The Promiseuous Pectoral Sandpiper

BEHAVIOR The promiscuous Pectoral Sandpiper "nothing evolvesNorth Slope tundra more certainly than a male Pectoral Sandpiper, hooting through chilled Alaskan mist" J.P. Myers [sBARROW,ALASKA, the Pectoral a pendulous, fat-filled organ hanging deep o6-ah, o6-ah, o6-ah each syllable andpiper seasonbegins with a few prominently even while the male stands separated by a moment's silence and distant hoots sometime between the 5th immobile (Fig. 1). Its outline is en- repeatedtwo or three timesper second and 10thof June. At first hearing one has hanced by sharp contrast with the white for l0 to 15 seconds½Fig. 3 and record). difficulty accepting its source as arian. vent, and more still by the way the male Viewing this display in profile is star- The hoot is a fog horn, a sonar beam, an erects his feathers to expose their tling, but imagine what a female Pec- electronic oscillator bearing no relation darker base. toral sees. More often than not she to the sounds about it. Even after bird But the sac comes into its own when serves as the focus of his flight: the and call are linked it seems preposter- the male takes flight to hoot (Fig. 2). He male's path takes him directly over her ous. The way the call is made, the bodily flies low over the tundra, often within a in mid-hoot, perhaps only 5 cm from her distortions that male goes through to few centimeters of the upper blades of head as she feeds in the grass. He make its hoot, are visually just as odd as grass and sedge. As he flies, the sac looms an additional one-fourth to one- is the sound unworldly. balloons out to a bosom of immense third bulkier than she and inflated in To appreciatethe full dimensionsof a proportions. He pumps it up and down, display, even bigger. Picture the view, Pectoral male in hoot display, one must in synchrony with the hoot and often were you she, of this throbbing, hoot- start with some anatomical details. The counterpoint to each wingbeat. The ing mass suddenly swooping in low chief character is the male's breast sac, hoot itself is vaguely owlish, a resonant, over the tundra, bearing down with sac Figure1. Male Pectoral Sandpipersurveying his territory.frothatop Figure 2. Male Pectoral Sandpiper in hoot display. The brettst a tundra polygon. inflates and pumps ttp and down as the ,tale hoot.• in flight. Volume 36, Number 2 119 N 15001 Seconds Figure 3. Sohographof hoot by male Pectoral Sandpiper. The hoots'increase in loudnessfrom first note to last note tindicated by increasingdarkness of sonographfrom left to right) occursbecause the bird wasflying towardthe mierophoneas it wasbeing taped. bouncing, wings pumping, and hoot OONHIS APPROACH to the female copulatory display (Fig. 7). The male pulsing all in your direction. In this becomes more direct. He begins maneuvers to behind the female, wings perspective, it is best described as with a guttural, low call a series of up and waving, neck stretched out but something out of the film "Close En- brief muted growls repeated from the weaving up and down through an arc of counters of the Third Kind." ground once every one or two seconds some 60 degrees. His calls take on a Once beyond the female, the male for up to several minutes..Tail cocked, frenzied, wheezing pitch. flaps on. He quickly stops calling and he then runs to her side, and if she If the female tums him down, and changes his wingbeat cadence to a stays, his posture becomes even more more often than not she does. this whole series of shallow, rapid flutters, each exaggerated {Fig. 6}. He droops his sequence can last but a few seconds. alternating with a soaring glide, never wings, the breast sac balloons down But if she staysit may go on a minute or risingmore than a few meters above the and starts to jounce, and suddenly he more before he finally mounts her. tundrasurface (Fig. 4). The glide entails escalates his voice, not in volume but Throughout copulation, his calls and an awkward, hangingposture (Fig. 5). in sheer fervor. It is a complex vocali- gestures continue unabated. Within 20 or 30 seconds,a sequence zation: a muted version of the hoot laid In sharp contrast to this reaction to of these bouts carries the male in a over a background of growls. height- visiting females, a resident male shows broad arc, perhaps 50 to 100 meters ened to an incessant. grating squawk. no tolerance to territorial violations by away at most, until he circles back to the These two sounds together. hoot over other males. Males employ a suite of tundra mound from which he first took growl, combine in a rolling boil of noise behaviors to repel intruders, and their off. He lands there abruptly, runs erect that rises and falls in volume through a interactions regularly flare into feather- to the crest, and stands to survey the repeated cycle of 2-3 seconds' dura- pulling fights. These break out in the scene while preening the dark bases of tion. midst of long border walks: neighboA the feathers on his breast. This ushers in the final stage of pre- marchingparallel along shared bound- A .. ; ; : Figure 4. Diagram •1 hoot di•'plav path of a mah' Pectoral Sand- piper. A. View fro,t abol e. TaMng oil downwind .