Ornithological Monographs 27

ECOLOGY
LEK

AND

EVOLUTION

MATING

IN

THE

BEHAVIOR

LONG-TAILED

HERMIT

HUMMINGBIRD

BY

F.

GARY

STILES

Escuela de Biologla, Universidad de Costa Rica,
Ciudad Universitaria, Costa Rica

AND

LARRY

L.

WOLF

Departmentof Biology, SyracuseUniversity,
Syracuse,New York 13210

ORNITHOLOGIC'•L

MONOGRAPHS NO 27

PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1979

D.C.

UNION

OF


ECOLOGY
LEK

IN

AND
MATING

THE

HERMIT

EVOLUTION
BEHAVIOR

LONG-TAILED
HUMMINGBIRD

OF


ORNITHOLOGICAL

MONOGRAPHS

This series,publishedby the AmericanOrnithologists'
Union, has been establishedfor major paperstoo long for inclusionin the Union'sjournal, The Auk.
Publicationhas been made possiblethroughthe generosityof Mrs. Carll Tucker
and the Marcia Brady Tucker Foundation,Inc.
Correspondence
concerningmanuscriptsfor publicationin the seriesshould
be addressedto the Editor, Dr. Mercedes S. Foster, Department of Zoology,
University of California, Berkeley, California 94720.
Copies of OrnithologicalMonographsmay be ordered from the Assistantto
the Treasurerof the AOU, Glen E. Woolfenden,Department of Biology, University of South Florida, Tampa, Florida 33620. (See price list on back and
inside back cover.)
OrnithologicalMonographs,No. 27, viii + 78 pp.

Editor of AOU Monographs,MercedesS. Foster
Editor of this number, John William Hardy

SpecialAssociateEditors of this issue,MercedesS. Foster, Department
of Zoology,Universityof California,Berkeley,and Barbara K. Snow,
The Old Forge,Wingrave,Aylesbury,Bucks,England
Authors,F. Gary Stiles,Escuelade Biologia,Universidadde CostaRica,
Ciudad Universitaria,Costa Rica, and Larry L. Wolf, Department of
Biology,SyracuseUniversity,Syracuse,New York 13210
First received, 15 January 1976; accepted,9 September1976; final revision completed, 15 March 1977
Issued September24, 1979

Price $8.50 prepaid ($7.50 to AOU members)

Library of CongressCatalogueCard Number 79-67267
Printed by the Allen Press,Inc., Lawrence, Kansas 66044
Copyright @ by American Ornithologists' Union, 1979

ECOLOGY
LEK

AND

EVOLUTION

MATING

IN

THE

OF

BEHAVIOR

LONG-TAILED

HERMIT

HUMMINGBIRD

BY

F. GARY

STILES

Escuelade Biologla, Universidadde Costa Rica,
Ciudad Universitaria, Costa Rica
AND

LARRY

L.

WOLF

Departmentof Biology, SyracuseUniversity,
Syracuse,New York 13210

ORNITHOLOGICAL

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1979

NO.

D.C.

UNION

27



TABLE
INTRODUCTION

OF

CONTENTS

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

MORPHOLOGY AND GENERAL BIOLOGY OF PHAETHORNIS SUPER½ILIOSUS ....

METHODS
AND MATERIALS
.....................................................................
STVVY AREAS ..........................................................................................
COLOR MARKING
LEK

3
3

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

3

OBSERVATIONS .............................................................................

6

FORAGING DATA AND NECTAR SAMPLING ...............................................

6

COLLECTING AND OTHER OBSERVATIONS ..............................................

6

LEKS, TERRITORIES,

AND LEK BEHAVIOR

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

SEX OF LEK RESIDENTS ............................................................................

CHARACTERISTICS OF LEK SITES ................................................................

7
7
7

SONG PERCHES AND TERRITORIES ...............................................................

10

VOCALIZATIONS

12

VISUAL

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

DISPLAYS ..............................................................................

MATINGS, TRUE AND FALSE ....................................................................
FORAGING

PATTERNS

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

FOOD PLANTS .............................................................................................

INTERSPECIES RELATIONS

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

15

18
21
21

25

STRATEGIES OF FLOWER EXPLOITATION ...................................................

28

NECTAR

30

VS. INSECTS ..........................................................................

TEMPORAL
PATTERNING
OF LEK ACTIVITY
......................................
BREEDING AND LEKKING SEASONS ..........................................................
DAILY PATTERN OF LEK ACTIVITY ..........................................................
LEK

1
2

DYNAMICS

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

32
32
35
43

SEASONAL VARIATION IN LEK COMPOSITION .............................................

43

SURVIVORSHIP AND RECRUITMENT

49

INTERMALE

OF LEK RESIDENTS ............................

RELATIONS ON THE LEK .........................................................

INTER- AND INTRALEK MOVEMENTS ......................................................
DISCUSSION

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

LEK EVOLUTION

56
58

SUPERCILIOSUS ....................................

58

COMPARISONS WITH OTHER HERMIT SPECIES .............................................

64

EVOLUTION OF LEK BEHAVIOR IN HUMMINGBIRDS

69

ACKNOWLEDGMENTS
SUMMARY
LITERATURE

IN PHAETHORNIS

51

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

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

...................................................................................................
CITED

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

71

71
74


LIST
Figure 1.
2.
3.

4.
5.

6.

7.
8.

9.

11.

FIGURES

Map of La Selva property ......................................................................................

4

Monthly variation in temperature and rainfall at Finca La Selva ........................ 5
History of spatial relations of three subleks in lek I from 1969 to 1972 ............ 8
Typical song perch .............................................................................................

9
Relation betweenterritory size and distanceof clear visibility from central song
perches .....................................................................................................................
11
Location of four songtypes on lek II in 1971 and 1972 ........................................ 14
Visual displaysof P. superciliosusgiven around songperchesin lek territories .... 16
Number of speciesof food plants of P. superciliosusin good bloom in different
months, according to use categories...................................................................
24

Daily nectar production of eight plant speciesfrequently visited by P. superciliosus

10.

OF

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

26

Cumulative use of food plants by P. superciliosusin relation to corolla morphology and use by other hummingbirds .......................................................................... 27
Records of distances at which individual male P. superciliosus foraged from
their

territories

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

31

12.

Estimates of the breeding seasonof P. superciliosus..............................................

13.

14.

Annual variation in calling activity among residentmales on lek Ic .................... 34
Daily variation in calling activity on leks II, Ia, and Ib for one day early and

15.

Variation in daily calling activity of five males resident on lek Ic on 29 March,

late in the 1970 lek season .......................................................................................
1971
16.

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

33

36
37

21.

Variation in daily calling by male RY on lek Ic, end of 1971 lek seasonand beginning of 1972 season.......................................................................................... 38
Frequencyof chaseactivity on areasobservedduring all-day watchesat lek Ic.... 39

Seasonalvariation in daily calling activity from one territory on lek Ic ................ 41
Presenceand territorial occupancyof male P. superciliosuson lek I, February
1971 to April 1973 ................................................................................................. 42
Locationsof lek Ia, "El Surfi," and lek Ic, "Surprise,"showingvegetationtypes,
major landmarks, and distribution of major food plants ....................................... 43
Locations of territories of males on leks Ia and Ic in March, May, June, July,

22.

Locations

17.

18.
19.
20.

1971

23.
24.
25.

26.

..........................................................................................................................
of territories

of males on leks Ia and Ic in December

uary-March, 1972 ...................................................................................................
Locationsof territories of maleson leks Ia and Ic in April, May, and August 1972
Locations of territories of males on leks Ia and Ic in January and March, 1973
Proportions of P. superciliosusmarked at one site that were recorded at other
sites different distancesaway .................................................................................
Hypothesizedrelationshipof dominanceand/or fitnessto lek positionin leks of
grouse and Ruff vs. leks of P. superciliosus..........................................................

vi

44

1971 and Jan-

46
47
48
56
62


LIST
Table

I.
2.

3.

4.

OF

TABLES

Mensural characteristicsof Phaethornis superciliosus...........................................

2
Numbers of territorial male Phaethornissuperciliosuson each of four leks during
February-March in five seasons....................................................................
8
Observed temporal relationships of displays in 85 behavioral interactions in
Phaethornis superciliosuslek territories ...................................................................
19

Morphology, period of good bloom, and hummingbird visitation of food plants
of Phaethornis superciliosus .................................................................................... 22

5.

Feeding records of Phaethornis superciliosusat La Selva ....................................... 23

6.

Dominance relations of Phaethornis superciliosusat several food plants ............ 28

7.

Dominance relations of Phaethornis superciliosusand other hermits at different
food plants ..............................................................................................................

29
Observedflower visitsby lek males and other individualsalong a 450-m transect

8.

between lek I and the field station ....................................................................
9.
I0.
I1.

Daily activity patternsof Phaethornissuperci#osus
in different habitats............. 32
Phaethornis superciliosusmist-netted at lek I, 1971-1973 ............................... 40
Survivorshipof resident male Phaethornis superciliosuswithin and between lekking seasons: lek I, 1971-1972 ................................................................................

12.
13.

52

Shifts in lek territories of resident male Phaethornis superciliosusin relation to
previous status ...................................................................................................

15.

50

Age structureof Phaethornissuperciliosuson lek I in 1971-1973 lekking seasons50
Subsequentstatus of young male Phaethornissuperciliosusfirst appearing on
lek I in 1971 and 1972 ...............................................................................

14.

32

53

Morphological and behavioral parametersof male Phaethornissuperciliosusin
relation to lek position ..............................................................................................

vii

55


INTRODUCTION

In a lek matingsystem,severalmalesgatherin a localizedarea in the breeding
season,where they display to other males and to females, the latter displays
sometimes
leadingto matings.Male courtshipassemblies
occurin a variety of
birds (e.g., Lack 1968), many frogsand toads (e.g., Emlen 1976), somemammals(Buechner1961;Leuthold1966;Bradbury,pers.comm.),and certaininsects
(Wynne-Edwards 1962; Alexander 1975). In anurans and some insects, the
concentrations
of malescompetingfor matingprivilegesoccurwhere femalesare
predictablylocalizedin spacedue to ovipositionrequirements.Although these
aggregations
may have a complexsocialstructure(Duellman 1967; Parker 1970;
Campanellaand Wolf 1974; Emlen 1976), their evolutionaryhistory is distinct

from that of certain birds and mammals,in which the male aggregations
are
generatedwithin the socialsystemitself. The actual site of bird and mammal
communaldisplaygrounds,or leks, is traditionalwithin the population. Only a
few of many potentialsitesare used over long periods. In most of the species,
at least the initial stagesof mating occur solely or principallyon the leks. It
generallyis assumedthat a numberof malesdisplayingtogetheris more attractive
or stimulatingto femalesthan would be the sum of an equal number of males
displayingseparately(Robel 1967); thus a male could potentiallyfather more
offspringby joiningan assemblythan by displayingor waitingfor femalessolitarily.
In lek speciesan individual male, to maximize his chancesof mating, must
be availablewhenevera receptivefemale arrives on the lek. The evolutionof
leks thusprobablyis limited to speciesin which malescan devotemost of their
nonmaintenance
time and energyto advertisingand defendingareasand courting
femalesas they arrive. This practicallyrequiresthe partial or total emancipation
of the male from the reproductiveeffort beyondthe inseminationof the female
(D. Snow 1962, 1963). The strong selectivepressureon males for effective
aggressive
and courtshipcharacteristics,
togetherwith the emancipationof the
male from reproduction,
have producedexaggerated
sexualdimorphismin many
lek species(Sibley 1957; Wynne-Edwards1962).
Hummingbirdsand at least some speciesof grouse, shorebirds,manakins,
cotingas,and birds-of-paradisemeet the prerequisitesfor the evolution of leks
(D. Snow 1963). Lek socialsystemsapparentlyare not uncommonin hummingbirds, but seemparticularlycharacteristicof the genusPhaethornis,the hermit
hummingbirds.This is somewhatanomalousin that the speciesof this genusare
rather dull colored,mostlywithoutmarkedsexualdimorphism.Publishedaccounts

of Phaethornisdeal with general descriptionsof lek behavior (Nicholson 1931;
Davis 1934, 1958; Skutch 1951, 1964a; Arp 1957; B. Snow 1974) and song
typeswithin and betweenleks (D. Snow 1968; Wiley 1971).
The patternof resourceexploitation
of the populationrarelyhasbeenintegrated
into any analysisof lek behavior (but see Kruijt et al. 1972; Campanellaand
Wolf 1974; Lill 1974, 1976; Pitelkaet al. 1974). Hummingbirds
are knownto
be highlydependent
uponnectarresources
for breeding(reviewin Stiles1973),

andcompetition
for nectarin hummingbirds
is welldocumented
(e.g.,Cody1968;
Wolf 1969, 1970; Stilesand Wolf 1970), yet thesefactorshave not been consideredin discussions
of the evolutionof lek behaviorin hummingbirds.
In this


ORNITHOLOGICAL

TABLE

MONOGRAPHS

NO.

27

1

MENSURAL CHARACTERISTICS OF PHAETHORNIS SUPERCILIOSUS
Sample

Sex

N

,•

SD

Range

6`
6`
9

146
32
29

6.08
6.13
5.87

0.25
0.25

0.23

5.5-6.7
5.6-6.7
5.4-6.3

6'

146

37.49

1.18

34.0--40.0

6'
9

32
29

37.68
36.10

1.01
1.23

35.5-39.5
33.0-38.5

143
32
29

59.96
60.07
57.22

1.46
1.46

55.0-64.0
57.0-63.5

1.44

54.0-60.0

139
31
27

66.82
66.61
66.54

2.11
2.38
2.26

61.5-74.0
62.0-71.5
62.0-70.5

Weight (g)
Known lek residents
Collected birds x

Bill length-•exposed culmen (mm)
Known lek residents
Collected birds

Wing length--flattened wing (ram)
Known lek residents
Collected birds

Tail leng•---central rectrices (mm)
Known lek residents
Collected birds

Sexed by dissection.

paperwe describein detailthe lek behaviorof the Long-tailedHermit (Phaethornis
superciliosus)in Costa Rica and showhow its socialsystemis intimatelyrelated
to patternsof flower exploitation;these are in turn stronglyaffectedby interspecificcompetitionfor nectar.
MORPHOLOGY

AND GENERAL

BIOLOGY OF PHAETHORNIS

SUPERCILIOSUS

Phaethornis
superciliosus
is a medium-sized
hummingbird(6 - g) with a long,
decurvedbill (37 mm) and generallydull-coloredplumage. The underpartsare
grayishbrown anteriorlyshadingto buff on the abdomen. The dorsumvaries
from dull bronzygreento dull purplishbronze,the feathersof the lower back
and rump havingbroad buffy edgings.The face is conspicuously
patternedwith
a bully postocularstripe,a whitish-buffmalar stripe,and a buff stripedown the
center of the throat; these contrast with the dark brown of the rest of the face
and crown. The maxilla is black, the mandible mostly dull pinkish orange. The

mouthlining is orange,and, togetherwith the facial stripes,producesa striking
patternwhenthe bill is open. The outer rectricesare grayishbrownbasally,and
brownishblack medially,with narrow buffy tips. The two central rectricesare
greatlyelongatedand conspicuously
white tipped.
Plumagesof the sexesare identical;however,most individualscan be sexed
by measurements
(Table 1). The plumageof immaturesdiffers from that of
adults chiefly in having much more conspicuous
buffy feather edgingson the
back, crown, and tertials;no markedchangein plumagecolor occurswith age.
In addition,in the horny sheathof the maxilla immatureshave corrugations
that

graduallydisappearover a period of months(Ortiz-Crespo1972), making it
possible
to determine
the approximate
agein monthsfor manyyoungbirds. (See
Stilesand Wolf 1974 for detailsof the agingprocedure.) P. superciliosus
lacks


LONG-TAILED

HERMIT

HUMMINGBIRDS

3

a postjuvenal
molt; youngbirdsfirst molt when aboutone year old. Adults have
a singlecompleteannualmolt, the timingof whichvariesgreatlyamongindividuals
but is quite constantfrom year to year in the sameindividual(Stiles and Wolf
1974).

The nestingof P. superciliosus
has been studiedin greatestdetail by Skutch
(1964a), and in generalappearssimilarto that of mostother hermits(cf. Ruschi
1950; Skutch 1951; D. Snow and B. Snow 1973; B. Snow 1974). The female
buildsthe nest,incubates,and rearsthe youngby herself. Presumedmalesappear
very rarely at nest sitesand apparentlyplay no constructive
role in nesting(cf.

B. Snow1974). Nestsare placedon the undersideof the tips of palm or cyclanth
leaves,or stripsof Heliconialeaves;thenesthasbeendescribed
by Skutch(1964a).
Nestsare foundmostoften alongtrails or streams,usuallywell away from leks
(Skutch 1964a; B. Snow 1974; presentstudy). Nestingsuccess
probablyis low,
perhaps15-25%, as is the casein mostotherhermitsstudiedto date (Skutch
1966; B. Snow 1974).

Phaethornis
superciliosus
inhabitsthe humidtropicalandlowersubtropical
zones
from southernMexico througheasternBolivia and AmazonianBrazil (Meyer de
Schauensee1966). Scatteredreportsin the literature and our own observations
indicatethat it is a lek speciesthroughoutthis extensiverange (Nicholson1931;
B. Snow 1973b; Wolf and Stiles,pers. obs.).
METHODS

AND

MATERIALS

STUDY AREAS

Most of this studywas done at Finca La Selva,in the Sarapiqullowlandsof
northeasternCosta Rica (10 ø 26'N,

84 ø 01'W; elevations 50-150 m).

About

75% of the roughly 700 ha of the La Selva propertyis primary tropical wet
forest, with sizeableareas of old cacaoplantationsand secondgrowth on the
northernand easternedgesof the property (Fig. 1). Much of the land north,
east,and westof La Selvahasbeenclearedwithin the last 15 years,but the forest
to the southis still continuous
up to the volcanoesof the CordilleraCentral. The
forest at La Selvais describedin detail by Holdridgeet al. (1971); the secondgrowth and light-gapvegetationsare discussed
by Stiles (1975) with particular
referenceto Heliconia. The avifauna of La Selva has been studiedin general
terms by Slud (1960).
Rainfall at La Selva averaged4,150 mm per year between 1960 and 1969.
A rather poorly defined dry seasonextendsfrom about late January through
April in most years; monthsof heaviestrainfall usually are June-July and/or
November-December.Temperatureshowslittle seasonalvariationwith monthly
averagesof 22.8-24.9øC and a maximumrangeof 14ø-37øC (Fig. 2).
A few supplementary
observations
were madenear Rinc6n, Peninsulade Osa,
in southwestern Costa Rica.

This is another lowland

wet forest area of similar

climateand vegetation(describedby Holdridgeet al. 1971).
COLOR MARKING

Nearly all of the observationsreported here were made on color-marked

individuals.Birds were capturedwith mist nets at leks or feedingareas. The


4

ORNITHOLOGICAL
MONOGRAPHS
NO.
27

!

Fig.
1.Map
ofthe
LaSelva
property.
Lek
sites
are
indicated
byRoman
numerals
(I-IV);
are
given
byhorizontal
dashes.
Abbreviations
are,

streams:
QSu
= Quebrada
E1
Surfi;
QS
=
Quebrada
E1
Salto;
QSt
=
Quebrada
E1
Saltito;
QSb
=
Quebrada
S•balo;
QA
=
Quebrada
Arboleda;
major
feeding
areas:
P= Point;
E• East
Boundary.
Cacao

and
second
growth
are
diagonally
hatched
areas
are
feeding
sites;
nest
locations
are
given
bytriangles;
swampy
areas
shown
byheavy
stipple;
pastures
arelightstipple.

back
feathers
were
marked
with
spots
ofmodel

airplane
paint,
and
aplastic
tag

with
stripes
ofcolored
plastic
tape
was
affixed
tothe
leg.
Each
individual
was
given
aunique
color
combination.
Further
details
ofthe
marking
method
are

given

byStiles
and
Wolf
(1973).
The
paint
was
lost
ateach
annual
molt,
and
tags
fell
orbroke
off
from
time
totime,
so
we
attempted
torecapture
individuals
one
ormore
times
each
year
toreplace

their
markings.
Attwo
leks
wenetted
atapproximately
monthly
intervals
during
1971-73
tofollow
indetail
the
progress
ofthe
annual
molt
inlekmales
(Stiles
and
Wolf
1974).
Over
the
course
ofthis


LONG-TAILED

HERMIT

HUMMINGBIRDS

5

A 32- 1969-1971

• 20*"---.,.,'/"
'""' -I

I

I

I

I

I

I

-I

I

I

I

I

B
1962-1971

80(

It ttJtt

•400
20O

I

I

I

I

I

I

I

I

I

I

I

I

J

F

M

A

M

J

J

A

S

O

N

D

MONTHS

Fig. 2. Monthly variation in temperatureand rainfall at Finca La Selva. A. Monthly mean
maximum, mean, and mean minimum temperatures,reading from top to bottom. B. Monthly
meanrainfall, plusand minusonestandarddeviation.

study, we marked over 500 individuals. From motion picturesand observations
we detectedno adversebehavioraleffectsof our marking system. Displays of
markedand unmarkedbirdswere indistinguishable,
and the presenceof markings
on one individualdid not appearto affect the behaviorof individualsinteracting
with it. In a few individuals,mostly near the beginningof the study, perching
ability and possiblysurvivalwere impairedby an improperlyattachedtag. Data
from theseindividualswere excludedfrom the analyses.


6

ORNITHOLOGICAL

LEK

MONOGRAPHS

NO.

27

OBSERVATIONS

Observations on behavior of lek birds were made with 7x

and 10x binoculars

at 3-20 m rangesby an observerusuallyseatedand partly concealed
by the undergrowth. We found that after a short period of habituationthe birds ignoredthe
observer,providedhe remainednearly motionless.Detailed reports of behavior
were made on the spot,often recordedby a secondpersonwhile the first watched.
We also made 16 mm motion picturesof behavioralinteractionsthat provided
documentation
of our field descriptions
and wereusedto draw Figure7.
We made periodiccensuses
of the leks during this study, attemptingto locate
all frequentlyused song perchesof each male and to map the extent of each
territory. We also made a/l-day singingrecordsat approximatelymonthly intervals for a year at one lek and lessfrequentlyat two other leks. For thesedata
the observerrecordedsingingor absenceof singingby eachindividualof a group
of 5-7 adjacentresidents(or for the entire lek when this comprised5 or fewer
birds), duringeachminuteof the day. All chasesoriginatingin or passingthrough
the sectorof the lek also were recorded. These data provide a quantitativeindex
of lek activity throughthe day for different seasons.
FORAGING DATA

AND NECTAR

SAMPLING

We recordedforagingat flowersby Phaethornissuperciliosus
in our regular

censuswalks throughvariousforest and second-growthhabitatsand wheneverwe
walkedcertaintrails passingthroughseveralhabitats. Each visit of a bird to the
flowersof a plant or clonewas treatedas a separatefeedingrecord. Thesedata
give a representative
pictureof flower usethroughthe year by the P. superciliosus
populationat La Selva. We carriedout regularnettingand observation
programs
at certain major foragingareas during periodsof bloomingof importantfood
plants,to documentuse of thesesitesby lek residents.
We mademonthlycensuses
of the floweringof the food plantsof P. superciliosus
from 1971 through1974. The averageperiodof "goodbloom" (= 50% or better
of maximum observedfloweringduring this period) was used to assessoverall
floweravailabilityto P. superciliosus
(for furtherdetailsseeStiles1977, 1978a).
We samplednectar of severalimportant food plants of P. superciliosus
with
fine capillarytubesat regular intervalsthroughthe day. Flowers were bagged
to prevent removalof nectar by birds or insects. Data on nectar production
reported here were from days with clear mornings,to minimize variations in
productionrates due to weather.
COLLECTING AND OTHER OBSERVATIONS

During1971 and 1972, we maderegulartripsto a localityabout1.5 km from
La Selvaacrossthe Rio PuertoViejo. We collected63 specimens
of P. superciliosusto documentgonad cyclesand to obtain measurementsof individualsof
known sex. Measurementsof malescollectedfrom this populationwere virtually
identical to those of known lek males at La Selva; hence the measurementsso

obtainedshouldapply equallywell to both sexesof the La Selvapopulation.In

addition, nine actively calling lek residentswere collectedfrom nine different


LONG-TAILED

HERMIT

HUMMINGBIRDS

7

territorieson a lek of P. superciliosus
near Rinc6nde Osa at about0800 on 8
August 1969. Thesebirds were collectedwithin a 10-min period to document
the sex of lek residents.

