It’s important to remember, that although birds are warm-blooded unlike mammals, they hatch from eggs. The placenta is the delivery system for mammals providing nourishment to their embryos. Colostrum is the substance mammalian mothers produce which provides antibodies and essential nutrients for newborns.
Within a few days, mammalian mothers produce milk which is a combination of water, fats, proteins, carbohydrates, minerals, vitamins, and other nutritional necessities. Mammals produce enzymes (lactase) that enable the digestion of lactose.
Birds are an entirely different story in that their embryos are found inside an egg. Nature must provide that egg with all of the nutrients and liquids that are needed to nurture the bird until hatch day. Regurgitation is a method that parent birds used to feed the chicks because they can’t nurse.
Food stored in the bird’s crop is regurgitated. Pigeons actually offer part of their crop itself as food for the chicks and although it’s called “crop milk” it has nothing to do with the milk that mammals produce. Crop milk is rich in nutrients but has no carbohydrates, calcium, or milk sugars. Pigeon chicks will get crop milk for 2 to 3 days but then are soon fed other types of food.
There is no milk offered to birds in the rainforest. Birds in the wild eat things that birds normally eat like seeds, nuts, vegetables, leaves, blossoms, nectar, and so forth. This means birds developmentally never acquired the enzymes that are needed to digest lactose (milk sugar). This is why we say birds are lactose intolerant (they just don’t know it). So milk products will usually pass through the entire digestive system undigested. Because the products contain sugar they may draw fluids into the intestinal tract which can cause diarrhea if ingested in large amounts. Dairy products in moderation are usually not harmful to most birds.
Cottage cheese contains no lactose. Usually, yogurt and low lactose cheese are your best bet offered in small amounts. Like a carrot cube size. Note Cheddar is high in lactose whereas Mozzarella is low in lactose.
It’s important to keep in mind that live-culture yogurt contains lactose when produced but the organisms in the yogurt consume the lactose which removes it entirely from the yogurt. Some cheese products have onions and garlic which is not good for birds – is best to avoid these.
Our birds love eating with us, so sharing a small bit of cold breakfast cereal with milk or oatmeal made with milk is okay. Caffeinated beverages like coffee should be avoided totally. And if you think about giving your bird products that are advertised for lactose-intolerant humans – DO NOT offer these to your birds as the compounds that break down the lactose within these products are highly toxic to all birds.