The slow-paced life history of many Neotropical birds (e.g., high survival and low fecundity) is hypothesized to increase lifetime fitness through investments in self-maintenance over reproduction relative to their temperate counterparts. Molt is a key investment in self-maintenance and is readily shaped by environmental conditions. As such, variation in molt strategies may be a key mechanism underlying life-history trade-offs and adaptation to new environments. Here, we review molt strategies from a diversity of lowland Neotropical landbirds and examine how variation in molt strategies, characterized by differences in molt insertions, timing, extent, and duration contribute to life-history variation and adaptation to diverse ecological conditions. In addition to our synthesis, we present a case study to examine the relationship between home range size and duration of the definitive prebasic molt of a well-studied subset of Amazonian landbirds. Our results suggest a connection between prolonged molt duration and larger home range size of small-to-medium-sized Amazonian landbirds. Our aims were to identify key gaps in our knowledge of Neotropical bird molt, to stimulate further comparative studies into the evolution of molt strategies, and to highlight how variation in molt strategies may be a key mechanism underlying life-history variation across latitudes.
LAY SUMMARY
Songbirds inhabiting Neotropical forests replace feathers, or molt, in a diversity of ways.
Our review found that closely related species exhibit similar molt strategies.
Because molt is an investment in self-maintenance and is readily shaped by a bird's environment, variation in molt likely reflects adaptation to different ecological niches.
To test whether molt reflects adaptation to a bird's ecological niche, we examined differences among molt duration, home range size, and wing length across multiple Amazonian bird species.
These results suggest that ant-following birds with small wings and large home ranges adaptively slowed molt duration to inhabit a new ecological niche.
Our findings demonstrate how variation in molt strategies may be a key mechanism underlying life-history variation and ecological differentiation across latitudes.
