Many birds, ringed at great distances have been recaptured in the mist nets of GVC. A blackcap (Sylvia atricapilla) ringed in October 2015 in Antwerp (Belgium), was recaptured at Gaia Biological Park in January 2016. The blackcap is a resident species in Portugal, however the Portuguese populations are reinforced with migratory individuals from northern Europe during the winter. The distance between both points is an extraordinary 1500 km, but is probable this passerine has travelled much more, mainly if we consider that the flight is done twice a year (point A to point B and B to A), every year. Another example is a Eurasian reed warbler (Acrocephalus scirpaceus). Weighing only 9,4 g, the animal was recaptured by the group one month after being ringed in the Netherlands, at 1578 km of distance. Although these distances are considerable, they are far from the longest migration on the planet, the great migration of the Arctic tern (Sterna paradisaea). This species sees two summers a year, since it nests in the Arctic and travels later to Antarctica, but then returns to the extreme north, being the maximum distance recorded until today of 96,000 km. Information such as these, often obtained through ringing, allows the understanding of the migratory patterns of birds, which is crucial for species conservation strategies.