Liebers D. & Peter H.U. (1998) Intraspecific interactions in Jackdaws Corvus monedula: A field study combined with parentage analysis. ARDEA 86 (2): 221-235

As part of a long-term population study, we investigated the social and reproductive behaviour of Jackdaws in a colony with 70 nestboxes and about 180 birds near Jena, Germany. Three kinds of social relationships were recognized between breeding pairs and non-breeding birds: 'Followers' were associated with a breeding pair, functioning as potential replacement mates and behaving either neutrally or cooperatively with resident pairs. They were mostly young birds without breeding experience and of unknown sex. 'Visitors' were birds of either sex that did not complete, or had lost, their own clutch during incubation. They appeared to be of low social rank and interfered little with resident pairs. 'Usurpers' were also failed breeders, but they had lost their nestlings late during rearing. They remained paired and made aggressive attempts to take over nestboxes from resident pairs. A parentage analysis using multilocus DNA fingerprinting was carried out on 15 broods with 39 nestlings,mostly of pairs associated with followers. It revealed one extra-pair offspring and ruled out intraspecific brood parasitism and pseudo-parasitism