Comparison of Offspring Growth Models in Atlantic Puffins <i>Fratercula arctica </i>

Growth of morphological traits in the offspring of many seabirds, including Atlantic Puffins Fratercula arctica, has typically been characterized by linear models despite displaying nonlinear patterns. We assessed the fit of six typical avian growth models to measurements of puffling mass, wing length, and tenth primary length. Across all three biometrics, the first- and second-best performing models were nonlinear (i.e., quadratic, logistic, extreme value function); these models were then used to generate separate growth curves for individual pufflings and extract easily interpretable and comparable parameter estimates. We recommend the reported models in future studies incorporating metrics of puffling growth and encourage the use of this methodology to explore nonlinear growth patterns across avian species.