Gouldian finches (Erythrura gouldiae) have become popular with bird enthusiasts worldwide for their bright and varied plumage. Found in very few numbers in the north of Western Australia and in parts of the Northern Territory, this bird has one of three different head colours: black, red or gold – gold being the rarest variation. They have purple chests, and the colour of their backs can be yellow, green or blue. Females are typically duller than males, but the differences are slight. Juveniles are predominantly olive green. Their bills vary in colour during the breeding season, changing from white with red or yellow to pearl (males) and dark grey (females). These colour variations are largely genetic, similar to eye- and hair-colour in humans.