Wright's stain, 500x

This microphotograph shows many nucleated red blood cells as well as many leukocytes. Many avian granulocytes possess a polymorphic nucleus similar to mammalian granulocytes. The granulocyte lineage in birds include cells called heterophils which are the equivalent of mammalian neutrophils, as well as basophils and eosinophils which resemble their mammalian counterparts. In this field, four heterophils and one monocyte (arrow) can be observed.  Avian monocytes are similar to mammalian monocytes and can be differentiated from other leucocytes, such as lymphocytes, by their more abundant cytoplasm and the presence of (not always) cytoplasmic vacuoles.