Interspecific Intolerance of the American Coot in Utah

Home , American coot, Cinnamon teal, Coot

[- Auk 424 LVoL76

INTERSPECIFIC INTOLERANCE OF THE AMERICAN COOT IN UTAH

BY RONALD A. RYDER

INTRODUCTION The American Coot (Fulica americana)is extremely territorial and vigorouslydefends its territoryagainst not only other cootsbut also a wide variety of vertebrates.The effectsof this interspecific intoleranceupon waterfowlproduction were investigated,with particular emphasisupon comparativebehavior, nesting and young- rearingsuccess of cootsand ducks. The followingobservations con- cern primarily the first aspect. Nestingand young-rearingsuccess will be discussedin a later paper. This studywas financedthrough the Utah CooperativeWildlife Research Unit, with the U.S. Fish and Wildlife Service, Utah Fish and Game Department, Utah State University, and the Wildlife ManagementInstitute cooperating.Dr. JessopB. Low assistedin the direction and supervisionof the project. Observations were made at various marshes in northern Utah but primarily on Ogden Bay Refuge,one of six waterfowlmanagement areasdeveloped by the Utah Fish and GameDepartment. A detailed descriptionand history of this important waterfowl area has been publishedby Nelson (1954). Most findingsrelate to five studyareas, varyingin sizefrom 15 to 76 acres,three on OgdenBay Refugeand two on the Bay View Club, two miles west of Westpoint in Davis

TABLE 1 GENERAL DESCRIPTION OF STUDY AREAS, WEBER AND DAVIS COUNTIF.•, UTAH

PercentagesX Total Open Emer- StudyArea AcreageX Water gents Upland Treatment Applied

Unit 3 76.4 45 49 6 Control, no treatment

Check Station N. Pond 17.• 21 48 •1 Control, no treatment S. Pond 14.8 16 46 •8 Coots reduced by shooting and trapping Westpoint N. Pond 48.0 38 1• 49 Cootsincreased by introduction S. Pond 44.5 28 28 44 Coot hatch delayed by nest destruction x Basedon planimeteringcover maps prepared from aerial photosand ground inspection. THE Au•., VOL. 76 PLATE 90

COOT[•TE•PECIFIC CONFLICTS. A. Patrolling coot "herding" a pair o[ Eedheads away ko• lh½ vicinily o[ lh½ cool's n½;l. B. •ot de[ending [o• source around Whistling Swan. C. Coot "sp]atterinp 31 Black-neckedStilt. D. Coot "sp]at- te•ng" at a male Cinnamon Tea]. E Coot "swanning" a• a G;•t Blue Heron F. Coo• "splattering"a• •Yhi•e-[afed 11)is. •050] RYDER,Intolerance o[ American Coot in Utah 425

County. Coots were reduced on the smallestarea by shooting and trapping,while their hatchwas delayed and reducedby systematicegg destructionon anotherarea. Unsuccessfulattempts were made to in- creasecoots on a third area by introduction of wild-caughtcoots. A generaldescription of thesestudy areas and the treatmentsapplied to each is given in Table 1. Weekly behavioralobservations of about four hours' duration were made from late March until mid-Augustduring both years. These observationswere from semipermanentblinds erectedon three of the areas (Unit 3, Check Station North Pond, and Westpoint North Pond). Weekly censuseswere made on all areas. Routine nesting surveyswere also conducted,followed by frequent brood counts. A few of the cootsdiscussed in this paper were marked with plastic neck tagssuch as usedby Gullion (1951), while most were identified by their location on the areasand by the shape and size of their frontal shields. Sex determinationwas basedupon voice differences,

TABLE 2 ESTIMATED BREEDING PAIRS ON STUDY AREAS, 1956 AND 1957

Westpoint CheckStation Species Unit 3 N. Pond S. Pond N. Pond S. Pond Total

Coot 1956 70 55 27 14 x 17 183 1957 65 48 29 12 2 9 163

Mallard 1956 8 2 1 4 2 17 1957 11 5 5 $ 2 26

Gadwall 1956 4 2 1 1 0 8 1957 $ 1 1 0 1 6

Pintail 1956 1 0 0 0 0 1 1957 1 0 0 1 0 2

G~w Teal 1956 1 1 0 0 0 2 1957 0 0 0 0 0 0

B-w Teal 1956 I 1 0 0 0 2 1957 1 1 0 0 0 2

Cin. Teal 1956 15 3 2 4 4 28 1957 14 2 2 2 1 21

Shoveler 1956 1 1 0 1 0 $ 1957 1 1 0 0 0 2

Redhead 1956 30 12 $ 9 0 54 1957 26 10 6 5 2 49 Ruddy Duck 1956 $ 5 5 2 2 17 1957 3 $ 2 2 1 I1 Coot population before control; after control 4 pairs estimatedin 1956. Coot population before control;after control 5 pairs estimatedin 1957. ]' Auk 426 RYDER,Intolerance o! AmericanCoot in Utah I.VoL 76 while agedetermination was based upon plumageand leg color. The terminologyused to describevarious coot displaysis, with few ex- ceptions,that usedby Gullion (1952).

