• Abstract and Figures
• Public Full-text

BREEDING BEHAVIOR A Lek's Icon The courtship display of a Guianan Cock-of-the. Rock Famous œor their œabulous plumage but little studied, the unique breeding behavior oœthis most spectacular cotinga is revealed œorthe first time Pepper W. Trail of neotropicalbirds whose mem- HEbersCOTINGAS include somecomprise of theafamily most beautiful, most grotesque,most behav- AtlanticOcean •,•o iorally bizarrebirds in the world (Snow, 1982). Like Howard Hughes and Greta Garbo, many cotingasenjoy a paradox- Figure !. The Guianan Cock-of-the-Rock ical notoriety:they are famous,but mys- feeds mosth'on fruit high in the tree-topsof terious. Family members include the - (• '• • Gu•ana neotropical forests. They also consume In- Amazonian Umbrellabird (Cephalop- sects and lizards. So }*'here's the beak? terus ornatus), whose gleaming black i i, Sunname i pompadourmakes it one of the world's .I., I'1• ' D,sputed I I I- most extravagantlyornamcnted birds, ' I '.T?r'tor¾ •f•.•%'•',111 , sightone can barely convince oneself that and the White Bcllbird (Procnias alba), one is lookingat a bird at all (Figure I). which produces,gram for gram, the Fieldstudies conducted over the past five loudest bird sound in the world. Al- yearsat the Raleigh Falls-VoltzbergNa- thoughfamiliar to ornithologistsevery- ture Reserve in Suriname, South Amer- where,they remain little-studied. Threat- StudySite ica, revealthat the matingbehavior of the ened by the devastationof their rain Guianan Cock-of-the-Rock is as elabo- forest habitat, these and other wonderful- rate as its plumage. ly-namedcotingas such as the Screaming The male Guianan Cock-of-the-Rock Piha (Lipaugus vociferans), the Bare- is neitherinvolved in any aspectof nest- necked Fruitcrow (Gymnoderusfoeti- ingor parentalcare nor does it somuch as dus), and the Handsome Fruiteater (Pi- defend food sources or nest sites with or preola formosa), may never receive for females.Instead, males spend virtual- detailed scientific investigation. rescent-orangemales are bedeckedfrom ly all of their time in courtshipdisplay. The most spectacularmember of this their helmet-like crests to their balloon- This courtshipis highly social, being spectacularfamily is the GuiananCock- ing puff of ruff featherswith an impres- conductedat a denseaggregation of dis- of-the-Rock (Rupicola rupicola). Fluo- sive array of display plumes. At first playingmales called a lek. The clustered Volume 39, Number 3 235 Certainmales in the displaygroup attract and successfullymate with females, whereasothers fail completely.In 1981, for example,61 malesdefended display territoriesat the lek, but only 26, or 43%, performedmatings, while the top male accountedfor 30% of matingsall by him- self (Figure 7). Why certain malesare preferred remains unknown. Observa- tions of marked (color-banded) individ- ualsreveals that courtshipin the Guianan Cock-of-the-Rockinvolves a prolonged processof samplingpotential matesby females.In the Voltzburgstudy popula- tion, the typical hen GuiananCock-of- the-Rockvisited the lek on six days. Dur- ing this time she visited three different males a total of nine times, but usually mated with only one. y IIE FEMALEGUIANAN Cock-of-the- Figure 2. Thefluorescent orange males with their brilliant helmet-likecrests aimoat glow fit the Rock approachesthe Ick in the leafy greenishjungle gloom.Nearly all male lek specieshave striking adorstmettt.• or ttttttsaaladapta- tions usedsolely to signalfemales. Males .•picallyremain perched above their courtsuntil the subcanopyof the forest, 10 or more me- arri*•al of a female at the lely. ters up, where her dark brown plumage hidesher in thejungle gloom(Figure 8). males glowing orange in the shadowy al malesper year. Duringthis time. more The malesare continuallyalert for female greenlight of the rain forestis a dazzling than 3500 courtshipsequences and 400 arrival and respondto it with a spectacu- and unforgettablesight (Figure 2). matingswere observed.With a singleex- lar "greetingdisplay," which is alsousu- Although the social organizationof ception,all matingswere performedby ally the first signto a field observerthat a males on the lek may appearchaotic, it individuallycolor-banded males, and in femalehas entered the Ick. The normally is, in fact, rigidly structured.Each male approximatelyone-third of the cases,the silentmales burst into ringingchoruses of defendshis own small display territory female was banded as well. raucous,crowing calls and drop from (Trail, 1985A). The display area is cen- Like other birds with lek mating sys- theirresting perches ( 1-2 metersfrom the tered on a cleared "court" on the forest tems, suchas the Sage Grouse(Centro- ground)down onto their courts. After hit- floor (Figure3). Thesecourts rarely mea- cercusurophasianus) (Wiley, 