This thesis aimed to detennine the interactions between social structure, genetic relationships and individual behaviour in a passerine bird, the vinous-throated parrotbill Paradoxornis webbianus. During the breeding season, nest dispersion was not random in tenns of distribution pattern or genetic relationship; more related males tended to breed closely together, especially in tre second laying peak. This relatedness was positively related to subsequent juvenile recruitment (Chapter 2). Local breeding density also influenced parental provisioning behaviour. When they had fewer neighbours, parents tended to coordinate their provisioning and the provisioning rate increased as local breeding density increased. Furthennore, parents breeding in the high local density appeared to meet more efficiently an experimental increase in chick demand (Chapter 3). However, parental provisioning behaviour was not affected by the extrapair paternity (EPP). Furthennore, the pattern of EPP (8% of offspring in 26% of broods) was not related to either local breeding density, breeding synchrony or male characteristic. However, most EPP (95%) occurred in the first laying peak and extrapair males were not always neighbouring males. In addition, there was no difference between within-pair and extrapair chicks in body condition and recruitment rate to their first winter flock (Chapter 4). Juveniles showed moderate rate of dispersal; about 40% of juveniles moved from natal flocks to neighbouring winter flocks and sibling coalitions including both sexes seemed to be the rule in these movements (Chapter 5). Once juveniles settled in their first winter flocks, they had a strong fidelity to the winter flocks throughout their life (Chapter 6). Overall, these demographic patterns generated significant genetic differentiation and a pattern of isolation by distance among winter flocks at a fine spatial scale and kin association within a winter flock. Despite these demographic and genetic circumstances, however, inbred mating was relatively infrequent (Chapter 6).