Ornithological Monographs 11

BEHAVIOR, MIMETIC
AND

SONG DIALECTS,

SONGS
AND

RELATIONSHIPS
OF THE
PARASITIC
INDIGOBIRDS
(VIDUA) OF AFRICA

ROBERT

ORNITHOLOGICAL

B. PAYNE

MONOGRAPHS NO. 11

PUBLISHED

BY

THE AMERICAN ORNITHOLOGISTS' UNION
1973


BEHAVIOR,

MIMETIC
SONGS AND
DIALECTS, AND RELATIONSHIPS

THE PARASITIC
OF

INDIGOBIRDS
AFRICA

SONG
OF

('?IDU..4,)


ORNITHOLOGICAL

MONOGRAPHS

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Correspondence
concerningmanuscriptsfor publicationin the series
shouldbe addressedto the incomingEditor, Dr. John W. Hardy, Moore
Laboratoryof Zoology,OccidentalCollege,Los Angeles,California90041.

Copiesof OrnithologicalMorrographsmay be orderedfrom the Treasurer
of the AOU, Burt L. Monroe, Jr., Box 23447, Anchorage,Kentucky40223.
(See price list on inside back cover.)
OrnithologicalMonographs,No. 11, vi + 333 pp.
Editor, Robert M. Mengel
Editorial Assistant, James W. Parker

IssuedJanuary31, 1973

Price $8.00 prepaid($6.40 to AOU Members)
Library of CongressCatalogueCard Number 73-75355
Printedby the Allen Press,Inc., Lawrence,Kansas66044

Erratum. For a time it was hopedthat publicationof OrnithologicalMonographsNo.
11 would occurin 1972, the year that appearson the running headsthroughout. Publication in 1972 was not realized, however,and through one of thosenoxiousoversightsthat
plague the publication processthe entire work had been printed before the failure to
change the running heads was detected.--Ed.


G

H

'

I

J

Breeding plumages of the males of ten kinds of indigobirds. A, Vidua chalybeata

chalybeata, form "aenea" (FMNH 278472, Richard-To!l, Senegal); B, V. c. amauropteryx ( RBP 4469, Sabi Valley, Rhodesia); C, V. c. ultramarina (FMN H 204118, Mojjio,
Ethiopia): D. l/. ]unerea codringtoni (RBP 4437. Penhalonga-Umtali. Rhodesia):
E, l/. 1. !usitensisssp. nov. (RBP 4575, Lusitu River, Rhodesia); F. V. 1. [unerea (RBP
4424, 6 mi. E. Tzaneen, Transvaal); G, V. wilsoni, form "nigeriae" (RBP 4937,
Panshanu Pass, Nigeria);
H, l/. wilsonL form "camerunensis" (RBP 4855, Zaria,
Nigeria); I, l/. wilsoni, form "wilsoni" (RBP 4960, Zaria, Nigeria); J, V. purpurascens
(RBP 4419, Merensky Reserve, Transvaal).


BEHAVIOR,
MIMETIC
SONGS
AND SONG DIALECTS, AND
RELATIONSHIPS
PARASITIC

(VIDUA)

OF AFRICA

B. PAYNE

MONOGRAPHS
PUBLISHED

THE

AMERICAN

THE

INDIGOBIRDS

ROBERT

ORNITHOLOGICAL

OF

ORNITHOLOGISTS'
1973

NO.

BY

UNION

11


TABLE

OF CONTENTS

INTRODUCTION ....................................................................................................................
ACKNOWLEDGMENTS

.......................................................................................................

4

ITINERARY................................................
z........................................................................

7

BREEDING BEHAVIOR OF INDmOBIm)S ................................................................................

9

Social Behavior and Mating Systems...................................................................... 10
Courtship Behavior ................................................................................................ 29
BROOD PARASITISM AND THE INTERACTIONS OF INDIGOBIRDS AND FIREFINCHES ............

39

Evidenceof Parasitismand Host Specificityin Indigobirds................................ 39
Ecology of Indigobird Parasitism ...........................................................................
42
Behavioral Interactions Between Indigobirds and Firefinches ........................... 44
Mimicry of Eggs and Young .................................................................................... 52
VOCALIZATIONS OF FIREFINCHES AND THEIR MIMICRY

Firefinch

Vocalizations

BY THE INDIGOBIRDS ................

.............................................................................................

61

62

Vocal Mimicry in Indigobird Song .......................................................................... 94
Discussion
NONMIMETIC
Chatters

.................................................................................................................

101

VOCALIZATIONS AND SoNG DIALECTS ........................................................

111

.....................................................................................................................

129

Complex Nonmimetic Songs ................................................................................... 131
Repertoire Size, Mating Systems,and Individual Recognition .............................. 146
Origin of Nonmimetic Songs and Song Dialects ................................................... 147
SoNG DIALECTS AND POPULATION STRUCTURE .................................................................

155

Estimatesof Population Structure from Song Dialects in the Indigobirds .......... 156
Significanceof Population Structure ....................................................................... 158
BEHAVIORALCONTEXT OF INDmOmRD VOCALIZATIONS AND Tm• RESPONSESOF BIRDS
TO SoNGS ......................................................................................................................
160

Analysis of Song Recordings ...............................................................................
Behavioral Context of Songs .............................................................................
Responsesof Wild Males to Recorded Songs .....................................................

160
161
164

Responses
of Captive Female Indigobirdsto Species-and Population-specific

Songs ................................................................................................................. 165

ASSORTATIVEMATING AND ISOLATING MECHANISMS .......................................................

Assortative Mating .............................................................................................
Breeding Biology and Potential Isolating Mechanisms .......................................

173

173
175

DISTRIBUTION OF FIREFINCHES AND INDIGOBIRDs ...................................................

Southern Africa ....................................................................................................
East Africa ................................................................................................................
North and West Africa ............................................................................................
Central Africa ..........................................................................................................
Discussion ...............................................................................................................

186
186
194
198
205
207

VARIATION AND RELATIONSHIPS IN THE INDIGOBIRDS ...................................................

209

Basis of Identification and Taxonomic Allocation of Specimens........................ 209
Analysis of Variation ....................................................................................... 211


Vidua chalybeata ........................................................................................... 218
Vidua purpurascens ..................................................................................
235
Vidua /unerea ................................................................................................. 240
Vidua

THE

wilsoni ..................................................................................................

250

The V. [unerea--V. purpurascensComplex ....................................................
Intergradation of V. chalybeata and Other Species.......................................

263
273

Discussion

277

................................................................................................................

IMPORTANCE

OF SONG BEHAVIOR AND GEOGRAPHIC

ISOLATION

IN

DIFFEREN-

TIATION AND SPECIATION OF THE INDIGOBIRDS ..........................................................

