The term 'Old World Thrush' refers to two species of birds, the CHAT and the Wheatear. The CHAT is a small, brownish-gray bird with a white throat and breast, while the Wheatear is a larger, grayish-brown bird with a white rump and tail. Both species are found in Europe, Asia, and Africa, and they are known for their melodious songs. They are also important insectivores, helping to control insect populations.