Bird Calendars

NOTES FROM NATURE

By Jerry Toll

Taxonomy: Biology, a system of arranging animals and plants into natural, related groups based on some factor common to each, such as structure, embryology, biochemistry, etc.

When I opened the new Sibley Guide to Birds, I was somewhat dismayed and frustrated to find that my old friends vireos and warblers were no longer closely related families.

The vireos can now be found related to shrikes and ordered just before the corvids such as jays and crows.

I think it is frustrating to many birders when they first see a new field guide or checklist and find that changes have been made to their orderly world of birds. They have either lumped two species together, split a species into one or more new species, or rearranged the families or genera. Baffling.

So I decided to look into how the system works and what criteria is used to create order out of chaos.

Science is about systematics—gathering bits of information, seeing how it fits with other bits of information, putting them into some kind of order, and then forever tweaking the information in the hopes that eventually it can be demonstrated to be correct.  I once heard someone say that nothing new has been learned since the 16th century. j

It took some thought, but I think it can be said if you take a narrow definition of the word "new," everything learned subsequent to the "old" has been an expansion of or systemization of fundamental knowledge from that century or before.

Taxonomy is a fundamental of the principles of biology. All living things are ordered in descending order from the most inclusive: phylum, class, order, family, genus and species.

And then there are prefixes such as sub- and supra- that can be affixed at any level because not all creatures easily fit into a system created by humans. For instance, there are creatures that share characteristics of both plants and animals. Nature is orderly but isn't as tidy as humans would like it to be.

Up until the mid-twentieth century, taxonomists relied heavily on describing the structure of an organism. A bird's bone structure, plumage, even eye color and shape of the beak helped to define what constituted a species.

Since that time, technological developments in other fields have been applied to taxonomy, particularly redefining what constitutes a species.

Advances in the fields of biochemistry and genetics have particularly had a strong effect. DNA testing of all species promises to revolutionize taxonomy.

In the interim, ornithologists are publishing information about bird behavior, vocalizations, ecology, and biochemistry. These characteristics are now factored in when reviewing a species and account for many changes birders have faced in recent years.

For example, enough analysis has now been done on bird vocalizations to theorize that vocal analysis can be used as a first step to realizing the true status of a species. This is particularly useful for neotropical and tropical species where virtually nothing is known about them except a description of plumage.

Perhaps the largest problem bird taxonomists must face is the enormous discrepancy between what is known about birds in North America and Europe and what little is known in the rest of the world. The developed world has had the resources to make advances in understanding birds on our continents, but it has created a bias in understanding the extent of diversity in the rest of the world, particularly the tropics where the greatest diversity lies.

For most tropical birds, only their plumage has been described. Not only that, ecological influences on speciation are more pronounced in the tropics, magnifying the need for behavioral and biochemical analysis.

For these reasons, avian diversity in the tropics is probably vastly underestimated. Conversely, a number of species in the tropics may only be geographical variants or subspecies. Having only plumage descriptions to address this problem is inadequate.

As you can see, the classification of birds is a work in progress.

References:

"Ecology and `Evolution of Acoustic Communication in Birds," edited by Donald Kroodsma. Cornell University Press, 1996.

The Sibley Guide to Birds, David Sibley. Alfred A. Knopf, 2000.

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