280

Determination of Mating Groups by Imprinting to Host Songs ........................ 280

GeographicVariation in Behaviorand the Breakdownof ReproductiveIsolation
Between Indigobirds ...................................................................................... 282
Two Models of Speciation.................................................................................... 284
Discussion
SUMMARY
LITE•a•JRE

..............................................................................................................

292

..........................................................................................................................

298

CITED

...........................................................................................................

302

AP2ENDIXA (Locality and Other Data for Audiospectrographs).........................

313

APPENDIXB (Distribution of Firefinches and Indigobirds) ..................................

322

vi

INTRODUCTION

Studiesof behaviorhave advancedour understandingof the relationships
of birds of the world, both amonggeneraand familiesand amongclosely
relatedspecies.While comparativestudiesof the behaviorof closelyrelated
birdshave generallyconfirmedthe ideasof speciesrelationships
basedon the
appearanceof birds, in a few instancesbehaviorstudy has been importantin
revealingspecieswhoseexistencewas previouslyunsuspected.The eminent
pioneerBritish naturalistGilbert White recognizedthe Chiffchaff (Phylloscopuscollybita)as a species
distinctfrom the Willow Warbler (P. trochilus)
by differencesin songsand call notesmany yearsbeforetaxonomists
became
aware of any morphologicaldifferences(Mayr, 1963: 52). Speciesdifferencesbetween extremely similar birds have been first recognizedthrough
behavioraldifferences,especiallysong,in severalgeneraincludingflycatchers
(Empidonax), warblers (Cisticola), and grackles(Cassidix) (Stein, 1958,
1963; Traylor, 1967; Selanderand Giller, 1961). Not only have cognate
speciesbeen detected;behaviorstudieshave also led to the recognitionof
morphologically
dissimilarpopulationsas membersof the samespecies(e.g.,
Lanyon, 1969; Thielcke, 1969b).

The indigobirds(subgenusHypochera,genusVidua, subfamilyViduinae)
are small parasiticfinchesdifferingslighfiyin the color of the glossof the
blackishbreedingplumageof the male and in bill and foot color; the nonbreedingmalesand the femalesare small brownishbirds. They are also
known as indigofinches,widow-finches,steelfinches,combassous
and Atlaswitwen. Museumworkershave reachedno agreementon the relationships
among the indigobirdsthrough studiesof the plumage charactersalone;

Mackworth-Praedand Grant (1949) recognizedeight species,whereas
White (1962, 1963a) has consideredthe indigobirdsto be a singlepolymorphic,polytypicspecies.Only a few previouslycollectedfemale museum
specimens
(both V. chalybeata,the Village Indigobird)havebeentakenwith
malesof knownform and havehad notedon the label the charactersby which
the femalesmay sometimesbe identified,namely the colorsof the bill and
feet. In the absenceof field reportsfrom Africa of differencesin behaviorit
was most surprisingand excitingwhen Nicolai (1961) discoveredthat V.
chalybeatain captivitymimicsthe songof its host, the SenegalFirefinch
(Lagonostictasenegala). This observationled him to a discoveryof hostspecificvocal mimicry in most other speciesof viduines (Nicolai, 1964).
Stimulatedby his observationsand by Traylor's (1966) study of variation
in this complexof forms, I visitedAfrica to observebehaviorand record the
songsof mostformsof indigobirds
and to collectthe singingmalesof each
kind of indigobirdas well as the females mating with them.
The songmodelsand fosterersof the indigobirds,the firefinches(Lagoho-


2

ORNITHOLOGICAL

MONOGRAPHS

NO. 11

stictaspp.), are membersof the subfamilyEstrildinae(the waxbills) in the

familyEstrildidae.Mayr et al, (1968) recognize
eightspecies

of firefinches,

buttwoof these
aremembers
of superspecies
groups,
andastheyare

knownto be specifically
distinctI am regarding
landanaeas conspecific
with
L. rubricam(as did Chapin,1954: 523) and nitidulaas conspecific
with L.
rufopicta(followingWhite, 1963b:202). The firefinchspeciesthat the
indigobirdsmimic and parasitizeare L. senegala,L. rhodopareia,L. rubricata,L. larvata,andL. rara. The remainingfirefinch,L. rufopicta(including
nitidula),is not knownto be a songmodelof the indigobirds.
The indigobirdsand other viduinesare usuallyregardedtaxonomicallyas
a subfamilyof the widespread
Old World weaverfinches,Ploceidae.Earlier
workersoftenregardedthe viduinesas closelyrelatedto the Estrildidae,but
Friedmann(1960) emphasized
that many similaritiesbetweenthe viduines
and estrildid.s
are adaptive,inasmuchas the viduinesmimic their estrildid

hostsin eggcolorandthe markings
of the young.Friedmann
and others
have reasonedthat the viduinesare mostlikely derivedfrom the Ploceinae,

the weaverfinches,and shouldbe placedin the samefamilywith them. On
the other hand Sibley (1970) has found that in somebiochemicalfeatures
the viduinesare moresimilarto the Old World sparrows(Passerandrelated
genera)than eitherof thesegroupsare to the Ploceinaeor the Estrildidae,
andhe suggests
thatthe closestrelativesof the viduinesmaybe the Old World
sparrows,whichhe regardsas a separatefamily, Passeridae.The present
studyis concernedwith the relationshipswithin the indigobirdspeciescomplex ratherthan with family relationships
amongthe Old World finchesand
sparrows,althoughsomecomparisons
of the behaviorof viduineswith the
weaverfinches,sparrows,and grassfinches
are included. For convenienceI
have followedhere the systematic
arrangement(exceptfor the viduinespeciesthemselves)of Check-listof Birds of the World, volumesXIV and XV,
in which the Estrildidaeare recognizedas a family and in whichPasserinae,
Ploceinae,and Viduinae (with the indigobirds) are subfamiliesof Ploceidae.
The viduinescompriseabout 12 speciesoften unitedin a singlegenus,
Vidua. All formsare African. Traylot (1968) recognizes
three subgenera-Hypochera(the indigobirds),Vidua (four species
in whichthe breedingmale
has a long, slendertail), and Steganura(the paradisewhydahs,in which the
tail is large and ornate).
In the presentstudyfour species
of indigobirds
are recognized
taxonomically as a resultof the field work, analysisof museumspecimens,
and long
contemplation.The forms "nigeriae,""camerunensis,"
and "wilsoni" are

regardedas conspecific,
and the name V. 'wilsoniis usedfor all of these,but
the form names,in quotationmarks,are usedto describethe appearance
of
the birds. The forms codringtoni,nigerrima,and [unereaare regardedas
subspecies
of a singlespecies,V. [unerea. The othertwo speciesare V. pur-


1972

PAYNE:

PARASITIC

INDIGOBIRDS

OF

AFRICA

3

purascensand V. chalybeata. The rationale behind this taxonomic schemeis

discussed
on pp. 209-210 and beyondin the systematic
section.
The relationships
amongthe indigobirds

are inadequately
described
simply
in traditionaltermsof eitherbiologicalor typological
species.As notedin
earlierreports(Nicolai, 1967, 1968;Payne,1967, 1968a, 1'968b)the indigobirdsthat look alikegenerallymimicthe songsof a singlespeciesof firefinch,
and differentformsliving in the samearea mimic differentfirefinches.For
example,in all of the localitiesthat I visited, V. chalybeataalmost always
mimickedthe songsof L. senegala.In my field work nearly three miles of
recordingtape were exposedto indigobirdsongs.Most recordedbirds were
subsequentiy
collected,oftenwith theirfemales.By comparingthe songswith
the male and female studyspecimensassociatedwith each behavioralobservation,it waspossibleto establishthat the indigobirdsmimic differentsongs
andbehaveas goodbiologicalspecies
in someareas. At otherlocalitiessome
of thesespeciesapparentiymimic the samesongsand interbreedwith each
other. The presentpaperattemptsin the first placeto describethe behavioral
and evolutionary
relationships
amongthe indigobirds,
and secondarily
to help
in identificationof the indigobirdsin museumspecimensand in the field.
Knowledgeof the behaviorof the indigobirdsallowsnot only evaluationof
their speciesrelationships
but alsoestimatesof their populationstructure,includingpopulationsizeand the degreeof isolationbetweenneighboringpopulations. The numberof individualsthat are likely to interbreedwith each
otheris probablyin generalmuchsmallerthan the total numberof individuals
in a species.In the indigobirdsthe localrestrictionof certainnonmimeticsong
dialectsto very smallregions,togetherwith estimatesof populationdensity,
makeit possibleto estimatethe "neighborhood

size" or "effectivepopulation
size"(in the senseof Wright, 1969) of thesebirds. By comparingthe manner
in whichthesesongdialectsvaryit waspossiblealsoto gainan ideaof whether
populationsare isolatedfrom eachotherand to seein what mannernew song
dialectsmayarise. Songdialectsseemto be idealmarkersfor studiesof population biology in certain birds.
The complexityof the relationships
amongthe indigobirdsmay resultfrom
imprintingby the youngupon the songsand calls of their host species,and
oneof the mainpurposes
of the presentstudywasto testthe hypothesis
proposedby Nicolai (1964, 1967) that speciation
in the viduinesis a directconsequence
of host-specific
imprintingrather than of geographical
isolation,a
much more commonconditionin differentiationof birds (Mayr, 1963: 481515). Relationshipsamongthe indigibirdswere further re-examinedin a
studyof all available-museum
material,including302 birds taken in the field
work, and comparingthe patternsof variationin morphologyas well as in
song.

Field observations
providedinformationabout the behavior,matingsys-


4

ORNITHOLOGICAL

MONOGRAPHS

NO. 11

tems,and techniques
of broodparasitismin the indigobirds.The behavioral
contextof the differentkindsof songswasstudiedto find the possiblefunc-

tionsof song,andsomeplaybackexperiments
weremadein the field andin
captivity.Additionalobservations
on the behaviorof indigobirdsand their
firefinchhostswere madein captivityat Norman,Oklahoma,and at Ann
Arbor, Michigan,wherecagedand aviaryfirefincheshavebred. I watched
the behavioralinteractions
betweenthe broodparasitesand their firefinch
hostsin the captivebirdsflyingfree in our housefor two years.
ACKNOWLEDGMENTS

Thisstudywasmadepossible
throughthe supportof the NationalScience
Foundation(Fellowship45166; GB-7720; GB-29017X). The Frank M.

ChapmanMemorialFundprovidedfundsfor examination
of specimens
at
the AmericanMuseumof NaturalHistory.
My wife Karen accompanied
me in the field and was especiallyhelpfulin

locating

birdsandin recording
theirsongs.Shealsoprepared
thefrontispiece
from specimens,
photographs,
and livingmodels.
Many peopleprovidedfacilities,assistance
with permits, and local dis-

tributional
information
whichaidedthefieldwork. I am gratefulto V. Ame,
A. Bauchi,C. W. Benson,D. H. Eccles,A. Forbes-Watson,H. Friedmann,

C. H. Fry, W. J. Hamilton,G. Harrison,D. Jackson,
J. G. E. Lewis,G. L.
Lombard,I. MacFadyen,A. P. Mead, C. K. Niven, D. H. C. Plowes,A. C.
Raines,G. Ranger,J. C. Ras, G. T. Roux, N.J. Skinner,M. Slogrove,R. H.
N. Smithers,J. G. Williams, and J. M. Winterbottom. The Director of Na-

tureConservation
permittedfield studiesat Hans MerenskyNatureReserve,
Transvaal.P. Britton,J. H. Elgood,C. H. Fry, andD. Wellsmadeavailable
their sightobservations
of Zambianand Nigerianbirds. Informationon Afri-

canlocalities
wasprovided
by R. C. Button,B. P. Hall, R. C. Long,K. C.
Parkes,G. T. Roux, H. Schouteden,W. Serle, R. Van Gelder, and C. J.

Vernon.

J. M. Winterbottom and R. K. Brooke made available the nest

recordsof the SouthAfrican OrnithologicalSocietyand the RhodesianOrnithologicalSociety. K. Immelmann,M.-Y. Morel, J. Nicolai, and H. E.
Wolters have discussed with me some of their observations on the behavior

of African finches.For many reasonsI am especiallygratefulto M.P. S.
Irwin, M. A. Traylor, and J. M. Winterbottomfor sharingtheir infomarion
on the distributionand systematics
of African birds.
Throughthe kindnessof the officialsandcuratorsof manymuseums
it was
possibleto examineon loan the specimensunder their care or to visit the
collections
concerned.I am indebtedto the followingfor their cooperation:
Academyof NaturalSciences
of Philadelphia(R. M. de Schauensee),
Albany
Museum,Grahamstown
(H. Deacon),AmericanMuseumof NaturalHistory
(D. Amadon), Berlin Museum: Universit•ityon A. Humboldt (G. Mauers-


1972

PAYNE:

PARASITIC

INDIGOBIRDS

OF AFRICA

5

berger, B. Stephan), BraunschweigUniversity (K. Immelmarm,O. von
Frisch),BritishMuseum(NaturalHistory) (I. C. J. Galbraith,D. A. Goodwin), CarnegieMuseum(K. C. Parkes), Durban Museumand Art Gallery
(P. A. Clancy,W. J. Lawson), East LondonMuseum (M. Courtenay-Latiruer,C. D. Quickelberge),Field Museumof Natural History(M. A. Traylor),
Institut Royal ScienceNatureliesBelgium (R. Verheyen), Kaffrarian Museum,King William's To•wn,SouthAfrica (C. J. Skead,D. M. Comins),
Kenya National Museum,Nairobi (A. Forbes-Watson),Los AngelesCounty
Museum(H. Friedmann),MacGregorMuseum,Kimberley(R. Liversidge),
Museo Civico di Storia Naturale di Milano (E. Moltoni), Mus6um National
d'HistoireNaturelie (C. Voisin), Museumof ComparativeZoology (R. A.
Paynter,Jr.), Natal Museum (T. Cashion), PeabodyMuseum (N. P. Ashmole), Port ElizabethMuseum (J. Spence,B. G. Donally), National Museumsof Rhodesiaat Bulawayo,Salisbury,and Umtali (R. H. N. Smithers,
M.P. S. Irwin, D. H. C. Plowes), National Museum of Zambia (C. Cro.ss),
Royal Ontario Museum (J. C. Barlow), Natur-Museum und ForschnngsInstitut Senckenberg,
Frankfurt am Main (J. Steinbacher),Mus6e Royal de
l'Afrique Centrale (R. Schouteden,A. de Roo), South African Museum and
South West African Museum (J. M. Winterbottom), Transvaal Museum
(O. P.M. Prozesky),AhmaduBello University(A. P. Mead), Cornell University (A. R. Weisbrod), LouisianaState University (G. H. Lowery, Jr.),
IbadanUniversity(R. H. Parker), Universityof Malaya (D. West), Universityof Michigan(R. W. Storer), UnitedStatesNationalMuseum(R. L. Zusi),
and Zoologische
MuseumAlexanderKoenig, Bonn (H. E. Wolters); D. A.
Zimmermanmade availablehis collection.G. L. Guy (Buiawayo) and P.
le S. Milsrein (Pretoria) identifiedthe seedsand insectsfound in the stomachs
of thebirds. For coloranalysisof plumageR. F. Johnstonkindlymadeavailablethe spectrophotometer
at the Museumof Natural History,Universityof
Kansas.

Facilitiesfor keepinglive birds and specimens
and equipmentfor song
analysis
wereprovidedby the Departmentof Zoology,the Animal Behavior
Laboratory,and the StovallMuseumof the Universityof Oklahoma,and the
MatthalBotanical
GardensandtheMuseumof Zoologyat theUniversityof
Michigan.C. C. Carpenter
andJ. F. Sassaman
aidedin the careof captive
birds,and Gloria Sullivanand D. R. Miller assisted
in the preparationof
audiospectrographs.
Martha Lackey, C. S. Adkisson, and J. R. Purdue
addedtheir illustrativeand photographic
talents.
For theirhelpfulsuggestions
andassistance
onthemanuscript
I thankR. D.
Alexander,Erica Dunn, D.C. Smith,R. W. Storer,J. G. Strauch,Jr., and
Gloria

Sullivan.

All specimens
collected
havebeendeposited
in the University
of Michigan

Museum of Zoology.


6

ORNITHOLOGICAL
MONOGRAPHS

NO. 11

FigureI. Location
of the mainstudyareasof indigobirds
in Africa. Letters
indicate
thenames
of countries
whereindigobirds
maybeobserved,
andnumbers
indicatethelocalities
of taperecording
or collections
in thepresent
study.A ----Angola,

Bo_--Botswana,
B •_ Burundi,
Ca = Cameroon,
Ch = Chad,CB m Congo
(Brazzaville),

C = Congo(Kinshasa),
CI: C6ted'Ivoire,
D: Dahomey,
E:
Ethiopia,
G = Gambia,
Gh= Ghana,Gu: Guinea,
HV = HauteVolta,K --Kenya,
L: Lesotho,
M -- Malawi,
Ma-• Mall,Mo= Mozambique,
Ni _--Niger,
N _--Nigeria,
PG = Portuguese
Guinea,
CAR_--Republique
Centrale
Africaine,
Rh= Rhodesia,
R: Rwanda,
S: Swaziland,
SA= South
Africa,Se= Senegal,
SL : SierraLeone,
SO = Somalia,
SWA= SouthWestAfrica,T = Togo,
TA = Tanzania,
U = Uganda,
Z : Zambia.Localities:
I Hluhluwe,

2 Ndumu,
3 Louw's
Creek,4 MarbleHall, 5 Tzaneen,
6 Merensky
Reserve,
7 Kondowe,


1972

PAYNE:

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INDIGOBIRDS

OF AFRICA

7

ITINERARY

My wife andI drovea coveredFord pick-uptruck whichwas our mobilehome
as we campedwith the birds,and we alsostayedwith friendswe met alongthe
way. Two yearsof field observations
and 55,000 miles of travel were completed
in the field study. The first year, 1965-1966, we spentin SouthAfrica during
the breedingseasonof the indigobirds,and the secondyear, 1966-1967, we
followed the breedingseasonnorthwardsfrom South Africa through Rhodesia,
Botswana,Mozambique,and Malawi to Kenya. I made observations

for two

additionalmonthsin northernNigeriafrom Julyto September,
1968. The study
localitiesare shownon the map of Africa in Figure 1.

Thefirstindigobird
appeared
on 14 January1966at Tzaneen,Transvaal(23o52'
S lat., 30ø16'E long.). We made observationsand collectionsof females from
singingmalesat Tzaneen, the Downs (24 ø10'S, 29ø19'E), Hans Merensky Nature
Reserve(23ø39'S, 30ø40'E), Kondowe (23ø45'S, 30ø48'E), the Lowveld Fisheries
ResearchStationnear Marble Hall (25ø00'S, 29 ø19'E), and Louw's Creek (25o40'
S, 31ø20'E) in Transvaal through 3 April. Observationswere continued in the
Zululand game reservesat Ndumu (27ø56'S, 32ø16'E) and Hluhluwe (28ø10'S,
32ø04'E) until 23 April, when we returned to the Cape Province for museum
studies and field work

with

other birds.