Specimens
collected
duringthisstudyare deposited
in the AmericanMuseum
of Natural History, the WesternFoundationof VertebrateZoology, and the
Universidad

de Costa Rica.

LEKS, TERRITORIES,

AND LEK BEHAVIOR

SEX OF LEK

RESIDENTS

In the absenceof discernibleplumagedimorphismin P. superciliosus,
sex of
live birdswas determinedby externalmeasurement.Males averagedheavierand
had longer bills and wings than did females (Table 1). Tail length was not
sexuallydimorphic.Althoughthereis overlapin all measurements,
a combination
of two or three enabledus to determinethe sex of most individualswith a high
degreeof certainty. Measurements
of 146 marked individualsknown to be lek
residentsagreepreciselywith measurements
of knownmalescollectedat a nearby
locality (Table 1). Eight known lek residentsat La Selva sexedby dissection
were all males. Of the 146 lek residentsmeasured (Table 1), 125 (86%) were
unequivocallymaleson the basisof measurements.Only 5 (3%) would probably
have been called females as all of their measurements fell near the low end of

the observedrangefor males;one of thesewas sexedas a male by dissection.
Furthermore, nine lek residentscollected on a lek near Rinc6n de Osa were all

found to be males upon dissection.Thus the evidenceoverwhelminglyindicates
that in P. superciliosusall lek territory holders are males (see also Nicholson
1931). This alsois the casein other speciesof Phaethornis(Arp 1957; B. Snow
1974, pers. obs.).
CHARACTERISTICS

OF LEK SITES

We found four leks of P. superciliosus
during this study. They were scattered
over the La Selvaproperty,the averagedistancebetweenthem being about 1 km
(Fig. 1). We feel surethis is a completeinventoryof the leks on the northern
two-thirdsof the property,which we searchedintensivelyin February, March,
and April 1972. However, we stronglysuspectthat a fifth lek existsnear the
southwestern
corner of the property. The densityof leks in the La Selva forest
is thus about one per km2, a surprisinglylow figure becauseP. superciliosus
is
one of the commonesthummingbirdsof La Selva.
When discoveredin June 1969, lek I was comprisedof two semi-isolated"subleks" about 150 m apart. The interveningarea, whichcontainedcacaoplantations
and a 1.5-ha bananapatch that had been clearedin March 1968 (R. Chavarr•a,
pers.comm.), wasnot suitablelek habitatin 1969. Prior to the clearingof the
bananapatch in 1968, the two subleksprobablywere much closertogether,if
not contiguous
(Fig. 3). The larger"El Sur•" sublek(Ia) waslocatedalongthe
QuebradaE1Sur•; in June1969 it wascomprised
of 8 birds,andgraduallydeclined
thereafter (Table 2). The smaller "Banana Patch" sector (lek Ib) contained
three birds during most of 1969 and 1970, with two birds being added along
the edgeof the bananapatch toward lek Ia by July 1970. By February 1971


8

ORNITHOLOGICAL MONOGRAPHS NO. 27

o

•o

•o

•farch 19•2

.3facIt 197t

Fig. 3. Historyof spatialrelations
of threesubleks
in lek I from 1969to 1972. Fromtwo

ratherisolatedsections
in 1969thelek hasgraduallychanged
to onecontinuous
groupof birds

asintervening
areas
undergo
secondary
plantsuccession.
Verticalhatching
= forest;
horizontal
hatching
= cacao;
stipple
= dense
thickets,

theheaviness
of thestipple
corresponding
to the
density of the vegetation.

thethirdor "Surprise"
sector(Ic) hadbeenestablished
aboutmidwaybetween
thefirsttwosubleks.Lek lb concurrently
declined
to a singlebird,whichshifted
tolekIc, leaving
lb empty.Sectors
Ia andIc gradually
merged
intoa single
large
lekbymid-1972(Fig.3) asundergrowth
grewupin theintervening
area.
LeksII (discovered
1969) andIII (discovered
1972) bothlie alongtheQueTABLE

2

NUMBERSOF TERRITORIAL
MALE PH.SETHORNI$
$UPERCILIOSU$

ON EACH
OF FOUR LEKS DURING FEBRUARY--MARCH
IN FIVE SEASONS
1969

1970

1971

1972

1973

Lek numberIa

9

8

3

3

-

Ib
Ic

3
-

5
-

(1)
13

15

18

I

12

13

16

18

18

19
NT
NT

23
NT
NT

19
8•
6

22
16
5

Total lek

II
III
IV
Incomplete census.
NT

= not taken.

14x
NT •
NT


LONG-TAILED

HFRMIT

HUMMINGBIRDS

9

Fig. 4. A typical song perch (male GR on lek Ic). Note the open space around the song
perch itself which is a slender, fairly horizontal twig or vine. The back paint and the tip of
the tag are also visible on this marked male. See Figure 21 for the locations of this male in
relation

to the rest of the lek.

brada El Salto, about I km apart (Fig. I ). The former contains20-25 birds, the
latter about 15 birds (Table 2).

Lek IV is small (Table 2) and is located on

the westboundaryof La Selva approximatcly600 m from lek I (Fig. 1).
Three of the four leks are locatedat least partly alongstreams,which represent
the largestand longest-livedgaps in the forest canopy at La Selva (Stiles 1975).
This is importantfor three reasons: ( 1) Where light reachesthe forest floor dense
thicketscan grow. (2) Streambanksprovide habitat for severalimportant food
plantsof P. superciliosus.(3) The streamsare convenientflight pathsfor residents
and visitors. All four leks are locatedin densethickets (Fig. 4), along a manmadeedge(lek IV), a stream(leks [I and III), or a combinationof these (lek I).
The rise of lek [c probablyrcsultedfrom invasionof the bananapatchby second
growthand the growthof densethicketsin the adjacentforestand cacao (Fig. 3).
The thicketsin which lek IV is locatedalmostcertainlydate from the clearing
of the adjoiningtract of land and the resultantpenetrationof the sun inside the

forestalongthe edge. The mostlikelysitefor thislek prior to 1971wasjustwest
of La Selva, possiblyalong the Quebrada El Surfi.

The two leksin undisturbed

habitat,I[ and 11I, are situatednearopenswamps


10

ORNITHOLOGICAL

MONOGRAPHS

NO.

