4.3. Conservation and management implications
Our study shows the negative impacts that alien species have on native bird communities, and also show that the functional and taxonomic diversity that alien species contribute does not compensate for that caused by the loss of native species. Urban and agricultural landscapes were more vulnerable to alien bird species invasion and, since we should also rely on these disturbed areas for biodiversity conservation (Batáry et al., 2020), future management strategies must prioritize habitat restoration in these areas (e.g. increasing urban green spaces, improving heterogeneity features in agricultural landscapes) to minimise the chances of establishment of alien species, and to increase the resistance of invaded communities. In our study region at least, this should include the classification of the near-ubiquitous Feral Pigeon as an alien species. Restoration strategies are well supported by the EU “Nature Restoration Law” (i.e. European Green Deal) and should be implemented along the impact assessment of alien birds on native bird communities, through functional and phylogenetic perspective, instead of focusing on a single alien species or diversity metric. Nonetheless, future study following this direction, would need to include also the three metrics of beta-diversity to have a better understanding of the role of alien species on biodiversity and ecosystem functioning ofinvaded communities (Soares et al., 2022).