Transformation rate of natural ecosystems due to human activities has recently accelerated. Habitat fragmentation and biological invasions are major threats on biodiversity, as both are main processes resposible for populations and species declines. Despite a large body of literature focusing on the impact of fragmentation or biological invasions on species abundance and diversity, changes in ecological and evolutionary processes due to these two global changes remain poorly understood. This project aims to assess effects of fragmentation on several attributes of individuals.populations in a set of bird species showing a gradual specialization on forest habitat: (i) genetic diversity, due to demographic changes (smaller and more isolated populations), (ii) phenotypic quality of individuals (i.e. morphological, ornamental, immunological, physiological stress), and (iii) host-parasite interactions. In addition, we will test two recent hypothesis explaining the success of biological invasions (the so-called enemy release hypothesis and the hypothesis of different immune defence strategies in invaders), and investigate some of their consequences for native species. This project will be conducted on four territories: French Guiana, Guadeloupe, Martinique, and Montserrat. If these territories host a high endemic biodiversity, they are faced with real problems of forest loss and fragmentation as well as species introductions or invasions, mainly due to human activities and demographic growth. In addition to contribute to a better knowledge of ecological and evolutionary consequences of habitat fragmentation and biological invasions, the integrated approach of this project will produce valuable results for decision rules in nature and wildlife management frameworks. The participation of scientific partners and partners concretely involved in local conservation plans ensures the integration of research and management.