1. Pigeons and Doves: Pigeons and doves produce "crop milk," a nutritious secretion from the crop that they feed to their squabs (baby doves). Both male and female parents participate in crop feeding.
2. Flamingos: Flamingo parents produce a special substance called "crop milk," which they regurgitate to feed their chicks. Crop milk is rich in proteins, fats, and other essential nutrients.
3. Emperor Penguins: Emperor penguins are known for their impressive parenting behavior. Male emperor penguins keep the eggs warm on their feet during the Antarctic winter, and once they hatch, the males continue to care for the chicks by regurgitating food.
4. Gannets: Gannets are seabirds that often regurgitate food for their chicks. They usually bring back fish to the nest and regurgitate it into the chick's mouth.
5. Owls: Owl parents tear up prey into smaller pieces and regurgitate them to feed their owlets. The regurgitated food may include small mammals, birds, insects, and other prey.
6. Herons: Herons are known to regurgitate food for their young. They typically capture fish, frogs, or other aquatic prey and store them in their expandable throat pouch. When it's time to feed, they regurgitate the stored food for their chicks.
7. Vultures: Vultures, such as turkey vultures and black vultures, feed their young by regurgitating partially digested meat. The chicks insert their heads deep into the parent's mouth to receive the regurgitated food.
8. Hummingbirds: Hummingbirds are unique in that they regurgitate nectar to feed their hatchlings. They consume nectar-rich flowers and store the nectar in their crop, later regurgitating it to feed their young.
9. Kingfishers: Kingfisher parents catch fish and bring them back to the nest. They stun or kill the fish before regurgitating it to feed their chicks.
10. Parrots: Some parrot species, such as cockatoos and macaws, engage in crop-feeding. They regurgitate partially digested food for their chicks, providing essential nutrients during the growth and development stages.
Please note that this list is not exhaustive, and there are other bird species that exhibit this behavior.