Every year, as more studies are completed, we learn more about hummingbird life and diets. However, we find that some people think that hummers can survive on nectar alone. Nectar provides quick energy to sustain their extremely high metabolic rate and little else. This is important enough that the shape of the bills of hummers have evolved in partnership with the flower shapes that they frequent. Consequentially, there is a wide variety of hummingbird bill lengths and shapes among the more than 300 species that exist.
There is another critical food source for the hummers. Essential vitamins, minerals, amino acids, proteins, oils and fats, fiber, etc. all come from the insects they eagerly consume, not the nectar. Their preferred insects include, but are not limited to: small beetles, true bugs, weevils, flies, gnats, mosquitoes, aphids, mites, leafhoppers, flying ants, and parasitic wasps. Their favorite insect food source is the spider and harvestmen (daddy long legs). Some ornithologists estimate that spiders are between 60% and 80% of their diet.
The insects that hummers need for a complete diet are captured in a variety of ways. In the past, naturalists thought that hummingbirds exploit the flowers not only for nectar, but for the insects found deep inside the flowers. This may be true to a certain extent, but it is not the primary method of hunting insects.
More often, hummingbirds use their exceptionally acute vision to find and identify insect prey. This, along with their unique hovering ability, incredible agility and quick speed in flight, allows them find insect prey. As they cannot see into a narrow flower tube, they can only blindly grope for insects inside flowers.
Additionally, how can hummers remove insects from the tubes of flowers? The narrow gauge of the flower tube prevents the hummer from opening its bills wide and grasping the insect. Hummingbird bills don't work like those of flycatchers and other insect eating birds. Nor do they have a sticky tongue like woodpeckers which could trap insects. Like woodpeckers, their tongues are forked, but their forked tongue does not act like pincers to seize and hold an insect. To depend solely on insects within the flower would mean starvation for most hummers.
When hummers hover around the outside surface of a flower or near tree bark, branches, leaves, along walls and in corners, they are searching for either cobweb or spider silk to make nests in breeding season or they are searching for insect prey. Spider webs provide fertile hunting grounds for hummers and many of them become adept at snaring insects from the web without becoming entangled themselves. Not only are the insects trapped on the webs taken, but sometimes the spider itself (if small enough) becomes a meal as well. This a hunting technique that requires dexterity and caution. There have been observations of hummers becoming entangled and trapped in large spider webs.
Hummers, much like flycatchers, catch insects on the wing in flight. Have you ever seen a hummingbird dashing into vegetation from its perch - or flitting back and forth, flying quickly for very short distances in mid-air, snatching minute insects? In “hawking” insects like this, changing course often and quickly, they catch the smallest and most elusive insect prey. With movement this swift and prey so small and quickly swallowed, it may be hart to actually see them in the process of eating.
Unlike other insectivorous birds that dismember their prey before eating, hummers select insects small enough to be swallowed whole. Flycatchers and swallows have broad, flat bills and rictal bristles around their mouth to help deflect flying insects into their mouths. Swifts, poorwills and nighthawks have wide bills and large, gaping mouths that assist in gathering insects as they fly through the air. Hummers have none of these advantages. Instead, they compensate for the narrowness of their bills with their superb speed and maneuverability in flight. Hummers simply pursue their prey until they catch it.
Since they cannot use their bills to manipulate or tear apart their prey, when a hummer catches an insect in flight, the forward movement forces the captured insect so far back into the mouth that it is easily swallowed. Other long-billed birds, like toucans, jerk their heads backward, tossing the food back into the throat. Sometimes captive hummers in zoos use a somewhat similar method, but wild hummers do not rely on this method of eating.
A few species of North American hummingbirds frequent the rows of tiny holes that sapsuckers drill in trees. They not only lick the sugary sap but also catch many of the small insects attracted to it. These sap-attracted hummingbirds frequent the sap holes more often than the sapsuckers themselves! In the tropics, hummers eat the insects that are attracted to the juices of ripe and over-ripe fruits, sometimes sipping the juices, too.
Female Anna's hummingbirds, which nest in Southeastern Arizona during the month of January, pick up tiny grains of grit and sand and eat them. Evidently, the purpose of this is to regain lost calcium that was used in forming eggshells. I frequently put overripe bananas of my fruit feeder to attract tiny fruit flies, which in turn attract the hummers. The hummingbirds eat every fly and return in a few hours to feast on the next batch of fruit flies that discover the overripe fruit. What an easy way to observe hummers eating insects