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Mighty midgets

Hummingbirds, small but mighty, head south

September 28, 2013
By GARRY BRANDENBURG , Times-Republican

They are small. They are fast. They are survivors. And they are fun to watch. HUMMINGBIRDS have all the acrobatic skills needed to fly, chase insects or each other, hover, fly backwards and think nothing of it. That is what they do. That is how they are made. It is amazing stuff. This scribe will continue to wonder at the intricate shoulder joint mechanisms of bone, muscles and tendons that allow a hummingbird to beat its wings 40 to 80 times per second.

From an engineering point of view, we may have been told that bird bones are hollow and filled with little cross member braces to add strength. That part is true. The next assumption by people is that bird bones must be lighter if the internal structure is not solid. That is an error to assume hollow means lighter. It may come as a surprise that bird bones don't actually weigh any less than the skeletons of similar sized mammals.

Research into this matter found that bird skeletons look delicate but are quite heavy. The answer turned out to be density. They are heavier for their size but also stronger and stiffer. Maximum stiffness and strength relative to weight are optimized strategies that are used in design of strong and stiff and lightweight manmade airframes. Density is a measure of mass per unit volume; dense bones are both heavier and stronger.

Article Photos

T-R PHOTO BY GARRY BRANDENBURG
A ruby-throated hummingbird (Archilochus colubris) guards a feeding station, always alert for other hummingbirds “invading” the territory of a food source. These mighty midgets of the bird world are about 3.5 inches long and tip the scales at 1/8 ounce or 3.1 grams. Adult males have probably already migrated. Last to leave are the females and the young of the year.

Ruby-throated Hummingbirds are the most common and usually the only species of hummingbird seen in the eastern on-half of North America. There are 20 other species of hummingbirds found in western states, Mexico and in Central America. To see these birds one must travel to where they live.

Hummingbird nest are the size of a walnut. It is built by the female of a foundation of bud scales from trees and attached to an upper limb with spider silk. Lichens camouflage the outside while inside the nest is lined with dandelion, cattail or thistle down. The nest will stretch to contain growing nestlings. The eggs are the size of a pea. Usually two are laid about 2 to 3 days apart. Incubation takes 12 to 16 days with the female doing 60 to 80 percent of time on the eggs. The first egg laid hatches first and in 18 days, the first baby hummer is ready to leave the confines of its silky nest bowl. For the first 10 days, mother hummer feeds her young.

A life span of a ruby-throated hummingbird can be 12 years, although most bird biologists think the average is closer to 3 to 5 years. Hummingbirds have a normal body temperature of 105 to 108 degrees F. Wing beats average 52 per second with a range of 40 to 80. Respirations are pegged at 250 per minute. Heart rates are 250 per minute resting and 1,200 per minute feeding. Flight speeds are 30 mph normally although 50 mph can be obtained to escape predators. Dive speeds are pegged at 63 mph. When these birds are tanked up on food fuel prior to their crossing of the Gulf of Mexico, they embark on a non-stop water crossing that will take 18 to 20 hours this fall. Then they repeat the process next spring when the urge to come to North America sets in. They are mighty midgets indeed.

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Here is another fascinating aspect of natural earth history to think about: EARTHQUAKES. This is Mother Nature's version of rock and roll dancing, only this time it is in slow motion, the result of ages old processes of plate tectonics. Plate tectonics is the recycling of the earth's thin ocean crust into subduction zones whereby the heavier basaltic rocks of the sea floor bend and flow under the lighter continental rocks of the continents. Mountain ranges are pushed up in the process. Volcanoes may burst from the underlying friction and re-sorting of deep bedrock. It happens all around the globe. When the strain and stresses of earth plates attempting to slide past each other becomes too great, a sudden release of tensions is expressed as a rumbling within the earth, an earthquake.

This scribe found an interesting bit of history of earthquakes felt in Iowa, not necessarily from epicenter sources within deep foundation rocks of Iowa. In fact most earthquakes that have been reported had origins in other states. Sept. 27 is an anniversary date for an earthquake felt in eastern Iowa. On this date in the year 1909, the Wabash River earthquake in Indiana took place. It measured 5.1 on the Richter scale, the strongest ever recorded for Indiana. The deep vibrations from this quake were felt over an area of 30,000 square miles including the states of Arkansas, Illinois, Iowa, Kentucky, Ohio and Tennessee.

People who were in these affected areas noted chimney bricks becoming dislodged and fell to the ground. Brick walls in St. Louis were shaken down. Windows broke. To say that people were frightened would be an understatement.

Dec. 16, 1811 was the date when the New Madrid earthquake happened in the wee hours of the morning. People had no way of knowing they would be jarred from their sleep by shock waves that ripped through the earth with such force that buildings collapsed, trees toppled, and the mighty Mississippi River changed course. The river actually flowed backward during this ripple in the earth's crust. This event was one of the most powerful earthquakes ever recorded in North America.

It wasn't over. During the next two months, the area would be rocked by three more quakes as powerful as the first in addition to hundreds of smaller after-shocks. The New Madrid quake had enough force to cause deep vibrations within the earth's crust to cause church bells to ring in Washington, D.C. Iowa felt this quake also. In 1811-12, scientists did not have instruments to accurately measure earthquakes. In time this would change with advancements in technology and the setting of ground stations to "listen" to the earth's rock and roll strains.

Sioux City felt a quake on July 3, 1858. A moderate quake near this same city on Oct. 9, 1872 was felt in an area of about 3,000 square miles. An intensity five (V) quake was reported in Keokuk on April 13, 1905. Iowa's southwest area corner at the city of Riverton felt a quake on March 1, 1935 from an epicenter source in southeast Nebraska. Two other significant events are of note. On Oct. 20, 1965, an earthquake in eastern Missouri affected 160,000 square miles that were responsible for cracks in a basement foundation to a home in Indianola. Then on Nov. 8, 1968, somewhere deep in the bedrocks of Illinois, an intensity V quake caused damage reports to come in from Albia, Bloomfield, Burlington, Clinton, Elkader, Muscatine, and Wapello.

Most of the earthquakes that modern super sensitive instruments can detect are not felt by Iowans on the surface. Only the moderate to larger quakes get our attention now. Other parts of the globe are not so lucky. But keep in mind that the dynamics of plate tectonics is an ongoing process. Periodic spasms within deep rock systems release tremendous amounts of pent up energy. We might as well get used to it because we are powerless to do anything about it. To learn more about Iowa Earthquakes, check out the Iowa DNR Geological and Water Survey home page.

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TEN YEARS of success stories will be the focus of the Anniversary of the Conservation Center's grand opening. The Grimes Farm setting is a natural for conservation education and exploration of forest, wetland and prairie environments. Next week's story will feature more details of this excellent facility that the Marshall County Conservation Board embarked upon to help serve you. Saturday, Oct. 12 from 1 to 4 p.m. will be a time to reminisce and celebrate the past ten years. Help in this celebration by attending. Add your name to the roster of previous visitors to the Conservation Center who have come from 48 states and 28 different countries. See you there.

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Remember the CLAY BIRD SHOOT on Oct. 6 at the Ikes grounds. Shooters can register beginning at 8 a.m. Proceeds to benefit Iowa River Hospice. And also note Oct. 19 as the PHEASANTS FOREVER fundraising banquet at the Central Iowa Fairgrounds.

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"There is no medicine like hope, no incentive so great, and no tonic so powerful as expectation of something tomorrow." -Orison Marden

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Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at PO Box 96, Albion, IA 50005.

 
 

 

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