2004). B-lymphocytes, the cells that produce antibodies, are initially produced in the embryonic liver, yolk sac and bone marrow, then move through the blood to the bursa of Fabricius (BF). Birds have a bursa of Fabricius (BF), which is an outpocketing of cloaca.
Most squirrels are vegetarians. There are a few exceptions like the flying squirrel. The flying squirrel will eat small birds, insects and definitely steal eggs from birds nest in order to make a meal. Generally speaking though, squirrels will mainly stick to things that are vegetarian related.
Squirrels love nuts, and would eat them 24/7, but like any diet where the same food is eaten exclusively, the balance of nutrition suffers. Squirrels are nut eaters, but they are also predominantly herbivores, and as such require a balance and variety of vegetables, vitamins and minerals in their diet!quirrels are like kids, given the choice, they will eat what they like first, and leave the rest. Whenever possible, it's a good idea to gather nuts that are native to your area. Where I live, there are an abundance of American Walnut, Hickory, Beech Nuts and Butternut trees.