El rol de las relaciones sociales en las hembras de paseriformes territoriales y coloniales

Tesis leída en la Facultad de Ciencias (Departamento de Ecología). Las ilustraciones de la presente tesis son una creación original de Jordi Jover (www.jordijover.com) que posee la propiedad intelectual de sus obras. Queda prohibida la reproducción o publicación total o parcial, así como la producción de obras derivadas sin la autorización expresa del autor.Explaining behavioural diversity and its origins is an historical challenge for biologists and the main focus of research for classical ethologyand for behavioural ecology. The main objective of this thesis is to increase our knowledge aboutthe influence of the social environment on reproduction, under an evolutionary perspective and through a largely experimental approach. This has been achieved by studying the effect of different types of social interactions between individuals ofthe same or opposite sex on different reproductive processes such as incubation or copulatory behaviourby emphasizing the role of females. We have used two model bird species with different social and reproductive systems, in captivity and in the wild: the pied flycatcher Ficedula hypoleuca (only studies in the wild), which is a territorial species, and the house sparrow, Passer domesticus, which is a gregarious species. This offers a broader perspective on passerines and ontheirstudy methodologies. Since nesting cavities are a scarce resource for hole nesters, there is strong competition for them during the breeding season.Their availability thus exertsa strong selective pressure during the incubation period. In the context of our first experiment (Chapter1), it was observed that a drastic reduction of the wing patch in pied flycatcherfemalesof the experimental treatment, caused higher values of vigilance against a simulated territorial intrusion by another female, decreasing their levels of incubation. Thus, wing patches may transmit information on female social status, mediating their interactions in contexts of intra-sexual competition. This would allow them to maintain high levels of incubationattendance by reducing the need for surveillance. Thus, these female plumage signals would be the result of social selection during breeding.In socially monogamous species, cases of extra-pair paternity (EPP) are frequent as the product of female copulations with other males rather than their mate. Although there are numerous studies on patterns of EPP, there is still no consensus on the reasons for its great variability between species and individuals.Through our second experiment (Chapter 2) in pied flycatchers we found that an experimental reduction in female wing area during the fertile period, which presumably caused a decrease in their flight ability, led to an increase in extra-pair paternity levels compared with control females. In addition, in a third experiment (Chapter 3) on the same species, it was observed that the increased mass of experimental females caused by an induced drastic reduction in nest building costs, produced an increase in EPP levels compared with control females. Considering that flight capacity (positively related to wing area and negatively associated with female body mass) is presumably linked to the capacityof females to avoidunwanted copulations by extra-pair males, our experimental results suggest that EPP can be the productof a sexual conflict which turns to the advantage ofextra-pair males in some situations.The social context is a key element during the reproductive period, since individuals establish relationships with conspecifics in order to feed, defend territories and mate. In Chapter 4 of this thesis, we studied therelative importance of the social environment in EPP for pied flycatchers by analyzing its individual inter-year repeatability. In addition, we studied the influence on EPP of individual features of territorial males and females such as age, plumage coloration and morphology, as well as contextual variables like breeding density or synchrony. The absence of inter-year repeatability in both males and females for EPP pointed out that variation in the social context in which sexual interactions occur may reduce the influence of individual traits.Personality affects different individual behaviours, which in turn have effects on fitness. For a trait to be considered part of personality, it must be consistent within individuals and differ among them. InChapter 5of thisthesis, we studied individual consistency in sociability traits of house sparrows. Sociability of individuals was measured through their interactions with others inside the socialnetwork of the population, in different contexts and at different time scales. The presence of individual repeatability (intra-individual consistency) in sociality measures makes them ideal personality traits. Finally, the relationship found in Chapter 6between sociality and the incidence of EPP in house sparrows, supports the idea that sociality can be considered part of a strategy for females to cope with their social environments and probably thereby increase their fitness.The relative importance of individual characteristics of both males and females on the one hand, and the influence of the social context on the other, should be considered as key factors in determining the resulting behavioural reproductive patterns.La presente Tesis Doctoral ha sido financiada por una beca predoctoral de Formación de Personal Investigador (FPI), BES-2014-0678, concedida por el Ministerio de Ciencia, Innovación y Universidades. Los estudios realizados han sido financiados por los fondos concedidos por el Ministerio de Ciencia, Innovación y Universidades a través de los proyectos CGL2013-48193-C3-3-P y CGL2017-83843-C2-1-P