Hi Stephanie,
Yes, there are vitamins and minerals that can be toxic to birds when given in high doses. Vitamin A will accumulate in the liver and can lead to death in high doses. Calcium also accumulates in the liver, and in high doses will cause lesions to form on the liver which will lead to death. Iodine is a necessary mineral that if given in high doses will lead to death over time. So you have to be careful to not overdose your birds creating hypervitaminosis. They need these vitamins and minerals, but in the correct doses.
They way to avoid overdosing your birds is to offer these vitamins in free choice foods, and let them forage for them as they need them. Never put vitamins in their drinking water, as this forces the vitamins on your birds, as they have no choice but to drink the water. The same goes for sprinkling a product like calcium powder in a homemade egg food. Again this forces the calcium into their diet, and can lead to overdosing. Use a free choice mineral grit like oyster shells or egg shells instead, or offer the calcium powder free choice in a treat cup.
The most recent example of forcing vitamins and minerals on birds causing problems that I can think of came from a customer who told me this story: He started using liquid iodine in the drinking water for balding in his Gouldians. He also used the same drinking water with the iodine in it for his doves. After about six weeks, the Gouldians started to show pin feathers, good news. At about the same time, he lost a dove. Then a few days later, another dove died. After a week, more doves had died, so he took the last two that had died to his vet for a necropsy. The finding, iodine poisoning.
The dosage for one bird species is not always appropriate for other bird species, and the way to avoid this is through allowing your birds free choice. For instance, instead of using liquid iodine in the drinking water, offer powdered kelp in a free choice treat cup.
So vitamins and minerals are an essential part of a bird's nutrition, but you need to let them select the levels they consume on a free choice basis through the food they eat.
Hope this helps!
Bill Van Patten
http://www.FabulousFinch.com
