Trace out similarities between birds and mammals.
Warm-Blooded - Both birds and mammals are warm-blooded, which means they can maintain a constant body temperature and do not need to rely on an external heat source to stay warm.
Vertebrates - All mammal and bird species are classified as vertebrates, meaning they have backbones and skeletal systems made of bone.
Blood - The blood of birds and mammals contains both red and white blood cells, called erythrocytes and leukocytes respectively. The red blood cells in both classes of animals contain hemoglobin, a protein containing iron that is responsible for oxygen transport and gives blood its red color.