On the Origin of Darwin's Finches

ON THE ORIGIN OF DARWIN'S FINCHES

LuIs F. BAPTISTA AND PEPPER W. TRAIL Departmentof Ornithologyand Mammalogy, California Academy of Sciences, SanFrancisco, California 94118 USA

ABSTRACT.--Wecritically reviewed recent attempts to identify the ancestorof Darwin's finches(Emberizidae, "Geospizinae"), and summarizednew information on taxa that have been suggestedas sistergroups of the geospizines,specifically the emberizinesTiaris, Mel- anospiza,and Volatinia.Reproductive behaviors and displaysare conservativeamong Darwin's finches,and havebeen neglected in discussionsof the ancestryof the group.We concentrate on thesecharacters. We found that Tiarisand Melanospizashare a largenumber of apparently derived epigamicbehaviors with the geospizines,none of which are exhibitedby Volatinia. Received5 February1988, accepted 10 May 1988.

DARWIN'Sfinches include 13 speciesthat in- by behavioral (Bowman 1983), karyotypic (Jo habit the Ga13pagosarchipelago, 1,000 km west 1983), and biochemical(Yang and Patton 1981, of Ecuador,and one speciesendemic to Cocos Polans 1983) characters. However, McKitrick Island, 500 km southwestof CostaRica (Swarth (McKitrick and Fink 1987; pers. comm.) has 1931, Lack 1945, Grant 1986). They have been pointed out that the evidence for monophyly variouslyassigned their own family, the Geo- is not strong. Darwin's finches possessa large spizidae(Swarth 1929,Beecher 1953); their own number of characters in common, but no un- subfamily (Geospizinae) of the Fringillidae ambiguoussynapomorphies have been identi- (sensulato, Ridgway 1901,Lowe 1936,Lack 1947, fied. McKitrick's analysisof cranial characters Bowman 1963); or included in the subfamily in Darwin's finches and other New World nine- Emberizinae of the Emberizidae (Tordoff 1954, primaried oscines failed to detect any such Paynter 1970, Steadman 1982). uniquely sharedderived characters(McKitrick Darwin'sfinches can be divided into 4 groups and Fink 1987). We recognize the need for ad- basedon charactersof the bill, plumage, and ditional evidencesupporting geospizine mono- foragingbehavior. These are the ground-finch- phyly, and discussbelow severalcharacters that es (Geospiza),the tree-finches(Camarhynchus, may uniquely define the geospizines. Platyspiza,and Cactospiza),the Warbler Finch Many researchershave consideredthe affin- (Certhidea),and the Cocos Finch (Pinaroloxias). ities of Darwin's finches an unresolved prob- The ground-finchesand tree-finchespossess lem. Swarth (1929: 41) wrote "I think that we finchlike beaksof varying sizes,whereas Cer- mustrealize that we are contemplatinga group thidea and Pinaroloxias have thin, warblerlike of birds that has been isolated on its island home beaks. The affinity of the CocosFinch to the sincea remote period of time, and that has de- Gal•pagosfinches was recognized early, on the veloped suchdistinctive group charactersof its basisof the similar black plumagepossessed by own as to have made it well nigh impossible males of Pinaroloxiasand Geospiza(Ridgway now to recognize the nearest collateral main- 1901). The brownish Warbler Finch, however, land stock." Lack (1947) and Bowman (1963) wasplaced originally in Parulidae(equals Mni- agreed that either the mainland ancestorhad otiltidae, Ridgway 1902).Snodgrass (1903) not- become extinct, or that the geospizineshad di- ed anatomicalcharacters linking Certhideawith verged so far from it that determination of re- other geospizines,and subsequentworkers have lationship was no longer possible. Other in- agreedthat Certhideais part of this group(Sush- vestigatorshave maintained a more optimistic kin 1925, 1929; Lowe 1936; Beecher 1953; Tor- view and pointedto the emberizinegenera Tiar- doff 1954). isand Melanospizaas the closestrelatives of Dar- Lack's classicwork on adaptive radiation win's finches (Sushkin 1925, Lowe 1936, Bond among Darwin's finches (1945, 1947) led to ac- 1948,Beecher 1953, Bowman 1983). These sug- ceptance of the monophyletic nature of the gestionswere based on general similarities to geospizines.This hypothesis is supported by Darwin's finches, not on explicit analysesof the anatomical studies cited above, as well as characters.Tiaris is a group of small finches 663 The Auk 105: 663-671. October 1988 664 B•sTA ANDTRmL [Auk,Vol. 105 widespread in the Caribbean and South Amer- behavioral and plumage characterswhich do ica. The little-known, monotypic Melanospiza not support a close relationship between these richardsoni is endemic to St. Lucia, Lesser An- taxa. tilles. Given these problems with the analysesof Two workers have singled out particular ex- Harris (1972) and