We examined the provisioning behaviours of helpers of differing sex and relatedness in the cooperatively breeding bell miner (Manorina melanophrys). In this system males remain in their natal colony while young females typically disperse to breed, and both often assist at multiple nests concurrently. Despite this system containing many features suggestive of helping as a signal, there was no quantitative evidence that male helpers were showing-off to gain social prestige with breeding females or as rent payment to dominants for acceptance into the group. Instead helping decisions, such as the prey types delivered and the use of begging signals of brood demand, appeared more consistent with helpers investing in nestling fitness, in a manner similar to parent birds. Consistent with this, we found an expected (although rarely demonstrated) kin-selected effect of genetic relatedness upon individual helping effort, which was the result of individual facultative adjustment. Surprisingly, however, no sex differences were detectable in any aspect of helping, and even non-relatives provided substantial aid. Unrelated individuals may gain direct fitness benefits by helping raise nestlings that later augment colony size, thereby increasing survival and reproduction prospects for resident helpers. These additional benefits apply primarily to male helpers, whose care should be biased toward male young. As expected, all-male broods were fed at higher levels by helpers (but not by parents) than were mixed-sex or all-female broods. However, this was due to greater numbers of related (rather than unrelated) helpers of both sexes attending these nests - there was no evidence that individuals facultatively adjusted their effort according to brood composition, nor any acoustic variation in begging calls that could have reliably signalled nestling sex. It therefore appears that female breeders skewed brood sex ratios to produce a greater frequency of (potentially) more expensive all-male broods, whenever large numbers of relatives were available to provide the requisite higher levels of help. Exactly why unrelated helpers of both sexes provision equally at all types of nest in bell miners remains a topic for investigation.