EVOLUTIONARY TRENDS IN THE NEOTROPICAL OVENBIRDS AND WOODHEWERS BY ALAN FEDUCCIA ORNITHOLOGICAL MONOGRAPHS NO. 13 PUBLISHED BY THE AMERICAN ORNITHOLOGISTS' UNION 1973 EVOLUTIONARY TRENDS IN THE NEOTROPICAL OVENBIRDS AND WOODHEWERS BY ALAN FEDUCCIA ORNITHOLOGICAL MONOGRAPHS NO. 13 PUBLISHED BY THE AMERICAN ORNITHOLOGISTS' UNION 1973 ORNITHOLOGICAL MONOGRAPHS This series,published by the American Ornithologists'Union, has been establishedfor major paperstoo long for inclusionin the Union's journal, The Auk. Publicationhas been made possiblethrough the generosityof Mrs. Carll Tucker and the Marcia Brady Tucker Foundation,Inc. Correspondenceconcerning manuscripts for publication in the series shouldbe addressedto the Editor, Dr. JohnWilliam Hardy, Florida State Museum, Universityof Florida, Gainesville,Florida 32601. Copiesof OrnithologicalMonographs may be orderedfrom the Treasurer of the AOU, Burt L. Monroe, Jr., Box 23477, Anchorage,Kentucky 40223. (See price list on insideback cover.) OrnithologicalMonographs, No. 13, iv q- 69 pp. Editor-in-chief,John William Hardy SpecialAssociate Editors for this Issue, Stuart L. Warter and Peter L. Ames Issued July 10, 1973 Price $2.00 prepaid ($1.60 to AOU Members) Library of CongressCatalogue Card Number73-81856 Printed by the Allen PressInc., Lawrence,Kansas 66044 TABLE OF CONTENTS INTRODUCTION ....................................................................................... COMPARATIVE ANATOMY OF THE SKULL ................................................. 9 Anatomical material ....................................................................... 11 Woodhewer skulls ............................................................................... 12 Ovenbird skulls ..................................................................................... 14 Philydorine skulls ........................................................................... 17 Skulls of the "intermediates" _................................................................. 22 Jaw muscles ......................................................................................... 24 Functionalaspects of the skull types................................................ 25 STERNUM ............................................................................................... 34 EVOLUTION OF THE SCANSORIAL FOOT ................................................. 36 Limb proportions........................................................................ ß..... 36 Distal end of the tarsometatarsus ......................................................... 41 Femur and tibiotarsus .................................................................... 42 The digits .............................................................................................. 43 TAIL ............................................................................................................ 45 SYRINGEAL ANATOMY ............................................................................... 45 ELECTROPHORESISOF HEMOGLOBIN ....................................................... 48 Methods and materials ......................................................................... 48 Results and discussion ..................................................................... 49 CLUSTER ANALYSIS ................................................................................. 51 A PHYLOGENY ...................................................................................... 59 A BEHAVXORIAL MODEL ....................................................................... 61 CLASSIFICATION ................................................................................. 64 SUMMARY .......................................................................................... 65 LITERATURE CITED ............................................................................. 68 INTRODUCTION The Neotropical ovenbirds (Furnariidae) and woodhewers (Dendro- colaptidae) have long been consideredto be closelyrelated on the basisof derivedcharacters which are sharedby the two groupsbut not foundin other suboscinebirds. Generalplumage patterns in the two groupsare amongthe significantlystriking similarities, as almostall specieshave light brownto red- dish-brownbody plumage with variousdegrees of spottingon the breastand back,often with light throat patches. A spinytail, usuallyof chestnutor ferrugi- nouscolor, which is usedin the woodhewersas a brace in climbing,is found in variousdegrees of developmentin many membersof the Furnariidaeand is well developedin certain ovenbirdswhich foragelike the woodhewers,by climbingup tree trunks. These scansoffalfurnariids, including Pseudo- colaptes,Xenops, Pygarrhichas, the Margarorniscomplex, and somespecies of