Molt patterns, aging, and sexing criteria for ten temperate Neotropic bird species: an important resource for bird monitoring programs

Within avian biology, molt represents a crucial and energetically demanding process that involves the periodic replacement of plumage. A comprehensive understanding of molt patterns enables bird monitoring programs and conservation efforts. We analyzed the timing, duration, and extent of molt for 10 bird species in central Argentina, and established sex and age determination criteria based on molt patterns and morphometric measurements. We confirmed the center of Argentina as molting grounds for nine species, except Elaenia albiceps , despite 69 captures over 51 months. Our analysis revealed distinct molting seasons, with eight species exhibiting a temporally restricted molt toward the end of summer following breeding, while Columbina picui displayed a prolonged molting season. The preformative molt extent varied from partial to complete for eight species, but incomplete to complete for Sporophila caerulescens and C. picui . Wing chord was significantly longer in males than in females in all 10 study species but was not entirely reliable as a sexing criterion. We present the first description of molt patterns for birds in central Argentina, which addresses the knowledge gap in the natural history of southern South America bird species. The identified patterns will facilitate field-based age and sex determination, thereby enhancing bird monitoring programs.