BREEDING POPULATIONS In addition to coots,the followingducks nested on the studyareas: Mallard (Anas platyrhynchos),Gadwall (Anas strepera), Pintail (Anas acuta), Green-wingedTeal (Anas carolinensis),Blue-winged Teal (Anas discors),Cinnamon Teal (Anas cyanoptera),Shoveler (Spatulaclypeata), Redhead (Aythyaamericana), and Ruddy Duck (Oxyura ]amaicensis). Table 2 summarizesthe numbersof these birds estimated to have nested on the areas.

INTERSPECIFIC INTOLERANCE OF COOTS Numerousreferences in the literature describeinterspecific territorial displaysand aggressionsby both AmericanCoot and European Coot (Fulica atra) (Table 3). These include attacksupon a variety of water birds, especiallygrebes and ducks,and even upon turtles, garter snakesand muskrats. Boyd (in litt.), writing of the Wildfowl Trust in Great Britain, said, "a few cootsspend the winter with our captive waterfowl, and hold their own successfullywith almost all speciesirrespective of size." Someinvestigations have been conductedto determinethe impor- tance of this interspecificconflict. Munro (1937) concluded,"The sizeof duck broodsis not conspicuouslyinfluenced by the presence of coots." Later Munro 0939) reportedhe found no direct evidence of cootsattacking or molestingyoung ducks. R. Smith (1955), however, felt that the belligerenceof territorial coots should not be overlookedasa factorpossibly limiting i0af spots for breedingducks. On his study areas at Ogden Bay Refuge, Smith found the coot dominant over all speciesof waterfowl with the exceptionof the Mallard and Canada Goose. He believedcoots can greatly reduce availablefeeding areas for waterfowl.Sooter (1945) believedcoot ter- ritoriality might be a factorin reducingthe area of suitablenesting territoriesfor other waterfowl,as well as limiting feedingof certain broods. Neither Hochbaum (1944) nor Low (1940 and 1941) re- ported any interferencebetween coots and Canvasbacks(Aythya valisineria),nor with Redheadsor Ruddy Ducks. Stevens(1947), referring to his Iowa studies,said, "There seemedto be no schism betweencoots and gallinuleson the onehand and the diving duckson theother." Harris (1954) however,believed that cootsmade small pot- Oct. Intolerance of American Coot in Utah 427

TABLE $

SvE½Irs AvrAc•o BY COOTS IN TEiattTor, txt• Dr•Ns• (Fulica americanain North America,F. atra in Europe and Asia)

