The Central American Tern is the world’s most restless migratory bird, flying from Northern Mexico to the jungles of Columbia and back again up to six times a year. Avian experts believe that the original Central American Terns were the product of relationships between Arctic Terns and Antarctic Terns who were resting in Central America when they were on their long annual migrations. This would mean that the Central American Tern would have tremendous innate stamina for flying for long periods of time, but would also mean the bird would be conflicted about where it wanted to be in the world, hence the almost constant flying north and south.
When they are at rest, Central American Terns have a tremendous appetite and one tern can strip a tree of all its fruit and berries in about an hour. These Terns procreate on the wing and use previously built communal nests when they are resting from their latest migration. If a female Tern is pregnant, she will not migrate with the other birds but will stay in the communal nest and sit on the eggs until they hatch. She will find food for the chicks, whilst her mate flies back
This is an extract from the book Animals Evolution Avoided