The use of sounds in avian systematics and the importance of bird sound archives

22 Pages·2003·11.8 MB·English

by  Per Alström

PerAlstrom&RichardRanft 114 Bull.B.O.C.2003123A
The use ofsounds in avian systematics and the
importance ofbird sound archives
&
byPerAlstrom RichardRanft
SUMMARY
Thesteadyincreaseintheglobaltotalofbirdspeciesisinpartduetothediscoveryof
distinctvocalisationswhichrevealhithertounrecognisedinformation,eitherthepresence
ofentirely new species orthe level ofdifferentiation in taxapreviously treated as
conspecific.Therearemanyexamplesofbothtypesofdiscovery(andsomewheretaxa
previouslygivenspeciesstatusproveconspecific).Theimportanceofvocalanalysisin
establishingtherelationshipsbetweentaxaisalsodemonstratedbynumerousexamples.
Aviansoundarchivesareclearlycrucialtotheadvancementofsuchstudies,butmany
morerecordingsareneeded,theirqualitymustbehigh,thecircumstancesofrecordings
needtobedocumented,theidentityofvocalisingbirdsneedstobefirm,andafuller
systemofcooperationbetweensoundarchivesisrequired.
Introduction
Thenumberofbirdspeciesintheworldwasestimatedtobec.8,600byMayr(1946),
c.9,000byBock&Farrand(1980),andc.9,700bySibley&Monroe(1990).This
increasewidelyexceedsthenumberofnewlydescribedspeciesinthattimeperiod.
Partofthisincreasecanbeattributedtothegrowingknowledgeofbirdvocalisations
incombinationwiththecurrenttrendtorecogniseallopatrictaxawithdistinctive
songs as speciesratherthanas subspecies (Sibley &Monroe 1990, Parker 1991,
Price 1996,Peterson 1998).
Although sounds have mainly been ofuse in the ranking ofclosely related
allopatrictaxa,vocalisationshavealsobeenusedtoinferrelationships,bothwithin
andbetweengenera,andhavebeencrucialinthediscoveryofseveralnewspecies.
Weherereviewtheuseofvocalisationsandotheracoustic signalsinsystematics;
seealsoPayne (1986)forathoroughreviewandMorel& Chappuis (1992)fora
reviewofWestAfricantaxa.Wealsodiscusstheimportanceofsoundarchivesand
suggesthowtheymaybemademoreusefultofutureresearchers.
Theimportance ofvocalisationsinthe discovery
ofnewspecies
Severalnew specieshavebeendiscoveredbecauseoftheirdistinctvocalisations.
Someoftheseescapedattentionbecausetheyarehighlysecretiveanddifficultto
see,andothersbecausetheyaresiblingspecieswhicharemorphologicallysimilar
tootherspecies.Severalexamplesaregivenhere.
ArallidheardinSeptember1997onasteepmountainslopeinprimaryforestin
theTalaudarchipelago, Indonesia, laterprovedtobe anundescribed species, the
TalaudBushHenAmaurornismagnirostris(Lambert 1998).
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TheexistenceoftwonewspeciesofAndeanpygmy-owls, SubtropicalPygmy
OwlGlaucidiumparkeri(Robbins&Howell 1995)andCloudForestPygmyOwl
G nubicola (Robbins & Stiles 1999), was first indicatedfromtape-recordings of
theirvoices.
TheCrypticWarblerCryptosylvicolarandrianosoloiwasfirstdetectedin 1992
ineasternMadagascarbyitsvoice(Goodmanetal. 1996)anditwassubsequently
foundtobecommon(Morris&Hawkins 1998).Likewiseitwasitssongthatfirst
disclosedthepresenceoftheJocotocoAntpittaGrallaria ridgelyiintheAndesof
southernEcuador(Krabbeetal. 1999).
TheAncientAntwrenHerpsilochmusgentryiwas discoveredbyJoseAlvarez
AlonsoandBretWhitneywhenWhitneyidentifieditasanewspeciesfromamong
Alvarez'sunclassifiedtape-recordingsofunseencanopybirdsfromPeru(Whitney
&AlvarezAlonso 1998).Theylatermanagedtofinditinthefield(andtocollect
twobirds),confirmingitsdistinctness.
FournewspeciesofScytalopustapaculosfromSouthAmerica,ChocoTapaculo
S. chocoensis, Chusquea Tapaculo S. parkeri (Krabbe & Schulenberg 1997),
DiademedTapaculoS.schulenbergi(Whitney1994)andTall-grassWetlandTapaculo
Scytalopusiraiensis(Bornscheinetal. 1998),werediscoveredbecausetheirsongs
differedfromotherknownspecies.
The observation that there were 'two markedly different vocal types', and
pronounced differences in display, in what was originally believed to be Suiriri
FlycatcherSuiriri suiriri led to the discovery ofthe Chapada Flycatcher Suiriri
islerorum(Zimmeretal.2001).
The song ofthe NepalWren BabblerPnoepyga immaculata (Martens &Eck
1991)waslongthoughttobeavariantofthesongofScaly-breastedWrenBabbler
P. albiventer. Itwaslaterrealisedthatthe individualswiththiskindofsongalso
differedmorphologicallyfromScaly-breastedWrenBabbler,andtheexistenceofa
previouslyunknownspecieswasthusrevealed.
ThreepreviouslyunknownspeciesofwarblerswerediscoveredinChinaduring
the 1990s as a result oftheir vocalisations. Emei LeafWarbler Phylloscopus
emeiensis, restrictedto a small areain central China, was firstnotedbecause its
songandcalldifferedmarkedlyfromtwoothersympatric,similar-lookingspecies,
Blyth's LeafWarbler P. reguloides and White-tailed LeafWarbler P. davisoni
(Alstrom&Olsson 1995).Vocalisationswerealsoofparamountimportanceinthe
discoveryoftwonewspeciesofSeicercuswarblers,S.sororandS. omeiensis,and
in the elucidation ofa group ofsibling species (Alstrom & Olsson 1999, 2000,
Martensetal. 1999; seebelow). Othernewwarblershavebeenfoundbecauseof
theirdistinctvocalisations,e.g.Dorst'sCisticolaCisticoladorsti(Chappuis&Erard
1991)andRiverPriniaPriniafluviatilis(Chappuis1974),bothfromWesttoCentral
Africa.
TheTaiwanBushWarblerBradypterusalishanensiswaspreviouslytreatedas
thesubspeciesmelanorhynchusofRussetBushWarblerB. mandelli(=seebohmi),
butwasdescribedasanewspecies(Rasmussenetal.2000a)whenitwasrealised
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thatitssongdifferedmarkedlyfromotherpopulationsofRussetBush-warblerand
thatnonamewasavailableforthispopulation.
Nofewerthanthreeindigobirds,JosPlateauViduamaryae,GoldbreastV.raricola
and Barka V. larvaticola, were discovered mainly because oftheir songs (Payne
1982, 1998,Payne&Payne1994).However,thediscriminationofthefirstofthese
speciesledtotheevenmoreremarkablediscoveryoftheRockFirefinchLagonosticta
sanguinodorsalis(Payne1998).Indigobirdsarespecies-specificbroodparasitesthat
mimic the songs oftheirhost species, mainly firefinches Lagonosticta spp. (e.g.
Payne 1968, 1973a, 1973b, 1982, Payne&Payne 1994), sowhenitwasrealised
that the song ofthe Jos Plateau Indigobird differed from the songs ofall other
indigobirds,itwaspredictedthattheremustbeanunknownfirefinchsongmodelin
thearea.
Atleasttwonewspeciesofcorvid,SinaloaCrowCorvussinaloaefromwestern
Mexico(Davis 1958)andLittleRavenC.mellorifromsouthernAustralia(Rowley
1967a,b),werediscoveredbecauseofdifferencesinvocalisationsfromotherspecies,
inthesecondcaseasympatricspecies(AustralianRavenC. coronoides).
Theimportance ofvocalisationsintheassessmentof
taxonomicrank
Therearemanycases,inawiderangeofgenera,whereallopatrictaxahavebeen
'upgraded' fromtherankofsubspeciesto species, orevenfromcolourmorphto
species,becauseofdifferencesintheiracousticsignals.Theconverseislesscommon.
Someexamplesarepresentedhere.
The North American Western GrebeAechmophorus occidentalis and Clark's
GrebeA.clarkiiwerepreviouslyconsideredtobecolourmorphsofthesamespecies
(Western GrebeA. occidentalis). However, Nuechterlein (1981) showed thatthe
'advertisingcall'usedinmateattractiondifferssignificantlybetweenthetwoand
that,inanareaofsympatry,each 'morph'respondedalmostexclusivelytoitsown
call.ThisconfirmedthestudiesofStorer(1965)andRatti(1979),whichhadshown
strongassortativematinginthese 'morphs'.
In many seabirds, especially those thatbreed in burrows and only visittheir
breeding islands at night, females probably identify conspecific males by their
vocalisations, atleastatlongrange (James &Robertson 1986,Bretagnolle 1990,
1995, Bretagnolle etal. 1990, Bretagnolle & Robinson 1991). Studies ofsounds
have sometimes revealed differences between populations that were considered
conspecific, andhavebeenusedinconjunctionwithotherevidenceto showthat
thesetaxaarebetterconsidered separate species. TheAntarctic PrionPachyptila
desolata,Salvin'sPrionPsalvini,Broad-billedPrionP.vittata,Slender-billedPrion
PbelcheriandFairyPrionP.turturhavebeentreateddifferentlybydifferentauthors
onthebasisofmorphologicaldata.Bretagnolleetal.(1990)studiedthesetaxaon
theirbreedingislands,wheretwotofouroccurredinsympatry.Theyshowedthat
their voices (as well as morphology, phenology ofbreeding and diet) differed
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consistently, especially in sympatrictaxa, andthey thereforeconsideredall tobe
separatespecies.
Bretagnolle (1995) analysed the vocalisations of Soft-plumaged Petrel
Pterodromamollisfromseveraldifferentlocalities. Basedonthis (inconjunction
withmorphologicalcharacters),heconcludedthattheSoft-plumagedPetrelshould
be splitintotwo species, oneinthenorthernhemisphere, P.feae, andone inthe
southernhemisphere,P. mollis. (Itshouldbementionedthatothers,followingthe
leadofBourne[1983],believethattheNorthAtlantictaxafeaeandmadeirashould
be treated as separate species based on morphological differences, although
Bretagnolle[1995]remarkedthattheircallsweresimilarandoverlapped.)
TheHeraldPetrelPterodromaheraldicawasformerlybelievedtohaveadark-
belliedandapale-belliedcolourmorph. However, Brooke &Rowe(1996) noted
consistentdifferencesinthevocalisationsofpaleanddarkbirds(especiallyinthe
rate ofdelivery ofthe calls in a series). These differences, in combination with
evidenceofassortativematingandlackofgeneflow,ledthemtoproposethatthe
twomorphsareinfactseparatespecies,HeraldPetrelP. heraldicaandHenderson
PetrelP. atrata.
The22currentlyrecognisedspeciesofmegapodeMegapodiidaedifferlittlein
plumage,butmarkedlyinbare-partcoloursandproportions(Roselaar 1994,Jones
etal. 1995).Althoughtheirvocalisationsareimperfectlyknown,thereare 'minor
differences between the races and sometimes marked ones between species',
supportingtheproposedclassification(R.W.R.J.DekkerinRoselaar1994).
EveningroupssuchasbustardsOtididae,whicharenotveryvocal,voicehas
provedusefulintaxonomicassessments.ItisnowwidelyacceptedthattheCrested
BustardEupodotisruficristainvolvesthreeallopatricspeciesowingtodifferences
invocalisationsandmorphology(Chappuisetal. 1979,Morel&Chappuis 1992,
Payne etal. 1997); and it has been suggested by Gaucher etal. (1996) that the
Houbara Bustard Chlamydotis undulata is better treated as two allospecies, C.
undulata and C. macqueenii, owingtodifferences in 'display call' andcourtship
display(supportedbymorphologicalandgeneticdifferences).
Acousticsignalshavebeenusedcomparativelyrarelyinwadertaxonomy,despite
the fact that most waders have distinct sound displays. TheAmami Woodcock
Scolopaxmiraisanexception.ItwasoncetreatedasasubspeciesoftheEurasian
WoodcockS.rusticola,butBrazil&Ikenaga(1987)pointedoutdifferencesin(among
otherthings)vocalisationsandtheapparentlackofadisplayflight.
Thonen(1969),Olsson(1987)andMiller(1996)remarkedthatthe'drumming'
madebythetail-feathersduringflightdisplaydifferedbetweenEuropean(nominate)
andNorthAmerican(subspeciesdelicata)populationsofCommonSnipeGallinago
gallinago. Based on this (in combination with morphological differences), they
suggestedthattheseshouldbeconsideredseparatespecies.
