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Home , Hoatzin, Turaco

Comparative of MU50phagidae ()

by Georgann B. Johnston Sacramento, CA Introduction proVides the red colored in he 20 which comprise species of the first two genera. Both the avian Musophagidae' pigments contain copper and spectral (commonly called turacos) data demonstrates that the former is have a number of physical and likely an oxidized version of the latter. anatomical characteristics that set them swered and many generalizations sus­ (Dyck, 1992) In fact, the two pigments apaI1 from many other . While pect in light of new information about are intermingled within individual uniformity among the 20 species is not these species' ecology including feathers in the breast patches and crests complete, ceI1ain generalizations can behavior and diet. of some species and turacoverdin be made. One ofthese is that the sexes occurs only in the presence of turacin. are visually indistinguishable in all of Feathers Other species outside the the species save C. Jeucogaster, in Probably the most distinguishing fea­ Musophagidae order have turacoverdin which the males have a black ture of these birds are two unique pig­ pigment, including Ithaginis () and the females a green beak. ments deposited in their keratin. and Rollolus (paI1ridge), both members Unfortunately, most of the literature One, turacoverdin, is a green pigment of the . An additional inter­ regarding the anatomy of these birds found in the rami in all species of esting note is that both pigments are was developed more than 40 and Musophaga, and in soluble in a weak base - which may ago, leaving many questions unan- Corythaeola cristata. The other, turacin, have led to the myth that wild birds lose

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the afa WATCHBIRD 43 feather color when exposed to rain. Internally, a single unifying factor is points to a possible evolutionary rela­ Another uncommon feature of that all species lack a vomer. (Sibley & tionship between turacos and the these birds is that the feathers of the Ahlquist, 1990) Additionally, the pala­ . The hoatzin is noted for being head and breast of most species are tine processes arise from the more an that has a crop, which deficient in barbules so that they seem proximal end of the maxillary bone acts as a glandular muscular stomach hairy or have a "down-like texture." and the distal ends of the uncinate used to grind up tough . Thus, a (Moreau, 1938; Moreau, 1958) These bone end in a sharp curve where they reexamination of the digestive anato­ feathers make up the characteristic meet the outer rim of the palatine. my ofthe Great Blue might be in order erectile "crests" found on all but three (Lowe, 1943) Moreover, the quadrate to see if its foregut differs from other ofthe species. In addition, the contour bone in turacos is pneumatized, one of turacos in conformity with its variant feathers have an aftershaft. (Sibley & the facts that earlier taxonomists relied diet. Likewise, the dietary research Ahlquist, 1990) upon to distinguish these birds from raises the additional question of The wing to tail ratios are uniform that have a solid quadrate. whether the Great Blue actually lacks a across the species, with the wing Finally, the tongue is short and thick ceca - since that organ is often length at four-fifths of the tail length. and of a triangular shape, consistent involved in the fennentation-digestion The wings are rounded with the sec­ with the tongue shape found in other of plant material. ondaries usually a bit shorter than the frugivorous birds. primaries. Also, some of the primaries Skeleton are slotted, probably related to the Digestive System The lack of a furcula is probably the short, slow flight patterns used by Turacos have no crop but do have most significant skeletal feature of these birds. (Moreau, 1958) None of an exceptionally large and well devel­ these birds. (Sibley & Ahlquist, 1990) the species have eyelashes but all of oped proventriculus, with walls twice This is consistent with the fact that they them do have a tufted, bilobed uropy­ as thick as those of the gizzard. The are "strictly arboreal, but poor flyers, gial gland. (Lowe, 1943) gizzard, in tum, has only a thin mus­ moving from canopy to canopy with cular structure with no horny cuticle or bursts of flapping and unstable-look­ Feet koilin lining its interior. Additionally, ing gliding." (Fry, et al., 1988) With These birds are defined as having turacos lack a caeca. These anatomical slight variation, all species have 15 cer­ semi-zygodactyl feet with the fourth features are consistent with the fact vical vertebrae, 19 presacral vertebrae toe being reversible and not perma­ that turacos are primarily frugivores, and five dorsal vertebrae. nently directed backwards. A typical though they have been known to eat With respect to the skull, character­ resting position will find the outer toe insects and snails, particularly when istics of note include relatively huge at approximate right angles to the they are feeding young in the nest. lacrymals that connect with the frontal main axis of the foot, but it can be (Fry, et al., 1988) The major exception bones and a large horizontal and back­ moved further back or directed for­ to this diet is seen in the Great Blue wardly projecting process of bone that ward, depending upon the bird's C. cristata which ingests a sig­ is deeply grooved for the passage of perching needs. Additionally, the nificant number of leaves, algae, and the nasal ducts. (Lowe, 1943) Turacos are short and abruptly curved. rootless floating plants as part of its are classified as desmognathous birds (Moreau, 1938) Some researchers have diet. (Sun, et al., 1997) as stated above, there is not a com­ reported that nestlings have a short Since so little has been published plete "shelf' between the nasal and (approximately Imm) wing- but regarding the digestive systems of the oral cavities. this seems to vary from species to turacos it is difficult to make accurate It is interesting to note that studies species and even among individuals generalizations regarding this portion of the record demonstrates cer­ within a species, and because of this it of their anatomy. Two studies regard­ tain similarities between the "basal cannot be said with certainty that it is ing intestinal parasites have been land bird assemblage" and turacos, tin­ a defining anatomical feature. undertaken, primarily for the purpose namous, gallifonnes, cuckoos, and (Moreau, 1958; Fry, et al., 1988) of determining the phylogenetic rela­ . (Olson, 1985; Houde, 1988) tionship ofthese birds to other species, This conclusion is based, primarily, on Beak & Head but these studies do not describe the the well-defined terminal iliac process All turacos have short strong anatomy in any detail. (Clay, 1947; of the modem birds resembling the with curved culmen. In some species Bennett, 1993) lithornithid pelvis. the culmen is ridged (T bannermani, As an aside, with the recent confir­ An observation based on ecology leucolophus, and macrorhynchus) and mation by Sun and his associates that alone seems to have been proved cor­ in others curves back into a frontal plate a significant portion of the diet of C. rect: all of these birds inhabit an area (M. rossae and violacea). The nostrils cristata is leaves and related plant mat­ surrounding the "equatorial rain belt" are located on the beak but vary in ter, it would be interesting to pursue which has been "remarkably stable in shape and position. Some species have the comparative anatomy of the diges­ shape and extension from early slit-shaped nares while others have cir­ tive system of the turacos generally Tertiary times - that is, for long as cles; in many species the nostrils are and the Great Blue in particular. Musophagidae are likely to have been covered with feathers. (Moreau, 1958) As stated below, recent research a distinct ." (Moreau, 1958)

