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.
Food and Feeding Habits Tree squirrels feed mostly on plant material, including seeds, nuts, acorns, tree buds, berries, leaves, and twigs. However, they are opportunists and also eat fungi, insects, and occasionally birdsâ eggs and nestlings.