Variation in the Extent of Preformative Molt in a Subtropical Asian Bird Community

Molt is an essential yet energy-demanding event in the avian life cycle. Most research on this topic has focused on birds in Europe and North America, leaving substantial knowledge gaps for species in other major regions. Here, we document the extent of the preformative molt (PF) from 62 passerine species across 18 families captured during a bird banding project in Southwest China. Among these species, 38 underwent a partial PF, four underwent an incomplete PF, and 20 underwent a complete PF. The relatively high number of species undergoing complete PF may reflect the year-round resource availability in this subtropical region and the absence of migration-induced energetic and time constraints on sedentary species. Both factors may result in greater investment in a more extensive molt. Furthermore, PF extent showed phylogenetic conservatism, with closely related species sharing similar molt extents. Our study addresses a major knowledge gap by documenting molt patterns of birds found in tropical and subtropical Asia and demonstrating that interspecific variation in PF extent is structured by phylogeny. We hope this work encourages ornithologists to continue documenting molt patterns to advance our understanding of avian molt, especially in regions where such knowledge remains limited.