Supplementary material from "Hard-working helpers contribute to long breeder lifespans in cooperative birds"

In many species that raise young in cooperative groups, breeders live an exceptionally long time despite high investment in offspring production. How is this possible given the expected trade-off between survival and reproduction? One possibility is that breeders extend their lifespans by outsourcing parental care to non-reproductive group members. Having help lightens breeder workloads and the energy that is saved can be allocated to survival instead. We tested this hypothesis using phylogenetic meta-analysis across 23 cooperatively breeding bird species. We found that breeders with helpers had higher rates of annual survival than those without helpers (8% on average). Increased breeder survival was correlated with reduced investment in feeding offspring, which in turn depended on the proportion of feeding provided by helpers. Female and male breeders showed similar patterns. Our results indicate that one of the secrets to a long life is reduced investment in parental care. This appears to be a unique feature of cooperative societies with hard-working helpers.This article is part of the theme issue ‘Ageing and sociality: why, when and how does sociality change ageing patterns?’.