Molting strategies of sapsuckers (Sphyrapicus): Effects of migration distance and age through the fourth and later plumage cycles (2024)

Woodpeckers have unique molting patterns in which primaries and rectrices are replaced during all molt cycles but primary coverts and secondaries can be retained during prebasic molts. Details concerning replacement sequences and extents, however, are poorly known. We investigated molt patterns in 5 sapsucker (Sphyrapicus) taxa through the examination of 675 museum specimens and additional analysis of digital images. Sapsuckers replace fewer feathers per molt than most other North American woodpeckers. All individuals in 3rd basic plumage (3rd/4th calendar years) and a proportion of sapsuckers in 4th basic plumage (4th/5th calendar years) can retain juvenile feathers and be aged, a novel finding among woodpeckers and most bird species with the exception of some owls and larger flighted birds. Primary coverts and secondaries are replaced convergently from the outsides of each feather tract and Staffelmauser-like molting patterns can ensue. Asynchronous replacement of primary coverts and primaries (which are replaced distally) is unique to woodpeckers and kingfishers and may indicate that it evolved prior to the split of Piciformes and Coraciiformes. Juvenile body feathering and secondary coverts are retained longer into the fall and winter in the more highly migratory Yellow-bellied (S. varius) and Red-naped (S. nuchalis) sapsuckers, adding crypsis for migration and due to time constraints for molting. The extent of prebasic molts correlated positively with migration distance, being greater in Yellow-bellied and Williamson’s (S. thyroides) sapsuckers and lowest in the nearly resident nominate subspecies of Red-breasted Sapsucker (S. ruber ruber), perhaps as related to the effects of solar exposure on an annual basis. Modeling of age structure through the 3rd and later basic plumages can inform conservation management related to salvage logging, climate-affected burn regimes, and the restoration of more favorable habitats.