How do anis and guiras cooperate in communal nesting?

Anis and guiras are notable among the cuculiform order for their unique social structure. Unlike most nonparasitic cuckoos that form stable pair bonds, these birds live in flocks of five to 20 individuals that defend a shared territory.1

Within these flocks, the birds exhibit high levels of social cooperation regarding reproduction:

• Nest Construction: Several members of the flock work together to build a single, loose platform nest made of twigs, typically placed in low vegetation.1
• Egg Laying: Two or more females within the flock contribute their eggs to this communal nest.1
• Incubation and Rearing: The flock shares the responsibility of incubating the eggs. Once the young hatch, many members of the flock participate in feeding and caring for them.1

This cooperative behavior stands in contrast to the obligate brood parasitism seen in other members of the cuckoo family, representing a specialized evolutionary strategy for group survival.21