we compared their immune function by assessing two haematological parameters, H/L ratio and immature erythrocyte frequency, and plasma complement activity. Our data show that farmed ducklings exhibit larger morphological parameters, a higher growth rates, and higher complement activity. In haematological parameters, we observed high dynamic changes in duckling ontogeny in relation to their morphological parameters. In conclusion, our data demonstrate pronounced phenotype divergence between farmed and wild mallard populations that can be genetically determined. We argue that this divergence can directly or indirectly affect fitness of farmed individuals introduced to the breeding population as well as fitness of farmed x wild hybrids.

• MeSH
• chov MeSH
• divoká zvířata růst a vývoj   imunologie   MeSH
• farmy MeSH
• fenotyp MeSH
• kachny růst a vývoj   imunologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH