Passerine birds, also known as perching birds or songbirds, are a large group of birds that make up the majority of the world's avian species. Wrens (5 letters) and vireos (6 letters) are two examples of passerine birds. Wrens are small, brown birds with short tails and long bills. They are found in a variety of habitats, including forests, grasslands, and deserts. Vireos are medium-sized birds with stout bills and short wings. They are usually found in wooded areas and are known for their loud, melodic songs.