AmericanGoldenPloverPluvialisdominicaandPacificGoldenPloverP.fulva
wereformerlytreatedasconspecific (underthenameAmericanGoldenPloverP.
dominica).Connorsetal.(1993)studiedthesetaxainanareaofsympatricbreeding
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inwesternAlaskaandshowedthattherewereconsistentdifferencesinvocalisations
('song', alarm calls and other calls) and in habitat choice, and that mating was
assortative. Byrkjedal &Thompson (1998) cametothe same conclusions. These
resultssupportedthepropositionbyConnors(1983),basedonastudyofspecimens,
thatthesetaxaareseparatespecies.
Miller(1996)noteddifferencesinfivevariablesinthedisplayvocalisationsof
CommonRingedCharadriushiaticulaandSemipalmatedC.semipalmatusPlovers,
but only very slight intra-taxon differences overlarge areas. These findings lent
supporttothewidelyacceptednotionthatthesetaxaarebettertreatedasseparate
species.
Song characteristics have been used to re-estimate species limits in several
cuckoos:Square-tailedDrongoCuckooSurniculusdicruroides,Round-tailedDrongo
CuckooS. lugubris,MoluccanDrongoCuckooS. musschenbroekiandPhilippine
DrongoCuckooS. velutinus (Payne 1997, inpress); Horsfield's Cuckoo Cuculus
optatus{-horsfieldi)andOrientalCuckooC.saturatus(Payne 1997,butlumpedin
Payne [in press] 'because a larger sample of songs shows some overlap, and
specimens showoverlapalso': R. B. Paynein lift.); CommonCuckoo C. canorus
andAfricanCuckooC.gularis(Payne1986,Morel&Chappuisl992);RufousHawk
CuckooHierococcyxhyperythrus,PhilippineHawkCuckooH.pectoralis,Whistling
HawkCuckooH.nisicolorandJavanHawkCuckooH.fugax(Payne1997,inpress,
King 2002); andAsian LesserCuckoo C. poliocephalus and MadagascarLesser
CuckooC. rochii(Becking 1988,Payneinpress).
Inowls,voicehasoftenbeenofmajorimportanceintheassessmentoftaxonomic
rank.TheclassicstudybyMarshall(1978)onsmallAsianowls,inwhichheclassified
taxa with dissimilar vocalisations as separate species and, conversely, taxa with
similarvocalisationsasconspecific,ledtoamultitudeoftaxonomicrearrangements.
Forexample,hesuggestedspeciesstatusfornofewerthansevenscopsowls(genus
Otus)thathadpreviouslybeentreatedassubspecies.Otherstudiesonthevoicesof
Asian scops owls have been importantinresolvingtaxonomic matters, andhave
furtherincreasedthenumberofrecognisedspecies(Roberts&King1986,Marshall
&King 1988,Becking 1994,Lambert&Rasmussen 1998).
AnotherexampleisthatallthetaxapreviouslyassociatedwithOtusrutilusof
Madagascarhavebeenshowntodifferinvoice(andmorphology),andhavebeen
suggestedtobetreatedasseparatespecies:O.moheliensis(Lafontaine&Moulaert
1998), O. capnodes (Safford 1993), O. pauliani (Herremans etal. 1991), O. [r.]
mayottensis(Lewis 1998), O. madagascariensisand O. rutilus (Rasmussenetal.
2000b). Chappuis (1974-1985) and Morel & Chappuis (1992) suggested that
European Scops OwlO. scopsandAfricanScopsOwl O. senegalensisshouldbe
consideredseparatespeciesbasedondifferencesinvoice.
TheLeastPygmyOwlGlaucidiumminutissimum,whichiswidelydistributedin
SouthAmerica, wasformerlytreatedas apolytypic species. However, Howell&
Robbins (1995) analysed vocalisations and in conjunction with morphology and
otherevidencesuggestedthatitoughttobetreatedasfourseparatespecies.
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Vocalisations havebeen usedextensively in taxonomic revisions ofnightjars.