27

alongthe QuebradaEl Salto. Heliconiapogonantha,the most importantfood
plant of P. superciliosus,
is commonin suchswamps;this suggests
that another
importantrequisiteof a lek siteis proximityof goodforagingareas. The situation
of lek I appearsto supportthis inference,althoughhabitatdisturbance
is a complicatingfactor. A large openswampwith muchHeliconiais some350-400 m
from the lek up the QuebradaArbolera; the banks of both this creek and the
QuebradaE1Surfisupportgoodstandsof severalspecies
of Heliconia(Stiles1975).
Moreover,lek I has increasedin sizein recentyears as thick secondgrowthcontainingmuchH. pogonantha
has grownup in the bananapatch. The locationof
lek IV is probablyatypical. However, H. pogonanthawas commonalong the
Quebrada E1 Sur• west of La Selva in 1968, and this area, now cleared, may
then have been an importantforagingarea for the birds of lek IV.
SONG PERCHES AND TERRITORIES

The foci of aggressive
and courtshipactivitieson a lek are the songperches
of the residentmales (Fig. 4). A male on the lek spentmost of his time on his
songperches,singing,displaying,preening,or sittingquietly. Thesesongperches
variedfrom 1 to 7 m aboveground,but mostwere 1.5-2 m. A male oftenused
a high, relativelyexposedperchduringthe dim light of dawn and then moved
to lower, more shadedperchesas the sun rose. The percheswere typicallybare,
slendertwigsor vinesof 1 cm diameteror less,horizontalor nearly so. Usually
the percheswere locatedin a small clear space0.5-1 m in diameter,amidstthick
vegetation,allowingthe residenta goodview of his immediatevicinity and providing room for the variousdisplaysthat involveflying near the perch. Males often
usedthe sameperchesfor weeksor months.Moreover,they wouldnearly always
singfrom preciselythe samespoton the twigs,andusuallyfacingthe samedirection.
Other males (and females7) hovered around these perchesas they flew through
the lek, evenwhenthe residentwas absent.It is probablethat mostor all of the
regularsongperchesof all other residentsare known to each male on a lek or
lek sector.

The territoryof a lek maletypicallyconsisted
of two to five songperchesand
the area aroundand betweenthem. There was no fixed boundary;the airspace
of a territorywas defendedmuch less consistently
than the songperchesthemselves. Someexpansionand contractionof territoriesoccurredon a day-to-day
basis,reflectingthe dynamicsof a male'sinteractions
with his neighbors.These
changes
in areasalwaysinvolvedthe takingup or abandoning
of songperches
on the peripheryof the territory; males did not defend areas that containedno
songperches.Othermalessometimes
werepermittedto fly throughthe territory

by the resident,but neverto singor to usea songperchunlessthe residentwas

absent.At times,a neighboring
residentchasedan intruderfrom a songperch
in the absence
of the residentof the territoryin question.
Territorysizevariedfrom 20 m2 to almost500 m2 and was closelycorrelated
with the openness
of the vegetation
as perceivedfrom the songperches(Fig. 5).
The smallestterritorieswere in the very densethicketsadjoiningbreaksin the
forest canopysuch as streams,treefalls,open swamps,and edges. Territories
tendedto be closertogetherin suchsituations,
leadingto a considerably
higher


LONG-TAILED

HERMIT

HUMMINGBIRDS

11

500'

r =.875

p(,001

400'

200100'

oo

o

o

ß

io

is

VISIBILITY
OF SONGPERCHES
Fig. 5. Relationbetweenterritorysizeand distanceof clear visibilityfrom centralsong
perches.Visibilitydistance
is the averagemaximumdistanceat whichthe paint and tag markingsof the bird on its perchwerevisibleto an observerfrom severalangles.

densityof individuals.
The largestterritories
werein relativelyopenforestunderstoryor cacao,usuallytowardslek peripheries.Openness
of the vegetation
influ-

encesthe abilityof a resident

to detectintruders
and defendhis songperches•
and may set the minimumspacingbetweenterritories.Two adjacentresidents
on theirsongperches
wererarelyin visualcontact.The few exceptions
usually
involvedthe temporary
territorialshiftsmentioned
aboveandwereaccompanied
by increases
in aggressive
interactions,
notablychases.Constantvisualcontact
amongseveralresidentsmay increaseaggressive
activityon the lek. This could
haveat leasttwo unfavorable
consequences:
(1) a high degreeof interference
with matingattempts,and (2) an extra energydrain on the males.
Lek territories of P. superciliosusseldom contained flowers that were used as

nectar sourcesby territory owners. Nearly all individualswe observeddid all of
their feeding away from the lek. A few males had suitableflowers on their

territories
that theyvisitedbut did not defendconsistently
againstotherhermits.
In at leasttwocases,
flowerson a male'sterritorywereusedmostlyby hummingbirdsof otherspecies.One lek maleabandoned
part of his territoryas a clump

of Heliconiaimbricatacameinto bloomthereand was occupiedby a territorial
male Thalurania furcata. The Thalurania chased the Phaethornis whenever the

latter attemptedto use a songperchlocated40 cm from an H. imbricatainflorescence.


12

ORNITHOLOGICAL

MONOGRAPHS

NO.

27

Phaethornis
superciliosus
alsoeat smallinsectsand spiders,obtainedby foliage
gleaning.Somemalesgleaned
occasionally
in theirterritories,
butneverfrequently
or
regularly.It seemsevidentthat territorieswere not beingdefendedfor their food
value,but were solelydisplaygroundsthat the malesleft to obtainvirtuallyall
their food. In all essentialsthe functional characteristicsof P. superciliosuster-

ritoriesagreewith thoseof the 'classical'
lek territoriesreportedfor a varietyof

birds and other animals.
VOCALIZATIONS

We recordeda variety of vocalizationsin P. superciliosus;
most were heard
chieflyor only on the lek. We madeno attemptto studyvocalizations
of juveniles
or femalesat the nest. Hencethe followingcatalogue
of vocalizations
of P. superciliosusprobablyis not complete.
Flightcall.•The flight call is a squeaky,whistledsweetor tseet. This wasthe
vocalizationmostcommonlyheard away from the lek. It was givenby a flying
bird in a variety of circumstances:
upon arrivingat flowers,upon sightinga
conspecific,
uponseeingthe observeror a predator,or sometimes
with no obvious
externalstimulus.The flight call appearsto announcea bird's presence,and it
probablyis analogous
to the chip notesof certainNorth Americanhummingbirds
in beinga generalcontactand spacingnote (Stiles1971b).
Aggressive
squealsandchatter.•Theseconsistof oneto four high,thin squeals,
endingin a rapid ascending
or descending
chatter. Each successive
squealis
lowerin pitchthanthe preceding
one;sometimes
the chatteris omitted,or it may

be followedby one or two ascending
squeals.This call usuallywas givenby a
male perchedeitheron his territoryor by a flower clump,upon the approachof
anotherhermit. We also once heard a female at her nest give this or a very
similarcall whenanotherhummingbird
flew by. The squealand chatterappear
to serveas a warningor threat, signifyingthe readiness
of the callingbird to
attack the intruder. Should the latter not leave, a chase would often follow.

