Preliminary Observations on Displays and Postures in the Oriental Magpie Robin Copsychus Saularis

7 Pages·2001·5.3 MB·

by  Anil Kumar

1
JOURNAL
OF THE
BOMBAY NATURAL HISTORY SOCIETY
April 2001 Vol.98 No. 1
PRELIMINARYOBSERVATIONS ONDISPLAYS ANDPOSTURES
IN THE ORIENTAL MAGPIE ROBIN COPSYCHUSSAULARIS1
AnilKumarandDineshBhatt2
(With oneplate andtwo text-figures)
Key words: Visual displays, communication, Copsychus saularis, flight display,
tail posture, courtship display, threat posture
Animals convey information to members oftheir own and other species through a number of
channels. Changesinpostureandcoloursaretheirmeansofvisualcommunication. Inthepresent
study, effortshave been made to characterize types ofvisual signals and their importance in the
social life ofa song bird, the Oriental magpie robin Copsychussaularis. Observations revealed
thatthisbirdusesanumberofvisualsignalsforcommunication. Displayflightsandtailpostures
are used by the male to attract females. Males perform various courtship ceremonies, stretching
the head forward and downward in front of females, spreading their tail feathers, left-right
movement ofneck, stretching the beak skywards in an ecstatic posture, and other actions that
eventuallyleadtocoition.Whenanintruderarrivesinthemale’sterritoryitdisplaysathreatening
posture by raising its head and sleekening the plumage. Nestlings and fledglings use specific
begging display by quivering theirwings and demanding food. In addition, one type ofresting
and three types ofsleeping postures have been observed.
Introduction onandoffbymovementsofthehead, body, tail,
wings and body feathers (Marler and Hamilton
Physicaldisplayorpostureisoneofseveral 1966). It is believed that species-specific
means of animal communication, as a wider morphological features of an animal may be
range ofexpression is possible by visual rather ritualized (‘ritualization’ refers to the
than vocal, chemical or tactile means. Birds are evolutionary modification of movements and
known to use visual signals (Collias 1943, structure to improve their signal function) and
Armstrong 1965, Butcher and Rohwer 1989). act as sign stimuli to which other members of
Special postures and movements are often used the species respond instinctively (Krebs and
todisplaythesesignals.Manymethodshavebeen Devies 1987). In the social context, these sign
developed by birds for switching visual signals stimuli are termed ‘social releasers’ e.g. the red
spot on the bill of herring gull has all the
‘AcceptedMay,2000 characteristics ofa sign stimulus. In ethological
departmentofZoology&EnvironmentalScience terms,theredspotofthebillreleasesthebegging
GurukulKangriUniversity,Haridwar249404,
response ofthe chick (Tinbergen 1951).
Uttaranchal,India.
JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(1), APR. 200 5
ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
Visualdisplaysorposturesinbirdsperform is glossy black and white with graduated long,
a variety of functions. The head-up posture is whitetail,withtwocentralpairsofblackfeathers.
frequentlyused infighting andterritorial defence Theblackportions ofthemale arereplacedby a
in many passerine families (Marler 1961). brownish, slaty grey in female. It is one ofthe
Aggressive displays often involve an apparent best songsters in a land where singing birds are
increase in size (Tinbergen 1959, Marler 1961). scarce (Whistler 1949, Ali 1996).
Themainweapons ofmanybirds are thebilland FieldobservationsweremadefromJanuary
wings,andtheseareoftenmaximallypresentedto 1995 to December 1998 on 33 individuals (24
theopponentina ‘head-forward’posture(Andrew males and 9 females) in and around Gurukul
1961). Many visual signals are directed partially KangriUniversitycampus,Haridwar(29°55'N,
or entirely towards members ofthe opposite sex, 78° 8' E). The habitat was composed ofgardens
coordinating reproductive activities. The andcropfields,dividedbyhedgesandtreerows,
ornamentation ofplumage is widely usedby the while houses/offices were often in close
buds to synchronize thereproductiveprocess and proximity. Data was collected by visiting each
mateacquisition(Mayr 1956,ButcherandRohwer siteonceaweek,betweenearlymorningandlate
1989). Colourful marks on various species, evening, using a binocular (7 x 50). Displays
especiallyonthebeak,areusedbybirdsforparent- wererecordedwiththehelpofSONYhandicam
offspring recognition(Tinbergen 1959). video camera and Pentax still photography
Despite the rich avifauna in the Indian camera with telelens (300-600 mm). To
subcontinent (about 1,228 resident species), our determinetheinformationconveyedby asignal,
knowledge of displays and postures of Indian the circumstances in which the signal occurred
birds is scanty and based on fragmented were examined. The characteristics and
observations made by ornithologists, naturalists components ofdifferent displays were defined,
and bird watchers (Ali 1996, Ali and Ripley analyzing video films and still photographs.
