HBW 2 - Foreword on organization of information in HBW by Walter J. Bock

Communication, or the exchange of information, is the cornerstone of sociality regardless of the species, its social structure and the nature of the information being exchanged. All types of information are exchanged, from simple expressions of the feelings and intents of individual animals, to complex hypotheses about the world around us. Most critical in the development of social organisms is the acquisition of communication abilities, both within and between species. These abilities involve sending proper signals and their correct receiving and interpretation. Humans, as social animals, must exchange information with one another and therefore must acquire the needed abilities to achieve this communication. Information held in isolation by a single person is quickly lost, and, indeed, may be considered as knowledge never gained. As individual humans learn new information about the world around them, they continually pass this knowledge on to others before it is lost. In science, as in other human endeavours, much attention is given to methods by which new knowledge is learned. Equally important are the methods by which this information is conveyed to other persons. Efficiency of communication is decisive. As the information becomes ever more complex and abundant, the organization of its communication is ever more critical. Included in this organization is the cost and time involved in the exchange of information. In planning the Handbook of Birds of the World, which will provide a vast amount of information about all living species of birds to ornithologists, professional and amateur alike, and will run to a number of large volumes, the importance of maximizing the efficiency of communication was a major consideration. Success of this undertaking depends not only on the correctness of the included information, but equally on the organization with which this information is presented. Correctness of the information is the responsibility of the authors of individual family and species accounts, but the responsibility for the organization belongs to the editors. The editors had to balance the kind and amount of information presented for each family and species of bird against the number and size of the volumes, and hence the ultimate cost of the entire Handbook.

At the onset of planning, the decision was taken to include information on all living species of birds with a summary of the biology of the family-level taxa. Herein, the first major decision was to cover all living species rather than all recent species included in J. L. Peters' Check-list of Birds of the World. Extinct birds are excluded, although mentioned in the family texts, partly because one of the goals of this project was to interact with BirdLife International (International Council for Bird Preservation) in raising the awareness of problems in the conservation of extant avian species. The next decision to be made was regarding the sequence in which the families and species were to be presented, as well as the internal classification of each family, including the species recognized. Readers of this Handbook do not have to be told that it is impossible to reach agreement between two ornithologists on the limits of all avian species taxa and the classification in which they are arranged.
Regardless of the species definition accepted, recognition of species taxa depends on how allopatric representatives are treated. Haffer (1992) has shown that advocates of each major species concept range from extreme lumpers to extreme splitters. An intermediate course was chosen for purposes of this Handbook, but there will be numerous cases in which allopatric species have been recognized herein which other workers include in a broader polytypic species taxon, and vice versa. The editors have attempted to ensure that such cases are commented on. It should be mentioned that the scientific definition of the species concept and recognition of species taxa is totally independent of the legal meaning of species in treaties and laws on the conservation of living organisms.
The arrangement of avian species taxa into higher level taxonomic groups and the order in which the families and orders of birds are treated within the Handbook is a much more complicated problem. Over the past decades much research has been undertaken on the macrosystematics of birds and many differing classifications have been published. In 1990, C. G. Sibley and his associates published a classification for birds (Sibley & Ahlquist, 1990; Sibley & Monroe, 1990) which differed radically from the Wetmore-Peters system published in the late 1920's and broadly adopted by ornithologists for most of the twentieth century. In turn, the Wetmore-Peters system replaced the very different system used for birds which was established in the early part of the nineteenth century (1825-1840) and used by most ornithologists into the beginning of the present century. This earlier system was adopted in Sharpe's Catalogue of the Birds in the British Museum.
The more neutral term “system” was used above to avoid confusions between the several different concepts embraced within it, namely phylogeny, classification and sequence, as discussed by E. Mayr and W. J. Bock (1994). Birds can be arranged in a phylogeny, or in a classification, or in a sequence, all of which differ from one another and can convey quite different information. Evolutionary relationships (which can be considered roughly equivalent to history) within any group of organisms, including birds, can be expressed either as classifications or as phylogenies, which are distinct, non-redundant ordering systems. Each provides different information about the evolutionary history of these organisms (Bock, 1977, 1981, 1992; Mayr & Ashlock, 1991, chapter 6). Both ordering systems reflect our current and still tentative knowledge of evolutionary relationships, and have to be modified as our understanding improves.
Phylogenies group organisms according to their branching phylogenetic history in which each cladon is holophyletic (containing all forms descending from a common ancestor), and they are often presented in a branching diagram. Cladistic classifications or Hennigian phylogenetic diagrams represent branching phylogenies only and are not general reference systems. Any group of organisms has had a single evolutionary history, and hence a single phylogeny exists for each group. Phylogenetic analyses attempt to discover this true phylogeny.
