their home foraging range, and to retain their established set of helpers. Females will also alter brood sex ratios to meet conditions. When a colony is in a new location with an inferior food source, the ratio will be biased towards more females, which will disperse from the colony at sexual maturity. Once the food supply has been increased, the brood sex ratio is shifted towards future helping males. Nest helpers Both parents and helpers provision and care for the nestlings. Nests may be attended by up to 20 helpers, and nest success has been observed to be higher when there are at least 6 additional helpers attending the nest, in addition to the breeding pair. Helpers feed the young, defend the nest against predators, remove droppings, and remove parasites. Nest helpers include both sexes, but are predominately young and breeding age males. Juvenile birds start helping as early as 1.3 months old. Older non-breeding males contribute the most food to nestlings and assist with multiple nests. The amount of help offered by a nest helper is correlated with its genetic relationship with the nestlings it is feeding. Bell miners use a provisioning call when they arrive at the nest to stimulate the young to beg. Provisioning calls are similar among closely related miners, so helpers preferentially help young with fathers that have provisioning calls similar to their own. However, it is important to note that even non-related helpers have been shown to contribute a significant amount to raising young, and no difference was seen in the amount of help offered by helpers, depending on the brood sex, even though male chicks tend to stay with the colony and become helpers, while females disperse. Helpers will delay bringing food to the nestlings when the female is brooding them, but will eventually bring food, even if the female continues to brood. The brooding female is more likely to allow the young to be fed if the attendant is her mate. Fledgling to adulthood Young bell miners leave the nest about 12 days post hatching, but continue to be fed by parents and helpers for a further 10 weeks. Bell miners will start helping at nests when less than 2 months old, but the transition is gradual, such that recently fledged birds will continue to beg from other helpers, and then either consume the offered food or give it to younger birds.