A study coordinated by the Doñana Biological Station (EBD-CSIC) and the Pyrenean Institute of Ecology (IPE-CSIC) shows that the physical attractiveness of birds does not determine their reproductive success.
The results, contrary to expectations, demonstrated that the density of mates and competitors did not influence whether the most attractive males had more or fewer descendants .

Telomere length is a marker of cellular senescence that relates to different components of individual fitness. Oxidative stress is often claimed as a main proximate factor contributing to telomere attrition, although the importance of this factor in vivo has recently been challenged.

Dispersal movements of animals may be jointly influenced by the phenotype of dispersers and the environmental and social conditions in the source and destination areas. Dispersal is often strongly influenced by population density, but the presence of conspecifics may affect dispersal motivation differentially depending on the social tolerance or size-based dominance of individuals, thus generating phenotypic differences between dispersers and non-dispersers. In this study, a pied flycatcher...

In this study, a cross-fostering experiment was conducted between an oakwood and an adjacent conifer plantation to investigate the role of early experience and genetic background in habitat selection in a pied flycatcher (Ficedula hypoleuca) population.