Classifications arrange organisms according to both the amount of phyletic evolutionary change (anagenesis) and the pattern of phylogenetic branching (cladogenesis), and are expressed as a series of monophyletic (having a common ancestor) taxa arranged in a Linnaean hierarchical system of inclusively nested groups. Classifications reflect the entire evolutionary history of organisms, not only the patterns of branching points. They serve as general reference systems and are heuristic (serving to aid learning, discovery, etc.) in nature. Classifications are used to summarize efficiently information about organisms, to formulate useful hypotheses for empirical testing, and as the foundation for all types of information storing systems. Generally more than one equally valid classification can correspond to the single phylogeny of the group. Classifications are usually presented in a linear form, but this is not essential. Because classifications are generally presented in a linear sequence, the concepts of classification and standard sequence are still confused by most systematists and are ususally considered to be identical.
Important distinctions exist between provisional classifications and standard sequences which serve two exceedingly different purposes in biology. Standard sequences serve strictly for arranging taxa in a linear order in books and all other information retrieval systems for the convenience of the user, who will be able to find the desired information more quickly. They exist for the general worker, who must organize and exchange information about organisms in a taxonomic group, such as birds. Classifications, on the other hand, are the result of taxonomic studies and serve as the basis of discussion among specialists in systematics. Unfortunately, most workers have confused classifications with standard sequences and have changed the sequences with every proposed modification in classification. The failure of biologists to make the proper distinction between them has caused enormous difficulties since the earliest days of biological taxonomy, and has greatly reduced the usefulness of standard sequences.
Standard sequences are strictly heuristic devices, made necessary because humans arrange knowledge in linear systems, such as books, libraries, information retrieval systems, and the like. These standard linear sequences are derived from classifications, and generally several equally valid standard sequences can be postulated from a single classification. Taxa in a standard sequence are listed in a linear order, following a few general rules, such as more primitive groups placed first, and closely related groups placed close to one another. Discontinuities in relationships will occur in the sequence between the end of one complex of related taxa and the beginning of the next. Most important is that when agreement has been reached on a standard sequence, it be maintained over a long period of time. Changes in a standard sequence should be made only when there has been wide acceptance of radical modifications in the underlying classification.
Hence in the early stages of planning the Handbook, the decision was made to follow the Wetmore-Peters' sequence, which has been the widely accepted standard version for ornithologists worldwide ever since its appearance in the late 1920's, as the foundation for the fourth edition of the AOU Check-list of North American Birds in 1931 (Wetmore, 1930, 1960). The sequence given in The Reference List of Birds of the World (Morony, Bock & Farrand, 1975) was followed rather than the Peters volumes, because it adopted many later revisions and included taxa described since the early volumes of Peters. Use of the Wetmore-Peters sequence will permit readers of the Handbook to compare most easily information given in these volumes with that in most other books on birds published since 1930. No claim is made on the correctness of the classification on which the Wetmore-Peters sequence is based relative to other published classifications. The principal object of this Handbook is the maximum exchange of information, rather than an attempt to promote the scientific merits of different avian classifications.
Walter J. Bock
International Ornithological Congress, 1986-1998.
Department of Biological Sciences,
Columbia University ,
New York , USA
References Cited
Bock, W.J. (1977). Foundations and methods of evolutionary classification. Pp. 851-895 in: Hecht, M. et al., eds. Major patterns in vertebrate evolution. NATO Advanced Study Institute, Ser. 14 Plenum, New York.
Bock, W.J. (1981). Functional-adaptive analysis in evolutionary classification. Amer. Zool. 21: 5-20.
Bock, W.J. (1992). Methodology in avian macrosystematics. Bull. Brit. Orn. Club 112A (Centenary Suppl.): 53-72.
Haffer, J. (1992). History of avian species concepts and species limits in ornithology. Bull. Brit. Orn. Club 112A (Centenary Suppl.): 107-158.
Mayr, E. & Ashlock, P. (1991). Principles of Systematic Zoology. Revised Edition. McGraw-Hill, New York.
Mayr, E. & Bock, W.J. (1994). Provisional classifications versus standard avian sequences: heuristics and communication in ornithology. Ibis 136: 12-18.
Morony, J.J., Bock, W.J. & Farrand, J. (1975). Reference List of the Birds of the World. American Museum of Natural History, New York.
Sibley, C.G. & Ahlquist, J.E.  (1990). Phylogeny and Classification of Birds: A Study in Molecular Evolution. Yale University Press, New Haven, Connecticut.
Sibley, C.G. & Monroe, B.L. (1990). Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven and London.
Wetmore, A. (1930). A systematic classification for the birds of the world. Proc. US Nat. Museum 76(24): 1-8.
Wetmore, A. (1960). A classification for the birds of world. Smithsonian Misc. Coll. 139(11): 1-37.