: the largest order of birds including more than 5000 species or more than half of all living birds, consisting chiefly of songbirds of perching habits that range in size from the smallest titmice to the ravens and birds of paradise, being usually divided into the four suborders Eurylaimi, Tyranni, Menurae, and Passeres, and comprising birds that are altricial, lack the ambiens muscle, and have the vomer well developed and truncate anteriorly with its forked posterior end embracing the basisphenoid, three toes in front and one behind and none reversible, 10 primaries of which the first is often rudimentary, and usually 12 rectrices
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Merriam-Webster unabridged
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