And other animals such as humans, reptiles, fish, chickens, horses, etc.
Was listening to the book Alex and Me which is interesting book about an African Grey Parrot which was trained to communicate with language.
Alex died in 2007, very early in its life. CLICK HERE for the Alex Foundation
Birds primarily get their vitamin D by preening and exposing themselves to UV (which is filtered out by glass)- see below
One of the reasons that pet birds pluck out their feathers is to get more Calcium in their diet - which is lacking if they do not have vitamin D
Preening is how a bird cleans, waterproofs and conditions feathers for skin protection, warmth and flight. Most birds have a uropygial or preening gland and it is located on a bird's back near the base of the tail. The preening gland secretes an oil like substance through multiple ducts. A cluster of small down feathers surround the ducts and act like a wick, holding the secreted oil. By wiping their beaks on the wick, birds are able to use the oil to clean, lubricate, condition and groom individual feathers daily. Birds will also remove pieces of dry skin and loose keratin from the shafts of new feathers that are growing in when preening as well. They will also preen their feet, removing dry skin, food or droppings that they may have stepped into. In addition to grooming, preening serves another vital function. The oil used for preening contains precursors to vitamin D that are activated when exposed to direct sunlight or full spectrum lighting that contains both UVA and UVB lighting. Vitamin D is ingested while preening and vitamin D is needed for the absorption of calcium in a bird's diet. This is why avian vets recommend that birds receive 15 minutes of full spectrum light from an avian light bulb , that contains both UVA and UVB rays each day. A cage near a sunny window has psychological benefits but the rays a bird needs can not penetrate through glass.
- UVB for african gray parrot - 2004.PDF has the medical details
- The Essential Nutrient Your Pet Bird is Likely Seriously Short On…
- describes the preening gland as well as the Harderian gland around the retina