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Urban areas provide breeding habitats for many species. However, animals raised in urban environments face challenges such as altered food availability and quality, pollution and pathogen assemblages. These challenges can affect physiological processes such as immune function and antioxidant defences which are important for fitness.Here, we explore how levels of urbanisation influence innate immune function, immune response to a mimicked bacterial infection and antioxidant capacity of nestling Black Sparrowhawks Accipiter melanoleucus in South Africa. We also explore the effect of timing of breeding and rainfall on physiology since both can influence the environmental condition under which nestlings are raised. Finally, because urbanisation can influence immune function indirectly, we use path analyses to explore direct and indirect associations between urbanisation, immune function and oxidative stress.We obtained measures of innate immunity (haptoglobin, lysis, agglutination, bactericidal capacity), indices of antioxidant capacity (total non‐enzymatic antioxidant capacity (tAOX) and total glutathione from nestlings from 2015 to 2019. In addition, in 2018 and 2019, we mimicked a bacterial infection by injecting nestlings with lipopolysaccharide and quantified their immune response.Increased urban cover was associated with an increase in lysis and a decrease in tAOX, but not with any of the other physiological parameters. Furthermore, except for agglutination, no physiological parameters were associated with the timing of breeding. Lysis and bactericidal capacity, however, varied consistently with the annual rainfall pattern. Immune response to a mimicked a bacterial infection decreased with urban cover but not with the timing of breeding nor rainfall. Our path analyses suggested indirect associations between urban cover and some immune indices via tAOX but not via the timing of breeding.Our results show that early‐life development in an urban environment is associated with variation in immune and antioxidant functions. The direct association between urbanisation and antioxidant capacity and their impact on immune function is likely an important factor mediating the impact of urbanisation on urban‐dwelling animals. Future studies should explore how these results are linked to fitness and whether the responses are adaptive for urban‐dwelling species. [ABSTRACT FROM AUTHOR]

Disassortative mating in color-polymorphic raptors is a proposed mechanism for the maintenance of color polymorphism in populations. Selection for such a mating system may occur if there are fitness advantages of mating with a contrasting morph. In the black sparrowhawk (Accipiter melanoleucus), mixed-morph pairs may have a selective advantage because they produce offspring that have higher survival rates. Two hypotheses, which may explain the mechanism, are the "avoidance-image" and "complementarity" hypotheses. The first suggests that, within a predator's territory, prey develop a search image for the more commonly encountered parental morph, for example, the male morph during incubation and brooding. Females of a contrasting morph to their partner would then have higher capture rates once they commence hunting in the later nestling phase. Thus, the "avoidance-image" hypothesis predicts higher provisioning rates for mixed-morph pairs. Alternatively, the "complementarity" hypothesis posits that different color morphs exploit different environmental conditions, allowing mixed-morph pairs to hunt under a wider range of conditions and predicts that food is delivered more consistently. We test these hypotheses using nest cameras to record prey delivery rates during the late nestling phase when both parents are hunting. We found support for the "complementarity" hypothesis, with mixed-morph pairs delivering food more consistently but not at a higher rate. This higher consistency in prey deliveries may explain the improved survival of the offspring of mixed-morph pairs and could, therefore, play a role in maintaining the stability of color polymorphism in this system. [ABSTRACT FROM AUTHOR]

Due to broad‐scale habitat loss, European Rollers (Coracias garrulus) have been decreasing in numbers rapidly during the 20th century in parts of their European distribution range. In Austria, as of 2017, only a completely isolated relict population of two breeding pairs and a few non‐breeders remained in Styria compared to about 270 pairs in the 1950s. In 2018, no breeders have been recorded. Since 2002, all nestlings and adult birds in Austria have been ringed. Given the small census size, combined with lack of immigration from other populations, genetic depletion seems likely. In the present study, mitochondrial control region sequence and microsatellite data based on blood samples of nestlings from recent years were collected and compared with museum samples from historical times (when Rollers were more common and widespread in Austria) and with birds across the distribution range to arrive at a first preliminary phylogeographic dataset for the species. The mitochondrial DNA showed a decrease in variation over time in Austria, eventually reaching monomorphism, while genetic diversity of 10 microsatellite loci was higher than expected and a change in genetic structuring through time was observed. These results indicate drift effects in this relict European Roller population caused by the fast population breakdown and small population size. Our phylogeographic analysis indicates a division into a European and an Asian group, roughly (but not exactly) in accordance with the two subspecies C. garrulus garrulus (Europe) and Coracias garrulus semenowi (Asia). The lack of substructuring in the European group along with the results from nuclear DNA markers show the Austrian Rollers to be part of a formerly continuous population and opens the way to restocking the present relict population with birds from Eastern Europe ("genetic rescue"). In this study, we present the first phylogeographic analysis for the species. On a broader scale, the European Roller is a species with high mitochondrial diversity and we distinguish two haplogroups that—with a few exceptions—reflect the classification of the two subspecies. Furthermore, we document the extinction of a relict European Roller population on a genetic level and a remarkable change of genetic structure within only a few generations. [ABSTRACT FROM AUTHOR]