Steadman (1982), we believe tant speciesas the ancestorof Darwin's finches. that the phylogeny of Darwin's finchesremains Harris (1972) argued that the evidence for a an unresolved question. Recent ornithological finchlike ancestor of Darwin's finches was weak. researchhas produced information bearing on He proposed that the least derived member of this problem, much of it concerningbehavioral the group is the CocosFinch, Pinaroloxiasinor- characters. We summarize these data, which in- nata,a specieswhose thin, slightly curved bill dicate that Tiaris and Melanospizashare more resemblesthat of the Bananaquit,Coereba fiave- characterswith the geospizines than does Vo- ola (Emberizidae,Coerebinae). The monotypic latinia. Moreover, some of the characters com- Coerebais a widespread Neotropical "honey- mon to Darwin's finches,Tiaris, and Melanospiza creeper" of uncertain affinities. Harris (1972) appearto be uniquely sharedamong thesetaxa. suggestedthat Coerebacould be ancestralto Dar- We were unable to find evidence for such syn- win's finches, based primarily on the appear- apomorphies between Volatiniaand the geo- ance of the bill and on the occurrence of a black spizines. morph in some populationsof Coerebathat re- sembles male Pinaroloxias. In addition, Coereba METHODS builds a domed nest as do Darwin's finches. Coereba,however, is not an emberizine (Tordoff Data on the behavior of geospizinesare basedon 1954, Paynter 1970, Raikow 1978) and Harris published sources(Lack 1945, 1947; Orr 1945; Bow- man 1961, 1963, 1983; Grant 1986), on our study of did not support his suggestionwith any mor- film footage taken by George Bartholomew,and on phologicalanalysis. Our review of behavioral discussions with Robert I. Bowman. Information on charactersdid not reveal any traits of song or Melanospizawas gatheredduring our field study of courtship display shared between Coerebaand this specieson St. Lucia in May 1987 (Trail and Bap- the geospizines.The resemblanceof Coerebato tista in press). We also made extensive field obser- Pinaroloxiasappears to be a caseof convergence vations of Coerebafiaveola (Puerto Rico, St. Lucia, (Steadman 1982, Grant 1986). Trinidad, Tobago, Panama, and Suriname); Volatinia In a much more ambitious attempt to deter- jacarina(Trinidad, Tobago,Panama, and Suriname); mine the ancestryof the geospizines,Steadman Tiarisbicolor (Puerto Rico, St. Lucia, and Tobago);and T. olivacea(Puerto Rico). Captive T. olivaceaand Vo- (1982) comparedthe cranial osteologyof Dar- latinia enabled us to observe details associated with win's finches with 19 genera of emberizine nest-building and precopulatory behavior which finches, Coereba, and 9 other nonemberizine would be most difficult to obtain in the wild . Ob- genera.He proposedthe monotypicgenus Vola- servationson captive T. bicolorcontinue. The other tinia,an emberizine finch widespreadthrough- speciesof Tiarisare not included in the present dis- out Central and South America, as the ancestor cussion,either becausethey are little known (T. fu- of Darwin's finches,concluding: "the Neotrop- liginosaand T. obscura)or becausetheir affinity to other ical Blue-blackGrassquit, Volatinia jacarina, ap- members of the genus is questionable (T. canora; pearsto be soclosely related to Darwin's finches Goodwin 1959, Baptistain prep.). We did not attempt that I propose it to be the speciesthat singly a generalcomparison of geospizineswith other Neo- tropicalemberizines, most of which are poorly known. gave rise to the entire radiation ... I regard We note below the few characters for which infor- Volatiniaand all speciesof Darwin's finches,both mation on a wider sampleof genera is available. on the Galfipagosand CocosIsland, to be members of a single, expanded genus Geospiza" RESULTS (Steadman 1982: 294). This arrangement has been acceptedby someauthors (Wetmore et al. MORPHOLOGICAL CHARACTERS 1984), but was questionedby others (Barrow- clough 1983, Ratcliffe and Boag 1983, Grant Plumage.--Mostscholars have soughta black- 1986).Potential problems with Steadman'swork plumagedancestor (or sistergroup) of the geo- include his failure to find any charactersthat spizines. In line with this assumption, Stead- are uniquely sharedby Volatiniaand the geo- man (1982: 282) stated that "... the plumage spizines,and the inadequateconsideration of pattern in primitive Darwin's Finches is more October1988] Onthe Origin of Darwin's Finches 665

Fig. 1. From left to right: Skinsof male Tiarisbicolor, female T. bicolor,male Caraarhynchusparvulus, and female C. parvulus.In both species,males exhibit black plumage only on the head and breast;females are unstreaked.

