Global diversity and adaptations of avian eggshell thickness indices

The amniote eggshell is a fundamental aspect of the embryo life-support system, protecting it from UV light, microbes and mechanical damage, while regulating gas exchange providing calcium for growth. thickness eggshells highly diverse across modern birds influences multiple functions, yet selective pressures driving have not been clearly identified. Here, we use global dataset avian indices 4260 (> 41%) species to assess trends in phylogeny, as these are strongly correlated with direct measures non-destructive sample. We analysed within phylogenetic framework relative importance climatic ecological explanations variation indices. distribution was found be primarily driven by relatedness, addition evolutionary processes that do match Brownian model evolution. Across birds, thicker were more prevalent (1) precocial young, (2) which exhibit scavenger-based diet, (3) feed on vertebrates or plants (excluding nectivores, seed fruit specialists) (4) breed open habitats. Thicker young probably enable higher rates removal advanced development. Excessive light transmission through shell damages developing embryos, too little can impede Eggs shaded habitats experience low exposure, thus thinner shells environments potentially increase shell. Overall, appears largely certain life-history traits linked growth rate, content their food, need mitigate excessive