In the last half century some of Europe's key animal species have seen population rebounds, according the report "Wildlife Comeback in Europe," which was made public Thursday.

The report sought to identify the main forces behind the recovery of a select number of wildlife species in Europe with the hopes of learning important conservation information for the future.

Among the species that have made remarkable recoveries are the Eurasian beaver, the European bison and the white-tailed eagle.

The report, commissioned by the conservation group Rewilding Europe, examines how, why and where 37 select mammal and bird species have recovered in the last 50 years. It was authored by scientists from the Zoological Society of London, BirdLife International and the European Bird Census Council.

One of the main reasons behind this recovery is the legal protection of species and sites, while active reintroductions and re-stockings have also been important factors, the report states.

Legal protection status for the white-tailed eagle, one of the world's largest birds of prey, has allowed for an impressive recovery. Between 1800 and 1970, the bird faced extinction or significant decline in numbers in many countries. After the bird was listed as a protected species, the European population grew from 2,500 pairs in 1970 to 9,600 pairs in 2010, the report stated, adding that the birds have recolonized some of their former range in northern and central Europe.

"It is essential that we both celebrate and learn from major successes in conservation," said Jonathan Baillie, Director of Conservation at the Zoological Society of London. "This study helps us understand the interventions and conditions necessary for a broad range of species to experience similar recoveries."

The European bison was another success story. After going extinct in the wild in the early 20th century due to overhunting and habitat loss, a large-scale breeding and reintroduction program led the successful reestablishment of the bison in some areas of Europe. The total population in Poland and Belarus is now almost 3,000.

"Wildlife will bounce back if we allow it to -- this report shows that," said Frans Schepers, Managing Director of Rewilding Europe. "With continued and strong legal protection, active boosting of existing wildlife populations and reintroductions to bring back lost species, combined with an increasing tolerance towards wildlife, more species will surely follow."