Aim: Every year birds prepare for their migration journey, and understanding how this phenomenon is carried out allows us to infer whether human activities have influenced and modified the way in which the birds migrate. Many bird species perform long-distance movements to find sites with better conditions and optimize the use of resources during the annual cycle. These migration movements in birds have been studied using different methods, from mist nets, mark and recapture techniques, geolocators to document movements, and stable hydrogen isotopes. In this study, we used a genetic tool to create a graphic representation of the genetic variation across the species breeding range or genoscape as a reference to assess the connectivity of a migratory bird across its annual cycle. The advantage of the genoscape approach is that it allows us to identify distinct genetic units in the breeding range and then detect the migration pattern of those units through time and space.

Methods: We studied migration in the Painted Bunting (Passerina ciris) using genetic data from 386 individuals across the breeding range, 230 samples from 28 migration stopover locations, and 178 samples from 16 wintering locations. We also combined population and individual-level genetic assignments to breeding areas in order to study migratory connectivity patterns in greater depth.

Results: Our results show the existence of four main genetic groups within the species: Eastern, Southwestern, Central, and Louisiana. We also found that most of the individuals migrate during the fall towards Western Mexico and Central America and return to their breeding sites through the coastal plains of the Gulf of Mexico; the Louisiana breeding unit migrates to the Yucatan Peninsula and Central America, returning to their breeding sites in the spring through the coastal plains of the Gulf of Mexico. We found strong support for the existence of a Leap-frog migration pattern.

Main conclusions: We use a genoscape approach to investigate population structure and broad-scale migration patterns in the Painted Bunting. By screening samples from across the annual cycle, we can reveal clear patterns of population structure across the breeding range and provide strong support for the existence of leapfrog migration.