Large reintroduction programs were instituted in Germany after the eagle-owl was deemed extinct in the country as a breeding species by the 1960s, as a result of a long period of heavy persecution. The largest reintroduction there occurred from the 1970s to the 1990s in the Eifel region, near the border with Belgium and Luxembourg. The success of this measure, consisting in more than a thousand eagle-owls being reintroduced at an average cost of US$1,500 per bird, is a subject of controversy. Those eagle-owls reintroduced in the Eifel region appear to be able to breed successfully, and enjoy nesting success comparable with wild eagle-owls from elsewhere in Europe. Mortality levels in the Eifel region, though, appear to remain quite high due to anthropogenic factors. Also, concerns exist about a lack of genetic diversity of the species in this part of Germany. Apparently, the German reintroductions have allowed eagle-owls to repopulate neighbouring parts of Europe, as the breeding populations now occurring in the Low Countries (the Netherlands, Belgium, and Luxembourg) are believed to be the result of influx from regions further to the east. Smaller reintroductions have been done elsewhere, and the current breeding population in Sweden is believed to be primarily the result of a series of reintroductions. Conversely to numerous threats and declines incurred by Eurasian eagle-owls, areas where human-dependent, non-native prey species such as brown rats ("Rattus norvegicus") and rock pigeons ("Columba livia") have flourished, have given the eagle-owls a primary food source and allowed them occupy regions where they were once marginalized or absent.