Global navigation in migratory birds: tracks, strategies, and interactions between mechanisms

The advancing development of tracking techniques has led to fascinating new insights into avian migration, documenting the immense diversity, complexity, and flexibility of this phenomenon. Tracking studies so far have confirmed many findings from ringing recoveries and cage studies, for example, the change from flying innate compass courses in the first migration to true navigation, as experienced migrants head toward familiar goals. First attempts to analyze the navigational mechanisms by tracking manipulated migrants indicate strong parallels to those of homing pigeons. Findings suggesting that the magnetic compass of migrants is regularly calibrated by the pattern of polarized light could not be replicated with a number of other birds, pointing out differences between species and possibly region and phases of migration. Tracking has become a valuable tool, complimenting traditional methods by documenting migration behavior in the wild; whether it can be used to further unveil the navigational mechanisms of migrants and the factor used remains an open question.

► Tracks of avian migrants reveal a great diversity of migratory behavior. ► First-time migrants reach their wintering area by innate directional information. ► Experienced migrants navigate toward their goals and compensate for displacements. ► The mechanisms employed by migrants appear similar to those used by homing pigeons. ► Calibration processes between compass mechanisms vary between species and regions.