The Family Vireonidae, commonly known as vireos, is a group of passerine birds found in the Americas. There are about 55 species within the family, including the red-eyed vireo, white-eyed vireo, and blue-headed vireo. Vireos are known for their slender builds and spectacular songs. They are small birds with a length of between 4 and 8 inches and a wingspan of 7 to 12 inches. Vireos are closely related to wood-warblers and are often referred to as greenlets or shrike-vireos. Other synonyms for the Family Vireonidae include Vireoninae and true vireos. They are predominantly arboreal birds found in woodlands, thickets, and forests.