For example, Jerdon's Nightjar Caprimulgus atripennis, Sulawesi Nightjar C.
celebensisandPhilippine Nightjar C. manillensis were all splitfromLarge-tailed
NightjarC.macrunisbecauseoftheirdistinctivevocalisations(Mees 1985,Ripley
&Beehler 1987, Rozendaal 1990). Likewise,Tawny-collaredNightjarC. salvini,
YucatanNightjarC. badiusandSilky-tailedNightjarC. sericocaudatushavebeen
judged to be specifically different on the basis ofdifferences in voice (Hardy &
Straneck 1989). Conversely,Dowsett&Dowsett-Lemaire(1993)pointedoutthat
thesongsofFiery-neckedNightjarC.pectoralisandBlack-shoulderedNightjarC.
nigriscapularisweresimilar,andsuggestedthattheseshouldbetreatedasconspecific.
Theyalsoshowedthatthetaxaruwenzorii(RuwenzoriNightjar),guttifer(Usambara
Nightjar)andpoliocephalus(AbyssinianNightjar),whichhaveatonetimeoranother
beenconsidered separate species, arebesttreatedasconspecific, underthe name
Montane Nightjar C. poliocephalus, owing to basically similar vocalisations. (It
should,however,benotedthatCleere[1995],alsousingvocalcharacters,disagreed
withthisassessment.)
Voicehasbeenimportantintheassessmentofspecies statusofataxonthatis
believedtobeextinctinthewild:Grayson'sDoveZenaidagraysonifromSocorro
Islandsouth-westofBajaCalifornia(Baptistaetal. 1983). Itwasestablishedthat
the voice (andvisual display) ofthisbirddiffersignificantlyfromthe Mourning
DoveZmacroura,withwhichithasoftenbeenconsideredtobeconspecific.Itwas
alsonotedthatitonlyrarelyinterbreedswithMourningDoveincaptivity.
Vocalisationshavebeenusedtoassessthetaxonomicrankinotherdoves.The
insularendemicGrenadaDoveLeptotilawellsiwasshowntodiffervocally(aswell
as morphologically) from the closely related continental Grey-fronted Dove L.
rufaxilla(Blockstein&Hardy1989).Playbacktestswerealsoofimportanceinthis
re-evaluation. Chappuis (1974-1985) andMorel & Chappuis (1992) showedthat
the vocalisations ofthe morphologically closely similarEurasian CollaredDove
Streptopeliadecaocto andAfricanCollaredDove S. roseogrisea differmarkedly,
andproposedspeciesstatusforthem.
Pittas Pittidae have loud, relatively simple songs which have been used (in
conjunctionwithespeciallymorphology)toshowthatthemainlyallopatricFairy
PittaPittanympha,Blue-wingedPittaP.moluccensis,IndianPittaP.brachyuraand
MangrovePittaP.megarhynchusarebesttreatedasseparatespecies(Lambert1996,
Lambert&Woodcock1996).
TheNeotropicalTyrannidaeincludemanyspeciesthatarepoorlydifferentiated
morphologically, and vocalisations have often been ofgreat importance in the
recognition of species. Lanyon (1978) used vocalisations and playback tests
extensively inhis monumental revision ofthe genusMyiarchus, because he was
'convincedthattheuseofvocalcharacters,inconjunctionwithmoreconventional
morphologicalcharacters,wouldbethekeytoanysuccessfulattempttodetermine
specificlimitsandrelationshipswithinthegenus'.Heproposedseveraltaxonomic
rearrangementsbasedonthisresearch.
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PerAlstrom RichardRanft 120 Bull.B.O.C.2003123A
Willow FlycatcherEmpidonax traillii andAlderFlycatcherE. alnorum were
formerlyconsideredconspecific,butStein(1958, 1963)showedthattheydiffered
invocalisationsandotheraspects,didnotrespondtoplaybackofeachother'ssongs
and were partly sympatric. Similarly, studies of vocalisations together with
morphologyandallozymesshowedthattheWesternFlycatcherE.difficilisofwestern
NorthAmericawas in facttwo separate, partly sympatric. species: Pacific-slope
FlycatcherE. difficilis andCordilleranFlycatcherE. occidentalis (Johnson 1980,
Johnson 1994).
