Data and code from: Coastal shorebirds delay maturity more than inland ones

On the basis of data from summer and winter counts of shorebirds, recaptures, and long-term banding studies from non-breeding grounds in Australia, we assess the age of first return migration (as a measure of maturity) and provide a comparative analysis of its association with habitat use (contrasting coastal and inland wetland habitats). Age structure: We used data from long-term banding studies of migratory shorebirds to describe the age structure of shorebird populations in south-eastern and north-western Australia during the breeding period. We analysed data collected between 1980 and 2005. Austral summer and winter comparisons:  We obtained data on winter-summer ratios from two sources. Shorebirds at key Australian sites are counted annually (Birdlife Australia 2020) during the austral summer (usually in January) and austral winter (June or early July). We analysed data collected between 1980 and 2005, when counts were carried out for the Population Monitoring Project of the Australasian Wader Studies Group. Ecological and life‐history traits: We assembled species-specific data on ecological and life‐history traits that may associate with age at maturity: non-breeding habitat, migration distance, breeding latitude and body size. Each species was classified into one of three categories of non-breeding habitat in Australia: ‘inland’ for species typically occurring in freshwater or other inland habitats; ‘coastal’ for species typically restricted to coastal habitats; and ‘mixed’ for species that use both habitats. This dataset is used for the statistical analyses shown in the article and the R code provided here.

Methods
We infer estimates of the age of first return migration from non-breeding grounds in Australia using (1) long-term banding datasets in which retraps and morphologically aged birds provide information on the age structure of birds that skip return migration; (2) comparisons of Australian summer and winter counts. We then compiled species-specific summaries of ecological traits (non-breeding habitat use, migration distance, breeding latitude, body size) and tested these as predictors of the age of first return migration using phylogenetic generalized linear mixed models in a Bayesian framework. Both estimates of the age of first return migration and statistical analysess re described in the Methods section in the article.