Substantial evidence for speciation due to natal philopatry has been gathered in studies of island-nesting albatross. Genetic difference is most often detected in microsatellites in mitochondrial DNA. Animals that spend much of their time at sea, but which return to land to breed exhibit high levels of natal philopatry and subsequent genetic drift between populations. Many species of albatross do not breed until 6–16 years of age. Between leaving their birth island, and their return, they fly hundreds of thousands of kilometres. High levels of natal philopatry have been demonstrated via mark-recapture data. For example, more than 99% of Laysan albatross ("Phoebastria immutabilis") in a study returned to exactly the same nest in consecutive years. Such site-specificity can lead to speciation, and has also been observed in the earliest stages of this process. The shy albatross ("Thalassarche cauta") was shown to have genetic differences in its microsatellites between three breeding colonies located off the coast of Tasmania. The differences are not currently sufficient to propose identifying the populations as distinct species; however divergence is likely to continue without outbreeding.