Cranioleuca,are of interestin that, althoughthey are behaviorallysimilar to the woodhewers,being tree-trunk foragers and possessingstiff, spinytails, they are clearlymembers of the Furnariidaeon the basisof suchcharacters asthe syrinx,cranial morphology, and feet. Commonwing patterns are found in the Furnariidaeand Dendrocolaptidae.In addition,syringeal and osteo- logicalcharacters ally the two groups.It is onlywithin the Dendrocolaptidae and Furnariidaethat two pairs of intrinsicsyringeal (tracheo-bronchial) musclesare found (Ames, 1971). This sharingof charactershas led manyornithologists to questionthe dis- tinctness of the two families. Thus the familial classification of the furnariids and dendrocolaptidshas long beenin a stateof uncertainty,and at present thereis little agreementamong ornithologists concerning the recognitionof familiesin the group. Recentclassifiers have generally followed either von Ihering (1915), who presentedevidence which he consideredfavored merg- ingthe two families, or Ridgway(1911 ), whorecognized two families. Strese- mann (1934) unitedthe ovenbirdsand woodhewersinto one family. In 1951 threeclassifications were proposed. Wetmore (1951) retainedtwo families becausehe consideredvon Ihering'sevidence inconclusive; Peters (1951) also recognizedtwo families. However,Mayr and Amadon (1951) treated the entiregroup as a singlefamily, as did Storer (1960). Early classifiers(see Garrod, 1873; and Beddard, 1898) placedconsider- able importanceon the condition of the nasal bones in the classificationof the higher categoriesof birds. Two basic arrangementsof the nasal open- ingswere distinguished,schizorhinal and holorhinal. In the former, the nasal openingextends posterior to the nasal-frontalhinge; in the latter, the pos- terior extent of the openingis anteriorto the hinge. The conditionin Furnar- ius and other ovenbirds,which was originallytermed schizorhinal(see Gar- rod, 1877), was later recognizedas not homologousto the conditionin other 1 2 ORNITHOLOGICAL MONOGRAPHS NO. 13 schizorhinalbirds (charadriiform birds, etc.), and F'tirbringer(1888) pro- posedthat the term pseudo-schizorhinalbe appliedto the conditionin those ovenbirdsin which the posteriorextent of the nasal openingis rounded,in- steadof endingin a slit asin "true" schizorhiny. Garrod (1877) emphasizedthat the conditionof schizorhiny(= pseudo- schizorhiny)in the ovenbirdswas of sufficienttaxonomic importance to sep- arate the groupfrom the holorhinalwoodhewers. However, Garrod had ex- aminedonly a small numberof species.Von Ihering (1.915) examineda muchlarger series of speciesand concludedthat therewas actuallyno clear- cut divisionbetween the pseudo-schizorhinalovenbirds and the woodhewers, and that the differencesbetween pseudo-schizorhiny and holorhiny repre- sentedslight modifications from a basicpattern and were thereforeof little taxonomicimportance, except perhapsin characterizinggenera. Ridgway (1911), however,had maintainedthat the differencein the arrangementof the nasal openingplus the differencesin the feet were of sufficientimpor- tance to separatethe Dendrocolaptidaefrom the Furnariidae. In the Furna- riidae(sensu Ridgway) the outertoe is shorterthan the middletoe and the hallux without the claw is not shorter than the inner toe (no. II) without the claw. The middletoe is unitedto the outertoe by lessthan the wholeof the secondphalanx. In the Dendrocolaptidae(sensu Ridgway) the outer toe is aboutas long as the middletoe and muchlonger than the inner toe, and the hallux without the claw is shorter than the inner toe. The three anterior toesare unitedfor the entirelength of the basalphalanx, and the middletoe is fusedto the outerby almostthe full extentof the secondphalanx. Ames(1971) in his systematicconclusions of the Furnariiemphasized that the syringealmusculature of the ovenbirdsand woodhewerswas an indication of closeaffinity of the two groups.Both groupspossess two pairsof intrinsic syringealmuscles, a characterwhich separatesthe two families from the antbirds (Formicariidae) and tapaculos(Rhinocryptidae). However, the ovenbirdsare apparentlyseparable from the woodhewerson the basisof the absencein the ovenbirds of horns on the Processi vocales (except in the genusGeositta). It is alsoof interestto note that thereis far more syringeal variation within the Formicariidae than within the woodhewer-ovenbird as- semblage. Attemptsby many classifiersto place animalsinto distinguishablegroups without examiningin detail the charactersinvolved has led in many cases to classificationsbased on the most adaptivefeatures of the birds, namely the bill and feet (the classicalexample being hawks and owls which were at one time classifiedtogether on the basisof havingsimilar feet and bills) with little emphasison decipheringthe