closelymatched by that in Volatiniathan by that trial speciesexhibit increasingamounts of black, in any speciesof Tiaris.... "He noted (1982: perhapsto enhancetheir crypticityagainst the 289) that Geospizamales are black and that dark lava which predominatesin their arid hab- females are streaked (characters shared with itat (Bowman 1963). Volatinia). There are two difficulties with this Steadman (1982) failed to mention several argument.First, the principal reasonfor assum- plumage charactersof Volatinia that are not ing that black plumage is primitive among geo- sharedwith any speciesof Darwin's finch, and spizines appearsto be that males of the best- did not discussstriking plumage similarities known speciesof Darwin's finches,those in the between geospizinespecies and other possible genus Geospiza,are black. However, basedon a relatives. The plumage of male Volatiniais a study of plumage sequences,Snodgrass (1903) shiny blue-black;that of the geospizines,Mel- proposedthat Darwin's finchesdescended from anospiza,and Tiarisis a dull black (Grant 1986). a yellow-olivaceousancestor. Recently, Yang Male Volatiniapossess a white axillaW patchthat and Patton (1981) and Polans (1983) presented is absentin all the geospizines,Tiaris, and Md- electrophoreticevidence that Certhideaolivacea anospiza,and alsomolt into an eclipseplumage, was the earliestspecies of Darwin's finchesto a characterabsent in Geospiza(Grant 1986), Tiar- diverge from the ancestralstock. Plumages may is, and Melanospiza.The strong resemblanceof thus have evolved from olive-colored to black- the black male plumage of Melanospizato the and-olive, to the black typical of the ground- ground-finches (Geospiza)has been noted by finches(Geospiza spp.). several authors (Ridgway 1901, Bond 1929, The secondproblem with assigninga polarity Bowman 1983), whereas the black-and-olive to plumage color is that current selectivepres- colorationof the male Tiarisbicolor bears a strong suresmay determine the amount of black in resemblanceto Caraarhynchusparvulus (Fig. 1). geospizine plumage. Arboreal speciesare pri- The interpretation of female geospizine marily olive or brown, and increasinglyterres- plumage is equally problematic, despite Stead- 666 B•orIST^AND TRail, [Auk,Vol. 105

T^I•LI•1. Wing to tail ratiosof Darwin's finchesand other Neotropicalemberizines (names in parentheses are of islandssampled). a

n Wing (mm) Tail (mm) Ratio Sporophilaaurita 10 51.9 43.2 1.2 Volatiniajacarina 29 47.2 40.1 1.2 Tiaris olivacea 31 51.8 39.6 1.3 T. bicolor 62 51.1 38.9 1.3 Melanospizarichardsoni 2 70.4 48.5 1.5 Geospizadifficilis (Culpepper) 10 71.9 47.9 1.5 G. conirostris(Gardner) 10 73.9 44.8 1.7 Camarhynchuspsittacula (James) 10 73.0 44.9 1.6 C. pauper(Charles) 10 69.6 41.6 1.7 Cactospizapallida (Albermarle) 10 69.9 43.3 1.6 C. heliobates(Albermarle) 10 71.5 43.3 1.7 Pinaroloxiasinornata (Cocos) 10 65.9 41.8 1.6 Certhideabifasciata (Barrington) 10 51.4 43.0 1.2 Sources:data for all geospizines(Swarth 1931);data on remaining taxa (Ridgway 1901). man'sassumption that streakedfemale plumage equalto that of Geospizadifficilis from Culpepper is a primitive character.Based on the extensive Island. Certhidea,however, has a relatively long seriesof skinsat the California Academyof Sci- tail, similar to Sporophila,Volatinia, and Tiaris. ences,Lack (1947) pointed out that females of The variability in relativetail length amongthe Cactospizapallida are almostunstreaked, and that geospizinesmakes this characterof little usefor streakingis absentaltogether in femalesof the reconstructingthe group's phylogeny. tree-finches(Camarhynchus spp.) (Fig. 1). There Scutellation.--Clark(1986) recently reported is considerable individual variation in the a unique pattern of foot scutesin the genera amount of streaking;some female tree-finches Volatinia,Sporophila, Oryzyborus, Dolospingus, and are as heavily streakedas typical female Geo- Charitospiza.This condition, which involves a spiza,while somefemale ground-finches are only partial fusion of scutesat the base of the outer faintly streaked.Additional variation is shown 2 toes,was not seenin any other passefinetax- among Warbler Finches(Certhidea olivacea). Both on. Clark suggestedthat it may indicate that adults and juveniles are typically unstreaked, these 5 genera are monophyletic.In contrast,a but juvenilesfrom Floreana(Charles) Island are divided scute characterizesother Neotropical streaked. Females of the St. Lucia Black Finch finches,including Tiaris,Melanospiza, and all the (Melanospizarichardsoni) exhibit faint streaking, geospizines,as well as all mainland genera of thus resembling some Camarhynchus(Trail and tanagers(Thraupinae). Although Clark appears Baptistain press).Females of Tiarisspp. are un- to accept Volatiniaas the ancestorof the geo- streaked. spizines,he pointed out that this would require In summary, the plumage characters that the scute character to have differentiated after Steadman(1982) cited as evidence linking Vo- the geospizinelineage diverged. latinia with Darwin's finches (black males, Syrinx.--All the geospizines possessa dis- streakedfemales) are typicalonly of the ground- tinctly structured syrinx, and exhibit a lower finchesamong the geospizines.In the absence tracheacompletely enclosed in a heavy sleeve of evidence that Geospizais the least derived of muscle (Cutler 1970, cited in Grant 1986). genus of Darwin's finches, the phylogenetic Cutler surveyedthe external aspectof the sy- significanceof these plumage similarities re- ringes of all the speciesin the Ames collection mains uncertain. (Ames1971), and severalhundred specimensof Taillength.--The relatively short tails of many her own. Her total sample was more than 600 geospizines has been mentioned as a group species,including 46 genera in the Fringillidae character (Swarth 1931, Bond 1947), and Bow- and Emberizidae.The only taxa which shared man (1983) pointed out that this condition was the distinctive external sleeve of muscle with alsoexhibited by Melanospiza.We computedan the geospizineswere Tiaris and Melanospiza. index of relative tail length (wing length/tail Syringeal anatomy in Tiarisbicolor was almost length) in several taxa of Neotropical emberi- identical to the geospizines;T. olivaceadiffered zines (Table 1). Melanospizahad an index of 1.5, in someways, but exhibitedthe enclosingsleeve October1988] Onthe Origin of Da•in's Finches 667 of muscle.Melanospiza syringes closely resem- bled thoseof the geospizines,but were lessmas- sive. Syringes in Volatinia lacked this heavy muscularsleeve (Cutler pers. comm.).