SpeciesAttacked by Coot Areasand Authorities

Mud turtle California (Gullion, 1958) Garter snake California (Gullion, 1953) Eared Grebe New Mexico (Wetmore,1920); Germany (Kornow- ski, 1957) Red-necked Grebe Germany (Kornowski,1957) Great Crested Grebe Germany (Kornowski,1957, and Heyder, 1911); England (Witherby, et al., 1949) Pied-billed Grebe California (Gullion, 1953) Little Grebe England (HShn, 1949, and Brown, in liter.); Ger- many (Kornowski,1957) "Ducks" New Mexico (Wetmore, 1920); Scotland (Berry, 1939) "Ducklingos" Oregon? (Job, 1915); Washington (Jeffrey, 1948, and Harris, 1954); England (Witherby, et al., 1949) Mallard Oregon (Sooter,1945); Washington,D.C. (Collins, 1944); California (Gullion, 1958);England (Boyd, in litt., and Cramp, 1947); Germany (Kornowski, 1957,and Libbert, 1926) Gadwall Oregon (Sooter, 1945); Utah (R. Smith, 1955); Germany (Kornowski,1957) Pintail Utah (R. Smith, 1955) Common Teal Germany (Kornowski, 1957); England (Brown, in litt.) Blue-wingedTeal Utah (R. Smith, 1955) Cinnamon Teal Oregon (Sooter,1945); Utah (R. Smith, 1955) Shoveler Utah (R. Smith, 1955.);Germany (Kornowski,1957, and Libbert, 1926) Garganey Germany (Kornowski,1957) Redhead Oregon (Sooter, 1945) Common Pochard Finland (Nylund, 1945); England (Hfhn, 1949) Tufted Duck England (Cramp, 1947); Germany (Kornowski, 1957) Ruddy Duck Oregon (Sooter,1945); California (Gullion, 1955) Ruddy Shelduck England (Cramp, 1947) Whooper and Mute Swans England (Burkill, 1911) Moorhen England (H/Shn, 1949, and Brown, in litt.); Ger- many (Kornowski, 1957) "Long-leggedwaders and Utah (R. Smith, 1955) shore birds" "Small birds" California (Gullion, 1953) Yellow-headed Blackbird California (Gullion, 1953) "Other birds" (than coot) North America (Blanchan, 1904); India (Stuart- Baker, 1929) Muskrat California (Gullion, 1953); Washington (Harris, 1954) [' Auk 428 RYDw,Intolerance of AmericanCoot in Utah I.Vol. 76 holesin Washingtonless desirable to duck broodsand wrote, "It is suspectedthat the high breedingpopulation of cootsserved to partially limit duck populationsin the Potholes." Allen Smith (1956) has written in regard to his Alberta studies: "Sincethe start of this studyin 1952,general field observations of coots and waterfowl on the Lousana area have led us to be- lieve that the aggressivenature of the coot during all periodsof the breeding seasoncould not but adverselyaffect the duck populationin coot habitats. Nevertheless,we have been able to collect no data to prove that this is so." Apparently the coot territorial defenseis not alwaysimpenetrable. Various authorsdescribe finding coot nestsparasitized by other birds such as the Common Gallinule (Gallinula chloropus) (Attwood, 1948),Redhead (Bryant,1914) and Ruddy Duck (Low, 1941;Weller, 1956). Similarly, Delacour and Mayr (1946) and Goodall, et al., (1951) mention the Black-headedDuck (Heteranetta atricapilla) parasitizingthe nest of the Red-garteredCoot (Fulica armillata) in South America. Munro (1919) found Red-neckedGrebes (Podiceps grisegena)nesting close to AmericanCoot nestsin British Columbia. In Europe, Kornowski (1957) noted Mallards, Common Pochards (Aythya [erina), Mute Swans (Cygnusolor), Black-headedGulls (Larus ridibundus), and Great CrestedGrebes (Podicepscristatus) nestingin EuropeanCoot territories. A total of 11 speciesof ducks,16 other speciesof birds, one fish, one reptile and two mammalswere seen pursuedor threatenedby coots on the Utah study areas. During the two years, 712 inter- specificattacks or threats involving cootswere recordedduring 359 observationhours (Table 4). The intensity of thesethreats varied considerably,from simple "patrolling" by a coot causinga duck or grebeto leavethe cootterritory (Plate 20A), to actualfighting between ducksand coots,ibises and coots. (Words in quotationsare used as definedand illustratedby Gullion, 1952,for stereotypedforms of coot behavior.) Most speciesof ducks seemedto recognizeand honor aggressive displaysof the cootsuch as "patrolling" and "charging",but frequently cootsresorted to "splattering" to drive ducks and other birds from their territories (Plate 20C, D and F). Coots were often seen "churning" at large adversaries,such as Great Blue Herons, which apparentlywould not retreat from "swanning",but which the coot feared too much actually to engagein fighting. In suchcases, coots Oct. 429 1959.a RYDER, Intolerance of American Coot in Utah

TABLE 4 SUMMARY OF INTEI•PECIFIC ATTACKS BY COOTS OBSERVED ON THE UTAH STUDY ARWAS,1956 AND 1957

Frequencyof conflicts Attacks/observationhour Species 1956 1957 Both Years 1956 1957 Both Years