In the secondseasonwe beganobservations
at Merenskyfrom 21 Decemberto
2 January,before the breedingseasonhad begun. From January 16 to 25, birds
were observed,tape-recorded,and collectedat the Lowveld Fisheries,and from
29 Januaryto 12 Februaryobservations
were continuedat Merenskyand Tzaneen.
Finding three distinctspeciesof indigobirdsassociatedwith three firefinchesin
eastern Transvaal, we then drove to eastern Rhodesia, where three firefinches

were known to occur, and found the expectedthree kinds of indigobirdsalong the
Penhalonga-Umtali road at 18ø5YS, 32ø40'E. On 2 and 3 March we looked for
indigobirdsbut found none at Mt. Selinda. From 3 to 9 March we stayedat the
Sabi Valley ExperimentalStation (20ø20'S, 32ø18'E) and recordedand collected
more indigobirdswithin three miles of this spot. Roadsideobservationsof indigobirds in Mozambiquewere made from 50 to 65 miles northeastof Tete (Tete ----

16ø10'S,33ø35'E) on routeto Malawi. A heavyrain (11 inchesin 24 hours) in
Malawi the next day madeit impossibleto drive to the Chididi regionof southern
Malawi, where R. C. Long had collectedthree kinds of indigobirds,so on 16
March we drove to Monkey Bay (14ø06'S, 34ø55'E) on Lake Malawi (---- Lake
Nyasa) wherewe worked until 21 March. On 22 March we saw a greenishindigobird along the roadsideat 15ø32'S, 35ø18'E, besidea creek nine miles south of the

8 Maun, 9 Shorobe, 10 Lusitu River, 11 Chipinga, 12 Sabi Valley, 13 PenhalongaUmtaliroad, 14 Salisbury, 15 Tete-Mwanza road, 16 Chileka, 17 Zomba, 18 Monkey
Bay, 19 Lilongwe, 20 Salima, 21 Malindi, 22 Olorgesailie,23 Nairobi, 24 KisumuKericho road, 25 Kakamega, 26 Sigor, 27 Sokoto, 28 Gusau, 29 Zaria, 30 Panshanu,
31 Bauchi 25 mi W, 32 Numan, 33 Kiri.


8

ORNITHOLOGICAL

MONOGRAPHS

NO.

11

market at Zomba, and we campedhere for the next few days. On 25 March we
drove to Lilongwe (13ø59'S, 33ø44'E) where we recordedand collectedfor two

days. We then droveover the rift escarpment
down to Lake Malawi againand
workednear Grand Beachand Salimaalongthe roadside,returningfrom there to

Blantyre. By thistime the roadswere dry only as far southas Chikwawa,where
we foundno indigobirds.We returnedto Sabi Valley, Rhodesia,from 4-7 April
and then to the Lusitu River area where we camped at 3,700 feet elevationat
Hayfield B campandworkedthe river valleybelowat 1,200 feet (20ø01'S,32059'
E) duringthe daysof 8-9 April. From therewe drovevia Francistownto Maun,
Botswana (19ø59'S, 23ø2YE) on 14 April and camped at the edge of town by
the Thamalakane River. We recorded and collected in Maun with excursions to

Boro, "Leomarin" safari camp, and Moremi Game Reserveuntil 24 April.
After returningto Transvaalwe flew to Nairobi, Kenya, on 4 May and there
rented a Volkswagen camper. After working in the museum and searching
Nairobi for indigobirdswe droveto the coastat Malindi (3 ølYS, 40ø07'E), where
red-billedindigobirdshad been reported, and remainedthere from 9-12 May.

We drovethen to Voi and alongthe Taveta road on 13-14 May without finding
maleindigobirds.On 15 May we drovesouthfrom Nairobi to Lake Magadi and
found indigobirdsat Olorgesailie(Iø3YS, 36ø28'E) on a gravellyhill at the edge
of the plain. We returned to Nairobi on 22 May and on 24 May left for the
Kisumu area. For the following five days we campedalong the Kericho-Kisumu
road near Muhoroni, working with indigobirdsat mile 34 (0ø15'S, 38ø00'E) east
of Kisumu. No indigobirdswere seen around Kakamega Forest. On 1 June we
reachedSigor, West Pokot (lø30'N, 35ø28'E), and here Karen found the second
speciesof indigobirdV. purpurascensas well as the widespreadV. chalybeata. On
5 Junewe left Sigor and later recordeda bird at 0ø39'N, 34ø45'E, about 22 miles
north of Kakamega. The followingday more birdswere recordedon the KisumuKericho road. A trip to Namanga turned up no indigobirds;we returnedto Lake

Magadi and Olorgesailiefrom 10-14 June. On 15 June we recordedthe songof
a V. chalybeatain Nairobi and flew to the Transvaal on the next day.
From 20-24 Junewe birded at Merenskyand Tzaneenand found the breeding

seasonto be nearly completedfor Transvaalindigobirds,thougha few malesof

eachspecies
herewerestillin breeding
plumage,
andin earlyJulywelooked
for
the birds in Natal and the easternCape Provincebut found none.

Fieldstudies
in 1968werebasedat AhmaduBelloUniversity
(11øi0'N,7o40
'
E), Zaria, Nigeria. All four forms of Nigerian indigobirds (V. chalybeataneumanni and also the "nigeriae," "camerunensis,"and "wilsoni" forms of V. wilsoni)

were observedhere from 10 July to 10 August and later, all within walking dis-

tance. Trips were taken to Dumbi Woods (10ø52'N, 7ø34'E) on 17 August,to
Gusau(12ø09'N, 6ø39'E) andSokoto(13ø04'N, 5ø15'E) on 12-14 Augustand to
Kogum (9ø17'N, 8ø13'E) on 19-21 August. A longertrip was made to Numan
(9ø30'N, 12ø0YE), Kiri (9ø41YN,12ø00'E), Ganye (8ø20'N, 12ø05'E), Bauchi,
and PanshanuPass(10ø06'N, 9ø12'E), 30 mileseastof Jos,where "nigeriae"again
was found, from 23-30 August. Field studies at Zaria were concluded on 3
September.

1972

PAYNE:

PARASITIC

INDIGOBIRDS

Ol • AFRICA

Figure 2. Mopane woodland. Hans Mererisky Nature Reserve.Transvaal. The top
left of the dead tree was a call-site of Vidtta purF.rasccns in 1966 and 1967. Habitat
of Lagonostictase,egala, L. rltodopareia, V. cltaly'beata,and V. pttrpttraacetts.

BREEDING

BEHAVIOR

OF

INDIGOBIRDS

In most kinds of birds the social behavior centers around the nest and the

territory and care of the young. As is the case with other brood parasites,
the parasiticfinchesdo not nestnor do they feed their young. Field observationsprovidesomeinformationabout the socialstructureand mating systems
of thesebrood parasitesas well as the behavioralrelationships
amongdifferent kindsof the indigobirdsliving in the samearea.
The main study area for behavioralobservations
was Hans Merensky

Nature Reserve, Transvaal, South Africa; the habitat and local birds have

beendescribedpreviously(Gilliland, 1962; Payne, 1968c). Here two species
of indigobirds(Vidua chalybeataand V. purpurascens)
live in brushy,grassy
vegetation(Figure 2) along a river with their firefinch hosts. They were
regularlycensusedfor two years in this habitat. Birds in the reservewere undisturbedby humanapproachto ascloseas60 feet. In otherareasthe indigo-

birdsof thespecies
V. chalybeata
livein villagesandwhenfeedingor singing
oftenpermitoneto approachwithin20 feet. In the field work singingmales
were observed at distances of 60 feet or more to avoid disturbance. More

than500 hoursof field observations
were madeduringthe breedingseason
of the indigobirds.