BEHAVIORAL CHARA•

Darwin's finches share a number of distinctive behavioral characteristics,particularly re- lating to reproduction. These reproductive characters show less interspecific variation within the geospizinesthan virtually any morphological characters(Grant 1986). Behavioral traitsmay thus be useful for reconstructingthe phylogenyof the group,or minimally confirm- Fig. 2. High intensitycourtship display of Tiaris ing its monophyly.Following the classicalwork o. olivacea.Note that the wings of the male are held of Delacourand Mayr (1945)on Anseriformes, over the backand quivered,a posturetypical of geo- courtship displays have been used to under- spizines. stand the relationshipsof other avian taxa (e.g. Gilttinger 1970, 1976; Baptista 1973). Immel- shapingthe nestand lining the interior. By the mann (1976) called attention to the conservative final day of construction,only she participates natureof courtshipdisplays and discussedtheir in nest building (Trail and Baptistain press). utility as taxonomiccharacters. The pattern in Tiarisis similar. Skutch (1954) Holdingbehavior.--Holding behavior hasbeen reportedthat the male of T. olivaceaselects the used as a taxonomic character in a number of nest site and begins construction.Only if the avian taxa (Clark 1973).All the geospizines,in- femaleapproves of the nestsite doesshe begin cluding the completelyarboreal Warbler Finch, to visit him. Her efforts increase as the nest arecapable of manipulating(holding) food items nearscompletion, and it is usuallyonly the fe- or nest material with their feet (Bowman 1961, male that completesthe nest by lining its in- pers. comm.). This behavior is also present in terior. Not all nests begun by a male are ac- Tiaris species(Baptista 1976) and Melanospiza cepted by the female. Field and aviary (Trail and Baptista in press), but is absent in observations of T. bicolor reveal similar behavior Volatinia(Lill 1977;pers. obs.). (Baptistaand Horblit in prep.). Domednest.--Ail speciesof Darwin's finches The limited information available on the nest- build very similar domed nests, a behavior building behavior of Volatiniais contradictory. sharedwith Tiarisand Melanospiza(Grant 1986), Alderton (1963) observed wild birds and re- and the little-known Caribbean finches in the ported that both sexesbuild the shallow cup generaLoxigilla, Loxipasser, and Melopyrrha (Bond nest, and that "the male takes the initiative." 1961). The domed nest of Tiaris is so character- In a captive pair observedby Baptistaand Hor- istic that it has been used to define the genus blit, almost all nest building was done by the (Collins and Kemp 1976). In contrast,Volatinia female,whereas only the malesperformed nest builds a cup nest, as do most Neotropical em- building in the captivebirds observedby Stahl berizinesincluding Sporophila,Oryzyborus, and (1984). Volatiniaappears to lack the consistent Atlapetes. roles of the sexesin nest building that charac- Role of the sexesin nest building.--Malesof terize the geospizines,Tiaris, and Melanospiza. geospizinespecies build the outsidedomed shell Displaysat thenest.--Nest-building and court- of the nestand the femaleprovides the interior ship displaysare closelylinked in geospizines lining (Lack1945). Males may build severalnests (Lack 1945). Nest building is accompaniedby and display near the nest entranceswhen fe- frequent song.The presenceof a female stim- males approach.The pair eventually settleson ulatesmuch singing and posturingat the nest one nest. entrance. Orr (1945) and Downhower (1978) In Melanospiza,the male constructsthe entire noted that songsand displaysincreased as the outer shell of the nest.Once this is completed, nest neared completion; and ceasedabruptly the female takesan increasinglylarger role in once incubation commenced.Nest building is 668 BAPTISTAAND TRAIL [Auk,Vol. 105

