The Condor 86~42-47 0 The Cooper Omthological Society 1984

THE SYSTEMATIC POSITION OF THE COCOS FLYCATCHER

WESLEY E. LANYON

ABSTRACT.-The Cocos Flycatcher (Nesotriccusridgwuyz), traditionally allied with , was recently placed in another subfamily, Fluvicolinae, near Ernpidonax and Cnemotriccus.A comparative study of the skull and syrinx dem- onstrates that the nearest relatives of Nesotriccusare Phaeomyias murina and Capsiempisflaveoluin the subfamily Elaeniinae, sinceall three generashare unique derived character states of the nasal septum and of the supporting elements of the syrinx.

In 1891 Charles Townsend collected a new I had decided on the basis of external mor- flycatcher on Cocos Island, which he later phology alone to exclude Nesotriccus from named Nesotriccusridgwayi (Townsend 1895). Myiarchus. I doubted that nestsof Nesotriccus, He called attention to the zoogeographicand, when discovered, would be located within tree inferentially, the morphological relationship cavities and lined with fur and feathers, the between his new monotypic genusfrom Cocos, derived nesting behavior that defines the over 500 kilometers off the Pacific coast of myiarchine flycatchers(Lanyon 1982, Lanyon Costa Rica, and an equally interestingflycatch- and Fitzpatrick, 1983). Subsquently I exam- er in the GalapagosIslands, magnirostris, which ined the skull of Nesotriccusand, contrary to Ridgway (1893) had recently removed from the findings of Warter (1965) found it to be Myiarchus and placed in its own , Eri- very distinct from the skull of Myiarchus. My bates. Hellmayr (1927) similarly was im- interest in Nesotriccuswas revived with the pressedwith the affinity of Nesotriccusand Er- descriptions of the first known nests (Sherry, ibatesand placed both close to Myiarchus, the in press)and the availability of alcoholic spec- widespreadand successfulmainland genus.As imens taken by Sherry. I was certain that a recently as 1955, Eisenmann followed Hell- careful study of the skull and syrinx would mayr in placing Nesotriccusnext to Myiarchus provide meaningful clues to the nearest rela- in a list of speciesof Middle American . tives of Nesotriccus.This paper presents the Subsequent recommendations (Swarth 193 1; results of that study. Lanyon 1978; Zimmer, unpubl. notes, Amer. Mus. Nat. Hist.) that magnirostris should be METHODS returned to Myiarchus left unresolved the sys- Research on the skull (Warter 1965) and the tematic position of Nesotriccus. syrinx (Ames 197 1) has demonstrated the The allegedaffinity between Nesotriccusand utility of these structures in determining re- Myiarchus was rejected by Swarth (193 1) and lationships within the suboscines.I have been Zimmer (unpubl. notes) on the basis of exter- influenced greatly by both of these important nal morphology. In a study of cranial anatomy, studies and I follow the terminology of these Warter (1965) concluded that Nesotriccus“ ap- authors. Two complexes in particular have pears intermediate in structure between the proven effective in diagnosinggroups of tyrant Myiarchinae (s.s.) and Todirostrum, but oth- flycatchers: (1) the nasal septum, and notably erwise is probably more closely related to the the degree to which there is ossification and former.” Ames (197 1) reported the syrinx of buttressingwith internal and/or laterally pro- Nesotriccusto be unlike the syringesof Myiar- jecting supporting elements, and (2) the mor- thus, Empidonax, Contopus, and Cnemotric- phology of the bony and cartilaginous sup- cus, but made no recommendation as to how porting elementsin the syrinx, and in particular Nesotriccusshould be classifiedon the basisof the number, shape,and position of the internal syringeal morphology. In the only definitive cartilages(Lanyon 1982, Lanyon and Fitzpat- classification of the Tyrannidae since Hell- rick 1983). mayr (1927) Traylor (1977) removed Neso- Thus far I have examined the skulls of 83 triccusfrom its traditional position among the genera and the syringesof 86 genera of the 9 1 myiarchine flycatchers and placed it in the genera of tyrant flycatchers (sensu Traylor subfamily Fluvicolinae, between Empidonax 1977) in a larger, ongoing study of the phy- and Cnemotriccus, on the basis of external logeny of the Tyrannidae. In addition to the morphology. anatomical collections at the American Mu- At the time that I was completing my re- seum of Natural History (AMNH), material vision of the genusMyiarchus (Lanyon 1978) hasbeen borrowed from the Carnegie Museum

1421 COCOS FLYCATCHER 43

Nesotriccus

Phoeomyias and Capskmpis’ Septa

/ Y

Fluvicoline Septa -v-

FIGURE I. Photographsof the skulls of selected tyrant flycatchers (ventral aspect; anterior end to the left) and diagrammatic representationsof cross sectionsof the correspondingnasal septa (projecting downward from the roof of the nasal capsule): I, 2 Nesotriccus ridgwuyi (AMNH 92 IO), I5 x and 20 x ; 3, Phaeomyias murina (AMNH 7306), 20 x ; 4, Capsiempisflaveola (UMM 200869), 20 x ; 5, Empidonax euleri (AMNH 6934), 15x ; 6, Cnemotriccusfuscatus (AMNH 6685), I5 x ; 7, Myiozetetes similis (AMNH 7 l73), IO x ; 8, Myiarchus tuberculifer (AMNH 7 l75), 10 x . Arrows indicate presenceof trabecular plates on the nasal septa of all skulls except those of the two tyrannines (7 and 8). ofNatural History in Pittsburgh,the Field Mu- gerkus and Uhler 1977) to facilitate the study seum of Natural History in Chicago (FMNH), of the supportingelements and to differentiate the Museum of Zoology at Louisiana State between bony and cartilaginous tissue. University in Baton Rouge (LSU), the Mu- seum ofZoology at the University of Michigan RESULTS AND DISCUSSION in Ann Arbor (UMMZ), the National Museum of Natural History in Washington, D.C., and NASAL SEPTUM the Peabody Museum of Natural History, Yale The nasal septum of Nesotriccusis character- University, in New Haven. Specimens cited ized by having (1) a well-developed internal here are identified to collection by the abbre- supporting rod that presumably servesto but- viations given above. Syringes were stained tress the septum (“r” in photographs 1 and 2, with alcian blue and alizarin red (after Din- Fig. l), and (2) a trabecular plate in the form 44 WESLEY E. LANYON of short and narrow lateral projections from The syringesof the fluvicolines with which the septum, elevated above the ventral edge Traylor (1977) associated Nesotriccus, i.e., of the septum and located near the ventral end Empidonax and Cnemotriccus, have a very of the internal supporting rod (indicated by different morphology: (1) the tracheal elements arrows in photographs 1 and 2 and the cor- are not fused into a drum, (2) the pessulusis responding cross-sectionaldiagram in Fig. 1). cartilaginous,narrow, and not well-developed, The posterior ends of these lateral projections and (3) the internal cartilages are large, very extend caudally in closeproximity to, but more broad, and nearly straight (photographs4 and or less free from, the septum. 5 in Fig. 2). Since none of the genera in Tray- Only two genera of tyrant flycatchers other lor’s Fluvicolinae has a well-developed drum, than Nesotriccushave the unusual character- as seenin Nesotriccus,I was puzzled by Ames’s istics of the nasal septum described above. (1971:61) description of a drum in the syrinx These are the monotypic Phaeomyias and of Cnemotriccuspoecilurus (=Knipolegus poe- Capsiempis,both placed by Traylor (1977) in cilurus in Traylor 1977). I reexamined the the subfamily Elaeniinae. Their nasal septa, specimen(AMNH 6743) that he had dissected illustrated in photographs 3 and 4, Figure 1, and found that it had been mislabeled; it was are remarkably similar to that of Nesotriccus. actually Mecocerculus leucophrys,which be- Traylor (1977) placed Nesotriccus in his longs in the Elaeniinae and has a well-devel- subfamily Fluvicolinae, between Empidonax oped drum. and Cnemotriccus. All of the