Newly hatched birds of some species learn to recognise their mother and form an attachment to her. They will then follow her around and gain food and protection. This learned behaviour is called imprinting.
Imprinting is partly innate because the young birds will only learn to recognise and follow objects that have certain features. For example, goslings imprint on the first object they see that moves, but mallard ducklings imprint on an object only if it moves and also quacks.
Imprinting is useful if the first object with the key features really is their mother. However, young birds can imprint on people, balls and even cardboard boxes if these happen to be the first things they see and they have the correct features.