The cooperative breeding hypothesis – originally developed with regard to primates – postulates that allo-parental care promotes social skills and pro-social behaviour due to increased social tolerance. However, to truly test the hypothesis it is paramount to also look at different animal orders and classes. Cooperative breeding is common in birds, with a particularly high incidence in corvids (41% of all corvid species show some degree of allo-parental care), which makes them the optimal target for investigating the cooperative breeding hypothesis in a group that is phylogenetically distant from primates. Therefore, here we investigated two closely related corvid species – ravens (Corvus corax, N=10) and crows (C. corone and cornix, N=9) – whose social systems differ in their extent of allo-parenting. While cooperative breeding is extremely rare in ravens, at least one population of crows shows extensive allo-parenting – a behavioural strategy that can also be induced in individuals transferred from different populations. In the current study both species were kept under identical conditions and subjected to regular behavioural observations and experiments over the course of more than two years. We found that the crows showed less socio-negative behaviour towards group members and behaved more tolerantly around monopolizable food sources than ravens. Further, manipulation of the same object by two or more birds at the same time was observed more frequently in crows than in ravens. Unlike crows however, ravens were tolerant towards specific individuals in their group from an early age on. These preliminary findings support the cooperative breeding hypothesis, but there additionally seems to be an effect of social bonding, which needs to be investigated – optimally in a larger set of species. To extend our investigation, we therefore compared our results to a more distantly related corvid species in which cooperative breeding is prevalent in all populations, the azure-winged magpie (Cyanopica cyana, N=9).