1998). According to Ali (1996), ‘our greatest
needtoday is for careful andrational fieldwork Results
on living birds in their natural environment’.
Thus,anattempthasbeenmadetostudythetypes 1. Flight display: An important display
ofdisplaysandposturesandtheirsociobiological in this species. The male uses flight display in
importance in the Oriental magpie robin theearlyphaseofthebreedingseason(i.e.March
Copsychus saularis. and April). When a male sees a female in his
territory,hefliestowardsher.Beforeapproaching
MaterialandMethods her, he stalls in flightfora few seconds. Inmost
cases(n=16),theflightdisplaymaylastfor4-10
The Oriental magpie robin (Family sec (x=7.38 ±0.46). However, in some cases
Muscicapidae, Subfamily Turdinae) is a (n=6)itcanlastfor20sec(x=18.83 ±0.55).This
conspicuously pied black and white bird, distinctiveandconspicuousdisplayflighthastwo
distributed throughout the Indian subcontinent, components: undulating flight with fully spread
up to about 2,500 m above msl, absent in arid wing and tail feathers (Plate 1, Fig. 1) and a
areas and is divided into three races on minor highlyvaried,complexsongtoattractthefemale.
sizeandcolourdifferences.Itisacommonplains The male also uses undulating flight with threat
species,avoidingbothdenseforestandopenbare calls when predators (spotted owlet, snake,
plain and prefers groves and gardens. The male mongoose) appear in his territory.
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ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
Kumar, Anil et al.: Copsychus saularis Plate 1
Figs (1-4): Magpie robin Copsychussaularis, 1: Flightdisplay ofmale, 2. Tail display ofmale,
3. Head forward (threat) posture ofmale, 4. Resting posture during winter.
JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(1), APR. 2001 1
ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
Fig. 1: Courtship display, male magpie robin in front ofthe female
Fig. 2: Sleeping postures exhibited by magpie robin (a) Neck shrinking posture (b) Neck hanging posture
(c) Neck turning posture.
JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, 98(1) APR. 2001
ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
2.Tailposture:Themalemagpierobinuses 5. Begging display: The nestlings and
this posture only until mating is completed. He fledglings were observedusingthis display. Itis
sitsonahorizontalperchandfansouthistail(Plate interesting tonote thatthe newly hatchedyoung
1,Fig. 2)forabout5 sec.(x=5.09±0.35,n=22),to opentheirbeaksafterreceivingevenaslightjerk,
show the white tail feathers which are normally caused by the perching of the parents on any
covered by the black, middle tail feathers. After branch of the nesting tree. However, once the
returningtohisnormalposition,heselectsanother nestlingsopentheireyes,theyrespondonlyafter
branch and repeats the posture. The male repeats seeing the parents. After their wings develop,
this posture 4-9 times (x=5.29 ±0.48, n=24) at a they shake them to make the display more
stretch. The male normally shows the dorsal side effective. Begging display is generally
ofhis tail feathers. However, sometimes he also accompaniedbybegging calls.
exhibitsananterio-ventralside.Mostmales(n=l8) 6. Resting posture: In winter, when the
displayedthetailposture afterpairformation,but magpierobinrestsinthe day, itcurlsup itsbody
insome cases (n=6) itwaspriortopairformation and fluffs the body feathers into an almost
and also when the territory owner saw a female spherical shape (Plate 1, Fig. 4). This posture is
approaching his territory. adoptedbymanybirdspecies, to savebodyheat
3. Courtshipdisplay:Adance-likedisplay during winter.
performed by the courting male bird in the 7. Sleepingposture:Themagpierobinwas
presence of a female. There are two types of observed inthree types ofsleepingpostures, i.e.
courtshipdisplays: (A)Themale sitsonaperch, neck hanging posture (NHP), neck turning
stretches his head forward and downward, posture(NTP),andneckshrinkingposture(NSP)
simultaneously displaying his tail feathers. He (Fig. 2). Most—individuals (66.4%) use the NTP
also moves his neck slightlyto the rightand left during sleep the birdturns its neck so that its
a number oftimes, simultaneously flapping his shape appears deformed. Predators cannot
wingslikeabeggingjuvenile.(B)Themalestarts recognize the bird easily in this cryptic
walking on a wall with his head towards the appearance.NHPandNSPalsodeformtheshape
female. After walking about a metre, he halts, ofthesleepingbird,protectingitfrompredators.
turns his head up andpoints his billtowards the ButNHP (28%) and NSP (5.6%) were used for
sky(atabout60°to the horizontalplane) for2-4 shortdurationonly. Thebirdmayhavebeenless
seconds (x=2.75 ±0.21, n=12), with his tail comfortable in these postures.
outspread. After this, he starts walking towards 8. Wing drooping display: In this
the female, finally performing the ‘A type’ display, the magpie robin stretches its tail
display(Fig. 1). The ‘A type’ behaviouris more upwards and then droops it in a few steps.
common than the ‘B type’. Simultaneously, it droops its wings in the same
4. Threat posture: When an intruder sequence. This posture is observed during the
arrives in the territory of a male, the territory post-breedingphase. Itsbiological significance,
ownershowsaspecificthreateningposture(Plate however, is notyet clear.
