A demonstration of the value of recapture data for informing moult phenology models for avian species with imperfect moult data

The Underhill-Zucchini model has revolutionised the study of moult in the context of birds' annual cycles, but, as for all statistical models, inferences are vulnerable to violations of model assumptions. In particular, the standard Underhill-Zucchini models for moult phenology are vulnerable to imperfect moult data arising, for example, from non-random sampling and/or the misclassification of non-moulting birds. Similarly, inference is challenging for species with dispersed moult periods (population-level moult extending beyond an annual cycle). Using ringing data from Cape Weavers Ploceus capensis and SAFRING data for Cape Sugarbirds Promerops cafer, we demonstrate how recent extensions to the Underhill-Zucchini framework can help the robust estimation of moult parameters in such situations, in particular when within-season recapture data is available.

Automated summary

The Underhill-Zucchini model has played an important role in the study of moult in birds' annual cycles, but the inferences are susceptible to imperfect moult data and violations of model assumptions. Recent extensions to the Underhill-Zucchini framework have been demonstrated to aid in the robust estimation of moult parameters, particularly when within-season recapture data is available.