1973), and ting the groundwith a thump,each male sure more than I-2 meters wide and in- the White-bearded Manakin (Manacus stands erect and violcntl5 beats his clude the adjacent defended perches. manacus) (Lill, 19741, the Guianan wings, flashing the dramatic, usually They containno food or other resources Cock-of-the-Rockis highly polygynous. concealed, black and white primary needed by females. The species' lek servessimply as the rendezvouswhere the sexes meet and mate. Followingmating, femalesnest unaid- ed and, exceptfor randomencounters at the fruit treeswhere both sexes feed, they do not interact with males again until their next breeding attempt. Nests are placed in rocky areas where caves and cleftsprovide shelter for the massivemud constructions(Figures 4 and 5). Protect- ed from the weather, these nests are reusedfrom year-to-year.Any necessary repairsare madeby the femalewith mud andvegetable fibers in the weeksprior to breeding(Figure 6). Not until this study was the complete sequenceof courtshipbehavior in the Guianan Cock-of-the-Rock known. Tan- talizing fragmentary descriptionshad, however, been previously published (Gilliard, 1962, Snow, 1971). The fol- lowingaccount is basedon morethan 24 Figure3. Uponarrival of thefemale. the male Guianan Cock-of-the-Rock lands on his court with monthsof field work over five breeding a loudsquawk and begins his greeting diaplay -- violentlybeating his wings and emitting seasonsat a lek thataveraged 55 territori- resound#tgraucous calls. 236 American Birds, Fall 1985 Figures4 and5. Theauthor (bottom of photos) prowdes the scale by which to measure thecliff face. Nests are concealed inor onrock clefts and in high caves, where they are protectedfrom the weather and reusable from year-to-year. The cock-of-the-rock is a somewhatsocial nester so that sometimes nests are builtwithin a few yardsof each otheron the samerock face. feathers(Figures 9 and 10). In additionto male. She lands on one of his defended tent: the crest fully expands, the chest being a real show-stopper,this wing- perches, 1.5 meters or less above the thrustsout, the filamentous fringes on the beating blows loose debris from the ground,thereby initiating a courtshipvis- secondarywing covertsdeploy, and the court,clearing the surfacefor thecoming it (Figures I l and 12). She has, at least puff of rumpfeathers fluffs out into a soft displaybout. The greetingdisplay may temporarily,restricted her courtship sam- and inviting cushion.An importantfea- involve a seriesof one or more flights pling to a particularmale by enteringhis ture of thisdisplay is that the male keeps betweenperches and the ground,accom- breedingterritory. his back turned to the female at all times. paniedby wing-beatingand loudchorus- The subdued nature of the Guianan This presentshis wing fringefeathers and ing. This vocalizationis audiblefor 100- Cock-of-the-Rockpre-copulation period rump puff to their best advantage.The 200 meters. Additional females ot•en contrastssharply with the wild calling male remains silent and motionless in this arrive within the next few minutes. andwing-beating of the greetingdisplay. posture,only occasionallygiving short The pandemoniumof the greetingdis- Males hunker down on their courts, vertical hops, rapid glancesback at the play usually lastsfrom one to five min- crouch low on their tarsi, and often rest female, and brief mutteredgrunts when utes, although it may continue much their chestson the ground. The male's the tension becomes unbearable. longer early in the breedingseason or displayplumage erects to its greatestex- Fromher low "stand-off'position, the when a large group of females (four or more)arrives simultaneously. As thevio- lent activity dies down, femalesmove to low perchesclose to the males' ground courts. Now the males assumethe static, crouchedposture of full courtshipdis- play. From perches2-6 metersup, the female Guianan Cocks-of-the-Rock are ableto surveythe displayof manyof the densely-clusteredmales simultaneously, without"committing themselves" by en- teringan individualmale's territory. The easeof suchscanning may be an impor- tantbenefit gained by the femalesof lek- breedingspecies. Scanning is energyef- ficient as it eliminates the need to travel betweenwidely-spaced males before se- lecting a mate. Eventually,often after repeated chases by both territorial and non-territorial Figure 6. The massivemud and vegetablefiber constructionholds a clutchof one or two eggs. males,the hen moveslow enoughto en- Theseare a pale brownor buffground color with lilac-gray blotches and spots overlaid with olive ter the defendedterritory of a specific brown. Volume39, Number3 237 PERCENT OF TOTAL 1o :#111,,,,......... •IT•IAL I• Figure 7. Mating distributionat the Voltzbergstudy lek. 1981.

Load more

  6

Copy Link