Still More Bills


Some years ago now, excellent birder and bird photographer Richard Ditch and WC co-authored a couple of articles on bird identification for bird photographers. Richard did most of the work, and made an excellent point: a bird’s bill is a good starting point for identifying the bird’s species and figuring out how the bird makes a living. With that credit to Rich, WC will undertake to give some examples of the astonishing evolutionary adaptations of birds’ bills to birds’ business.

WC has looked at raptor bills and spear-fishing bills; in the post we’ll look at bills of birds that target nectar as a primary food source. Often, the bird and the bill have co-evolved, with the flower’s goal being to get its pollen spread to other flowers.

This is a Green Violetear, a fairly common in Costa Rica.

Green Violetear, Savegre, Costa Rica

Green Violetear, Savegre, Costa Rica

Note the delicately decurved bill. It turns out that bill first exactly a few specific blossoms.

Green Violetear foraging, Savegre, Costa Rica

Green Violetear foraging, Savegre, Costa Rica

You can make out the silhouette of the bill in the blossom and see that if fits the curve of the blossom exactly.

This gets carried to an extreme in the case of the Sword-billed Hummingbird.

Sword-billed Hummingbird, Yanacocha, Ecuador

Sword-billed Hummingbird, Yanacocha, Ecuador

This is the only bird species whose bill is longer than its body, and if specializes on feeding on nectar of Passiflora and Datura blossoms. The long corolla of these flowers coevolved with the bird’s bill as a pollination strategy. By the way, the Sword-billed hauls that immense bill around while flying at an altitude of 12,000 feet.

By contrast, Peru’s Bearded Mountaineer had a more modest, but very straight bill. It forages on tubular flowers, which have evolved to exclude insects but allow Mountaineers.

Bearded Montaineer, Ollyantambo, Peru

Bearded Montaineer, Ollyantambo, Peru

No discussion of bills adapted for pollinating would be complete without a note on birds that cheat. A genus of birds called flowerpiercers have evolved to get at the nectar without troubling themselves with pollen.

Slaty Flowerpiercer, Savegre, Costa Rica

Slaty Flowerpiercer, Savegre, Costa Rica

A spcially adapted hook on the tip of the upper bill allows the flowerpiercer to pierce the base of the blossom, and its long tongue then lets it extract the nectar, completely bypassing the pollen lining the inside of the blossom. In its way, the adaptation of the flowerpiercer’s bill is as remarkable as any pollinator’s bill.

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