genera in this The syrinx of Myiarchus and near relatives subfamily, except Nesotriccus,have a large, (Lanyon 1982, Lanyon and Fitzpatrick 1983) conspicuoustrabecular plate located along the differs from that of Nesotriccusin (1) the lack ventral edge of the nasal septum, i.e., not el- of fusion of tracheal elements into a drum, (2) evated above the ventral edge (indicated by the absenceof a well-devloped bony pessulus, arrows in photographs 3 and 4 and the cor- and (3) the presence of two pairs of internal responding cross-sectionaldiagram in Fig. 1). cartilages, the larger of which attaches to the Moreover, the plate in the fluvicolines is no- ventral portion of the trachea-bronchial junc- ticeably concave when viewed in crosssection. tion and is L-shaped (photograph 6 in Fig. 2). All of the genera in Traylor’s (1977) third subfamily, the Tyranninae (which includes TAXONOMIC CONCLUSIONS Myiarchus and relatives), have nasalsepta that The first conclusionto be drawn from this study lack a trabecular plate. When viewed from be- of the nasal septum and the syrinx of Neso- low, the ventral edge of the septum in all tyr- triccusis that the notion of close relationship annines is thin and almost knife-like as illus- with the myiarchine flycatchers, through trated in photographs 7 and 8, Figure 1, and Myiarchus magnirostris of the Galapagos Is- there are no lateral projections of any kind. lands, should be put to rest once and for all. There simply is no morphological support for SYRINX this old contention, and therefore Traylor For the purposesof this study, the significant (1977) was correct in removing Nesotriccus characteristics of the supporting elements of from his subfamily Tyranninae. the syrinx of Nesotriccusare: (1) the fusion of What did Warter (1965) see in the septum the bony elements A2 through A4 into a drum of Nesotriccusthat suggestedmyiarchine char- (“d” in photograph 1, Fig. 2) (2) the presence acteristics?I borrowed the single Nesotriccus of a well-developed bony rod or pessulusin skull (LSU 42902) that he examined and found the trachea-bronchial junction (“p” in pho- it to be like the one I describedabove (AMNH tograph 1, Fig. 2) and (3) a single pair of rel- 9210). I suspectthat, when Warter (1965, Ta- atively narrow internal cartilages,attached an- ble II) classifiedthe nasal septa of Nesotriccus, teriorly to the dorsal ends of the Al elements Phaeomyias and Capsiempisas the same type and the drum, and moderately forked at the that he found among the myiarchine flycatch- free end. These cartilages are slightly curved, ers (Type 2) he did so because of the con- with the forked end pointing away from the spicuousinternal supportingrod. This feature, medial plane (“c” designatesthe right internal though present in the myiarchines (see “r” in cartilage in photograph 1, Fig. 2). photograph 8, Fig. l), is not unique to that I know of only two tyrant genera that share group; many other tyrants have a comparable with Nesotriccusthe combination of syringeal structure, though usually not nearly as con- characteristicsdescribed above. These are the spicuous and well-developed. What distin- monotypic Phaeomyias and Capsiempis,and guishes the myiarchines from all other fly- their syringesare illustrated in photographs 2 catchers is the presence of the conspicuous and 3 in Figure 2. internal supporting rod in the absenceof any COCOS FLYCATCHER 45

