by Dan and Diane True BLACK CHINNED HUMMINGBIRD NESTING (PART I)
We observed fifteen Black-chinned hummingbird nests over a two year period in Texas and New Mexico. Some nests were in trees. Nesting platforms known as Hummingbird Houses served as sites for other nests. Hummingbird Houses were installed under eaves, porch ceilings, and covered patios.
Migrating female hummingbirds follow males in spring into the United States and Canada from wintering grounds in Mexico by three to ten days. The birds come north for one purpose: to raise young, and they waste no time in getting down to that business. Nest construction generally begins the day they arrive. Distended abdomens on some of the hens indicated those little birds arrived impregnated.
Top priority in a female hummingbird’s mind for nest site selection is: Find A Place Out of the Wind. The importance of selecting a protected nest site was emphasized from the experience of Jay and Carrie Hollifield of Roswell, New Mexico. Winds catapulted ten hummingbird eggs out of five nests from elm branches in their ranch yard in 1999. Broken hummingbird eggs were often found on the ground by Dave Dunnigan after strong winds raked his ranch yard in Amistad, New Mexico. Twenty to thirty Black-chinned hummers nest in Dunnigan’s yard trees each year. Obviously, for nesting hummers, winds are a major problem.
Nests we observed were established in places providing as much wind protection as was available. Nests were sheltered either by an outer perimeter of trees, or by buildings. Six to twelve feet above the ground in the first row of inner branches where protection is increased from weather elements were prevalent locations. Trees of choice, in order of preference, were sycamore, fruitless mulberry, maple, elm, and Russian olive. Note the larger the leaf, the higher the preference.
A fork in a branch about 18 inches from its end was a repeating tree nest location. The chosen branch averaged 1/4” in diameter...too small to support a cat, but dangerously whippy in high winds. A hen’s search image includes the coincidence of either a large leaf or a cluster of leaves three inches or less directly above the fork. She utilizes this leafy “umbrella” to protect her nest against sun and rain, and to shield her eggs and chicks from prying predator eyes.
Nest construction averaged five days. She brings materials to her site at a rate of 34 trips per hour. The little hen’s first load of material is spider webbing. She applies that material as a sticky foundation on the forked area of her nest site. Thereafter, her sequence is orderly. She airlifts plant down or other soft material in her beak and tucks it into the fork. After shaping and molding that material, she flies in another load of spider webbing. Most often she carries a glob of webbing clinging to the underside of her beak, under her throat, and down across her breast. Transfer of the webbing onto her nest is achieved by pressing her chin and breast against the nest and wiping the webbing onto her work. Stickiness of spider webbing appeared to be the only element binding the nest. Frame by frame scrutiny of video tapes revealed no sign that she used her spittle as glue. In that regard, for her little system to produce enough spittle to construct her nest seems beyond a hummingbird’s physical capacity.
Bits of camouflage followed the spider webbing and were applied to her work-in-progress. Another load of plant down was followed by spider webbing followed by a bit of camouflage, and so on. Four hours straight was usually her work schedule before she quit for the day. Some of the little hens worked mornings, others were afternoon types. Since developing eggs burdens her with extra weight throughout nest building, it made sense that she work on the nest no more than four hours per day.
Concealing her work from its beginning is probably a reason the female hummingbird camouflages her nest as she builds. One hen was so picky about hiding her work that on the sun bleached side of a branch she chose light colored camouflage material to match. On the shaded, and therefore darker side of that same branch, she camouflaged that side of the nest darker to match that side’s coloration. Such attention to detail created a nest that was camouflaged slightly differently on each side. Hummingbird House nests were camouflaged against the color of the eave, ceiling, or patio cover where the House was installed. Sometimes the hens gathered flakes of paint chips from the building and applied the chips to their nest. A male bird was never seen near a hummingbird nest. So, where is Daddy Bird during the female’s flurry of nest building activity?
Flashy gorgets transform Daddy Birds into Mr. Neon. To protect her children from predators, the female would be foolish to tolerate a male spotlighting her work during nest building, or during chick raising. In whatever ways hummingbirds communicate, after she has been impregnated, a probable reason we don’t see hummingbird males near hummingbird nests is that she has told Daddy Bird to take his brightly colored flashy suit and hum off.
Happy Humming.
Dan True is the author of Hummingbirds of North America, published by the University of New Mexico Press. He is an aviator and former weatherman for the Albuquerque and Amarillo, Texas markets. He and his wife, Diane, write extensively about hummingbirds. Visit their web site to learn more.
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