Classifying Birds

Morphological Classification System

It was based on the hierarchical sequencing of taxonomic categories: kingdom, phylum, class, order, family, genus, and species. The idea was to compare various anatomic features in order to develop the relationship among bird orders, families, genera, and species. Since bird groups tend to be homogenous, this created significant problems in separating convergent anatomic features from those that reflected true genetic relations among similar-looking species. Developed by Linnaeus (the Latinized name for Swedish naturalist, Carl von Linné) in 1758, it is still used today.

Biochemical Classification System

It provides a better, more detailed picture of the relationship and branching patterns within bird groups. A more defined bird classification system was undertaken by Hans Friedrich Gadow in 1892 and, until very recently, his system formed the basis for the contemporary avian classification system. It was based on shared anatomical characters within each bird group; characters that would indicate a common ancestral lineage. In the 1980s, a group of scientists, Dr. Charles Sibley, Jon Ahlquist, and Burt Monroe developed what is now known as the SAM classification system. This technique allows for exploration of the similarities in the genomes of hundreds of pairs of bird species and is based almost entirely upon genetic relations derived from data received through the DNA-DNA hybridization technique.

One of the most startling results of this new classification system is the change made in the Order Ciconiiformes. Previously, it had included herons, ibises, storks, flamingos, and other related wading birds. Under the new system, Order Ciconiiformes now incorporates these former orders:

Comparing the Systems

Morphological Classification System is considered the old method. It was based on the hierarchical sequencing of taxonomic categories:

Biochemical Classification System is the new method. It provides a better, more detailed picture of the relationship and branching patterns within bird groups. The range is as follows:

Species Numbers

It is estimated that there are more than 10,000 species of birds left in the world. Countless others are now extinct. The estimated breakdown is as follows: