Whistlers: Pachycephalidae

Whistlers range from 5 to 11 inches (12.5 to 28 cm) in length and weigh 0.8 to 3.84 ounces (12.5 to 110 grams). They have sturdy bodies and large, round heads, giving this family of birds the name "thickheads." They have small, round wings and strong feet and legs, making them more suited to hopping about on tree branches, rather than flying and diving. Their bills are thick and strong with a hook at the tip, allowing them to grasp insects and other small invertebrates. Some species have powerful jaws and bills that are shorter and fuller so that they can pry up bark to look for insects. Other species have small crests on the backs of their heads.

Most species are subdued brown, reddish brown, gray, or olive-gray for both males and females. However, there are some species that have bright markings in yellows, whites, and reds for males; females have duller coloring. Young birds are usually reddish brown.