Carp 0 1 1 0 0.005 0.003 Turtle 0 2 2 0 0.009 0.006 Eared Grebe 0 4 4 0 0.018 0.011 Pied-b Grebe 23 18 41 0.166 0.082 0.114 White Pelican 0 1 1 0 0.005 0.003 Gr Blue Heron 1 7 8 0.007 0.032 0.022 SnowyEgret 7 8 15 0.050 0.036 0.042 B-c Night Heron 2 5 7 0.014 0.023 0.020 Wh-faced Ibis 27 75 102 0.195 0.341 0.284 Mallard 12 27 39 0.086 0.123 0.109 Gadwall 5 23 28 0.036 0.105 0.078 Pintail 3 18 21 0.022 0.082 0.059 G-wingedTeal 3 9 12 0.022 0.041 0.033 Bl-wingedTeal 1 11 12 0.007 0.050 0.033 Cinnamon Teal 48 45 93 0.339 0.205 0.256 Shoveler 2 9 11 0.014 0.041 0.031 Redhead 40 162 202 0.288 0.736 0.563 Corn Goldeneye 0 2 2 0 0.009 0.006 Buffiehead 1 0 1 0.007 0 0.003 Ruddy Duck 12 45 57 0.086 0.205 0.159 Sofa 0 1 1 0 0.005 0.003 Killdeer 0 2 2 0 0.009 0.006 SpottedSandpiper 2 1 3 0.014 0.005 0.008 American Avocet 4 15 19 0.029 0.068 0.053 B-necked Stilt 2 2 4 0.014 0.009 0.011 California Gull 3 4 7 0.022 0.018 0.020 Franklin's Gull 1 0 1 0.007 0 0.003 Forstcr's Tern 0 4 4 0 0.018 0.011 Black Tern 1 1 2 0.007 0.005 0.006 B-billedMagpie 1 0 1 0.007 0 0.003 Y-h Blackbird 3 4 7 0.022 0.018 0.020

Muskrat 0 2 2 0 0.009 0.006 Weasel 0 1 1 0 0.005 0.003

Totals 203 509 712 1.463 2.314 1.985

Hours observ. 138.75 220 358.75

would alternate "churning" with "swanning". Often when coots charged trespassingvertebrates which escapedby diving--such as youngercoots, Ruddy Ducks,grebes and muskrats(Ondatra zibethi- cus)--the defenders"churned" directly over the point where the trespasserhad dived. "Swanning"and "churning" were often accompaniedby a guttural "growl," especiallywhen in defenseof young or nests. Interspecificconflicts mainly occurredon water in closeproximity to the nest platform and/or young but occasionallyextended over F Auk 430 RYDER,Intolerance of AmericanCoot in Utah I.Vol. 70

mudflatsor solid land. Gullion (1953) observedthat cootsseldom pursuedother coots on to land, but in Utah I frequentlysaw this behavior. Kornowski(1957) mentionedintraspecific but not inter- specificpursuits over land. Of the many birds noted in coot territories,Canada Geese•(Branta canadensis)and White Pelicans (Pelecanuserythrorhynchos) were the only speciesconsistently avoided by cootsas if feared. However, on one occasiona coot was seen making a half-heartedcharge at a pelicanwhich threatenedin return, causingthe coot to swim away. Usually cootsswam scoldinginto emergentcover when their terri- torieswere invadedby large flocksof fishingpelicans. Cootswere observeddriving from their territoriesflocks of as many as 17 White- facedIbis (Plegadischihi), l0 Mallards and 9 Shovelers. Aggressiveactions of cootsagainst coots were observed each spring when field observations were commenced late in M•rch. In 1957 cootswere frequentlyobserved "attending" Whistling Swans (Olor columbianus)at both Ogden Bay and Be•r River Refuges during late March and throughoutmost of April. Not only did one to four cootscircle about a feedingswan, picking up bits of debrischurned up by the treading and dabbling of swans,but some coots even defendedthis sourceof food from Redheads(Plate 20B). Later in the summer coots attended Mallards, Pintails, and Redheads in a similar

manner. Intraspecificconflicts reached a peakabout the lastweek of April, whereasinterspecific conflicts were most frequent per hour of observation the first half of June in 1956 and the latter part of June in 1957. Admittedly,various factors influence the frequencyof coot conflictsrecorded. As the emergentvegetation increased in height with the progressof the season,it becameincreasingly difficult to confirmvisually all cootconflicts detected aurally. Moreover,later in the seasonwhen there were more birds (diving ducksand ibises,in particular)moving through coot territories,there was more oppor- tunity for conflicts. Intraspecificconflict peaks seemed to correspondwith the estab- lishmentof coot territoriesand the building of displayand egg platforms. Interspecificterritorial peakswere not reacheduntil the young cootshad hatched. Thus, in 1956 the peak coot hatch occurredin the weekof May 13-19,the peak of interspecificconflict frequenciesthe firsthalf of June. In 1957the peakof coothatchings occurredlate in May, the peakof interspecificconflicts late in June. This is more or lessin agreementwith Gullion's (1953) California •959o•t.] I•YI•ER,Intolerance o! AmericanCoot in Utah 431 findings. He found that ducksand other specieswere usually ignored until after the coot broodshatched. Sooter (1945), too, apparently noticedmore interspecificconflicts after the coot broodshad hatched.

