Summary from a study concerning turkey:
In the past centuries attempts have been made to introduce various of the six subspecies of wild turkeys inhabiting North America into practically all countries in Europe. Particularly many trials were conducted during the period 1880 to ca. 1914. Except for the trial in Grafenegg/Lower Austria which lasted from 1880–1945 all others were of short duration. At the end of World War II there were no occurrences of wild turkeys in Germany nor in Austria.
In the Federal Republic of Germany including the former German Democratic Republic 11 naturalization trials were conducted during the period between 1953–1993. Some of these introductions were to be permanently established and others existed for only a short duration. Five trials were conducted in North Rhine-Westphalia (Bönninghardt, Senne, Kottenforst, Mindenerwald, Ochtentrup); two each were in Rhineland-Palatinate (Bassenheimer-Wald, Taunus) and Lower Saxony (Gartow, Springe) respectively; and one each in Baden-Württemberg (Schutterwald) and Schleswig-Holstein (Wacken). At the present time (1993) only four occurrences including a total of 150 turkeys (spring populations) are still extant. All of these occurrences are endangered due to the low number of birds. This is especially true for the trial at Bassenheimer-Wald.
The cause of the population declines in the naturalization trials despite early success during the 1980's is not lack of suitable habitat, but rather high predator pressure, especially from foxes, hawks, and wild boar. Of interest is the fact that the trial conducted in Taunus using wild turkeys caught in and imported from North America had no better success than attempts using birds raised in flight cages.
Since many free-living wild species at present show signs of isolation, the four still extant occurrences of wild turkeys in Germany should continue to be under scientific observation. The wild turkeys present the ideal possibility to conduct population ecological investigations and also represent an attractive game species.