Fig.3. Whistlesongs of (A) Melanospizarichardsoni, St. Lucia,West Indies, and (B) Geospizafortis, Isla Santa Cruz, Gal•pagos. alsoaccompanied by singingin Melanospiza,and the amount of singing increasessignificantly just prior to laying. The one male on which we made detailed observationsoften sang to the fema'le from inside the nest while he was ar- D E rangingnest material within (Trail and Baptista in press).Male geospizineshave been observed 2-1 ' to sing inside the nest in captivity (Bowman I 1983), and similar observations have been made 0 S 0.5 on Tiarisbicolor both in field and aviary (Baptista and Horblit in prep.). Fig. 4. Spectrogramof songsof (A) Geospizamag- nirostris,(B) Platyspizacrassirostris, (C) Tiarisbicolor from The presenceof a female inside the neststim- Puerto Rico. Arrows point to introductory note with ulates singing in the male Tiarisolivacea. He an overtonecharacteristic of songsof mostspecies of usually perchesa few inches outside the nest geospizinesand T. bicolor.(D) and (E) Spectrograms and sings to her with his bill facing the nest of two songsof Volatiniajacarina from Trinidad and entrance, the songsoften accompaniedby vig- Tobago,respectively. In "D," the songbegins with a orouswing-flicking (pets. obs.). In contrast,nest vibrato. In "E," the songbegins with a soft vibrato building and displaysare not coupled in Vo- followed by a note and then a secondvibrato. latinia (pets. obs.) nor have we observed this speciessinging while on the nest. beenobserved. In Melanospiza,the malesang to Courtshipdisplay.--Geospizine courtship dis- the female with both wings held up over the playsare uniform within the group(Lack 1945, backduring the only courtshipdisplay we ob- Orr 1945,Grant 1986).This is true of the genera served (Trail and Baptistain press).This is a Camarhynchusand Certhideaas well asthe better- typical geospizine posture. known members of the genus Geospiza(Bow- The precopulatorydisplay of the Volatiniamale man pets. comm.). The male geospizine ap- bearsno resemblanceto that of the geospizines. proachesthe female and faces her with body Stimulatedby the female'ssoliciting display, held horizontally and with wings spread, the male raises the feathers of the forehead to droopedand quivering. At higher intensity the form a crest, a feature found at the bottom of wings may be raised over the back and quiv- its jump display (illustratedin Weathers1986). ered. This is accompaniedby swaying move- The body is erectand the carpalsof the wing ments of the body. Copulation is followed by held out to displaythe white axillarypatch. He a postcopulatorydisplay accompaniedby ex- sings to her in this posture, mounts, and leaves tended and quivering wings (Orr 1945). with no postcopulatorydisplay (Baptistaand The displayof T. olivaceais identical with that Horblit in prep.).In a seconddisplay, the male of the geospizinesin all aspectsincluding wing- raises its crest, then faces the female with tail raising (Fig. 2), body swaying,and a postcopu- held straightup like a Troglodyteswren (Stahl latory display. Raised wings or lowered and 1984,Baptista unpubl.). Wing-raising is alsoab- quivered wings were often seen in T. bicolor sentin the widespreadNeotropical finch genus courtship displaysin the field and in the lab- Sporophila(Godfrey Bournepets. comm.). oratory; and body swaying has been observed Songflight displays.--Volatinia is known for a in captives. Complete copulation has not yet jump-displaywhich has earnedit the local name October1988] On theOrigin of Darwin'sFinches 669

TABLE2. Characterstates of Darwin's finchesand proposedsister groups.

