Hmm....sounds like Gouldian colors just cannot be manipulated in the way some other species can be -- just as they don't like to have their diet manipulated to try new foods, as we all know very well!
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I also found your observations about the lighting to be of interest. I'm sure the widely varying lighting conditions in which we keep our birds definitely can make a very notable difference in the hues of Gouldians, in no small part because of their vivid coloring.
I had devoted quite some time to researching avian lighting needs several months before picking up my birds, even speaking with a couple of avian vets on the issue -- and while I'm no expert, for whatever it's worth, here's what I decided seemed to make the most sense to me personally, on the 2 main considerations of cage lighting. (Since I can't provide my birds with an outdoor aviary with access to natural sunlight, I've tried to mimic that experience as closely as possible.)
1)
UV: There is just too much conflicting opinion on this issue to know the truth. Some insist there is no real benefit at all, while others insist that birds critically need a UVA/B-emitting bulb when they're deprived of the sun's natural UV rays. But the birds apparently have to stay within 6-8 inches or so of the bulb to absorb very much UV, and the UV emitted apparently begins decreasing after six months or so -- requiring more frequent bulb changes than regular bulbs. After giving it considerable thought and becoming more and more frustrated that there seemed to be no real clear-cut answer to this question, I finally had an epiphany! I realized:
so what if the bulb doesn't provide a benefit by helping with Vitamin D production? Even if that's the case, I'm left with just a bulb that still provides quite good lighting. I'm not out anything, other than a few extra dollars. And IF the bulbs DO help the birds produce Vitamin D, then great -- that's a bonus! Why take the chance of possibly denying my birds that benefit, when I stand to lose nothing really by giving it to them -- just in case? So I opted to include one Arcadia 18w fluorescent as the 1st of 2 bulbs in a timed fixture sitting directly on cagetop. It claims to emit 2.4% UVB and 12% UVA.
2)
FULL-SPECTRUM: Unfortunately, the term "full-spectrum" is widely abused, and often used as nothing more than a marketing gimmick. And while "daylight" bulbs are a far better choice than regular fluorescents, they still are nowhere near natural daylight in terms of correctly showing an object's true colors. But there ARE a few truly full-spectrum bulbs out there, so I took extra care to locate the bulb with one of the closest possible matches for both color temperature and color-rendering index (CRI -- which refers to the quality of color light), as that provided by natural outdoor lighting. (As a point of reference, natural sunlight has a CRI of 100 at high noon around the equator, and a color temperature of 5,000K -- or 5,500K when both sunlight and skylight are combined.) As I understand, you should always aim for a bulb with a CRI of around 94 or greater, and a color temperature ranging somewhere between 5,000k and 5,800K. I found several fluorescents that met both these parameters, but there were 2-3 that were by far the closest matches. The one I opted for is the 17w Philips TL90 F17 T8/TL950. It offers a CRI of 98 and color temperature of 5,000K -- you really can't get any closer than that to natural outdoor lighting. Several other excellent bulb choices are listed here:
http://users.mis.net/~pthrush/lighting/kinds.html
This combination of both a UV bulb with a high-quality truly full-spectrum bulb seems to really make the birds' natural colors "pop" -- I've even had two different friends who've seen their photos ask if I keep the cage outside, because the lighting looks so amazingly natural. But the main thing is, I feel as if I'm providing them the next-best-thing to the great outdoors. And on the occasional day when I've got the windows open, they even get a natural breeze!
