Behaviours whose primary function is not signalling can convey information that other individuals can use to make relevant decisions. In cooperatively breeding vertebrates, feeding young that are not own offspring typically provides indirect fitness payoffs, but group members may also benefit directly by advertising their contribution to their social mates, to either increase their ‘social prestige’ or obtain a share of territory commodities (‘pay to stay’). Evidence of such a signalling component of brood provisioning, however, remains controversial. In the cooperative society of carrion crows, Corvus corone, male subordinates have little chance of independent reproduction and do the best of a bad job by helping to raise the current brood. The value of future reproduction is instead higher for subordinate females, which, because they have better prospects of finding a breeding vacancy, generally invest less than males in helping at the nest. Under these circumstances, dominants are expected to be more vigilant over the contribution to brood provisioning by female subordinates, which in turn, might need to show their helpfulness to retain group membership. In accordance with this idea, we found that female retained offspring increased the ‘visibility’ of their contribution by provisioning in front of the dominant breeders significantly more than any other category of group members. In addition, retention of group membership for female offspring was associated with their perceived effort in chick feeding. Our results are consistent with the hypothesis of ‘pay to stay’ and suggest that a signalling component of helping can arise in a ‘typical’ kin-based cooperative society.

主要功能不是发出信号的行为可以传达其他人可以用来做出相关决策的信息。在合作繁殖的脊椎动物中，喂养非自己后代的幼崽通常会提供间接的健康收益，但团体成员也可能会通过广告宣传其对社交伴侣的贡献而直接受益，以增加其``社会声望''或获得一部分领土商品（ “留下来付费”）。但是，关于育雏准备的这种信号成分的证据仍然存在争议。在腐肉乌鸦合作社中，乌鸦座Corone，男性下属几乎没有独立繁殖的机会，并且通过帮助提高当前的血统来尽其所能。下属雌性的未来繁殖价值更高，因为下属雌性在寻找繁殖空缺方面有更好的前景，因此在育雏方面的投入通常少于雄性。在这种情况下，期望下级领导者对女性下属对育雏的贡献更加警惕，而这反过来可能需要表明他们在保持团体成员资格方面的帮助。按照这个想法，我们发现雌性保留后代通过在优势育种者面前进行配种比其他任何种类的组成员显着增加了其贡献的“可见性”。此外，保留雌性后代的群体成员身份与她们在雏鸡饲养方面的努力程度有关。我们的结果与“留守薪水”的假说是一致的，并表明在“典型的”基于亲属的合作社中可能会出现帮助的信号成分。