1902 Encyclopedia > Owl > Classification of Owls

(Part 1)

OWL, the Anglo-Saxon Úle, Swedish Uggla, and German Eule, -- all allied to the Latin Ulula, and evidently of imitative origin -- the general English name for every nocturnal Bird-of-prey, (Footnote 88-1) of which group nearly two hundred species have been recognized.

Classification of Owls

The Owls form a very natural assemblage, and one about the limits of which no doubt has for a long while existed. Placed by nearly all systematists for many years as a Family of the Order Accipitres (or whatever may have been the equivalent term used by the particular taxonomers), there has been of late a disposition to regard them as forming a group of higher rank. On many accounts it is plain that they differ from the ordinary diurnal Birds-of-prey, more than the latter do among themselves; and, though in some respects Owls have a superficial likeness to the GOATSUCKERS (vol. x. p. 711), and a resemblance more deeply seated to the GUACHARO (vol. xi. p. 227), even the last has not been made out to have any strong affinity to them. A good deal is therefore to be said for the opinion which would regard the Owls as forming an independent, or at any rate Sub-order, Striges. Whatever be the position assigned to the group, its subdivision has always been a fruitful matter of discussion, owing to the great resemblance obtaining among all its members, and the existence of safe characters for its division has only lately been at all generally recognized.

By the older naturalists, it is true, Owls were divided, as was first done by Willughby, into two sections -- one in which all the species exhibits tufts of feathers on the head, the so-called "ears" or "horns," and the second in which the head is not tufted. The artificial and therefore untrustworthy nature of this distinction was shewn by Isidore Geoffroy St-Hilaire (Ann. Sc. Naturelles, xxi. Pp. 194-203) in 1830; but he did not do much good in the arrangement of the which then proposed; and it was hardly until the publication ten years later of Nitzsch’s Pterylographie that rational grounds on which to base a division of the Owls were adduced. It then became manifest that two very distinct types of pterlosis existed in the group, and further it appeared that certain differences, already partly shown by Berthold (Beitr. zur Anatomië, pp. 166, 167), of sternal structure coincided with the pterylological distinctions. By degrees other significant differences were pointed out, till, as summed up by Prof. Alphonse Milne-Edwards (Ois. Foss de la France, ii. pp. 474-492), there could no longer be any doubt that the bird known in England as the Screech-Owl or Barn-Owl, with its allies, formed a section which should be most justifiably separated from all the others of the group then known. Space is here wanting to state particularly the pterylological distinctions which will be found described at length in Nitzsch’s classical work (English translation, pp. 70, 71), and even the chief osteological distinctions must be only briefly mentioned. These consist in the Screech-Owl section wanting any manubrial process in front of the sternum, which has its broad keel joined to the clavicles united as a furcula, while posteriorly it presents an unbroken outline. In the other section, of which the bird known in England as the Tawny or Brown Owl is the type, there is a manubrial process; the furcula, far from being joined to the keel of the sternum, often consists but of two stylets which do not even meet one another; and the posterior margin of the sternum presents two pairs of projections, one pair on each side, with corresponding fissures between them. Furthermore the Owls of the same section shew another peculiarity in the bone usually called the tarsus. This is a bony ring or loop bridging the channel in which lies the common extensor tendon of the toes -- which does not appear in the Screech-Owl section any more than the majority of birds. The subsequent examination by M. Milne-Edwards (Nouv. Arch. Du Muséum, ser. 2, i. pp. 185-200) of the skeleton of an Owl known as Phodilus (more correctly Photodilus) badius, hitherto attached to the Screech-Owl section, shews that, though in most of its osteological characters it must be referred to the Tawny Owl section, in several of the particulars mentioned above it resembles the Screech-Owls, and therefore we are bound to deem it a connecting link between them. The pterylological characters of Photodilus seem not to have been investigated, but it is found to want the singular bony tarsal loop, as well as the manubrial process, while its clavicles are not united into a furcula and do not meet the keel, and the posterior margin of the sternum has processes and fissures like those of the Tawny Owl section. Photodilus having thus to be removed from the Screech-Owl section, Prof. Milne-Edwards has been able to replace it by a new form Heliodilus from Madagascar, described at length by him in M. Grandidier’s great work on the natural history of that island (Oiseaux, i. pp. 113-118). The unexpected results thus obtained preach caution in regard to the classification of other Owls, and add to the misgivings that every honest ornithologist must feel as to former attempts to methodize the whole group -- misgivings that had already arisen from the great diversity of opinion displayed by previous classifiers, no two of whom seem able to agree. Moreover, the difficulties which beset the study of the Owls are not limited to their respective relations, but extend to their scientific terminology, which has long been in a state so bewildering that nothing but the strictest adherence to the very letter of the laws of nomenclature, which are approved in principle by all but an insignificant number of naturalists, can clear up the confusion into which the matter has been thrown by heed less or ignorant writers -- some of those who are in general most careful to avoid error being not wholly free from blame in this respect.

A few words are therefore here indeed on this most unprofitable subject. (Footnote 89-1) Under the generic from Strix Linnaeus placed all the Owls known to him; but Brisson most justifiably divided that genus, and in so doing fixed upon the S. stridula—the aforesaid Tawny Owl—as its type, while under the name of Asio he established a second genus, of his contemporary’s S. otus, afterwards to be mentioned, is the type. Some years later Savigny, who had very peculiar notions on nomenclature, disregarding the act of Brisson, chose to regard the Linnaean S. flammea -- the Screech Owl before spoken of—as the type of the genus Strix, which genus he further dissevered , and his example was largely followed until Fleming gave to the Screech-Owl the generic name of Aluco, (Footnote 89-2) by which it had been known for more than three hundred years, and reserved Strix for the Tawny Owl. He thus anticipated Nitzsch, whose editor was probably unacquainted with this fact that when he allowed the name Hybris to be conferred on the Screech-Owl. No doubt inconvenience is caused by changing any general practice; but, as will have been seen, the practice was not universal, and such inconvenience as may arise is not chargeable on those who abide by the law, as it is intended in this article to do. He reader is therefore warned that the word Strix will be here used in what is believed to the legitimate way, for the genus containing the Strix stridula of Linnaeus, while Aluco is retained for that including the S. flammea of the same naturalist.


(88-1) The poverty of the English language -- generally so rich in synonyms -- is here very remarkable. Though four well-known if not common species of Owls are native to Britain, to say nothing of half a dozen others which occur with greater or less frequency, none of them has ever acquired an absolutely individual name, and various prefixes have to be used to distinguish them. In Greece and Italy, Germany and France, almost each indigenous species has had its own particular designation in the vulgar tongue. The English Owlet or Howlet is of course a simple diminutive only.

(89-1) It has been dealt with a greater length in The Ibis for 1876 (pp. 94-105)

(89-2) The word seems to have been the invention of Gaza, the translator of Aristotle, in 1503, and is the Latinized form of the Italian Allocco.

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