We foundthe indigobirds
by drivingor walkingin bushyhabitatuntil we
heardor sawthe tiny blackfinchesperchingon the topsof treesor bushes.


10

ORNITHOLOGICAL

Figure 3.

MONOGRAPHS

NO.

11

Singing Vidua chalybeata at Ivlaun, Botswana, 19 April 1967.

The confidingbehaviorof singingmalesmadepossible
prolongedobservations
at their singingperchesor call-sites. The term "call-site"is an appropriate
one for the songperchesof the indigobirds. Ranger (1955: 70) earlier used
it in describingthe specialplace where a honey-guide(Indicator sp.) sings
"day after day of certainmonthsyear after year." Rangernoted that a callsite "may form a centre point round which the world of the honey-guide
revolves. It has been shown that not only are the females attracted by the
site-call, but at least in the case of Indicator indicator are other males, sub-

adults and still youngerbirds attractedby it as well" (Ranger, 1955: 80).
Justas a honey-guidehas a certaintree on which it perchesand calls or sings,

and at which all mating occurs,the indigobirdsuse a specialperch as the
point of focus of their breedingbehavior. Both the honey-guidesand the
indigobirdsare brood parasites,and in both the call-sitetakes the place of a
nest as the center of most breedingactivity.
SOCIAL

BEHAVIOR

AND MATING

SYSTEMS

Male activity at the call-site.•In the breeding seasonthe indigobirdssing
on their call-sites. The call-sitesare usually dead, leaflesstwigs on the tops

of trees in open woodland,often at the edge of a clearing,fiver, or road.
Each breedingmale spendsmore than half of each day singingon the same
twig. Hour after hour, day after day, visitsto indigobirdcountryshowthe
malessingingin the full sunlight,even when temperaturesexceed100øF.
The routineis broken occasionallywhen the birds fly to the groundand feed


1972

PAYNE:

PARASITIC

INDIGOBIRDS

TABLE

ACTIVITY

11

OF AFRICA

1

OF MALE INDIGOBIRDS IN THE BREEDING SEASON

Activity of male at

first encountereach day
Singing on call-site, c•
Feeding
Intruding at active call-site, B
Chasing,c• -B
Perched quietly in tree, alone
Flew by
Drinking

chalybeata purpurascens funerea
90
4
30
10
5
6
3

38
3
18
6
1
2
0

19

2
8
5
3
2
0

Unidentified
11
2
6
8
3
1
0

on the fallengrassseedsnear the call-site,whenthey chaseoff othermales,or
when they court and mate with the femalesat the site.
Singingmalesassumean erect postureduring song (Figure 3). Plumage
is held closeto the body althoughthe head feathersare often erected. The
bill is directedforward and is openedonly slightly,makingit necessaryto
look carefullyto seethat the bird is singing.During songthe headis turned
from sideto sidewith everyfew phrases.The birds often shift positionand
face in differentdirectionson the perch. Occasionallyin mid-afternoona
singingmale movesinto the shadeof the lower branchesand singsor rests.
Althoughbirds in the studywere not individuallymarked, a few singing
maleswere individuallyrecognizable;
each was the sole occupantof its callsiteover a periodof days. A male Vidua chalybeataat Maun, Botswana,was
recognizable
by a patternof brown feathersevidentlyretainedfrom the sparrow-likenon-breeding

plumage.In the temporaryabsenceof the mottledmale
othermalesin full breedingplumageoccasionally
perchedon the sitebut did
not sing. Each time, within a few minutesthe mottled bird returned,chased
off the intruder,and then resumedits songon the site. A male V. chalybeata
at Merenskyhad a protruding,bent,longwingcovertthat wasentirelyresistant
to effortsof the bird to preen the featherinto position. On all my visitsto
the tree this bird was the singingoccupant.Another male at Merenskywas

recognizable
because
it mimickedLagonosticta
rhodopareia
althoughthe bird
was a Vidua chalybeata,the only chalybeataheard to mimic this firefinch.
The bird was recordedcontinuouslyover three days on the site; no other
malesappeared.The constancy
of eachof thesebirdsat its call-sitesuggests
that an individualmale generallyremainsas the singingbird at a call-sitefor
a period of severaldaysor longer.
The way in which males spendtheir time is evident in Table 1, which
recordswhat each individual male was doing the first time I found it each
day in the breedingseason.Birds chasingor flying over a certainsite were
countedonly once on each day; an effort was made not to count the same


12

ORNITHOLOGICAL

bird more than once.

More

MONOGRAPHS

NO.

11

than half of the encounters were with the con-

spicuoussingingmales on the call-sites. Nearly a fourth of the males met
each day were birds other than the alpha (a) males or stud males at the
sites;theseintruderswere repeatedlychasedfrom the sitesby the dominant
a-malesbut were sometimessuccessfulin the end in establishingthemselves
at the sites. Males spentrelativelylittle time feeding,drinking,or consorting
with femalesaway from the call-sites.
Aggressive
behaviorat the call-site.--Thesingingmalesvigorouslydefend
their call-sitesand the immediatearea aroundthe sites. Aggressiveencounters betweendefendinga-malesand the intruderswere commonearly in the
breedingseasonand at siteswheredominantmaleshad beencollectedearlier.
In the breedingseasonin southernAfrica intrudersinvadedthe call-siteareas
59 times during 159 site-hoursof observation;this figure includesonly intrusionsby apparentlydifferent individual males at each site. Sometimes
threesomesand foursomesof males in breedingplumagevisited the sites
together.
A challengeto a singingmaleusuallytakesthe form of the intruderflying
directly into the lower branchesof a call tree whether or not the a-male is
present. An intruder bill-wipesand hops a few inchesat a time towardsthe
dominant maleswhen present in the top of the tree. As an intruder approacheswithin a few feet, the a-male flies toward the intruder, and the

intruder then flies to the temporarilyunguardedcall-sitetwig. The a-male
then supplantsthe intruder,who eitherflies off or attemptsagainto gain the
top twig after a seriesof supplantingattacks. As many as 60 supplanting
attacksmay occur in a five-minuteperiod; seriesof supplantings
may continue as long as 12 minutes. The intruder often faces away as he continues
to approachthe a-male on the songtwig (Figure 4). By concealingits bill
the intrudermay appeasethe a-male. Supplantingattacksare usuallysilent;
sometimes,
however,they are accompanied
by harshsongsor chattersusually
givenby the a-male. The intrudersobservedneverdirectlyattackedor supplantedthe dominantmale at his call-site.
Supplantingattacks are usually performedwith the dominantbird in a
crouchedposition;both birds may bill-wipe. The a-male often extendsits
head towardsthe intruder. Only once in my field observationswas the tail
raised, althoughthis posturedoes appear often in captiveindigobirds,and it
is a commoncomponentof agonisticbehaviorin variouspasserinesincluding
the sparrows,Passerinae(Andrew, 1961: 337).
Aerial

chases are often involved in male-male

encounters at the call-site.

