Western Tanagers are rather interesting in that the bright red on their heads is not part of their "natural" coloration. The birds are not able to produce the pigment, known as rhodoxanthin, by themselves. Instead, it comes from the insects that they eat, who in turn get it from plants.
Insects make up a large bulk of their diet, followed by fruits. They live in groups of up to 30 birds, and between 1 and 5 eggs are laid in cup sized nests. Western Tanagers are preyed upon by a variety of raptor species.
Interestingly, Western Tanagers are in a state of taxonomic confusion. They once belonged to the actual Tanager family, Thraupidae, but have since been moved to Cardinalidae, which is the home of the Cardinals. Some locations still list them in their previous family.