Yes, this is true! There is a part of light whose colors are visible to human eyes. It is called ultraviolet (UV) light. Scientists have found that birds have four types of cones. This helps them to detect UV light. This is why birds can see a lot more colors than humans. In addition to this, the color sensing pigment in their cones is many shades of the same color. Recent studies show some fish and turtles too have four types of cones, helping them to see UV light as well!