Birds and Birding's Guide to:
Watching THE SPARROW-LIKE BIRDS
(Order Paseriformes)
We have now come to the last, but by no means the least, of the twenty-one orders into which birds are here divided, for within its limits are included approximately seven thousand species and subspecies, or nearly half of all known birds. To give these the general designation of Sparrow-like birds implies a more or less close resemblance to a typical Sparrow, but as a matter of fact only a comparatively few would probably be so recognized by the casual observer, and it is to be understood as standing, in the absence of a better popular term, for the general passerine type, the actual resemblance between them being often confined to agreement in minute, though relatively important, anatomical characters.
The difficulties of satisfactorily dividing and arranging this vast assemblage are well set forth by Mr. Robert Ridgway, who says: “Notwithstanding this enormous number of specific forms, the type of structure is remarkably uniform, and the group far more homogeneous than the lower groups of equal rank. Consequently, subdivision of the Passeriformes becomes a matter of extreme difficulty, and no arrangement has thus far been proposed which can be considered entirely satisfactory. Indeed, it seems impossible to subdivide the order, beyond a very limited extent, into lesser groups, which are equivalent in taxonomic rank to the families of other orders, and the extent to which this may be done is a matter concerning which systematists differ widely in their views. ... It may be, and doubtless is, perfectly true that no more than three passeriform groups can be defined which will be equal in taxonomic rank to the families of other orders of birds; but the objection to this meager allowance — and it is a very serious one — is that two of the three groups contain together only about one fifth the total number of the species, so that there are still left about five thousand species in the third. Obviously, these five thousand species (more or less) must be susceptible of segregation into a considerable number of more or less trenchant groups; and there being so few grades of rank between a family and a genus, what to call these groups becomes a very serious question."