Passerines include more than half of all bird species.  They are sometimes known as perching birds. One of the features that sets them apart from other orders of birds is the arrangement of their toes (three forward, one backward) which facilitates perching.  

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Although Hummingbirds do perch, their legs are small and have limited function besides perching.  Thus, they belong to the bird order Apodimorphae, and are the most diverse order of birds after the Passerines.  They are among the smallest of birds.

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