AMERICAN MUSEUM Norntates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2741, pp. 1-20, figs. 1-4, table 1 July 30, 1982 A Revision of the Sub-Buteonine Hawks (Accipitridae, Aves) DEAN AMADON1 ABSTRACT This paper is a taxonomic review of the 25 species. Changes from usual treatment include rec- species and approximately 10 genera of chiefly ognition ofthe genus Asturina, merger ofthe genus Neotropical hawks called sub-buteonines and al- Heterospizias with Buteogallus, and transfer ofthe lied to the more advanced genus Buteo. Generic genus Geranospiza to the sub-buteonines. Finally, diagnoses supported by logarithmic ratio diagrams the broad systematics of the chief components of of measurements are presented along with com- the family Accipitridae and the place of the sub- ments on intraspecific variation in a few of the buteonine group within it are discussed. INTRODUCTION The term "sub-buteonines" is here used Eight of the 10 sub-buteonine genera here for a group ofhawks and eagles closely allied recognized are Neotropical. Three of the to the large and nearly cosmopolitan genus species in as many genera, cross the United Buteo. As noted later, certain other genera or States border. Two of them, Asturina nitida groups ofgenera may be regarded as sub-bu- and Buteogallus anthracinus, have distribu- teonines in a more general sense, but they are tions that are primarily tropical and subtrop- less closely allied to Buteo and beyond the ical. The third, Parabuteo unicinctus, extends main scope ofthe present paper. As the name a little farther north to Kansas and farther implies and as defined below the sub-bu- south to central Chile. One of the two Old teonines, though often specialized in various World genera, Kaupifalco, is African, the ways are on the whole more primitive than other, Butastur, African and Oriental, with Buteo; they represent offshoots or continua- one species ranging north in summer to Ja- tions ofthe stock from which Buteo evolved. pan. By way of contrast, Buteo is well rep- Indeed, the group merges more or less insen- resented in the Holarctic, Neotropical, and sibly with the more primitive species ofButeo Ethiopian regions, but virtually absent from and some authors have included certain sub- the Oriental and entirely so from the Austra- buteonines, notably Asturina and Parabuteo, lian regions. The most primitive species of in that genus. Buteo, such as magnirostris, are Neotropical. ' Lamont Curator of Birds, Emeritus, Department of Omithology, American Museum of Natural History. Copyright ©) American Museum of Natural History 1982 ISSN 0003-0082 / Price $1.85 2 AMERICAN MUSEUM NOVITATES NO. 2741 Unlike some species ofsub-buteonines, none figures of features usually used in generic di- ofthe buteos is characteristic oflowland rain agnoses-beak, foot, wing, and tail. All the forest. The 10 genera ofsub-buteonines have species of Accipitridae are illustrated in a total of 26 species; Buteo alone has almost Brown and Amadon (1968). Even those fa- the same number-24. miliar with all or most of the taxa involved Of the 10 genera of sub-buteonines no may find these paintings useful in visualizing fewer than six are monotypic and another the characters of the genera and species. two, Harpyhaliaetus and Butastur, may with Many of the genera and species of birds, more or less uncertainty, be termed what I especially large conspicuous ones such as (Amadon, 1968) have called "quasi-mono- hawks, were described by Linnaeus and by typic," that is, comprised of a single super- those who shortly followed him. At that time species. While the number of genera seems little was known of relationships and generic excessive, the sub-buteonines are a rather diagnoses were skimpy and often misleading. diverse lot and additional information is Still, the synonymies given in such relatively needed before contemplating further changes. early works as Sharpe (1874) show that the The principal changes made herein are to rec- conclusions of early students as to the affin- ognize Asturina (often regarded as a synonym ities ofvarious genera and species were some- of Buteo), to merge Heterospizias with Bu- times sounder than those expressed decades teogallus, and to transfer Geranospiza to the later. sub-buteonines. The phylogeny of the Accipitridae will in There has been relatively little recent dis- the course of time be increasingly dependent cussion of the status and interrelationships upon the fossil record. Birds ofprey, because of the genera of the family Accipitridae. of their large size and because some were Brown and Amadon (1968) outlined a clas- engulfed at sites such as the Rancho La Brea sification for the Accipitridae and diagnosed tarpits, are not so scarce as fossils. Nonethe- the genera in somewhat general terms. This less, fossils contribute relatively little as yet paper may be regarded as a more formal to our understanding of the sub-buteonines. statement