COOT-DUCK CONFLICTS Among the waterfowl there was considerablevariation noted in the number of attacksby coots. Redheadswere the duck most frequently noted in interspecificconflict with cootsas regardsactual attacksand threats. Over 40 percentof the coot-duckconflicts observed involved Redheads. Cinnamon Tea] were second most frequently attacked,about 20 percento{ the coot-duckconflicts; Ruddy Duckswere third, accounting{or about 12 percentof the coot-duck conflicts. Of thesethree species,Redheads were most abundanton the studyareas involved, Cinnamon Tea] were next, but Ruddy Ducks ranked only fourth in abundance;Mallards were third. CinnamonTeal, Redheadsand Ruddy Duckswere apparentlyin conflict with cootsout o{ proportion to their abundanceon the areas. Mallards, on the other hand, were not in conflict with coots as o{ten as might be expectedfrom their abundance. Many things other than the mere abundanceo{ a specieson the study areas apparentlyinfluenced the frequencyof coot-duckconflicts, {or example: 1) time of the breeding cycle at which contactsoccurred, 2) activity of the ducks at the time o{ contact, and 3) size and aggressivenesso{ the ducks. Coot-Mallardconflicts. The peakof coot-Mallardconflicts per unit time of observationduring the nestingseason occurred late in April, when most Mallard females on the study areas were laying or incubating. Most coots were just beginning to lay and mainly seemedto attack only those Mallards that ventured close to coot nests. Drake Mallards,in particular,were involvedin theseconflicts, as they loafedor fed near emergentvegetation, apparently awaiting their mates. Cootswere not alwayssuccessful in their Mallard encounters,losing six of the 39 coot-Mallard conflicts noted in the two years(Table 5). In contrast,Gullion (1953) observedMallards to be the speciesmost successfully attacked by cootson his areas. In Utah most of the Mallard courtshipand pairing activitieswere com- pleted by the time cootswere establishingtheir territories. Coots might conceivablyinterfere with renestingsuccess of Mallards which lost their first or earlier nest attempts. Mallard drakesdesert their mates early in incubation and might be even more inclined to abandona particular loaf spot if harassedby coots. However,even F Auk 432 RYDER,Intolerance o[ AmericanCoot in Utah LVol.76 into May and June a few Mallard drakeswere still on station in the studyareas. These maleswere probablyable to mate with any hens which were unsuccessfulin their earlier attempts. Coot-CinnamonTeal conflicts.The peak of coot-CinnamonTeal conflictsoccurred somewhatlater than that for Mallards (in early May), but they were almostas frequent throughoutthe latter part of April. Cootsdominated all of the 93 observedencounters with Cin- namon Teal except two, where female teals with broodsdrove coots away. Over half (47) of the conflictsinvolved mated pairs of teals, but almost as many (41) involved lone males. As with Mal-

TABLE 5

SUCCESSOF COOTS IN DR•NG DUCKS FROM THEIR TERRiTORiES, 1956 A•D 1957

PercentageOutcomes No. o[ Coots Coots Species Conflicts won lost Draw

Mallard 39 82.0 15.4 2.6 Gadwall 28 100.0 -- -- Pintail 21 47.6 33.3 19.1 Green-wingedTeal 12 I00.0 -- -- Blue-winged Teal 12 100.0 -- -- Cinnamon Teal 93 97.8 2.2 -- Shoveler 11 100.0 -- -- Redhead 202 77.2 20.3 2.5 Common Goldeneye 2 100.0 -- -- Bufliehead 1 100.0 -- -- Ruddy Duck 57 80.7 19.3 --