Geospi- Tiaris Melano- zines olivacea T. bicolor spiza Volatinia Courtship display components Wing up + + + + - Wing down and quivered + + + ? - Lateral body sway + + + ? - Postcopulatorydisplay w/wing quiver + + ? ? - Display w/nest material + + + + - Display associatedw/nest building + + + + - Male builds dome, female lines nest + + + + - Horizontal song flight + + + + - Whistle song + - ? + - Other character states Syrinx in sleeve of muscle + + + + - Black male plumage• + - - + + Holds items w/feet + + + + - Domed nest + + + + - Total characters shared w/Darwin's finches 13 I! !0 !0 !

Amonggeospizines, Cactospiza and Certhidea lack black male plumage; Tiaris species are black and olive-brown, as in the geospizineCamarhynchus.

"Johnny-Jump-Up"(ffrench 1973). In this dis- derived song is characteristiconly of Geospiza, play, the male flaps its wings vigorously,some- Cactospiza,and Camarhynchus. times producing a snapping sound (Webber Bowman (1983) described in detail the simi- 1985; pers. obs.), ascends20-50 cm above its larities between the songs of Melanospizaand perch, and then drops on the spot where the the 5-part basic song of Certhidea.The Mela- display commenced.Song is produced at the nospizasong available to him consisted of a apex of the ascentphase. Steadman (1982) sug- whistle attachedto the basicsong proper, as in gested that the jump display is a homolog of Certhidea.We found that Melanospizaalso deliv- the song-flight display common to all geospi- ers a long descendingwhistle song similar to zines. Grant (1986) pointed out, however, that that found in Geospizaspecies (Fig. 3). The whis- the display of Volatiniais on a vertical plane tle in Melanospizaterminates in a vibrato as in (illustrations in Weathers 1986) whereas that in Pinaroloxias.The derived songis absentin Mela- the geospizinesis on a horizontal plane. A hor- nospiza,Platyspiza, Pinaroloxias, and Certhidea. izontal song-flightdisplay is highly developed The basic song of many geospizinesconsists in Tiarisbicolor (ffrench 1973; pers. obs.), and is of a note with an overtonefollowed by a series also present in T. olivaceaand Melanospizaal- of buzzy phrases.Songs of Tiarisbicolor are sim- thoughin lesselaborate form (Trail and Baptista ilar (Fig.4), includingthe introductorynote and in press). buzzy phrases.In contrast,the songof Volatinia Song.--All geospizinesongs can be classified lacksthis introductory note and phrase struc- as one of 3 distinct song types (Bowman 1983). ture (Fig. 4). The highly variable song of Vo- Whistlesong is a long continuouswhistle start- latiniahas been describedas "szeeyew" (Slud ing at a high frequencyand descendingeither 1964), "bzee-eep" (Wetmore et al. 1984), and gradually or precipitously,depending on the "weezit" (Peterson and Chalif 1973). Volatinia species, to a lower frequency. In the genus does not produce the whistle song, based on Camarhynchus,this songis a long seriesof short published accounts(Webber 1985) and our own whistles. In Certhidea,the whistle is attached to extensivefield and aviary observations. the "basic song." Basicsong consists of several For 13 characters exhibited by Darwin's dissimilar buzzy phrases.There are a number finches,Melanospiza and Tiarisspp. share 10-11 of versionsof this songtype. Derivedsong is the characterstates with the geospizines,in con- final type, and differs from basicsong in that it trast to Volatinia,which sharesonly one char- consistsof trills made up of identical syllables acter state (Table 2). We suggestthat the suite repeatedin series.All geospizinesproduce vari- of epigamicdisplays shared by the geospizines ants of the whistle song and basic song, but and Tiaris/Melanospiza(namely the horizontal- 670 BAPTISTAAND TRAIL [Auk, Vol. 105 flight song, whistle song, unique basicsong, taxonomicsignificance in grassquits,Tiaris species. displayat the nest,display with nest material, Ibis 118: 218-222. andwing-up posture) are derived displays pres- BARROWCLOUGH,G.F. 1983. The origin of Darwin's ent in their common ancestor. We conclude that Finches (review of Steadman 1982). J. Field Or- nithol. 