Worldwide, the areas covered by native forests are declining while those of tree plantations are increasing. This has raised the question of whether tree plantations are able to preserve native forest species. In Argentina, the main native forests of the Pampas region, called talares, are endangered and their disappearance is imminent. Although exotic tree plantations are increasing in this region, their role in maintaining native bird diversity has not been studied in Argentine Pampas. We compared the bird community attributes and vegetation structure of talares native forest with those of tree plantations. Plantations exhibited markedly lower bird richness than talares, up to 80% lower, and all forest-dependent bird species were absent in plantations. Talares and plantations differed also in some aspects of vegetation structure, which usually are key determinants of bird abundance. Given the extreme importance of talares for forest birds, this bird community will be deeply affected if it continues to decline, as nearby plantations do not offer suitable habitat. In order to maintain the bird diversity of talares, and probably the diversity of other unstudied taxa related to them, we recommend management actions that should be applied urgently in these endangered forests of the Argentine Pampas.