All ducks 478 84.1 13.8 2.1 lards, most of these lone drakes apparently were awaiting their mates, who were laying or incubating nearby. R. Smith (1955) found Cinnamon Teal had the smallest home ranges and areas of intolerancewithin those rangesof the four speciesof dabblershe studied at Ogden Bay (Mallard, Shoveler,Gadwall and Cinnamon Teal). This was also true on the coot-waterfowlstudy areas. The pair bond in CinnamonTeals is maintained longer after incubation has commenced than is true in Mallards; thus drake teals would seeminglybe more available to insure the fertilization of hens at- tempting to tenest. Here again, by harassingloafing drakes, coots might intereferewith this function. Cootscould conceivablyhave an even greater effect on teal, since they were much more successfulin driving teal from their territories than Mallards. As were the Mal- lards, however, Cinnamon Teal were repeatedly seen on the study •959aOct.'] RYDER,Intolerance o! American Coot in Utah 433 areas,week after week, frequentingapproximately the same areas, occasionallygetting too closeto a coot nestor brood and then being chargedand made to fly. Courtshipactivities of CinnamonTeal and Shovelersseemed to evoke aggressivebehavior in coots. Neck- bobbing and rather monotonouscalling in these two speciesas several males swim around a female seems to attract the attention of territorial coots,which frequentlywould chargewhole courtship parties. Kornowski (1957) reportssimilar unrest in EuropeanCoot territoriescaused by nuptial displaysof courtingducks. Coot-Redheadconflicts. Coot-Redheadconflicts were prevalent in late May and early June, when Redheadswere activelynesting or seekingnests to parasitize. Most cootshad broodsat this time and were increasinglyintolerant of all forms of bird life that entered their territories. Coots were less successful in their encounters with Redheadsthan with any other ducks nesting on the areas except Pintails. Both drake and hen Redheads often threatened and occa- sionally even fought cootsthat attempted to repulsethem. Female Redheadswith broodsdominated every conflict with coots. In all, however,coots were successfulin 156 (77 percent) of the 202 coot- Redheadconflicts observed. Unlike the dabblerspreviously discussed, Redhead drakesdid not defend any definite portionsof their home range exceptthat immediatelyaround their mate. When approached by another Redhead drake, pair or female, a male would display aggressiveness.Drake Redheadsusually followed closebehind their mates when the latter swam from open water into emergentcover as if seekingnest sites or nests to parasitize. When attacked by defendingcoots at such times, the drakesusually brought up the rear in retreat and often threatenedor repulsedthe coot charges. Severalinstances of actual fightingbetween coots and Redheadswere noted. Redheads,however, were exceptionallypersistent in returning and re-attemptingpassage through coot territories. For example,on May 16, 1957, a pair of Redheads(or possiblytwo pairs were involved)was driven from a coot territory on the CheckStation North Pond area nine times in four hoursof observation,returning eight times at intervals of five to 96 minutes! Similar attempts may have continuedafter observationswere terminatedthat day. Coot-RuddyDuck conflicts. Coot-Ruddy-Duckconflicts were noted somewhatlater in the nesting seasonthan were those with Mallards, CinnamonTeal or Redheads. Two peaksof frequencyof attacks were noted, one in mid-May and a secondin early July. The first came at a time when many cootshad young,whereas Ruddy Ducks [' Auk 434 RYDER,Intolerance of American Coot in Utah LVoI.?6 were just seekingnesting sites and a few beginning to lay. These early encounterswere dominatedby coots. Unlike the ducks previouslymentioned, Ruddy Ducks commonlyescaped by diving and swimmingaway underwater. A coot would usually churn over the submergedRuddy and on occasionsactually scratchand peck the duck'sback. These earlier encountersmainly involvedlone drakes and pairs. Courtingparties oœ Ruddy Ducksdid not seemto evoke coot attacksas regularlyas did similar anticsin tealsand Shovelers, probablybecause Ruddy groupswere usuallysmaller and remained in one placeless time. FemaleRuddies pursued by one or several drakes swam considerabledistances diving and surfadng, usually passingthrough several coot territories in rapid succession.Teals and Shovelers,on the other hand, remained in relatively small areasand rarely dived. As pointedout by Gullion (1953), three or œourdives on a Ruddy Duck'spart would usuallydiscourage an attackingcoot. However,on the CheckStation North Pond,in particular,coots were observedpursuing Ruddy Duckspersistently, and waiting,dive aœter dive, œorthe duck to surface. The Coot-RuddyDuck conflictswhich occurredlater in the seasonmainly involved Ruddy henswith broods, which often initiated the aggressions.In all observedinstances the Ruddy hen, whether the aggressoror not, dominatedthe coots. Coot conflictswith other specieso[ ducks. In addition to the previouslymentioned ducks, Gadwalls, Pintails, Green- and Blue- wingedTeal, and Shovelerswere occasionallycharged by cootson the studyareas. With the exceptionoœ those involving the Pintails, mostoœ these conflicts took place during the earlypart of the ducks' breeding cycles. Small parties oœcourting dabbhng ducks were frequentlydispersed by territorialcoots. In oneinstance, copulation in a pair oœGadwalls was disrupted by a deœendingcoot. On other occasionscopulation of Mallard and Redheadpairs took placein coot territorieswithout interference. Coots may causesome disruption of the normal breedingsequence of ducks,but it is doubtful that this is oœany great consequence.Only a œewattacks by cootswere noted againstspecies oœ ducks not nestingon the studyareas. Once a cootcharged a male Bufflehead(Bucephala albeola) that had been displayingin the vidnity oœthe coot's nest. A drakeCommon Golden- eye (Bucephalaclangula) was seen on the Westpoint North Pond throughoutmuch oœ the summerof 1957. It wasin poor plumageas earlyas May and apparentlywas crippled. Twice in separateweeks, a coot (or coots)drove the loafinggoldeneye off a bare spit of land at least 50 yardsfrom any emergentcover. 1959] RYDER,Intolerance ofAmerican Coot in Utah 435

