Birds can see UV-A, so using normal 'daylight' or cheap 'full spectrum' bulbs, while increasing the light levels, still leaves them colourblind.
John is partially right. the UV-B is minimal, but 2.4% is better than 0%, especially if you have no way of getting your birds outside. But the figures I quoted earlier were for the UV-B. We are really concerned with a birds living conditions, and using a lamp that gives a good level of UV-A (as most avian lamps do) does that by letting them see everything as nature intended. The lamps I use give 12% UV-A, comparable to natural sunlight.
The ZooMed lamps from Avian Sun are good, in that they are a whole lot better than a standard full spectrum lamp. The figures they quote can be trusted. 5.0 means 5% UV-B. The UV-A they give off will be much higher than that though that info sheet doesn't mention %.