African Harrier-Hawk, on Sociable Weaver nest, figure from wikipedia
The African Harrier-Hawk (or Gymnogene) has a flexible tibio-tarsal joint, allowing it to search for prey in crevices and cavities. It often raids the nests of weaver birds - it hangs from the nests, flaps to keep its balance, and reaches into the nest with one foot to extract nestlings.
Weaver species that have had nests raided by the African Harrier-Hawk:
