Hummingbird Bills and Tongues

HUMMINGBIRD BILLS AND TONGUES

By Shani and Jon Friedman

Photo by Doris Evans

Introduction

According to Nature's grand design, hummingbirds have evolved so that their entire body form and purpose assists their ability to forage effectively. This accounts for their remarkable flying abilities (they can fly forward, backward, sideways, straight down and straight up, and hold their exact position while hovering), the development of their wings and muscular structure which enables that flight, and their tiny legs and feet. Of course, the bill has evolved as a highly specialized tool, which enables them to forage very efficiently on particular flowers and preferred foods.

Flying and use of feet

The details of the mechanisms of hummingbird flight are better addressed in a separate article, but it should be understood that their special abilities of flight help them in many ways. The ability to fly in almost direction, and to hover, is of critical concern when it comes to foraging. And, concerning their tiny feet, the primary uses of the feet are for perching and preening. Rarely does another purpose come into play. The rare exceptions come from observations of South American hummingbirds that are primarily insectivorous and use their feet for very short distances in their search for insects on the forest floor. Even when a perching hummingbird wants to turn around 180 degrees, it flies straight up, turns in mid-air, and lands in the desired position.

There is general agreement among ornithologists that certain nectar producing flowers have evolved along with hummingbirds, resulting in flowers whose general shapes and sizes accommodate the particular characteristics of the hummingbird's bill size and shape. Hummingbird bills are as distinctive as the flowers upon which they feed. The size of the bills ranges from 1/2" to equal to their total body length (from tip of bill to tip of tail). They range from very straight to extremely curved. As is true with many hummingbirds that are generalist feeders (meaning they can forage on a variety of flowers), other hummers are much more specific in the flowers they use. Generally, the specialists have the more uncommon, highly curved bills to enable them to reach nectar that other birds and insects would otherwise be unable to see or reach. Almost all flowers on which hummingbirds forage lack a landing place or perch from which the hummer can reach the nectar. For this reason, they depend on their ability to hover and feed. (It's believed that feeders with perches enable the hummers to conserve more energy than expended while foraging flowers).

Variety of bill length and curvature

The differences in hummingbird bill curvature and length vary greatly, but among the most widespread hummers of temperate North America, this diversity is less apparent than in the hummingbirds of the tropics. Hummers and flowers found closer to the equator have greater diversity and numbers than those further from the equator.

Among North American hummingbirds, the tiny male calliope has a bill about 9/16 of an inch long while the female Black-chinned's bill can exceed 3/4 inch in length. Female hummingbirds often have slightly longer bills than males. Among tropical hummingbirds, the variety of bill lengths and curvature is enormous. In length they range from the four inch shaft of the Sword-billed (video), nearly as long as its body and tail together, to the abbreviated bill of the Purple-backed thornbill (video), only 5/16 inch long. In curvature they range from the upturned bills of the Fiery-tailed awlbill and Mountain avocetbill to the strongly down curved bill of the White-tipped sicklebill (video), which is shaped like a crescent moon. Their names - Saw-billed hermit, Western Long-tailed Hermit (video), Hook-billed hermit, Green-fronted lancebill (video), etc. - suggest the individual forms of many other hummingbird bills.

Hummingbird tongues

Observing a hummer's tongue while it feeds at flowers is nearly impossible. However, at backyard nectar feeders, close focusing binoculars greatly make this observation possible. Hummers insert their tongues into nectar at a rate of around 13 times a second! For many decades it was assumed that hummers lap up nectar with their long tongues. More recently, it was thought that some sort of capillary action was the mechanism that allowed hummers to feed on nectar. In 2011, even newer research was posted to the Internet. See the following link for up-to-date, slow-motion looks at the amazing mechanical functioning of hummingbird tongues.

If this research is correct, the tongue is split into two parts at its end. Each half is lined with hair-like appendages called lamellae. As the hummer extends its tongue, the lamellae capture tiny amounts of nectar. Then when the tongue is withdrawn into the bill, the nectar is mechanically carried into the bird as the lamellae are compressed.

Hummingbird's Forked Tongue

Insects - Staple in hummer diets

Hummingbirds do not live on nectar alone. In fact, they consume considerable quantities of insects. Insects insure vitamins, minerals, amino acids, animal proteins, fiber, and essential oils in their daily diet. In places where nectar is not available at all times, most hummers switch to an insect diet.

Photo by Richard at SerachNetMedia

The bill and tongue play a role in foraging for insects. Hummers glean insects in several ways. Some are caught in the lamellae of the tongue when ingesting nectar. Other insects are gleaned from various plants. Hovering around the bark of a tree or other plant (tree tobacco here in Arizona is a good example) hummers find minute insects that occupy niches other birds could not reach or find. Hummers search the rough texture of the plant or tree. Because they can hover and fly upside down, they explore the underside surfaces of leaves that might otherwise go unnoticed. Hummingbirds find spider webs and eat the insects caught in the web or even the spider itself. Spiders are, in fact, the major insect in their diet and baby spiders are preferred. On occasion, a spider's web fatally traps hummers who then become a food source for the spider.

When insect hatches are plentiful, hummingbirds hawk tiny insects, like gnats and mosquitoes, on the fly - not unlike the flycatchers. While most flycatchers are equipped with stiff "whiskers" to assist in trapping insects in mid-air, they also have wide mouths to help ensure successful hunting. Hummingbirds don't have these adaptations. Instead, they rely on their superb flight control. They outmaneuver and pursue insects until they catch them.

Tree Sap

Hummers have often been seen frequenting the holes made by sapsuckers. They adeptly pick out insects trapped in the oozing sap. Some have seen hummers actually lick the sap as an important source of needed nutrients.

The tongues and bills of hummingbirds are as unique as their flying ability. Even though they are the smallest of birds, they are so well constructed, designed and adapted to their surroundings that they inhabit nearly all of the Americas. Their very existence makes the impossible seem possible.