of part of that classification which Occasionally, in fact, faulty assignment of is set forth with original citations and ranges fossils has confused the issue (Amadon, for species and subspecies in a checklist of 1963). A complete list of all known fossil the order Falconiformes by the late Prof. E. hawks has been provided by Brodkorb Stresemann and the writer which forms part (1964). of volume 1, revised edition, of "Peters Genera of birds are difficult to define; one Check-List of Birds of the World" (Strese- reason why one finds so few recent ornitho- mann and Amadon, 1979). Original citations logical publications in which there is any at- and other technical details may also be found tempt to do so. This state of affairs is in part in Peters (1931), Friedmann (1950), Hell- the result of the well-known structural ho- mayr and Conover (1949), and Jollie mogeneity of birds. On the other hand, to (1976-1977). make a point that is seldom emphasized, a Dropping back to a somewhat earlier era genus ofbirds may be comparable in geologic one must mention especially Ridgway (1873, age, in degree of ecological uniqueness, and 1876) who in his earlier years was particularly in every other respect except overt morpho- interested in raptorial birds. Since his papers logical characters, to genera of mammals, have been largely forgotten and are scarce, reptiles or other groups. The generic diag- I have quoted from them rather freely. Some noses indicate the size and proportions of of Ridgway's conclusions were incorporated each genus; a more detailed analysis of mea- in Friedmann (1950), that volume being a surements follows in a separate section. continuation of Ridgway's "Birds of North A general discussion ofthe sub-buteonines and Middle America" but the geographical and of their place in the family Accipitridae limitations of this work and its general ap- is postponed until the genera have been dealt proach restricted the treatment of genera as with individually. Inasmuch as Buteo is con- such. Nevertheless, it is an important refer- sidered a later, more derived genus it would ence and, for the genera treated, includes line seem logical to define the sub-buteonines and 1982 AMADON: SUB-BUTEONINE HAWKS 3 then compare Buteo with them. This is re- Color phases rare. Outer primaries less versed here, first because the sub-buteonines sharply notched on inner vanes than in Bu- are the main thrust ofthis paper, and second teo; often more than four outer primaries because they are a group of several genera, with emarginations on inner vanes thus sug- as against the single genus Buteo. gesting that they are in general less skilled at I am indebted to Drs. Wesley E. Lanyon soaring than the species of Buteo. Legs usu- and Lester L. Short for reading the entire ally long, coarse, unfeathered; scalation usu- manuscript and for numerous valuable sug- ally as in Buteo but reticulate rather than scu- gestions. The late Dr. Eugene Eisenmann also tellate in Harpyhaliaetus and partially so in read and criticized the entire paper. Many Butastur and Kaupifalco. In general rather others provided useful assistance on one sluggish; several ofthe species feed primarily point or another, among them Dr. Tom J. on cold-blooded vertebrates or upon crabs Cade, Dr. and Mrs. Frederick N. Hamer- and large centipedes or other arthropods. strom, Dr. Ned K. Johnson and Dr. Helmut Most sub-buteonines are tropical or subtrop- Sick. I am grateful to all of them. ical in distribution, where, according to species, they are found in a variety of habi- COMPARISON OF BUTEO WITH tats, including lowland rain forest. SUB-BUTEONINES GENUS BUTEO LACEPEDE, 1799 THE SUB-BUTEONINE GENERA TYPE: Falco buteo Linnaeus. GENUS BUTEOGALLUS LESSON, DIAGNOSIS: Medium-sized to large hawks, 1830 usually of robust form. Bill of moderate size TYPE: Falco aequinoctialis Gmelin. and normal shape. Head fully feathered. SYNONYMs: Urubitinga Lafresnaye, 1842; Wings rather long, longer than tail, broad and type, Falco urubitinga Linnaeus. Hypo- rounded. Outer three or four primaries morphnus Cabanis, 1844, same type. Hetero- notched on inner vane. Tail of moderate spizias Sharpe, 1874, type Falco meridional- length, usually slightly rounded. Tarsus of is Latham. There is dispute as to whether variable length; feathered for at least one- the generic name Urubitinga was properly third of its length on anterior surface. Tibial introduced, so Hypomorphnus has been used feathers usually long, forming "flags." Adults by some authors; now considered a synonym usually barred or monocolored below; im- of Buteogallus, the problem becomes aca- matures usually streaked. Melanistic and er- demic. ythristic phases present in a high proportion RANGE: Southwestern United States (Texas ofspecies. Habitat plains, semi-open or tem- to Utah and Arizona) south to central Ar- perate woodlands, never the interior oftrop- gentina; also Cuba and the Lesser Antilles.