FIGURE 2. Photographsof the syringesof selectedtyrant flycatchers(dorsal aspect): 1, Nesotriccus ridgwuyi (AMNH 8067), 20 x ; 2, Phaeomyias murina (FMNH 29 1280) 20 x ; 3, Capsiempisflaveola (AMNH 7709) 20 x ; 4, Empidonax euleri (LSU 102573) 20x; 5, Cnemotriccus fuscatus (LSU 101499) 20 x; 6, Myiarchus swainsoni (AMNH 799 I), I5 x Letters designate structuresas follows: d, fusion of bony supporting elements into a drum; p, well-developed bony rod or pessulusin the trachea-bronchialjunction; c, right internal cartilage.

kind of trabecular plate. Nesotriccus,Phaeo- external morphology. I believe the additional myias and Capsiempis all have a small but syringeal evidence presented here, which also distinctive trabecular plate. denies relationship with the fluvicolines, pro- A secondconclusion is that Nesotriccuscan- vides a compelling and convincing argument. not be assignedto the Fluvicolinae. No genus Thirdly, Nesotriccusridgwayi alone, of those in that subfamily, as constituted by Traylor studied thus far, shares with Phaeo- (1977) is known to have a trabecular plate myias murina and Capsiempis jlaveola de- elevated above the ventral edge of the nasal rived states of the nasal septum and of the septum, or to have the bony supporting ele- supporting elements of the syrinx. The con- ments of the syrinx fused into a well-developed cordance between these two very different drum. Traylor (1977: 162) was aware that Ne- character complexes in all three genera is truly sotriccuslacks featuresof the nasalseptum that impressive and cannot, I think, be accounted characterize the Fluvicolinae, but chose to for other than by relatedness.The suggestion override this considerationwith emphasisupon that Nesotriccusand Phaeomyias are near rel- 46 WESLEY E. LANYON atives, though novel, is compatible with con- myias, and its distribution is compatible, ex- siderations of external morphology, nesting tending as it does from Nicaragua through behavior (Haverschmidt 1970; Sherry, in press) much of South America. and zoogeography. Nesotriccusis a somewhat Presumably all three genera, Nesotriccus, larger edition of Phaeomyias,sharing with that Phaeomyias and Capsiempis, belong some- widespread mainland form (Panama and where within the subfamily Elaeniinae as con- widely scatteredregions of South America) the stituted by Traylor (1977). Since I have doubts dull brownish upperparts, a pale superciliary about the monophyly and hence the compo- line, and buffy wingbars. The most obvious sition of this assemblage,I can make no rec- difference in their appearance is the propor- ommendation as to the relationship between tionately longer, more spatulate bill of Neso- them and other genera presently assignedto triccus, a characteristic that might easily be the Elaeniinae until we have a more satisfac- acquired under the insular conditions of Co- tory phylogeny of the family Tyrannidae. cos, and one that would enable greater ex- ploitation of the available food supply in the ACKNOWLEDGMENTS absenceof competitors (Grant 1968). It was the field work of Thomas Sherry on Cocos Island As a general rule, I question the utility of that rekindled my interest in the endemic flycatcherthere. vocal charactersfor determining relationships I am indebted to him for comments on an earlier draft of this manuscriptand for providing the alcoholic specimens among genera of tyrant flycatchers, and would (by way of the Field Museum of Natural History) that insist on judging relatedness primarily upon were crucial for this study. I thank F. Gary Stiles for send- the sharing of derived morphological charac- ing me a copy of his CocosIsland recording,and for shar- ters. A consideration of vocal characters,how- ing with me his field experience with