The striking plumage of the Java sparrow has resulted in this bird being one of the few globally threatened species which have actually expanded in range, as it has been introduced all over the world as a consequence of the cage-bird trade. The Java sparrow has largely pearly-grey plumage, turning pinkish on the belly and white towards the tail. The head is black, which contrasts with the sharply defined white cheeks and large, vivid pink bill. The rump and tail are also black. The song of the Java sparrow begins with single notes, somewhat like a bell, developing into a continuous trilling and clucking, interspersed with high-pitched and deeper notes.