1. Nucleated Red Blood Cells: Bird red blood cells contain a nucleus, while mammal red blood cells are enucleated (lacking a nucleus). The presence of a nucleus in bird red blood cells allows them to synthesize hemoglobin, the oxygen-carrying protein, throughout their lifespan.
2. Shape of Red Blood Cells: Bird red blood cells are oval or elliptical in shape, while mammal red blood cells are typically biconcave (disc-shaped). This difference in shape affects the surface area available for oxygen binding and may influence blood flow dynamics.
3. Hemoglobin Structure: The hemoglobin molecule in bird blood has a different structure compared to mammals. Bird hemoglobin has a higher affinity for oxygen than mammalian hemoglobin, allowing birds to extract oxygen more efficiently from the air at higher altitudes.
4. Hematocrit Level: Hematocrit refers to the percentage of red blood cells in the blood volume. Birds generally have a higher hematocrit level compared to mammals. This means that bird blood contains a greater concentration of red blood cells, enabling them to carry more oxygen.
5. Leukocyte Types: Birds have different types of white blood cells (leukocytes) compared to mammals. For instance, birds have heterophils instead of neutrophils and thrombocytes instead of platelets, which perform similar functions but have distinct morphological characteristics.
6. Plasma Protein Composition: The composition of plasma proteins, including immunoglobulins and other proteins involved in immune responses, may differ between birds and mammals. This variation can impact the immune system's ability to recognize and respond to pathogens.
7. Metabolic Rate and Respiration: Birds have a higher metabolic rate and faster respiratory rates compared to mammals of similar size. These factors influence the oxygen demand and the efficiency of gas exchange in the respiratory system, which can be reflected in the composition and function of their blood.
It's important to note that there can be variations in blood characteristics among different species of birds and mammals, and further research may uncover additional differences.