Wednesday, August 8, 2018

Birds--A Special Class

Fantasize with us: If visitors from a faraway planet were to visit our Solar System, what would be their impression of our planet ? If our visitors have sensory systems similar to ours, they would be impacted by the enormous multitude of life forms. To comprehend and catalog even a small part of Earth’s life forms, our visitors would need many years of Earth time. There are 1.2 million animal species already catalogued by scientists. Over eight million species of animals are known. Many remaining species may never be catalogued. The task would be overwhelming.

In biological science, living things are classified according to special systems. Various classification schemes have been offered to students of biology. The most recent widely accepted system was formalized in 1990 in which three domains of life were proposed: archaea, bacteria, and eukaryota. Animals are eukaryotes. Older classification systems listed five kingdoms of Earth life—Monerans, Protists, Fungi, Plants, and Animals. According to the most recent system, there exist 35 phyla (major body plans) of animals under eukaryota (animals). There are 14 plant and 8 fungi phyla. Classification systems have changed as more information became available.

Earth dwellers are most interested in animal and plant phyla. Let us illustrate by referencing the 35 different animal phyla. Of 35 major body plans, by far the two most numerous are arthropods and chordates. Arthropods include about 90% of all animals. Chordates comprise approximately 75,000 catalogued species—a distant second to arthropods. A sub-phylum of chordates is vertebrates, backboned animals with which we are most familiar. For example, birds belong to this sub-phylum. More specifically, they are also included in the next category—the class aves (birds). They are represented by over 10,000 species worldwide.

How does Wikipedia describe class aves? Birds are “…a group of endothermic vertebrates characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a chambered heart, and a strong yet light weight skeleton.”

On a recent walk I encountered a neighbor who thought he had not observed as many birds this year as in previous years. After considering his observation, I stated that our neighborhood bird census varies from year to year. There may be reasons for this variation. It is, however, a normal phenomenon. We must not think that our favorite birds will favor us with command performances all year, every year. For example, we have not heard great horned or barred owls calling for several months. 

A substantial majority of the roughly 5-6 dozen birds we commonly observe in our “Driftless Area” neighborhood have appeared this year, as if “on cue.” (The Driftless Area is a unique geological region of the upper midwest related to an anomaly of the last Ice Age.) One neighbor informed me that she has observed 153 different bird species during her residency in this area. The official list of different bird sightings in the entire state of Illinois is 444. This number includes nearly 50 different warblers, 30 sparrows, and 50 diverse waterfowl which do not frequent our neighborhood. A confession is in order: I counted “warbler” and “sparrow” in my personal list but once.

The incredible physical and behavioral variety of our northwest Illinois birds inspires praise and thankfulness to our Maker. No doubt readers could affirm the same degree of inspiration for their personal place of abode. Many times I have expressed to our children and grandchildren that, “God had great ideas.” We acknowledge Him, “…who richly gives us all we need for our enjoyment.” (I Tim. 6:17 NLT).

In examining the list of several dozen birds we have personally sighted in our immediate neighborhood, it is apparent that a significant number of them merit detailed description in terms of size, physical appearance, diet, nesting habits, song, flying characteristics, and other unique behavioral categories. If we assign the number of identifications at 60, we are dealing with only 0.6% of the 10,000 worldwide bird species. In the phylum, class, order, family, genus, species scheme of biological classification, class aves broadens to many thousands of species as we descend through the classification system of living things. Our hypothetical visitors from a faraway planet could barely scratch the surface attempting to describe the magnificent profusion of life on Planet Earth on a visit of several months or years.  

We close with links to two past posts. They describe a single species, a favorite, tiny, colorful Driftless Area bird. The enjoyment indigo buntings supply is remarkable visually, auditorily, and behaviorally. When almost all birds have given their avian vocal cords leave by late afternoon, this summer our avian dynamo continued to sing  mightily. I suspect these birds may be descendants of an indigo bunting which sang from the same dead branch several years running early in the current decade after annually returning from a migration route of thousands of miles.