54: 110. the bulk of the available evidence doesnot sup- BEECriER,W. J. 1953. A phylogeny of the oscines. port Steadman's(1982) identificationof Volati- Auk 70: 270-333. nia as congenerand direct ancestorof the geo- BOND,J. 1929. The rediscoveryof the St. Lucian spizines.Resolution of the affinitiesof Darwin's BlackFinch (Melanospizarichardsoni). Auk 46: 523- fincheswill require further work on morpho- 526. logical characters,and the use of biochemical 1948. Origin of the bird fauna of the West techniquesto examine the relationshipsbe- Indies. Wilson Bull. 60: 207-229. tween the geospizinesand their proposedsister 1961. Birds of the West Indies. Boston, groups.We are currently engagedin suchstud- Houghton Mifflin. ies. BOWMAN,R. I. 1961. Morphological differentiation and adaptationin the Gal•pagosfinches. Univ. Calif. Publ. Zool. 58: 1-302. ACKNOWLEDGMENTS 1963. Evolutionary patterns in Darwin's finches.Occ. PapersCalif. Acad.Sci. 44: 107-140. We acknowledgewith thanksthe birds,space, and 1983. The evolution of song in Darwin's manyhappy hours discussing this project with Klaus finches. Pp. 237-537 in Patterns of evolution in Immelman (University of Braunschweig).For all the Gal•pagosorganisms (R. I. Bowman,M. Berson, kindness and assistanceshown Baptista at Braun- and A. E. Leviton, Eds.). Pacific Div. AAAS. schweig,we thank Hans Kilngel, EkkePr6ve, Roland CLARK,G. A., JR. 1973. Holding food with the feet Sossinka, and Otto von Frisch. Dr. R. Piechocki, Sek- in passerines.Bird-Banding 44: 91-99. tion Biowissenschaften der Martin-Luther Universi- ß 1986. Systematicinterpretations of foot-scute tat Halle-Wittensberg,and Dr. R. Crumrot, Tierpark patternsin Neoptropicalfinches. Wilson Bull. 98: Berlin, providedthe original wild-caught Tiarisfrom 594-597. Cuba. COLLINS,C. T., & M. H. KEMP. 1976. Natal pterylosis We thank Paul Butlerand ChristopherCox for their of Sporophilafinches. Wilson Bull. 88: 154-157. assistanceand hospitality on St. Lucia, and Julio Car- CUTLER,B.D. 1970. Anatomicalstudies of the syrinx dona Alonso,Betsy Anderson, Kelly Brock,Paul Gert- of Darwin's finches. M.A. thesis, San Francisco, let, JeanLodge, Frank Milan, Rolf Olson,Jose Vivaldi, San FranciscoState University. and JosephWunderle Jr. for their help during our DELACOUR,J.,& E. MAYR. 1945. The family Anatidae. work on Puerto Rico. Wilson Bull. 57: 3-55. Discussionswith Robert Bowman were most help- DOWNHOWER,J.F. 1978. Observationson the nesting ful. He kindly provided the spectrogramsof geo- of the SmallGround Finch Geospiza fuliginosa and spizinesongsß Betsey Cutler generouslydiscussed her the Large Cactus Ground Finch G. conirostrison studiesof geospizinesyringeal anatomyß George Bar- Espafiola,Gal•pagos. Ibis 120:340-346. rowclough,Walter Bock,Betsey Cutler, Sylvia Hope, FFRENCH,R. 1973. A guide to the birds of Trinidad and Mary McKitrick read earlier versions of the and Tobago.Wynnewood, Pennsylvania, Living- manuscript and provided valuable commentsßWe ston Publishing Co. thank Ann Giordanofor the photograph(Fig. 1). GOODWIN,R. 1959. Breeding of the Black-faced Researchfunds were provided by the Max Planck Grassquit,Tiaris bicolor, in captivityand somenotes Gesellschaft,the Forschungsmitteldes LandesNie- on the comparativebehavior of the genus.Avi- dersachsen,N.A.T.O., and the CaliforniaAcademy of cult. Mag. 65: 131-134. Sciencesto Baptista,and by the National Geographic GRANT,P. R. 1986. Ecologyand evolution of Dar- Societyto Trail and Baptista. win's Finches.Princeton, New Jersey,Princeton University Press. LITERATURE CITED G'frFrINGER,H.R. 1970. Zur evolution von Verhalt- ensweisenund Lautiiusserungenbei Prachtfin- ALDERTON,C.C. 1963. The breedingbehavior of the ken (Estrildidae).Z. Tierpsychol.27: 1011-1075. Blue-blackGrassquit. Condor 65: 154-162. ß 1976. Zur systematischenStellung der Gat- AMES,P.L. 1971. The morphologyof the syrinxin tungenAmadina, Lepidopygia, und Lonchura(Aves, passerinebirds. Bull. Peabody Mus. Nat. Hist. 37. Estrildidae). Bonn. Zool. Beitr. 27: 218-244. BAPTISTA,L.F. 1973. On courtshipdisplays and the HARRIS,M.P. 1972. Coerebafiaveola and the Geo- taxonomicposition of the Grey-headedSilverbill. spizinae. Bull. Brit. Ornithol. Club 92: 164-168. Avicult. Mag. 79: 149-154. IMMELMANN, K. 1976. The use of behavioural char- --. 1976. Handedness,holding, and its possible actersin avian classification.Proceedings of the October1988] On theOrigin of Darwin'sFinches 671

