Final answer:
EDTA is the preferred anticoagulant for conducting hematology in pigeons, as it effectively binds calcium ions, necessary for blood clotting, ensuring the blood remains un-clotted for analysis.
Step-by-step explanation:
The preferred anticoagulant for conducting hematology in a pigeon is EDTA (Ethylenediaminetetraacetic acid). EDTA is commonly used in blood collection tubes for hematology because it binds calcium ions, which are necessary for blood clotting processes. When EDTA binds to the calcium, it prevents the blood from clotting, which makes it an ideal anticoagulant for hematological analyses. Other substances like heparin, citrate, and oxalate also act as anticoagulants by binding calcium or altering the coagulation process, but in the context of avian hematology, EDTA is typically the preferred choice given its effectiveness at preserving cell morphology and preventing clotting.