Chasingmalessometimesfluff out the body plumageas in the "bumblebee"
flightdisplayof Euplectesa[er (Emlen, 1957). The chaseis sometimes
slow.
The two males usuallywere less than three feet apart in the chasesseen at
Merensky,and oncethe a-malehit the intruder. Often after a seriesof chases

1972

PAYNE:

PARASITIC

INDIGOBIRDS

OF

AFP, ICA

13

Figure 4. Two male Vidua cbalvbeata contesting an agave stalk used as a call-site,
34 miles east of Kisumu, Kenya. The dominant bird (above) faces the intruder. the
intruder stays lower and faces away between supplantingattacks.

the two birds land togetheron thc groundand feed with no apparentaggression for severalminutesbefore they resumetheir chase.
Singingmalesalsochaseoff othermaleson nearbybushesuponsight. The
a-males fly directly at the intruders. Usually the intruding bird flies and is
pursuedby the a-male; at other times the intruder remains on the perch as
the a-male perchesand peersat him. On only two ob•-ervedencountersdid
one bird make physical contact, knocking the other from the perch and
tumblingwith him to the ground. At the end of the chase,when the intruder
finally retreats, the a-male chatters in flight while returning to the call-site,
perches,and sings.
The chasesat the call-site involve a considerableexpenditureof time and
effort especiallyduringthe periodof call-siteestablishment
in early summer

and at sites where the dominant

bird had been removed

and two males at-

temptedat the sametime to establishthemselves.At Marble Hall, Transvaal,
two malesat a site where the a-male had been shot had prolongedseriesof
chasesand were in flight during most of the daylightminutesfor two full
days. In one 80-minute period the two made 200 passesat the call tree.
Chaseswere ovoid in shapewith the narrowend of the ovoid focusinglike a
yo-yo at the call-sitetwig. When one bird broke off in the chasethe other
perchedon the twig and assumedcontrolof the call-site. As the average


14

ORNITHOLOGICAL

MONOGRAPHS

NO.

11

diameterof the figure traced around the call-siteby the chasingmaleswas
about200 feet,the seriesof chasescumulatively
involvedas muchas 120,000
feet in litfie over an hour, or more than 20 miles!
Establishment

o[ call-sitesin summer.--I madeeightcensuses
between22
December1966 and 2 January 1967 before any indigobirdshad laid their
eggsat Merensky (as determinedfrom the ovariesof femalescollected). The
two species(Vidua chalybeataand V. purpurascens)coexistingat Merensky
eachestablished
occupancy
at their traditionalcall-sitesin early summer.Of
the 19 sitesusedin the previousyear, 10 were occupiedduringlate December. Malesin earlysummerspentonly the morningson the sitesand often
perchedquietly for many minutesrather than singingcontinuouslyas they
do in the breedingseason.Groupsof non-breedingmaleswere seentogether
at times;Irwin (1952) has alsonotedflocksof malesearly in the season.
Much supplanting
and chasingbetweenmalescontending
for a siteoccurs
in early summer. At a site observedfor five hourson 25 Decembertwo male
V. chalybeataspentvirtually all but 10 minutes(when they fed) in chases
and supplantingattacks. Chasesessions
lastedas long as 15 minutes. At the
end of eachperiodof chasing,both birdsflew to the call-sitetree whereone
male repeatedlysupplantedthe other. During one period of 47 minutesthe
birds made fully 333 supplantingattacks. At the end of the day the two
malesflew to a nearbygrassyfield and fed for 20 minutes,and on the followingday conflictcontinued.Other call-sitesremainedunoccupiedduring
thesecontests.The contestedsiteswere perhapsoptimalin somefeature,but
field observations
later in the breedingseasonshowedno differencein the
frequencyof matingsat sitesestablished
in Decemberand at sitesoccupied
in early January.
The sametreeswere usedas call-sitesin successive

years,and at Merensky
the same speciesgenerallycame to occupycertain call-sitesfrom year to
year. Figure 5 showsthat only four of the sitesoccupiedin Decemberwere
occupiedby the samespeciesusingthe sametreesin the previousbreeding
season,but a local changein siteoccupancyhad takenplaceby late January,
sinceby that time all but two siteswere occupiedby the specieswhich had
usedthe samesitesin the previousyear (floodspreventedcensushag
the north
bank in 1967). One site was shiftedwhen the earlier one was flooded, and
anotherwas shiftedwhen the originalcall-sitetree 200 feet away was felled.
Two new sitesfoundin 1967 were not usedin the previousyear. A tree in
theapparenfiy
unoccupied
areain the middleof the census
stripwasoccupied
in 1966 only on Sundays,whenthe loudwaterpumpby it was silentand the
singingbird couldbe heard. The othercall-siteswere the samein both years,
and a highdegreeof traditionin the useof certaintreesas singingplacesand
matingsitesis evident.The treesusedas call-sitesare not obviouslydifferent
in structureor surroundinghabitat from many other treesin the samearea.


1972

PAYNE:

PARASITIC

INDIGOBIRDS

TABLE

TIME

15

2

SPENT BY BREEDING MALES AT THE CALL-SITE

Status

Species

OF AFRICA

Number of minutesper hour

Number

of male

of hours

Max.

Min.

Mean

t.95•

alpha
replacement

32
30

59
48

3
0

42.7
20.9

4.78
6.77

alpha
replacement

40
9

59
52

14

16

42.1
30.3

3.78
10.27

alpha
replacement

23
5

55
56

12
7

43.7
32.8

5.00
--

V. chalybeata

V. purpurascens

V. [unerea

In the breedingseasonindigobirdsoccasionally
calledfrom other trees,but
thesewere abandonedwithin a few days,and I never saw a female visit a
male excepton the traditionalcall-sites.
Dominancerelationsat the call-sites.--Defenseof the call-sitesis important in the socialbehaviorof indigobirdsas all matingtakesplaceexclusively
by the a-malesand exclusivelyat the call-sites.In all copulationsobserved
the a-male,not a peripheralmale,was the one that mated. Dominantmales
spendmuchtime singingon the call-site,advertisingtheir presenceto other
indigobirds.Continuousperiodsof an hour or moreof observation
in southern and eastAfrica weremadeto determinethe time spenton the siteby the
singinga-males;theresultsaregivenin Table2. Dominantmalesof eachspecies spendan averageof 40 to 45 minuteseachhour on the call-sitesat all
times,morning,midday,and afternoon. Males fed intensivelyfor a few minutes by the site beforethe beginningof singingat sunrise,and at sunsetthe
malesdepartedfrom the sitesto feed and roost.
The defenseby a-malesof the traditionalsingingand matingsitesprevent
othermalesfrom breedingthere,and thesenon-breeding
birdsquicklyassume
occupancyof the siteswhen the a-malesare removed. The many intruding
males which the a-males chase from the call-sites indicate the existence of

many adult maleswithout sitesof their own. Four intrudingmale Vidua
chalybeatacollectedhad testesof the same size (4 to 5 mm) as the a-males.

