Christian Ludwig Brehm (1787–1864) on species and subspecies of birds | Christian Ludwig Brehm (1787–1864) über Spezies und Subspezies von Vögeln

C. L. Brehm’s main ornithological objective was to increase the knowledge of the natural history of the European bird species including their seasonal migrations. For this reason he analyzed in detail the variation of birds and described many subspecies from different regions of Europe. 55 of his geographical subspecies have later been accepted as valid. In addition, Brehm suggested that,during the breeding season, most widely distributed species of birds form an ecologically determined microgeographical mosaic of slightly differentiated populations each of which he also distinguished by a separate subspecies name. However, these named groups later turned out to have been based on individual variants of widespread breeding populations which cannot be designated with separate taxonomic names. On the other hand, during the 20ᵗʰ century, the existence of ecological forms within subspecies differing in certain biological characteristics has been confirmed for many bird species. Like his colleagues, Brehm distinguished species and subspecies of birds. Beginning in 1826, he treated the subspecies as separate reproductive communities conceptually like „species“. At the same time, however, he grouped most of them into polytypic species. In hisHandbook of the Natural History of all the Birds of Germany (1831) Brehm numbered the subspecies of a particular species consecutively (e. g. 1–3) and gave each of them a Latin binomen followed in parentheses by their common species name. The sequence of subspecies composing the next species (e. g. 1–5) begins again with that species’ subspecies number 1. Monotypic species are not numbered. In later lists (1855a, b) he presented the hierarchic system of genus, species and subspecies more clearly than in his earlier publications. Generally speaking, Brehm emphasized in his work the analysis of the smallest morphological-ecological units (subspecies), while his colleagues and adversaries F. Faber and C. W. L. Gloger practiced the combination (synthesis) of subspecies into broadly delimited taxonomic species.