Most Coot-Pintailconflicts occurred after June 15, following the first arrivalsof the northernbirds that congregatein Utah marshes for their annual molt. Many of theseconflicts involved adult or nearlygrown coots that gatheredabout up-ending Pintails, picking up bitsof aquaticvegetation the duckstore loose from the pondbottoms. In someinstances the Pintailsdrove the cootsaway, or a coot and a Pintail threatenedeach other but neither gave ground. Cootswith small young frequentlydrove feedingPintails out of the coots'territories. Interspecificconflicts of ducksand cootsduring brood rearing. A few conflicts between coots and ducks with broods were noted in both 1956and 1957. In all, 16 suchconflicts were seen (Table 6), compara- tively few consideringthe 111 differentobservations made from blinds of duck broods in coot territories. Eleven of the 16 conflicts were initiated by the duck hensinvolved. CinnamonTeal, Redheadsand Ruddy Ducks were seen driving coots away from the vicinity of their ducklings. On one occasion,a Redhead hen leading one duckling drove a femalecoot off of a loaf site. Later the Redheadpermitted the coot and one of her young to preen on the sameloaf site but threatened them frequently, keeping them at the other end. Another time, a femaleRuddy Duck with 11 downyyoung chased two immaturecoots out of the water on to the beachwhen theyapproached her brood too closely. Five different observationswere made of cootsattacking duck broods. In only three of these eventswere cootssuccessful, twice againstmotherless Ruddy Duck broodsand once against a

TABLE 6

COOT-DUCK BROOD CONFLICTS ON ALL Ara•AS, 1956 AND 1957 COMBINED

Total brood- Coot-duck No. conflicts observation conflicts per brood- Species hoursx noted ohserr.hour

Mallard 28 0 0 Cinnamon Teal 16 2 0.125 Pintail 16 0 0 Gadwall 36 0 0 Shoveler 3 0 0

Redhead 157 5 0.032 Ruddy Duck 1lB 9 0.080

All ducks 369 16 0.043

x One brood-observationhour equals one brood observedfor one hour or two broods observed for one half-hour, etc. 436 RYDER,Intolerance o[ AmericanCoot in Utah œVol.[ Auk76

Ruddy Duck hen and brood. Twice female ducks were seen to repulsecoot attacks. Most coots,with or without young,seemed to give wide berth to duckswith broods. Kornowski(1957) reportedsimilar dominance of duckswith broods over territorial EuropeanCoots. H. Hays (in litt.) noted female Ruddy Duckswith broodsthreatening coots. Boyd (in litt.) told of seeing European Coots attack Mallard ducklings but concluded, "lossesfrom such attacksmust have been unusual." Sooter (1945) observedcoots attacking Gadwall and Ruddy ducklingsin Oregon but noted that cootswere usually repulsedwhen the broodswere accompaniedby hens. In WashingtonState, Jeffrey (1948)and Harris (1954) both reportedcoots pursuing duck broods. Jeffrey (1948) told of motherducks repulsing such attacks and commentedthat he had never observedany damageinflicted on young ducklingsby attackingcoots. Harris (1954) said of coot attackson duck broods: "In most instances,the attendingmother quickly led the brood away from the antagonists." Attacks of captive cootson ducklingshave beenreported by Collins (1944) and Job (1915).

COOT CONFLICTS WITH VERTEBRATES OTHER THAN DucKs A wide variety of aquatic and marsh birds used the study areas during the coot nesting season,and, as might be expected,several specieswere occasionallyattacked by territorial coots. The various long-leggedwaders were mostabundant and much inclined to enter coot-defendedareas in their feeding. White-faced Ibises were fre- quentlysubjected to aggressivecoot displays. This wasundoubtedly becauseof their abundance (an estimated10,000 ibisesnest in the Ogden Bay-Howard'sSlough area) and their habit of feeding along the edgesof emergentvegetation. Then perhapstheir dark plumage and white facesmay act as releasers,somewhat resembling the dark shapesand white frontal shieldsof coots. At any rate, next to the Redhead, more coot interspecificconflicts involved ibises than any other species. The various herons--GreatBlue Heron (Ardea herodias), Snowy Egret (Leucophoyxthula) and Black-crownedNight Heron (Nycti- corax nycticorax)--werealso attackedby coots. Many of the coot- heron conflictswere obviouslyparental defensesof young. American Bitterns (Botauruslentiginosus) were rather rare on the studyareas and only onceobserved to influencecoot-waterfowl behavior--a low- flying bittern quite innocentlyfrightened coot and duck broodson the Check Station North Pond, causingthe young birds to flee for cover. •959.• RYDER,Intolerance of AmericanCoot in Utah 437

