Final answer:
Fertilization in birds occurs in the infundibulum, which is the upper part of the avian oviduct and corresponds to the ampulla in human fallopian tubes.
Step-by-step explanation:
In birds, fertilization typically occurs in the segment of the oviduct known as the infundibulum. This is the upper part of the oviduct, where the egg released from the ovary is first received. The infundibulum is analogous to the ampulla in the human fallopian tube, where fertilization commonly occurs in mammals. It is important to note that avian oviducts have a similar structure to human fallopian tubes, with both serving the function of transporting the egg from the ovary towards the uterus and being the site of fertilization. Within the avian oviduct, there are other named segments such as the magnum, which is responsible for secreting egg white proteins, and the isthmus, where the shell membrane is added. However, these are not the sites of fertilization. Hence, the correct answer to the question is D) Infundibulum.