Why do bee-eaters dig burrows for nesting?

Bee-eaters (family Meropidae) are members of the order Coraciiformes that utilize burrows as their primary nesting sites. These birds typically excavate their burrows into earthen banks, such as the cut banks found along stream bends in grassland areas.12

The choice of a burrow for nesting is a specialized behavioral adaptation that provides a secure environment for the birds to raise their young. While bee-eaters are aerial feeders that hunt for insects over forests or grasslands, they require these specific earthen structures for breeding. In some instances, bee-eaters may even nest colonially in the same banks used by other species, such as swallows, or occasionally utilize the walls of larger animal burrows, like those of an aardvark, for their nesting sites.234