ThespeciesintheSouthAmericansuboscinegenusScytalopus(tapaculos)are
extremelysimilarinplumageandstructure,andareverysecretiveanddifficultto
observe(e.g.Fjeldsa&Krabbe 1990,Ridgely&Tudor1994).Untilrecently,their
classification was based on comparative studies ofmuseum specimens (Zimrner
1939,Peters 1951).AreviewbyKrabbe&Schulenberg(1997)usingvocalisations
(incombinationwithmorphologyanddistribution)ledtoavirtual 'explosion' of
species, from 11 recognisedbyZimmerandPeterstonofewerthan 37. Threeof
these,ChocoTapaculoS.chocoensis,EcuadorianTapaculoS.robbinsiandChusquea
Tapaculo S. parkeri, were new to science, and an additional two or three were
consideredtobeundescribed. Severalofthespecieswereshowntobesympatric.
Krabbe & Schulenbergclassifiedallopatrictaxawithunique songs as species, an
approachthatwassupportedbyDNAdatapresentedbyArctander&Fjeldsa(1994).
The use ofvocalisations has led to the recognition ofmany SouthAmerican
Thamnophilidae and Formicariidae as species. For example. Isler et al. (1997)
suggested that the widely distributed polytypic Slaty Antshrike Thamnophilus
punctatus is bettertreated as at least six separate allospecies: Isler etal. (1999)
arguedthatStreakedAntwrenMyrmotherulasurinamensisshouldbetreatedasfour
species; and Whitney et al. (2000) concluded that the Black-cappedAntwren
Herpsilochmuspileatuscomplexconsistsofthreespecies,ofwhichone.Caatinga
AntwrenH.sellowi,waspreviouslyundescribedbecauseithadbeenconfusedwith
pileatusforalmostacentury.
TheBengalBushlarkMirafraassamica waspreviouslytreatedas apolytypic
speciesranging fromIndiato Sri Lanka andVietnam. However,Alstrom (1998)
showedthatthere arepronounceddifferences in songs, calls andsong-flights (as
wellasmorphologicaldifferences,andinonecaseinhabitat)betweenfourallopatric
taxa.Basedonthis,heproposedthattheybetreatedasfourseparatespecies.
Bicknell'sThrushCatharusbicknellihasreceivedmuchinterestlately,because
ithasbeenshowntodifferfromGrey-cheekedThrush C. minimus (withwhichit
wasformerlyconsideredconspecific)inanumberofaspects,includingsong(and
lack ofresponse to playback to two other subspecies ofGrey-cheeked Thrush.
minimusandaliciae)(Ouellet1993).
OldWorldwarblersarerenownedforbeingmorphologicallypoorlydifferentiated.
althoughthespeciesusuallydiffermoreclearlybytheirsongs.Thiswasnotedmore
than200years ago, whenWhite (1789)remarkedthat Thavenow, pastdispute,
made out three distinct species ofthe willow-wrens (motacilla? trochili) which
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constantlyandinvariablyusedistinctnotes.'HewasreferringtoWillowWarbler
Phylloscopus trochilus, Common ChiffchaffP. collybita and Wood Warbler P.
sibilatrix,ofwhichonlythefirsthadatthattimebeennamed.Infact,inthegenus
Phylloscopus(leafwarblers)inEurasiaexcludingthePhilippines,GreaterSundas
andWallacea,thenumberofrecognisedspecieswentupby31%inthelastdecade,
and in all except two species, songs were important in the assessment oftheir
taxonomicrank(Irwinetal.2001).Twoexamplesaregivenbelow.
Pallas'sWarblerP.proregulususedtobeconsideredawide-rangingpolytypic
species, breeding in Siberia, northern Mongolia and north-east China (nominate
proregulus); central China and the Himalayas west to central Nepal (subspecies
chloronotus); and western Himalayas (subspecies simlaensis); a fourth taxon,
kansuensis, from northern central China, was treated as a synonym of either
proregulusorchloronotus.First,Alstrom&Olsson(1990)proposedthatproregulus
and chloronotus/simlaensis should be treated as two separate species based on
pronounceddifferencesinvocalisations andlackofresponsetoplaybackofeach
other'ssongs. Subsequently,Alstrometal(1997)pointedoutthatkansuensisalso
differedconsiderablyinvocalisationsfromtheothers,anddidnotrespondtoplayback
oftheir songs, and concluded that it ought to be treated as a separate species.