Sometimes
squealsand/or chatterswere givenduringthe chase,apparentlyby
the attackingbird (presumablythe residentduringa chaseon the lek).
Chasenotes.•Theseare a varietyof staccatopip or chip notesgivenduring
a chase. When the chaseoccurredon the lek and involved two P. superciliosus,
it was impossible
to tell whetherchasenoteswere beinggivenby the chaser,
the bird chased,or both. However,whena P. superciliosus
waschasedby another
hummingbird(e.g., from flowersdefendedby the latter), it often gave chase
notes,suggesting
that in lek encounters
the bird chasedusuallygivesthesenotes.

Lonebirdsflyingrapidlythroughthe lek, not involvedin anychase,gavesimilar
notes.The functionof the chasenotesremainsunclearat present,and they do
not seemto be strictlyconfinedto chases.

The precedingvocalizations
were heard both in and away from leks, and

probablyweregivenby both sexes.Thosethat followwereheardmainlyon or
nearleks,and appearedto be givenchieflyor onlyby males.The songwasthe
mostcharacteristic
lek vocalization,
but severalothers,includingsqueals,
chatters,
and chasenotes,were given in aggressive
encounters.
Song.--The songof this speciesconsistsof a singlephrase,repeatedmonot-


LONG-TAILED

HERMIT

HUMMINGBIRDS

13

onouslyfor periodsof up to 30 min. Singingoccupied
mostof a male'stime on
territoryand was his major meansof announcing
his presence.A male often
spentup to 50% of the daylighthourssingingduringthe earlypart of the lekking
season.

A malesinging
onhisterritoryin theabsence
of conspecifics
usuallygave60-70

songsper min. When an intruderapproached,
this increasedto 90-110 songs
per min, and the songsbecamelouderand shriller.Neighboring
residents
often
countersang,
alternating
their songswith nearlyperfectregularity.The singing
rateof eachsuchmaleusuallydroppedby abouthalf, so that the numberof songs
per min by the two malescombinedwas only slightlygreaterthan the number
givenby a male singingalone.
Nonresidentmalesattemptingto invadeor gain controlof a lek territoryalso
sang,but at leastinitially their songswere soft and very irregularin tone and
rhythm,particularlywhenthe invaderwas a youngbird. If the nonresident
went
unchallenged
for anylengthof time,hissongsbecamelouder,moreuniform,and
regular.Thusthe rate,volume,uniformity,andrhythmof the songsprovideda
fairly goodindexof the stimulusinput, aggressive
state,and territorialstatusof
the singingmale.
We found a numberof distinctsongtypesin the P. superciliosus
population
of La Selva. Someidea of the distinctness
of thesedialectscan be gainedfrom
some of our transliterations: chink, churk, kaching, chrrik, shree, beeyurr, and

kisink. The numberof songtypesrepresented
on a lek was relatedto lek size.
Lek II, with 20 or moreresidents

in mostyears(Table 1), had 4 distinctsong
types. Lek Ia (5-8 residents)and Ib (3) had 1 songtype each,while Ic, formed
in partfromtheamalgamation
of these2 leksandcontaining
approximately
15 birds,
had2. In 1973lek III had 16 birdsand3 songtypes,lek IV 5 and 1, respectively.
Within a lek the individualssinginga particularsongtype usuallyconstituteda
geographically
definedsubunitof the lek. Thesesubunitsmaintaintheir integrity
from year to year in spiteof a considerable
turnoverof adult males(Fig. 6).
On large leks with severalsubunits,membersof one subunitsometimescould not
hear membersof another,althoughinterveningsubunitsnormallyconnectedthe
two.

Similargroupings
of songtypesoccurwithinleksof P. guy and P. 1onguemareus
(D. Snow 1968; Wiley 1971; B. Snow 1974). Further detailsregardingsong
dialectsin P. superciliosus
are presentedelsewhere(Wolf and StilesMS). For
the present,sufficeit to saythat individualsappearto learn their songsin their
first year and singthe samesongthereafter.
Chip-churr.•This call consists
of oneor severalstaccatonotes,oftenon different
pitches,followedby a nasal,rolling churr or chirr. Sometimes
the chip notes
were omitted,and severalchurrswere given consecutively.The chip notes are
quite similarto chasenotes;however,the churr was never heard in a chase. The
chip-churrusuallywasgivenby a maleon his songperchin a varietyof situations,

e.g.,whena conspecific
or a chasecamethroughthe territory,whena potentially
dangerous
animal (squirrel,weasel,humanbeing,etc.) was near, or preceding
flightin the apparentabsence
of otherhummingbirds
or animals.The chip-churr

appearsto be a generalized
preflightnotesignifying
the readiness
of the calling
birdto takeflight,for whatever
reason.Whena singing
malewasaboutto leave


14

ORNITHOLOGICAL

'lOrn'

MONOGRAPHS

NO.

