Early differences in maternal food allocation precede later aggression toward dependent offspring in domestic canaries

Maternal aggression (MA) toward offspring is typically observed near nutritional independence and interpreted as conflict over care duration. In domestic canaries, however, MA arises while offspring still depend on provisioning, raising the question of whether it is associated with pre-existing differences in maternal reproductive strategies or in interactions between females and individual offspring. We tested whether females that later express MA differ in reproductive investment and food allocation rules before aggression begins, and whether nestlings later exposed to MA already differ from their siblings. Midway through the nestling period, we experimentally manipulated hunger and recorded begging and maternal food allocation. MA and noMA females did not differ significantly in initial reproductive investment, overall provisioning rates or within-brood inequality in food allocation. However, they integrated offspring traits differently, with the association between begging duration and food allocation depending on begging order in opposite ways in the two phenotypes. Within MA nests, we found no clear evidence that nestlings later exposed to aggression differed from their siblings in food received, body mass or begging behaviour. Together, these findings indicate that differences in maternal food allocation rules precede MA, while the processes linking them to its onset remain unresolved.