"Birds, the reptilian descendants of dinosaurs, are tetrachromats: they can see four colour dimensions, making them able to discern colour ranges from black to white, blue to yellow, green to red, and violet to ultraviolet. They can see colours we would never imagine. What to our impoverished eyes appears as drab, dun-coloured sparrows, which birders disparaginly refer to as LBJs (little brown jobs), may very well appear to other birds as brilliantly bejewelled as a peacock. In fact, we may be seeing only some of the colours of a peacock. Researchers suspect, for example, that species that seem to us to be monomorphic -- both sexes appearing identically coloured, like blue jays or crows -- are in fact sharply differentiated in the UV spectrum. It is also entirely likely that in birds' ability to see UV lights lies the secret of annual migration."From:
Bringing Back the Dodo
Wayne Grady
McClland & Stewart, Toronto 2006
ISBN 0-7710-3504-7
Pages 48-49