27

LONG-TAILED

HERMIT

HUMMINGBIRDS

15

histerritoryin the absence
of anyintruderor challenger,
he oftenmixedchipchurrswith his songsandfrequently
stretched
his wingsand/ortail andfluffed
hisfeathers.The chip-churr
appears
to lackthe aggressive
character
of the other
preflightnotes,the squealand chatter.
Bill-pop.--A dry, snappingsoundresembling
a sharp,explosivekissis called

the bill-pop.It is produced
simultaneously
with a suddensnapping
openof the
bill (thegapedisplay,described
below). Thissoundwasgivenby resident
males
in aggressive

encounters
at songperches,
butwasoccasionally
givenby anintruding
maleas well. The socialsignificance
of thiscall is discussed
morefully in connectionwith the gape display.
VISUAL

DISPLAYS

In the absenceof an intruder,a singingmale sat uprighton the perchwith the
wingtipsheld belowthe tail (Fig. 7A). Usuallythe headwas movedthrougha
smallhorizontalarc while the tail was waggedthrougha small verticalarc (less
than 30ø). Motion picturesindicatethat neitherhead nor tail movements
were
timedto coincidewith singing,and that one or both couldbe absent. The throat
featherswere raisedslightlygivingthe throat a raggedappearance
and possibly
accentuating
the patternof light and dark stripes.
Whenan intruderflew into or pasta territory,the residentbegansinginglouder
and faster. Simultaneously
the tail was spreadwith the two long central rectrices
separatedfor mostof their length,and was waggedvigorouslythrougha vertical
arc of up to 90ø. At the apexof a wag,the tail formednearlya right anglewith
the body. The throatfeatherswerevery noticeablyfluffed, and the crownfeathers
were often raised,accentuating
the facial pattern (Fig. 7B).
The followingdisplays(Fig. 7C-7I) occurredchiefly at the songperchesof

the residentmales. Certain displaysor componentswere given by lone birds,
probablyyoung males, at some distancefrom the lek.
In the float display,the displayingbird flies slowly back and forth over a
distanceof 7-15 cm in front of a perchedbird. The flying bird movesparallel
to the perchat the samelevel as, and facingthe sittingbird. As it traversesthis
path, the bird pivotsits body throughan angle of approximately75ø to either
side of the vertical. The bill is held at an angle well above the horizontaland
is usuallywide open,presentingthe orangemouthlining and lower mandibleas
well as the throat patternto the perchingbird. The latter usuallypresentsits
bright orangegape to the hoveringbird. The perchedbird "tracks" the movementsof the hoveringbird, alwayskeepingits bill pointed at the latter. This
displaywas givenmost often by the residentmale, but also was givenby the
intruder, particularlywhen it was another residentof the same lek.

Gapeand bill-pop(Fig. 7D).--This displaywasgivenmostoftenby the territoryresidentbut alsoby the intruder,especially
if it belonged
to the samelek.

Fig. 6. Locationof four songtypeson lek II in 1971(above)and 1972(below). Each
songtype (a-d) is indicatedby a differentsymbolicoutlineof the territoryof each resident

(line,heavydash,etc.). Despitethe turnoverof someresident
individuals
betweenyears,the
song type locations remained constant.


16

ORNITHOLOGICAL

• ,,,'/

MONOGRAPHS

NO.

27

\•,•'

Fig. 7. Visual displaysof P. superciliosus
given aroundsongperchesin lek territories. A,

postureof residentmale singingin the absence
of an intruder--thenormalposture;B, resident
male singingwith vigoroustail waggingas an intruderapproaches;
C, float; D, gapeand billpop; E, F, perchexchangesequence(F is a continuationof E as the flying bird settlestoward
the backof the perchedbird); G, side-by-side;
H, copulation.See text for descriptions
of the
displays.


LONG-TAILED

HERMIT

HUMMINGBIRDS

17

The displayingbird hovers 15-20 cm from and facing the perchedbird. The
bird closesits bill and raisesit to almostverticalas it startsa short,rapid dart
in a shallowarc towardsthe perchedbird. At the top of the arc the bird snaps
its bill open and downward,flashingthe bright orangegape and simultaneously
producingthe poppingsounddescribedearlier. The rami of the mandibleappear
to be spreadslightlyas the bill is opened,but much less conspicuously
than in
the corresponding
rock displayof P. guy (B. Snow 1974). As the bird reaches
the closestpoint of the arc to the perchedbird (ca. 10 cm away), the head is
lowered and the bill dosed. Severalof these displaysoften were given in rapid
succession,
the displayerbacking down and away to regain its original starting
position. The gape and bill-pop was seen most often in aggressiveencounters
and frequentlyprecededor followed a perch exchange.
Perch exchange(Fig. 7E-F).-•The perch exchangeis usually initiated by the
residentand is often given reciprocallyby residentand intruder. After starting
in a mannersimilar to a gape and bill-pop, the hoveringbird circlesover the
sittingbird to approachit from above and behind. The circlingbird has its bill
open and pointedtoward the perchedbird; the throat feathersusually are fluffed.
The circlingbird settlesdown as thoughto land on the back of the perchedbird,
which flies from the perch,and the circlingbird landsin its place. The formerly
perchedbird is now hoveringin front of the perch,the positionsof the two birds
havingbeenreversed.This perchexchangesequence
was oftenrepeatedas many
as 10 timesin rapid succession;
betweenperchexchangesthe hoveringbird might
gape and bill-pop.
Side-by-side

(Fig. 7G).-•The hoveringbird alights12-15 cm from the perching
bird, usuallyfacing the oppositedirection,or both birds land togetherfollowing
a hover-up. On the perch, each bird movesits head througha horizontal arc of
approximately60ø toward and away from the other. The bills are wide open
and held at an angle of 30 ø or so above the horizontal. The facial feathers are
fluffed accentuatingthe pattern of dark and light stripes. The tails are usually
fully spreadand waggedvigorouslythrough a vertical arc of 60-90 ø, and often
from sideto.sideas well. The wingsare vibratedor flutteredbelow the body, and
the back feathersmay be raised. The high intensityside-by-sidedisplayappears
in both aggressive
and sexualcontentsand is seenless often than the preceding
displays.
Hover-up.-•Resident and intruder hover 15-25 cm apart, facing each other,
as they rise togetherfor a meter or more (dependingpartly on the configuration
of the vegetation). The birds hold their bodiesvertically;their bills are horizontal
and usually closed. The postureresemblesthat of the bird that has just billpoppedin Figure 7D; in fact, one bird, usually (always?) the resident,may gape
and bill-pop during the hover-up. Immediately following this display the resident
usuallydartsslightlydownwardtowardthe intruder,chasingit away and pursuing
it. Occasionallythe birds hover up and down severaltimes, sometimesfinally
perchingin a side-by-side.The hover-upappearsto be a high intensityaggressive
interactionwithout sexual significance.
Chase.-•Althoughnot a display,chasesare considered
here becausethey •re
by far the commonestconclusionto any behavioralinteractionbetweenresident
andintruder. The intruderfliesrapidlyfrom theterritory,pursuedby the resident