Ringing and the study of mechanisms of migration

The ringing of birds has unveiled many mysteries of avian migration, notably routes and destinations, but has also contributed to the elucidation of migration mechanisms. The understanding of orientation and navigation mechanisms, stopover and fuelling strategies, and of migration strategies has gained much from the analyses of recoveries from ringed birds, and ringing and recapture approaches still make a major contribution to our understanding of migration. Detailed single-site studies could reveal internal and environmental factors governing stopover strategies, especially with sophisticated field experiments, but comparative multi-site approaches would be of considerable value to unravel migration strategies and carry-over effects between non-breeding and breeding periods. This is particularly important in view of the fact that long-distance migratory species are the ones with the most serious population declines.