I photographed a specimen of the South American sword-billed hummingbird, Ensifera ensifera, in the bird collection at the Universidad de Los Andes, using a pen for scale. The bird is found throughout the northern Andes, and is the only species in the genus Ensifera.
Most important, it’s the only living bird whose beak (3.5 to 4 inches long) is longer than the rest of its body (ca. 2-3 inches)!
Here’s a skeleton of the bird, showing how disproportionately long the bill is. Wikipedia reports (and there’s verification in a video below) “since the Sword-billed Hummingbird’s beak is very long, it grooms itself with its feet”.
You’ve certainly guessed that the long bill is an adaptation for feeding. These birds feed largely on passionflowers (Passiflora), which have long corolla tubes that contain the nectar. The birds approach these pendant flowers from below, deftly inserting their beak like so [note: as several alert commenters note below, the flower shown is not Passiflora but Brugmansia]:
The paper by Lindberg and Olesen (citation below) strongly suggests that these birds are also important pollinators of Passiflora, since they carry pollen on their beaks from flower to flower. But the authors also warn that their specialization on one genus of flower, and the increasing habitat fragmentation in the Andes, may put these birds on the verge of extinction.
There are some lovely videos and photos of this bird at The Internet IBC bird collection, including a female supping from a feeder and another female using her feet to groom herself. Arkive has another grooming video and a marvelous video of feeding from a Passiflora.
Hummingbirds are truly the jewels of the avian world, and display some of the most remarkable adaptations seen in animals. I am always amazed at seeing how these birds hover, absolutely rock still, while they feed. No helicopter is as agile. And how some of these nectar-guzzling species make a 600-mile nonstop journey across the Gulf of Mexico—20 hours of straight flight—is beyond belief.
Here are a few words, and some dramatic videos, about how the PBS film “Hummingbirds” was made (I haven’t seen it).