There are other cell types in avian blood, although you may have some difficulty in making them out in sections. A demonstration has been provided for the most conspicuous of these, the thrombocyte . Thrombocytes are smaller than erythrocytes, have large round nuclei, and in most smears have a faintly bluish tinge to their cytoplasm. One immediately recognizable feature in good preparations is a small eosinophilic vacuole located at one end of the nucleus. It appears as an orange dot in most preparations.
Birds have leukocytes , too, and the most numerous leukocyte is the lymphocyte .
The cell as a whole is usually round in smears, and the nucleus may be slightly indented. To see some thrombocytes and a leukocyte, click here. One very conspicuous leukocyte is the heterophil . The heterophil sometimes has a distinct ruby colored central granule, and often in smears the rod shaped granules are dissolved, leaving the central one only. The eosinophil is often mistaken for a heterophil, but it can be distinguished by its slightly basophilic cytoplasm and granules which are round, not rod shaped.