Meanwhile,Alstrom etal. (1992) found a species withunique vocalisations that
wassympatricwithchloronotusincentralChina(differingalsoinmorphology,habitat
choiceandnestsite). Itwasdescribedas anew species, ChineseLeafWarblerP.
sichuanensis,thoughitwaslaterrealisedthatthisnamewaspre-datedbyyunnanensis
(Martens&Eck1995,P.Alstrom&U.Olssonunpublished).
ThetaxonomyoftheCommonChiffchaffPhylloscopuscollybitacomplexhas
receivedmuchattentioninrecentyears.Itwasformerlyconsideredasinglepolytypic
species,althoughextensivestudiesofitsvocalisationsandotherdata(e.g.Martens
&Hanel1981,Martens1982,Salomon1987,1989,Martens&Meincke1989,Helbig
etal.1996)haveledtothesuggestionthatatleastfourspeciesoughttoberecognised:
Common ChiffchaffP. collybita, Iberian ChiffchaffP. brehmii, Canary Islands
Chiffchaff P. canariensis and Mountain ChiffchaffP. sindianus, leaving the
relationships ofthe Siberian taxon tristis unresolved (Helbig etal. 1996). These
taxa are allopatric, except for Mountain and Common Chiffchaffs, which occur
togetherinwesternAsia,andthelattermeetsIberianChiffchaffinanarrowzonein
thePyrenees.Hanssonetal. (2000)showedthatSwedishpopulationsofCommon
Chiffchaffofthe subspecies collybita and abietinus responded more strongly to
songoftheirownthantotheothersubspeciesand,basedonotherdifferencessuch
ashabitatchoice, theypredictedthattherewouldbeonlylimitedhybridisationif
thesetaxametinthefuture.
TheGolden-spectacledWarblerwasuntilrecentlytreatedasasinglepolytypic
species, Seicercusburkii, withawide distribution inmountains ofsouthernAsia
(mainlytheHimalayasandChina).Alstrom&Olsson(1999,2000)andMartenset
al.(1999)demonstratedthatthisisactuallyacomplexofnofewerthansixsibling
species,withuptofouroccurringatdifferentaltitudesonthesamemountain(two,
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S.sororandS. omeiensis.werepreviouslyundescribed: seeabove).Differencesin
vocalisationsandplaybacktestswereofmajorimportanceintheelucidationofthis
situation.
SonghasbeenusedextensivelyintheclassificationofAfricancisticolasCisticola,
bothtosplitandtolumptaxa(e.g.North 1964,Chappuis 1974, 1980,Erard 1974,
Morel&Chappuis 1992).Keith&Gunn(1971),Chappuis(1974-1985),Chappuis
(1980)andMorel&Chappuis(1992)usedvocalisationstoreviewthetaxonomyof
someapalisApalisspecies.
One remarkable case where possible cryptic species were revealed by their
vocalisations is the study ofNorth American Common (Red) Crossbill Loxia
curvirostrasensulatobyGroth(1988, 1993a,b).He(1988, 1993a)studiedalarge
numberofindividualsfromacrossthecontinent,andcorrelatedsonogramsofcalls
with measurements ofthe same individuals. Based on these variables, the birds
clusteredintoeightdifferentgroups. Severalofthesearesympatric,e.g. sixinthe
PacificNorthwest. Strongassortativematingwasshowntooccurintwodifferent
populationsintheAppalachians(1993b).Heconcluded(1993a)that'L.curvirostra
isagroupofsiblingspecies'but,owingtothemorphologicalsimilarityandoverlap
inmeasurements,hewasunabletoassignnamestoallofthesespecies.TheAmerican
Ornithologists'Union(1998)recognisedonlyone speciesbutinterpretedGroth's
resultsasindicatingtheprobableexistenceofatleastninedifferentspeciesinNorth
America.StudiesofvocalisationsbyRobb(2000)havesuggestedthattheremaybe
crypticspeciesofcrossbillsalsoinEurope.
SomeofthemostamazingdiscoveriesinvolvingvocalisationsinvolvetheAfrican
indigobirds Vidua(e.g.Nicolai 1964,Payne 1968, 1973, 1976, 1982, 1990, 1998,
Payne &Payne 1994, 1995, Payne etal. 1992, 1993; see above).Althoughmost
indigobirdspeciesaremorphologicallypoorlydifferentiated,theirsongsareoften
markedlydifferent.Thisinsighthasledtotherecognitionofseveral'forms'asdistinct
species (all 10 indigobird species now recognised were at one time or another
considered to be either subspecies or colour morphs ofVillage Indigobird V.
chalybeata,oroverlooked).
