Vitamin D3 and pet birds
From internet Feb 2010
http://www.birdsnways.com/wisdom/ww22eii.htm 1000 IU per kilogram  also talks about levels of Calcium and Phosphorus 1998 publication
http://www.birdchannel.com/bird-magazines/bird-talk/2008-february/bird-light.aspx 
Birds’ skin is protected by feathers, so how do they get their vitamin D? Dr. Greg Burkett, DVM, of the Birdie Boutique in North Carolina said it has to do with a bird’s preening gland. “Birds have a unique way of producing vitamin D3. The oil for the preen gland contains a precursor to the vitamin. Birds spread the oil containing these precursors over the feathers. The precursor is activated and transformed into vitamin D3 by UVB light. When birds preen, they ingest the vitamin D3.
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“The avian retina has four types of cones, the fourth being sensitive to UVA,” Burkett said, “This gives birds a fourth ‘primary color,’ to make up their complete visible color spectrum. UVA plays a role in species recognition, mate selection and food recognition. For example, a fruit reflects a different wavelength of light when it is ripe. This allows a bird from a great distance to observe if the fruit is ready to eat. Realizing that UVA provides birds the ability to see a fourth color, without UVA, birds are experiencing a condition similar to color blindness in humans.”

Search Google "avian retina" (uv OR uvb)
http://www.pigeon.psy.tufts.edu/avc/husband/avc4eye.htm

Detailed discussion of avian vision and theory of how primates lost the ability to see UV

http://www.bio-nica.info/Biblioteca/Mullen2008Aves.pdf  2007 analysis of 1000 bird species – feathes reflective in UVA