[roma tundra polygon. the ntale circles upwindtsmall thattedline) and then htwer• into a hoot display over thefemale (lar.•,edotted line). After passing the female. he rises into an alternative sequenceof power fiutter.• (dashedline) and soars(solid line). circling broadly bac• toward his starting point. B. View .f?Ottlside. WitHe hooting the ituHe is only tl few centintetersabove the tltndra sitfinite. In hi.• post-hootsoar he rises 2-3 m above the ground. The cross-section of tuntb'a ,•hows the stronglypolvgonized ground characteristicof Alaska's North Shape Figure 5. Male Pectoral Sandpiper in post-hoot soar. As he holds coastal pittin. this posture he swivelshis tail to controlflight direction 120 American Birds, March 1982 Figure 6. Display by male Pectoral Sat,dpip- Figure 7. Final preeopuhttorystage.• of di.•phty.fl.' .tale Pectoral er as he approaches a female. Wing• are Sandpiper.These post.res tire aceotrlpaniedby it f•'lTetttsqlalw]• drooped.tail is cocked.and he is growling. that ri.•e• in intensity tls he prepto'esto tttolttlt. aries, bowing and feinting with necks fitlicarhts, and yet another court un- hatch and raise the brood alone (Fig. outstretched and wings lowered (Fig. fledged Dunlin. No Pectoral male, 9), and they leave the breedinggrounds 8). moreover, is deterred by already having well before the young do. As unlikely as all of these events and a mate in the thick of egg-laying: males This pattern of mating shares several displays may seem, the full extrava- will alternate within the hour, first at- features with that of lekking species-- gance of a Pectoral male's behavior can tending one female with an egg or two male promiscuity and absence of male be appreciatedonly with completede- laid toward her final clutch of four, and parental care. females visiting more tail on its promiscuoussocial ways. Pec- then switching to other, new arrivals. than one male and possiblyhaving more toral Sandpiper, Calidris melanotos, than one male lather her clutch. It dif- belongsto a subfamily of shorebirds, EMALEBEHAVIOR is more enig- fers however, in a few key regards. Pec- the calidridinesandpipers, that contains matic. No female has ever been toral Sandpiper territories are spread a remarkable array of mating systems seen mating with more than one male, broadly over the tundra, and show feu {Pitelka et al. 1974, Myers 1981}. This and a female spends most of her time hints of clusteringother than what might group's social patterns run the gamut within the confines of a single male's result as birds crowd together in more from boringly monogamousDunlin, C. territory. Yet she strays to other areas desirable sites. The territories range in alpina (Holmes 1966}, all the way to on occasion. And when she does, her size from under one hectare to over 10. lekking specieslike Ruff, Philomachus response to other males' attentions is Moreover, the territory is an important pugnax {Hogan-Warburg 1966}, and much the way she interacts with her food source for both male and female Buff-breasted Sandpiper. Tryngites usual mate in precopulatory display. sandpipers. In contrast, males of lek- subruficollis.Pectoral Sandpipers'be- Thus it may be that females allow sev- king species defend territories often haviors fall near these latter species eral males to sire a single clutch--but only a few meters in diameter, tightly {Pitelka 1959). we need more observations. clustered together in an arena, the lek. Males mate promiscuously.They dis- A male's role in parenthood stops These defended sites are used for display toward almost any female that with clutch completion. He takes no play, but generallynot for feeding,espe- lands on their territory, or to those part in incubation or brooding, nor does cially not by females. merely flying by. In fact, male Pectoral he help build the nest. In fact, most For all the drama and intensity of Sandpipers can be even less dis- males depart for wintering grounds in events that lead to copulation in Pec- criminating: we have seen one mount a southernSouth America before the eggs toralSandpiperS, actual observations of dead male Red Phalarope, Phalaropus have pipped. Thus females are left to the final step are infrequent. without Volume36, Number 2 121 tions. The Naval Arctic Research Labo- ratory provided logistic support; our research there was aided greatly by Terry Hall.

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