Miami - Baby ducks can learn the difference between two objects of varying shape and colour, a capability previously known only to exist in apes, crows and parrots, scientists said on Thursday.This ability is linked to imprinting, a powerful learning process whereby a new chick follows the first adult it sees, likely its mother, researchers said in the US journal Science. In some cases, such as when wildlife is rescued, a baby bird can imprint on the person who cares for it. Imprinting may seem primitive, but it is actually a complicated skill that the bird develops quite soon after it hatches and begins waddling around, said lead author Alex Kacelnik of Oxford University's Department of Zoology."What the duck needs is to recognise its own mom, and because of that it has to involve learning, because every female duck may look a little bit different," he said."When you think of it, it is terribly complicated, because mom can turn around, be at different distances, flap her wings," he added."And you still have to form a general concept of mom."So his lab decided to study just how refined this ability was, by having baby ducks see and follow objects that showcased the concept of equal and different.As soon as the duckings were born, they saw either a pair of objects that were the same, or a pair that were different - moving in a circular path that they could follow.For instance, a duckling could have been shown two spherical objects so it would imprint on them.Or, it could have been shown a pair of different shapes, like a pyramid and a cube. Again, the two objects would move together in a circular path.When the ducklings were shown a new set of objects, either that matched or that did not, three-quarters of them followed the pair that resembled the first pair they had seen.Those that saw a pair of spheres at first were more likely to follow a pair of cubes than they were to follow a mismatched pair of objects, for instance.This shows that birds can learn the concept of equal or different, said Kacelnik."It was the same whether we did the experiment with shapes or colours," he said."To our knowledge this is the first demonstration of a non-human organism learning to discriminate between abstract relational concepts without any reinforcement training."Other creatures that have demonstrated this ability, did so after being rewarded for the correct choice, he said. "Our ducklings did it spontaneously, thanks to their predisposition to imprint when very young."To learn that one-day-old ducklings could be so discriminating came as a surprise, according to co-author Antone Martinho, a doctoral student in Oxford's Department of Zoology."When a duckling is young, it needs to be able to stay near its mother for protection, and an error in identifying her could be fatal," he said."Still, this is an unexpected feat for a duckling, and a further reminder that 'bird-brain' is quite an unfair slur."