White-fronted bee-eaters (Merops bullockoides) nest in colonies by digging holes in cliffs or banks of earth. They have one of the most complex family-based social systems found in birds.
Colonies comprise socially monogamous, extended family groups with overlapping generations, known as “clans”, which exhibit cooperative breeding. Some non-breeding individuals become helpers to relatives and assist to raise their brood. In white-fronted bee-eaters, this helping behaviour is particularly well developed with helpers assisting in half of all nesting attempts. These helpers may contribute to all aspects of the reproductive attempt, from digging the roosting or nesting chamber, to allofeeding the female, incubating and feeding the young; and have a large effect on increasing the number of young produced.
Whether or not an individual becomes a helper and to whom it provides aid is heavily dependent on the degree of kinship involved. They are most likely to help breeding pairs who are close genetic relatives. When faced with a choice of potential recipient nests, helpers preferentially help the breeding pair to whom they are most closely related, suggesting that this behaviour may serve to increase the helper’s inclusive fitness.