Hummingbirds feed on more than nectar
<p>Hummingbirds, such as this female rufous hummingbird, often make daily rounds between flowers and feeders in a predictable sequence (which is called trap-lining).</p><p></p>
As I walked through the yard an unfamiliar buzz came and went that was louder than a bee. I looked around and finally looked up to see a hummingbird diving towards the ground.
As I watched, the hummingbird climbed high in the sky and then dived towards the ground with a high buzzing sound before pulling up into a climb. The U-shaped aerobatics were repeated several times before the hummingbird rested for a few minutes on the power line. Then the hummingbird began the stunt again.
Without a close glimpse at the hummingbird, I couldn’t tell the species. But most likely it was a male performing a courtship or territorial defense display since both involve steep climbs followed by rapid dives. The range hummingbirds climb up varies and the Calliope hummingbird will climb 100 to 130 feet before diving.
The Calliope hummingbird is one of three species of hummingbirds found in North Idaho along with the rufous hummingbird and the black-chinned hummingbird. Since hummingbirds can fly up to 60 miles per hour, distinguishing the species in flight isn’t easy.
However, their ability to hover at flowers and feeders provides a chance to catch a glimpse of their magnificent colors. The males are more colorful than the females though the females aren’t drab.
Often the easiest way to distinguish the males is by the patch of color on their throat which is called a gorget.
The male Calliope hummingbird has magenta-red rays against white feathers. The aptly-named black-chinned hummingbird is for the males who have a velvety black upper throat and a violet iridescence on their lower throat. The male rufous hummingbird has a bright, iridescent orange-red gorget.
Rufous hummingbirds are also easy to distinguish from the Calliope and black-chinned hummingbirds because they are tinged with a rufous color (red-brown). The male has red-brown on his back, sides and top of tail while the female has rufous on her sides and top of tail.
Both the male and female black-chinned hummingbird can be distinguished by the white spot behind their eye.
While the best spot to watch hummingbirds is at feeders and flowers as they sip nectar, they don’t exclusively feed on nectar. Hummingbirds supplement their nectar diet with invertebrates, such as fruit flies, mosquitoes, aphids, spiders and caterpillars, to help meet their protein, vitamin and mineral requirements. They catch invertebrates mainly by hawking and gleaning.
Hawking is when the hummingbird perches on a bare, open twig and scans the area for insects. When it spots a flying insect, the hummingbird quickly flies out and engulfs the unsuspecting insect.
Gleaning involves a few different techniques. Hummingbirds search the leaves at the tips of branches for tiny moth caterpillars. They also glean by poaching arthropods trapped in spider webs and stuck in the sap of sapsucker wells.
The rufous hummingbird also “leaf-rolls” for insects. By hovering over the forest floor, the rufous hummingbird will disturb the leaves enough so they roll over. Then it can scan the underside of the turned leaves for arthropods and their eggs.
Hummingbirds also pick insects and their eggs from cracks and crevices of bark like nuthatches and brown creepers. However, hummingbirds will move about the tree by flying instead of walking because with their flight capability (and weak legs) it is easier for them to fly than walk.
With the unique figure-eight motion of their wings in flight, hummingbirds can fly forward, backwards, sideways, up, down, upside down and can hover to feed and perform spectacular aerobatic displays.
For previous columns, visit http://goexploreit.blogspot.com.