44 July/August 1999 Muscles this order need to be refined and more Yeterinarians The muscles of the wings and accurately delineated, particularly in Commercial embers brea t are "relative to most other birds, light of recent discoveries with respect feehly developed, and are long, thin to ecology, diet, and DNA structure. Bobbie Faust, DVM and narrow slips." (Lowe, 1943) The With many of the turaco species listed Faust Hospital, Al, 602-482-2191 pelvic muscles include the caud­ as endangered or threatened by CITE , Ross Babcock, DVM Palo Verde Animal Hospital, Al, 602-944-9661 ofemoralis, iliofemoralis, semi-tendi­ new information about their anatomy Hillary Frank, DVM, nosus, accessory semi-tendinosus, and physiology, which could con­ North Central Animal Hospital, Al, 602-395-9773 iliofemoralis externus, iliacus plantaris tribute to succes ful captive breeding and the popliteus. (Sibley & Ahlquist, programs, is critical before the popula­ Edvardo Acosta, DVM Sunset Cliffs Animal Clinic, CA, 619-224-0773 tions are lost entirely. 1990; Lowe, 1943) Turacos have very Four Comers Veterinary Hospttal, CA, 510-685-0512 well developed M. fibularis longus, Alan Fudge, DVM which end in strong, rounded, cord­ Avian Medical Center of Sacramento, CA like tendons above the tibiotarsal joint. Footnote 916-727-2663 (Lowe, 1943) It is likely that the exag­ , Currently, authoritie believe that turacos Brian Speer, DVM should be afforded eparate statu a their Oakley Veterinary &Bird Hospttal, CA, 510-625-1878 gerated development of this muscle is own order (Mu ophagaformes) instead of in keeping with the mode of locomo­ being categorized a a family under the order Rhoda Stevenson, DVM tion utilized by these birds - short Cuculiformes. Regardless, there are six gen­ Exotic Bird Hospital, FL, 904-268-0204 hops from branch to branch. era of turacos - Corythaeola (1), (2) Kitty Remington, DVM Corythaixoide (2), Criniferoide (1), Animalhouse Vet Services, GA, 912-243-0380 DNA & Phylogeny Mu .. ophaga (4), and Tauraco (10). Initially, taxonolnists classified tura­ Drs. Nye, Ness, McDonald, Mori, DVMs cos with cuckoos as two families in the Midwest Bird &Exotic Hospital, IL, 708-344-8166 order Cuculiformes, based primarily References Ellen K. Cook, DVM, IN on external appearance. Beginning in the early part ofthe 20th century, how­ B nnett, G.F. 1993. Leucocytoxoide of 'outh African bird pecie. Ostrich, 64:73­ Pulaski Veterinary Clinic, MD, 410-686-6310 ever, detailed examinations of the 78. skeletal structure, feather tracts and Clay, T. 1947. The systematic po ition of the Wendt Emerson, DVM Musophagi as indicated by their Mobile Veterinary Services, MA, 978-887-3836 digestive systems ofboth types ofbirds Mallophagan parasites. Ibi ,89:654-656. William Sager, DVM led to the conclusion that they were Dyck J 1992. Reflectance pectra of Littleton Animal Hospital, MA, 508-486-3101 not as closely related as had been areas colored by green feather pig­ ments. Auk, 109:293 301. Pulaski Vet Clinic, Baltimore, MD believed. (Lowe, 1943) Fry, C.H. S. Keith and E.K. Urban. 1988. The Even as recently as 20 years ago, Bird of Africa. 01. 3. Academic David Kersting, DVM some researchers continued to press Pre ,San Diego. Houde, P.W. 1988. Paleognathous bird fron1 Bird Medicine &Surgery, MO, 314-469-6661 the association hased on an analysis of the early tertiary of the northern -white proteins. (Sibley & Ahlquist, hemi phere. Publication of the Amory Animal Hospital, MS, 601-256-3548 1972) However, in the mid-1980s, a Nuttall Ornithological Club. o. 22. Cambridge. 148pp. Ridgewood Veterinary Hospital, NJ, 201-447-6000 comparative chromosome banding Lowe, P. R. 1943. Some note on the anatomi 'al Woodbridge Veterinary Group, NJ, 908-636-5520 study was undertaken which revealed differences obtaining bet een the a lack of phylogenetic relatedness Cuculidae and the Mu ophagidae, Patrick J. Hauck, DVM with special reference to the pecial­ Las Vegas, NV between turacos and cuckoos, justify­ ization of the oesophagus in Cuculu. ing their assignment to a family oftheir canorus Linnaeus. Ibis 85:490-515. Moreau, R.E. 1938. A contribution to the biolo­ J.e. Adsit, DVM, NY, 518-463·0600 own. (Tuinen & Valentine, 1984) Even gy of the Mu ophagiforme I the so­ more important, however, is the fact called Plantain-Eaters. Ibis, 11 :639 Bob Dalhausen, DVM, MS that based on this chromosome study, 671. Research Associates Laboratory, OH, 513-248-4700 Moreau, R.E. 1958. Some aspect of the it appears that turacos as a group are Donn Griffith, DVM Musophagidae. Ibis, 100:67-112, Exotic Animal Consultants & Bird Hospital, OH more closely related to the gallina­ 238270. 614-889-2556 ceous birds from an evolutionary Olson, S.L. 1985. The fos il record of birds. In Wallace Wendt, DVM Farner, D.., JR. King and K.C. Parks. Drs. Roberts & Wendt Animal Hospital, OH standpoint. (Houde, 1988) Avian Biology vol. 3, Academic Pres Orlando, pp. 79-238. 216-521-0533 Sibley C.G. and JE. Ahlquist. 1972. A compara­ Linda Wiley, DVM Conclusion tive tudy of the egg-white proteins of Metropet Animal Hospital, OH, 219-826-1520 While a brief flurry of investigation non-passerine birds. Peabody into the anatomy of the Musophagidae Museum Nat. Hist. Yale Univ. Bull., Bruce Puchat, DVM 39:1 -276. was undertaken nearly 50 years ago, Pleasant Valley Animal Hospital, PA, 610-346-7854 ibley, C.G. and J.E. Ahlqui t. 1990. Phylogeny Lee Simpson, DVM nothing significant in the realm of and Classification of Bird . Yale Pre , Kutztown Animal Hospital, PA, 610-683-5353 comparative anatomy or physiology New Haven. Sun, C., T.C. Moermond and T.]. Givni h. 1997. James F. Gaines, DVM, Chan illy, VA has been published since. The broad Nutritional determinant of diet in generalizations regarding certain phys­ three turacos in a tropical montane ical characteristics of the members of . Auk, 114:200-211. •

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