Nesotriccus.I am grateful to the following for arrangingloans of specimens ever, may provide interestingsupplemental ar- under their care: John W. Fitzpatrick, Storrs Olson, Ken- gumentsfor confirming the clusteringof genera. neth C. Parkes, JamesV. Remien, Charles G. Sibley, and While I was still debating whether or not to Robert W. Storer. The photographsof skullsand syringes acquire some field experience with Nesotric- were made with equipment in the laboratory of Charles cus, as part of continuing studies of the puta- W. Myers, my colleagueat the American Museum of Nat- ural History. tive relatives of Myiarchus, I received a copy of a recording of Nesotriccusvocalizations that LITERATURE CITED F. Gary Stiles had made during a visit to Cocos AMES,P. L. 1971. The morphology of the syrinx in pas- in 1978. I subsequentlyplayed that recording serine birds. Bull. Peabody Mus. Nat. Hist. No. 37. for Theodore A. Parker (Museum of Zoology, DINGERKUS,G., AND L. D. UHLER. 1977. Enzyme clear- Louisiana State University) and John W. Fitz- ing of alcian blue stained whole small vertebratesfor patrick (Field Museum of Natural History, demonstration of cartilage. Stain Technol. 52:229- Chicago), both of whom remarked on the great 232. EISENMANN,E. 1955. The speciesof Middle American similarity between the vocalizations of Neso- birds. Trans. Linn. Sot. N.Y. 7. triccusand Phaeomyias. I was impressedwith GRANT, P. R. 1968. Bill size, body size, and the ecological their view, since I had just made a similar adaptationsof speciesto competitive situations conclusionregarding the skullsof thesegenera. on islands. Syst. Zooi. 17:319-3337 HAVERSCHMIDT.F. 1970. Notes on the life historv of the A closerelationship between Nesotriccusand Mouse-colored Flycatcher in Surinam. Condor 72: Capsiempis is less evident on external mor- 374-375. phological grounds,because the latter is olive- HELLMAYR,C. E. 1927. Catalogueof birds of the Amer- green above and bright yellow below, with pale icas and the adjacent islands, pt. 5. Publ. Field Mus. yellow wingbars and superciliary line. Traylor Nat. Hist., Zo&. Ser. 13. LANYON.W. E. 1978. Revision of the Mviarchus flv- (1977) recommended merging Capsiempisinto catchersof South America. Bull. Am. M&. Nat. Hi&. a much enlargedgenus Phylloscartes, although 161:427-628. he voiced some hesitancy because of differ- LANYON,W. E. 1982. Behavior, morphology, and sys- ences in ecology and nesting behavior. Con- tematics of the Flammulated Flycatcher of Mexico. Auk 991414-423. sideration of the nasal septum and syrinx fur- LANYON,W. E., AND J. W. FITZPATRICK.1983. Behavior, ther arguesstrongly against this merger. With morphology and systematicsof Sirystessibilator (Ty- respect to these character complexes, Phyllos- rannidae). Auk 100:98-104. cartes ventralis, Phylloscartesorbitalis, Pogo- RIDGWAY,R. 1893. Remarks on the avian genusMyiar- notriccuseximius and Leptotriccussylviolus (all thus, with special referenceto M. yucatanensisLaw- rence, Proc. U.S. Natl. Mus. 16:605-608. placed in Phylloscartes by Traylor) form a SHERRY,T. W. In press. Notes on nesting,seasonal cycle, closely-knit group, while Capsiempisjlaveola and nematode parasitesof the Cocos Flycatcher, Ne- is completely distinct from this group and re- sotriccusridgwayi Townsend (Tyrannidae). Condor. markably similar to Nesotriccusand Phaeo- SKUTCH.A. F. 1960. Life histories of Central American birds, pt. II. Pacific Coast Avifauna 34:3 19-32 1. myias as indicated in this study. Capsiempis SWARTH,H. S. 1931. The avifauna of the Galapagos builds a cup-shaped nest and lays white eggs Islands. Occas. Pap. Calif. Acad. Sci. 18. (Skutch 1960) as do Nesotriccusand Phaeo- TOWNSEND,C. H. 1895. Birds from Cocos and Malpelo COCOS FLYCATCHER 47

