Overview of EU Nature Protection Regime
The Birds Directive
The oldest and, together with the Habitats Directive, the most important piece of legislation protecting nature is the Birds Directive. 
The Birds Directive was adopted by the Member States in 1979 as a response to increasing concern about the decline in Europe's wild bird populations resulting from pollution, loss of habitats as well as unsustainable use. Its aim is to create a comprehensive scheme of protection for all wild bird species, their eggs, nests and habitats, naturally occurring in the European Union (Article 1 Birds Directive). This indicates that the Birds Directive does not apply to specimens of birds born and reared in captivity.
The most serious threats to the conservation of wild birds are loss of habitat and degradation, (Preamble (6) Birds Directive). The directive therefore places great emphasis on the protection of habitats for endangered as well as migratory species (Preamble (8) and Article 4 Birds Directive). The species involved are listed in Annex I of the Birds Directive.
The directive protects the sites and species. Site protection is ensured by the Member States, who must designate and protect the sites for endangered and migrating birds. Species protection, however, protects all European birds from intentional killing, capture and significant disturbance and therefore the Member State’s responsibility even extends to species living outside their territory. Furthermore the Birds Directive promotes research to underpin the protection, management and use of all species of birds covered by the Directive (Annex V).
Source: Joseph van der Stegen, DG Environment, European Commission