To find the effectof the exclusive
behaviorof the a-malesin keepingother
malesaway from the site, and consequently
upon restrictingthe number of
malesbreedingin the area, I observedthe sequenceof eventsat more than
60 call-siteswhereI had shotthe a-male. The importanceof the dominant

male in excludingother maleswas readily evident, as in almost all sitesanothermaletookits placewithina few hours. In one instanceas soonas eight
minutes after the a-male V. chalybeatawas removed another male flew to the


16

ORNITHOLOGICAL

MONOGRAPHS

NO.

II

unoccupied
siteand sangfor nearlyan hour;he matedwith a visitingfemale
onthe sameday. Removalof a-malesat mostsiteswasfollowedby theestablishmentof replacement
malesusuallywithintwo hours. Continuedremoval
of malespermitteda seriesof previouslynon-breeding
malesto occupythe
call-sites.At Marble Hall nine male V. chalybeatain turn held one call-site
and were collectedin eightdays. Throughoutthis time breedingmalesremainedon other nearbycall-sitesand themselves
chasedoff other potential
replacement
males. Smithers(1961) alsohasobservedreplacement
of males
taken from their call-sites.

In theabsence
of theoriginala-malea seriesof potentialreplacement

males
often conflictedas eachattemptedto establishitself at the site and the contendersspentmuch time chasing.Table 2 indicatesthat suchreplacement
maleswerepresenton the call-sitesa significantlysmallerproportionof the
time than were the a-males. Considerablesingingtime (about 30 percent)
was lost in the establishment
of a new dominancesystemat a call-site. The
proportionof time andenergyspentin establishing
socialorderis dearly high.
Throughthe aggressive
neglectof their call-sitesthe newly established
maleswere lessoften availablefor mating. (The term "aggressive
neglect"
describes
the decreased
breedingsuccess
observedwhen a bird spendsits
time in aggressive
behaviordirectedtowardsotherbirds ratherthan in behaviordirectlyrelatedto its reproductive
success.Presumably
a bird could
avoid interferencewith its breedingif it toleratedother birds nearby. The
term has usuallybeen appliedto interspecific
aggressive
behavior(Hutchinson and MacArthur, 1959; Ripley, 1962), but the conceptof reproductive
interferenceseemsequally appropriatefor the result of aggressive
behavior
directedtowardsbirds of the same species.) On severalinstancesa female
indigobirdvisitinga replacement
male at the sitewas ignoredas he flew out
and chasedan intrudingmale. The averagenumberof visitsby femalesto

the call-sites was less at sites where the a-male had been removed and was

replacedby a new singingmale thanat siteswherethe a-maleremained(Table 3). The differencewasstatistically
significant
for V. chalybeata(p < .05).
Evidentlythe femalesceasecomingto siteswherethe maleis too oftenabsent
or perhapsthe femalesare lessattractedto siteswherethere is lesssinging,
althoughfemalesdo alsovisit activesiteswhen malesare not immediately
present.The significant
decrease
in femalesvisitingthe siteswherethe amaleshad been collectedprovidesdirect evidenceof the functionof a stable
socialsystembasedon local dominancein maintainingthe breedingsystem
of a population.
Dispersionand territorialbehavior.--The call-sitesof breedingindigobirds
are spacedout a few hundredyardsapart,on the average,althoughlocally
the densityof singingmalesmay be considerably
greater.At Merenskythe
averagedistance
betweeneachsiteand the nearestneighboring
sitewas485


1972

PAYNE:

PARASITIC

INDIGOBIRDS

TABLE

EFFECT

OF THE STABILITY

OF

AFRICA

17

3

OF SOCIAL STRUCTURE UPON

MATING

OPPORTUNITIES

IN

INDIGOBIRDS

Species

Number
o[

Numbero[ [emalevisitsto

call-site
perhour

Status of
male

hours
observed

Max.

Min.

Mean

t.95•

•pha
replacement

30
30

3
2

0
0

1.10

.80

.22
.04

alpha
replacement

37
12

3
2

0
0

.68
.58

.14
.19

•pha
replacement

23
5

8

1

0
0

1.17
.60

.36
-

V. chalybeata

V. purpurascens

V. funerea

feet. Populationdensitywas evidentlylower in areas such as Kisumu,
Malindi, and Olorgesailie,Kenya, as only a singlecall-sitewasfound in each
of theseareas. Indigobirdsat Marble Hall usedone of the densestaggregationsof call-sitesthat I found. There four male Vidua chalybeatasangsimultaneouslyon adjacenttreesno morethan 300 feetfrom eachother. The adjacentmaleshad frequentchasesback andforth midwaybetweentheir call-sites,
but they spentaboutthe sameamountof time eachday on their call-sitesas
the birds at Mererisky;laying femaleswere taken at three of the sites and
copulationwas seenat the fourth. I found densepopulationswith more than
four birds each within 200 feet of another and each on its call-site also on the

Umtali-Penhalongaroad in easternRhodesiaand a mile southof Monkey
Bay,Malawi. In generalthe densityof singingmalesappearedto parallelthe
local abundanceof the firefinch hosts, but no good data are available on
populationdensitiesof the firefinches.
In areaswheretwo or morespecies

of indigobirds
coexist,the singingmales
defendedtheir call-sitesagainstall maleindigobirds
in breedingplumageregardlessof their species. The majority of intrusionsinto a call-site area,
however,were by birds of the samespeciesas the singingmale. During 40
hoursof observation
at Mereriskyin 1967 I notednine conspecific
intrusions
at call-sitesof Vidua chalybeatawhereasV. purpurascens
challengedthese
birdsthreetimes. At the sitesof V. purpurascens
six conspecific
challenges
and six challengesby male V. chalybeatawere observed. In all instances
whenthe intrudingmaleswereof a species
otherthan the singingmalethey
were chasedoff just as were conspecific
males. The high proportion(9 out
of 24) of heterospecific
challenges
at Merensky,wherethe two indigobirds
are equallyabundantand havemanyopportunities
to interact,showsclearly


18

ORNITHOLOGICAL

MONOGRAPHS

NO.

11

that indigobird territorial behavior is not restrictedto the exclusionof males
of a singlespecies,even thoughthe malesmay differ in songand in the color
of gloss in thc black plumage.
The censusdata for 1966 and 1967 at Merensky (Figure 5) permit com-