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How large is the bee hummingbird?

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Illustration of a chestnut-collared swift (Cypseloides rutilus) in flight, showing its dark brown body and wings with a distinctive reddish-brown collar around its neck. — Apodiform Chestnut-collared swift (*Cypseloides rutilus*)

The bee hummingbird (Mellisuga helenae) is the smallest living bird in the world. It measures slightly more than 5.5 cm (2.2 inches) in length, with its bill and tail accounting for approximately half of that total size. Weighing about 2 grams, this species is comparable in size to pygmy shrews, making it one of the smallest warm-blooded vertebrates.1