Remarks on the Taxonomy of Some American Doves
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330 •.vo•F Auk• REMARKS ON THE TAXONOMY OF SOME AMERICAN DOVES BY DI•RI•K GOODWIN In the courseof current examinationand re-arrangementof the pigeons in the collection of the British Museum (Natural History) certain conclusionshave been reachedon the status of severalAmerican genera, which somewhat differ from current treatment. Zenaida, Zenaidura, Nesopelia, Melopelia In his catalogueof the pigeonsSalvadori (1893) listed the four genera Zenaida, Zenaidura, Nesopelia and Melopelia in his sub-family Zen- aidinae. He distinguished the first two as having "moderate and straight" bills and fourteen tail feathers, the tail of Zenaidura being "rather long, graduatedor cuneate"and that of Zenaida "moderateand rounded". Nesopelia(containing the GalapagosDove) he characterised as having twelve tail feathers, a "rather short and rounded" tail and the bill "rather long and much bent downwards",Melopelia (the White- winged Dove) on its lack of certain signal markings and possession of others, and also on slight differencesin the shapeof the inner webs of the first two primaries. Ridgway (1916) followedthis classification. Peters(1934) pointedout that only oneof the species,the SouthAmerican auriculata, placed in Zenaida by theseauthors had in fact fourteen tail feathers,the othershaving twelve. He accordinglyplaced auriculata in the genus Zenaidura. He made Melopelia congenericwith Zenaida, remarking that he had looked in vain for any characters "of generic value" to separate them. He maintained Nesopeliaby reason of its "short tail... and strongly decurved bill". Hellmayr and Conover (1942) followedPeters, placing the Mourning Dove Zenaidura macroura (Linnaeus) and the Eared Dove Z. auriculata (Des Murs) in Zenaidura; the Zenaida Dove Zenaida aurita (Temminck) and the White-winged Dove Z. asiatica (Linnaeus) in Zenaida, and the Galapagos Dove Nesopeliagalapagoensis (Gould) in the monotypic genus Nesopelia. The A.O.U. Check-list (1957: 260-262) similarly separatesZenaidura and Zenaida. I feel diffident about "lumping" genera, but in this instance there seemsto be justificationfor so doing. Genericlimits are largely a matter of opinion and one's opinion is guided by an appraisal of charactersand the way in which other speciesin the samefamily are, or can best be groupedinto genera. A genusneed not consistof a discretegroup (Cain, 1956) and if, as is the case with the fruit-doves of the genusPtlinopus for example,it is a natural groupit neednot be capableof definitionby July•9.•8.1'] GOO•)W•N,Taxonomy ofAmerican Doves 331 evena singlecharacter common to everyoneof its members(Cain, 1954). In the current arrangement(Hellmayr and Conover,loc. cit.) the genus Zenaidura, •onsistingof macrouraand auriculata, differsfrom Zenaida, speciesaurita and asiatica, in possessingan extra pair of tail feathers and proportionatelyslightly smallerfeet and tarsi. I do not think the possessionof fourteen instead of twelve rectricescan be considered a valid reasonfor separatinginto different generatwo specieswhich are so alike in their characters as are auriculata and aurita. The same view has beenexpressed by Bond (1940: 53, footnote33). In coloration,and especiallyin detail of color-pattern,there is a great deal of uniformity in the speciesof both genera. All have a blackishband acrossthe lower part of the face with an iridescentpatch on the neck immediatelybehind it and similarand homologoustail markings. There are alsoblack spots on the wings,although in asiaticathese are reducedto tracesof spotson the concealedbasal portionsof the feathers,suggesting, as was pointed out by Whitman (1919), that their reductionoccurred comparatively recentlyin their evolutionaryhistory. Anotherfeature also lacking only in asiatica,is a black mark extendingfrom the cornerof the eye. In my opinion these plumagecharacters, which are correlatedwith a general similarity of size are, in this instance,of greater phyletic importance than the differencesin the length, shapeand number of feathersin the tail. This conclusionis emphasisedby the fact that the tail of auriculata (genusZenaiclura) is intermediatein length and shapebetween those of macrouraand aurita (genusZenaida). Similarly the GalapagosDove, galapagoensis,does not appear to be sufficientlydistinct for genericseparation. Its tail is only a little shorter than that of aurita. Its bill (as so often in island forms) is relatively largerand the culmenperhaps slightly more curved, but thesedifferences of bill size are not greater than those often found between racesof a single species. There seem to be no groundsfor Peter's opinion that "Its affinities are not clear" or that it bears only "a faint general resemblance" to aurita and asiatica. It doesin fact bear a strong