Seasonal neuroplasticity of the song control system in tropical, flexibly, and opportunistically breeding birds.

The avian song control system is one of the primary models used to study neuroplasticity and neurogenesis in the adult vertebrate brain. A great deal of progress has been made in understanding the mechanisms controlling seasonal neuroplasticity of the song control system. However, relatively little work has been done to identify how prevalent this phenomenon is and if a diversity of environmental cues can regulate it. Photoperiod is the primary environmental cue used by mid- to high-latitude seasonally breeding birds to time growth of the song control system but many birds display flexible or opportunistic breeding patterns that are less reliant on photoperiodic cues. In addition, approximately 75% of birds are tropical and in only one such species has neuroplasticity of the song control system been studied. Our goal is to outline some of what is known and expand on the ways that studying tropical, flexibly, and opportunistically breeding birds can advance our understanding of plasticity in the song bird brain.