1, Fig. 3) before chasing and fighting the rival.
In this posture, the male turns his head up and Discussion
sleekens the plumage, facing the rival. If the
intruding rival does not escape immediately, a It has been suggested that display flights
fightfollows, inwhichthesubmissiveindividual are directed at females and associated with the
delivers submissive calls. malequality,orsometimesfunctioninmale-male
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ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
interactionstodefendterritory(Andersson 1982, courted, but also in the courting bird, through
McGregor et al. 1990). The magpie robin selfstimulation. Thisreciprocalstimulationmay
exhibits individual differences in song quality be the chief function of the mutual courtship
(Bhatt and Kumar 1998a b, Kumar 1999) and ceremonies of many colonial birds such as
therearesuggestionsthatthesemaybeassociated gannets, gulls and penguins. Such stimulation
with variations in strength or fighting ability commonlyresultsintheincreaseofsexhormones
(Krebs and Devies 1987). When differentmales in a bird’s body, which in turn intensifies
engaged in song production exhibit differences courtship display (Welty and Baptista 1988).
insong quality, the femalehas anopportunityto The courtship display ofmagpie robin is
selectamalethatexhibitsmore strengththrough simple and takes little time (16 ±3.2 sec, n=4).
his song signal than othercourting males. Inthe It is believed that species with complex songs
present study, the magpie robin used flight and pronounced territories often have rather
display in the presence ofa female or predator. simple courtship displays, whereas species with
From this it can be inferred that flight display, smallterritoriesandsimpleornosongsgenerally
like song, also helps the male to show his have more elaborate courtship displays. It may
strength, to attract a female or repel predators. be thatpronouncedterritoriality and song serve,
Flight displays have also been reported in other in part, to initiate pair formation and
birdslikethejayGarrulusglandarius.(Goodwin maintenance throughout the breeding period.
1956), fantail warblers Cisticola juncidis When territories are small and/or songs are
(McGregor et al. 1990), and white-throated absent, displays seem to serve the function of
manakinCorapipogutturalis(Davis 1982,Pmm pair bonding. In colonial birds, these displays
1986, Gaunt 1994). However, the acoustical may continue throughout the nesting cycle as a
featuresofthesong/callsofthesespeciesareless device to ensure individualrecognitionbetween
varied than magpie robin. Therefore, in these the paired birds (Faaborg and Chaplin 1988).
birds with simple song/calls, the development The threat posture appears to help
of visual display for mate attraction is minimizethecostofterritorydefencebyavoiding
understandable, butinspecies likemagpierobin chasing/fightingtherival.Likethemagpierobin,
where vocalization is complex and varied, the head-up posture is used by several species of
interpretation ofthe genesis offlight display is birds for territory defence and fighting (Marler
rather difficult. Observations revealed that the and Hamilton 1966). It has generally been
male used not only flight display, but also tail observed that aggressive displays often involve
displaytoattractthefemale. Obviously,thisbird an increase in apparent size. Larger animals
has a good repertoire ofboth vocal and visual dominate smaller ones in many species, and
signals. intimidating orrepelling signals oftenmaximize
In almost all avian species, courtship thisparticularproperty(Tinbergen 1959, Marler
behaviour is exhibited by males. The bird may 1961). The ‘head-forward display’ is used not
revealhis gaudynuptialplumage, spreadhis tail only for threatening, but also for pairing with
feathers, erect his crest or inflate brilliantly females by many male finches (Hinde 1956).
coloured patches, parade, dance, fly with Begging display is common in birds, and
dizzyingaerobatics, singhismostfetchingsongs almost every avian nestling uses it to demand
all this just to impress his prospective mate foodfromparents(McFarland 1995a,b, Alcock
(Welty andBaptista 1988). Courtship stimulates 1988). Our causal observations revealed that
sexual readiness, not only in the bird being higherfrequencyofwing-movement(quivering)
10 JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(1) APR. 2001
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ONDISPLAYSANDPOSTURESINTHEORIENTALMAGPIEROBIN
mightstimulateparentstofeedyoungonesmore Acknowledgements
frequently as compared to low frequency
quivering. In addition, it may strengthen the We thank Prof B.D. Joshi, Coordinator,
flight muscles of the wings. The inside of the Environmental Science and Dr. A.K. Chopra,
beakofamagpierobinnestlingisbrightyellow, Head,DeptofZoologyandEnvironmentalScience
which helps parents locate the exactposition of for facilities to carry out this research. Financial
the nestlings’ mouths while feeding them inthe assistanceffomDST(ProjectNo.SP/S0/C03/96),
dark environment ofthe nest hole/nest-box. GovtofIndia is also acknowledged.
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