resem- blance to aurita and there can be very little doubt that both have derived from a common stock. Whitman (1919) suggestedthat gala- pagoensisrepresents a form ancestralto both aurita and asiatica. He pointed out that the profuse black and white markings on its wings could well be the "raw materials" from which the signalmarkings on the wings of aurita and asiaticahave been developed. It seemsprobable that the short tail and large bill are adaptationsto its island habitat rather than ancestral characters. Of the five specieswhich I think shouldbe groupedin the singlegenus Zenaida the North American Mourning Dove, macroura,and the South 332 GOODWIN,Taxonomy o!American Doves I.FVol. Auk American Eared Dove, auriculata,are sufficientlyalike to be considered as membersof a singlesuperspecies. The White-winged Dove appears to stand furthest apart both in morphologyand in voice and behavior (Whitman, 1919a) but its relationshipwith the othersis quite evident and I agreewith Petersthat it shouldnot be put in a separategenus. Ectoplstes The questionarises as to the genericstatus of the PassengerPigeon, Ectopistesmigratorius (Linnaeus), whose affinity to the Mourning Dove is at once evident when skins or photographsare compared. Salvadori (1893) placed the Mourning Dove in his family Peristeridaeand the PassengerPigeon in Columbidae. His criteria for recognisingthe former family were,tarsus as long or longerthan the middletoe and from twelve to twenty tail feathers instead of always only twelve. Presumably he was influencedin placing the Mourning Dove in Peristeridaeby its having fourteenfeetrices. On its toe and tarsusproportions it would have qualifiedfor his restrictedversion of Columbidae. The Passenger Pigeondiffers, or rather differed,from Zenaiclaspecies in its larger size, in lackingthe dark facial markings,in its pronouncedsexual dimorphism, in laying only one egg to a clutch, in its markedly distinct voice and behaviour(Craig, 1911) and in its ecology(Schorger, 1955). It seems that the sum total of these differencesare a good deal greater than those betweenany of the five specieswhich I suggestshould form the genus Zenaida, and therefore there is sufficientreason to keep the Passenger Pigeonin a separategenus. At the sametime its very dosephylogenetic relationshipto Zenaida, shouldnot be overlooked. Geotrygon, Osculatla, Starnoenas It is possiblethat the AmericanQuail-Doves may be closelyrelated to Zenaida. Most of them have facial markings very similar to and apparentlyhomologous with thoseof Zenaida, but they showno such resemblanceto Leptotilaor to the old world genusGallicolumba between whichthey are usuallygrouped. Apart from their white-tippedtails the Leptotila speciesdo not have any striking or well-definedmarkings, so their lack of the facial markings common to Zenaida and Geotrygon may be of little phylogeneticsignificance. The caseis different with Gallicolumbaspecies which show very distinctive color-patternsthat do not at all resemblethose of Geotrygon.Affinity betweenthese two genera seemsto be indicated only by a striking resemblancein generalform and ecology. This may be ascribedto parallel evolution--adaptation to fit similar habitats in the old and new worlds--from more divergent stocks of arboreal pigeons. However, I do not feel confidentenough to argue July19,•8J'] GOODWIN,Taxonomy ofAmerican Doves 333 a case in favor of this conclusion,but only to suggestthe possibility. There seems no valid reason for keeping the Purple Quail-Dove saphirina,in the monotypicgenus Osculatia. Salvadori(1893)recognised this genuson the groundsthat the primariesare rather narrow and more or lesstapering to a point, the first primary is attenuated at the tip and the tail shorter than half the length of the wing. Of these supposed differencesthe only real one is the attenuated first primary, for Geotrygon costaricensis(Lawrence) and G. veraguensis(Lawrence) have the tail shorterthan half the length of the wing, and G. montana(Linnaeus) and G. veraguensishave all their primaries, exceptingthe outermost one, as narrow and pointed as thoseof saphirina. I do not think this single character of an attenuated first primary warrants generic separation of a specieswhich in every other respectshows its closeaffinity to others not possessingit. It is proposed,therefore, to unite Osculatiawith Geotrygon. The Cuban Blue-headedQuail-Dove, Starnoenascyanocephala (Lin- naeus),is placedby Peters(1937) betweenthe two monotypicold world generaMicrogoura and Otidiphapsand further separatedfrom Geotrygon by the genera Gallicolumba,Leucosarcia and Trugon. In spite of the unusual blue coloration of its head, it seems evident that the affinities of Starnoenasare with Geotrygonrather than with any old-worldgenus. The color-patternof its head is very similar to thoseof Geotrygonfrenata