16th International Ornithological Congress SKIJTCH, A. F. 1954. Life histories of Central Amer- (Canberra, 1974): 206. ican birds. PacificCoast Avifauna 31. Berkeley, Jo, N. 1983. Karyotypicanalysis of Darwin'sfinch- California,Cooper Ornithol. 50c. es. Pp. 201-217 in Patterns of evolution in Galfi- SLIJD, P. 1964. The birds of Costa Rica. Bull. Am. pagos organisms(R. I. Bowman, M. Berson, and Mus. Nat. Hist. 128. A. E. Leviton, Eds.). Pacific Division of AAAS. SNODGRASS,R. E. 1903. Notes on the anatomy of L^cK,D. 1945. TheGalf•pagosfinches(Geospizinae): Geospiza,Cocornis, and Certhidia.Auk. 20: 402-417. a study in variation. Occ.Papers Calif. Acad. 5ci. STAHL,J. 1984. Haltung und zucht des Jakarinifin- 21: 1-159. ken (Volatiniajacarina). Gefiederte Welt 108:103- --. 1947. Darwin's finches.Cambridge, Cam- 105. bridge Univ. Press. .STEADM•N,D. 1982. The origin of Darwin's finches LILL,A. 1977. Foodmanipulation with the feet by (Fringillidae,Passeriformes). Trans. San Diego Neotropical emberizines.Ibis 119: 88. Nat. Hist. Soc. 19: 279-296. LOWE,P. R. 1936. The finchesof the Gal•pagosin SUSHK•ta,P. P. 1925. The Evening Grosbeak(Hes- relation to Darwin's conceptionof species.ibis, periphona),the only Americangenus of a pale- ser. 1, 36: 310-321. arcticgroup. Auk 42: 256-261. McKITR•CK,M. C., & W. L. FItaK.1987. Phylogenetic 1929. On some peculiaritiesof adaptive ra- puzzles in emberizine finches.Paper presented diation presentedby insular faunae. Proc. 6th Int. at 105thAnnual Meeting of the A.O.U., SanFran- Ornithol. Congr. (Copenhagen,1926), pp. 375- cisco, California. 378. ORR,R.T. 1945. A studyof captiveGalf•pagos finches SWARTH,H.S. 1929. A new bird family (Geospizidae) of the genusGeospiza. Condor 47: 177-201. from the Gal•pagosIslands. Proc. Calif. Acad.5ci. ?AYNTER,R.A., JR. 1970. SubfamilyEmberizinae. Pp. 18: 29-43. 3-214 in Checklist of birds of the world, vol. 13 ß 1931. Theavifauna of the Galf•pagosIslands. (R. A. PaynterJr., Ed.). Museum of Comparative Occ. PapersCalif. Acad. of 5ci. 18: 1~299. Zoology,Harvard University,Cambridge, Mas- TORDOl•F,H.B. 1954. Relationshipsin the New World sachusetts. nine-primaried oscines.Auk 71: 273-284. PETERSON,R. T., & E. L. CH^LIF.1973. A field guide TRAIL,P. W., & L. F. BAPTISTA.In press. The behavior, to Mexicanbirds. Boston,Houghton Mifflin Co. status,and relationshipsof the endemicSt. Lucia POLANS,N.O. 1983. Enzymepolymorphisms in Ga- BlackFinch. Nat. Geogr.Res. l•pagosfinches. Pp. 219-236in Patternsof evo- WEATHERS,W. W. 1986. Thermal significance of lution in Gal•pagosorganisms (R. I. Bowman,M. courtship display in the Blue-black Grassquit Berson, and A. E. Leviton, Eds.). Pacific Division (Volatiniajacarina). Nat. Geogr.Res. 2: 291-301. of AAAS. WEBBER,T. 1985. Songs,displays, andotherbehavior R•KOW,R.J. 1978. Appendicularmyology and re- at a courtshipgathering of Blue-blackGrassquits. lationshipsof the New World nine-primariedos- Condor 87: '543-546. cines(Aves: Passeriformes). Bull. CarnegieMus. WETMORE,A., PASQUIER,R. F., & OLSON, 5. L. 1984. Nat. Hist. No. 7: 1-43. The birds of the Republic of Panama, part 4. RATCLIFFE,L. M., & P. T. BOAG. 1983. Forward in Washington,D.C., Smithson.Inst. Press. Darwin's Finches,2nd ed. by David Lack. Cam- YANG,5. Y., & J. L. PATTON1981. Genic variability bridge, CambridgeUniv. Press. and differentiationin Gal•pagosfinches. Auk 98: RIDGWAY,R. 1901. Birds of North and Middle Amer- 230-242. ica, part 1. Bull. U.S. Nat. Mus. 50: 1-715. 1902. Birds of North and Middle America, part 2. Bull. U.S. Nat. Mus. 50: 1-834.