Characterising Migratory Bird Assemblages in Understudied Regions by Integrating Radar and Citizen Science Data

Aim Migratory birds are declining globally. In regions where bird migration patterns remain poorly documented, comprehensive data and tools are needed to advance conservation efforts, support sustainable development and fulfil international biodiversity commitments. We aim to enhance understanding of migratory birds in understudied regions by quantifying migration dynamics and identifying overlooked species, using Eastern Australia as a model to demonstrate how multi‐method approaches can resolve uncertainties in migration patterns. Location Eastern Australia. Time Period 2018–2022. Major Taxa Studied Migratory birds. Methods We estimated migration phenology from eBird data in ten regions across Eastern Australia based on abundance changes of species throughout the year; we cross‐validated phenology estimates with those estimated from movement traffic measured by weather radar. We identified species with movement indicative of migration in each region and investigated their legal protection status in Australia. Results Radar and eBird data showed strong correlations in mid‐latitude regions (Victoria to Southeast Queensland), with median migration dates aligning closely, but weaker agreement in Tasmania and tropical Queensland. We identified 311 species with fluctuations of relative abundance suggestive of migration—far exceeding prior estimates—averaging > 90 migratory species per region. Eleven of 18 avian orders included migratory taxa, but legal protection varied: 70% of migratory Charadriiformes (e.g., internationally migrating shorebirds) were listed under national law. In contrast, Passeriformes, Psittaciformes, Anseriformes, primarily moving within Australia, have lower representation, with only 19% of identified Passeriformes formally protected. Main Conclusions This study uncovers a hidden diversity of migratory birds in Australia, many of which lack formal protections, especially short‐distance and intracontinental migrants. We recommend additional conservation measures and targeted surveys focused on these species to better assess threats and support nature‐positive development, including potentially impactful renewable energy projects. Our approach—combining radar and citizen science data—offers a replicable framework to document and protect poorly understood migratory systems globally.