islands, with notes on petrels obtained at sea. Bull. Unpubl. Ph.D. diss., Louisiana State Univ. Baton Mus. Comu. Zool. 27:121-126. Rouge.Available throughUniversity Microfilms. Ann TRAYLOR, M. A. JR. 1977. A classificationof the tyrant Arbor, MI, no. 66-161: flycatchers(Tyrannidae). Bull. Mus. Comp. Zool. 148: 129-184. Departmentof ,American Museum of Natural WARTER, S. L. 1965. The cranial osteologyof the New History, New York, New York 10024. Received 10 De- World Tyrannoidea and its taxonomic implications. cember 1982. Final acceptance23 April 1983.

The Condor 86:47 0 The Cooper Ornithological Society 1984

RECENT PUBLICATIONS

Check-list of North American birds, 6th edition.-Amer- deservesapplause for sponsoringthis new publication as ican Ornithologists’ Union. 1983. Am. Omithol. Union, a way to advance knowledgeand understandingof issues Washington, DC. 877 p. Deluxe edition, limited to 100 in bird conservation. copies,bound in leather, signedby members of the check- list committee, $90.00; regularedition, $35.00 ($28.00 to AOU members). Source:Allen Press,P.O. Box 368, Law- Perspectivesin Ornithology/Essays presented for the rence. KS 66044. Lonn awaited, this new edition of the Centennial of the American Omitholoeists Union.-Ed- Check-list will surely be the most lasting and important ited by Alan H. Brush and George x Clark, Jr. 1983. memorial to the AOU Centennial. It differs from its 1957 Cambridge University Press, Cambridge. 560 p. $29.95 predecessorchiefly in expanded geographic scope (now ($24.00 to AOU members). Source: Cambridge Univ. including Hawaii, Middle America, and the West Indies), Press, 32 East 57th St., New York, NY 10022. The AOU restriction of coverageto the specieslevel, and adoption has a useful tradition of sponsoringvolumes of omitho- of several major changesin classification.These last are logical essaysat intervals in its history, first in 1933, next not new proposalsby the “Check-list” Committee but its in 1955, and now once again. While the subject matter acceptanceof revisions that have already been published itself is of coursethe focus, it is also revealing to compare elsewhere.As explained in a carefully written preface, the the style and selectionof topics in these collections.Most Committee has striven to steer a course between tradi- of the topics in the present volume were not mentioned tional views and bold innovations. The specific entries at all in the previous one, clearly showingthe areasof new themselvesgive in customary manner the recommended growth in the field. Perhaps in awareness of this-and names, citation of the original description, habitat, and encouragedby the editors-the present authors are more distribution.Additionally, in many casesthey includenotes open to the possibilities of further change. Their articles on other nomenclatureor , thereby pointing out are not so much reviews of the state-of-the-art as exam- matters of uncertainty or controversy. While this check- inations of some important questions and the ways of list embodies many notable changes from the Fifth, it addressingthem in future research.The existence of fer- clearly looks toward further changesin the Seventh. The ment and controversyis underscoredby the commentaries Committee and its longtime Chairman, the late Eugene that follow most of the chapters,giving alternative view- Eisenmann (to whom the volume is fittingly dedicated) points, specific criticisms, or additional material. In his deserve great appreciation for the thought and work they Introduction, Ernst Mayr offers insights about recent have put into this book. Four appendicesof special lists, changesin ornithology as well as his comments on several list of AOU numbers, index, endpaper maps. of the chapter topics. The essaysare as follows: Captive birds and conservation: William Conway; Research col- lectionsin ornithology:Jon C. Barlow and Nancy J. Flood; Bird Conservation,No. l.-Edited by Stanley A. Temple. The study of avian mating systems: Douglas W. Mock 1983. Published for the International Council for Bird (commentary by Sara Lenington); Cooperative breeding Preservation,U.S. Section.by the University of Wisconsin strategies:Stephen T. Emlen and Sandra L. Vehrencamp Press,Madison. 148 p. Paper cover. $12.95. Source:Uni- (J. David Ligon, Ian Rowley); Ecologicalenergetics: Glenn versity of Wisconsin Press, 114 North Murray St., Mad- E. Walsberg (William A. Calder III); Optimal foraging: ison, WI 53715. This is the first in a projected series of John R. Krebs, David W. Stephens,and William J. Suth- annuals intended to publish information on bird conser- erland (J. P. Myers); Biochemical studies of microevolu- vation activities, primarily in the U.S. “Each annual will tionary processes:George F. Barrowclough(John C. Av- include severalmajor reportson specificconservation pro- ise); Organization of the avian genome:Gerald F. Shields; grams written by the biologistswho are involved directly Origin and early radiation of birds: Larry D. Martin (Da- with the projects. Usually these reports will focus on a vid W. Steadman. Pat V. Rich): Avian communitv ecol- singleor a few key issues.”This one, for example, focuses ogy:John A. Wiens (JamesR. K&r); Biogeography:Daniel on falconiforms with specificarticles on the PeregrineFal- S&berloff (Joel Cracraft, Dennis M. Power); Bird song con, Bald Eagle, and California Condor. A secondregular leamine: P. J. B. Slater (Luis F. Bautista. Donald E. section for news and updates will give current, concise Kroodcma);and Bird navigation:Charles Walcott and An- reports on various bird populations, conservation activi- thony J. Lednor (Kenneth P. Able). The essaysdiffer in ties, and international treaties.Finally, there will be a com- format almost as much as in content, yet the editors have pilation of referencesfrom the recentliterature that pertain seento it that they are all well written. This is a stimulating to endangeredbirds or conservationtopics. This yearbook and timely book: not just for those whose specialitiesare itself valuably fills a niche between the scientific and the included, but for all ornithologists who care about the popular press by disseminating reliable information in a processand progressof their science. Lists of references not-overly technicalmanner. The U.S. Sectionofthe ICBP accompanyeach chapter and commentary. Index.