Crows Corvus aremorphologicallyrelativelypoorly differentiated,buttheir
voicesareoftenclearlydifferent.Vocalisationshavebeenofmajorimportancein
the classification of the North American species American Crow C.
brachyrhynchos,North-westernCrowC.caurinus,TamaulipasCrowC.imparatus,
SinaloaCrowC.sinaloaeandFishCrowC.ossifragus(Brooks1942,Davis1958,
Hardy 1990).
Use ofvocalisationsininferringrelationships
Althoughvocalisationshavemainlybeenusedtoanswerquestionsofspeciesstatus,
someauthorshaveusedvoicetojudgerelationshipsamongspecies.Inafewcases,
features of songs and calls have been used as characters to infer phylogenetic
relationships.
PerAlstrom&RichardRanft 123 Bull.B.O.C.2003123A
Bretagnolle(1995)comparedthevocalisationsofseveraldifferentPterodroma
speciesanddrewconclusionsabouttheirrelationshipsbasedonthesimilaritiesand
dissimilaritiesbetweenthem.
ThecallsofdownyAnatidaeyoungwereanalysedbyKear(1968),whoconcluded
thattheyhadphylogeneticinformation.Theshapeandfrequencyrangeofthedistress
calltendedtobesimilarincloselyrelatedspeciesandtobemoredivergentinmore
distantly related ones. For example, she remarked that the call ofWhite-backed
DuckThalassornisleuconotus,whosetaxonomicpositionhadbeenindoubt, was
'very like those ofDendrocygna andquite unlike the distress call ofOxyura". A
recentphylogeneticanalysis(McCrackenetal. 1999)confirmsthatThalassornisis
not closely related to Oxyura, but also suggests that the similarity between
ThalassornisandDendrocygnaisduetoretentionofancestralcharacterstatesinthe
former.
Andersson(1973, 1999)studiedcallsanddisplaysofskuas(Stercorariini)and
concludedthatsomeoftheseare synapomorphies (sharedderive—dcharacters) for
Great Skua Stercorarius skua and Pomarine SkuaS. pomarinus supporting the
controversialbutnowwell-supported(seeAndersson 1999)viewthatthelatteris
more closely related to the large skuas (which are often placed in the genus
Catharacta)ratherthantothesmallerArcticS.parasiticusandLong-tailedSkuaS.
longicaudus.
Miller(1996)usedcharacteristicsofnuptialvocalisationstoinferrelationships
among Pluvialis plovers and some Calidris sandpipers. He also concluded that
'acousticcharactersseemtohavegreatpotentialforresolvingspeciesrelationships
atvariouslevels' inGallinagosnipesandCharadriusplovers.
AcousticdatawereusedbyWinkler&Short(1978)toinferrelationshipsamong
pied woodpeckers {Picoides/Dendrocopos). In many cases, their analysis
corroboratedpreviousstudies(e.g.theprobablemonophylyoftheNewWorldgroup).
Inothercasesthevocaldatawereinconflictwithotherevidence(e.g.MiddleSpotted
WoodpeckerDendrocoposmediuswasconsideredtobemoredistantlyrelatedto
White-backedWoodpeckerD.leucotosthanpreviouslythought,andthesameapplied
toBlack-backedPicoidesarcticusandThree-toedP. tridactylusWoodpeckers).
Vocalisationswereusedtodetermineprobablerelationshipsofsomeantwrens
inthegenusMyrmotherula(Whitney&Pacheco1997).Basedpartlyonvocalisations,
Whitney(1992)suggestedthatBicolouredAntvireoThamnomanesoccidentalisbe
placed in the genus Dysithamnus instead. Whitney & Pacheco (1994) also used
vocalisations in discussing the affinities ofthe little-known monotypic genera
GyalophylaxandMegaxenops.
Songs,callsanddisplayflightwereusedinadditiontootherdatatoshowthe
closerelationshipbetweenBerthelot'sPipitAnthusberthelotii,endemictotheCanary
Islands and Madeira, andTawny PipitA. campestris (Alstrom & Mild 1993), a
circumstancelatercorroboratedbymoleculardata(Arctanderetal. 1996,Voelker
1999).