Three grebeswere fairly commonat OgdenBay Refugeand vicinity during the waterfowlnesting season. Western Grebes (Aechmophorus occidentalis) nested on the larger bodies of water. Eared Grebes (Podicepscaspicus) were very abundantduring the springmigration, althoughnone was known to have nestedin the study areas. Pied- billed Grebes (Podilymbuspodiceps) were common and nested in all of the studyareas. WesternGrebes were observed pursuing Eared Grebesbut seemedto feed in moreopen water than that frequented by territorial cootsand, perhapsfor this reason,were neverobserved in conflict with coots. Coots rarely drove Eared Grebes from coot territories but often were seen in conflict with Pied-billed Grebes, especiallyin closeproximity to the latter's nests. Pied-billedGrebes are particularlypugnacious in the defenseof their nests,not only against others of their kind but against various ducks and coots. Unlikecoots, Pied-billed Grebes seemed r•ore aggressiveduring in- cubationthan followinghatching but did defendtheir youngto some extent. Like coots, both sexes of Pied-billed Grebes shared in defense of their nestingterritory. Of all the vertebratesobserved in conflicts with coots, adult Pied-billed Grebes seemed to be the most successful in repulsingcoot attacks or, moreoften the case,winning thoseattacks they initiated. Juvenile and immature grebes, in contrast, were completelydominated by adult and nearly grown coots,in either territorial or neutral waters. Many speciesof shorebirdsfrequented the studyareas in migration, and severalremained to nest each summer. Attacks by cootswere noted against Killdeer (Charadrius voci•erus), Spotted Sandpiper (Actitis macularia), American Avocets (Recurvirostraamericana), and Black-neckedStilts (Himantopus mexicanus)in approximate proportionto their numberson the studyareas. With the exception of the avocets,all seemedto be easilyejected from coot territoriesor from stretchesof beach upon which territorial cootsfed. Near their nests,however, avocetswere very belligerent and would mob large birds suchas gulls, heronsand Marsh Hawks (Circuscyaneus). An occasionalavocet would repulsea coot chargeeven when feedingin a coot-defendedarea. One pair of avocetswas observed escorting their four small chicksas they swamacross a small coveof the Westpoint North Pond. The adult avocetsmobbed a pair of cootsand their young and made another adult coot dive. In all, the avocetsled their brood unmolestedthrough at lea•t two coot territories. Both Soras(Porzana carolina) and Virginia Rails (Rallus limicola) were often heard although only occasionallyseen on the study areas. In spiteof being rather closerelatives of the coot, theserails did not 438 RYDER,Intolerance o[ AmericanCoot in Utah œVol.I' Auk76 seem to have very similar habits and were not often in situations for possibleconflicts with coots. Only once was a coot (a nearly grown juvenile) seen to charge a Sora, one which ventured into a coot feeding area. The various gulls and terns were attacked by cootsin apparent defenseof their broods. The single attack againsta surfacingcarp (Cyprinuscarpio) seemedto be in the samecategory, whereas the attacksagainst a turtle seemedto be mere curiosityon the part of somejuvenile coots. It is interestingto note that native turtles are unknownin the Great Salt Lake Basin (Woodbury,in litt.). A small turtle seen on the Check Station North Pond for several weeks in 1957 was most likely an escapedor released"pet," possiblyfrom Ogden via the Weber River or irrigation canalsto the east of the refuge. PARENTAL DEFENSE BY COOTS OF THE BROOD Coots were observedto defend their young actively from various possiblepredators and harassmentby other coots. Feigning or tolling, which were commonlyobserved with ducks,were never seen with coots. On at least six occasionsadult cootsdefended against California Gulls (Larus cali[ornicus)obviously trying to grab the coots'young. This defenseconsisted primarily of swarming,churning and growling,but in two instancesone adult coot splatteredat a gull as it hoveredover the coot'sbrood. When directly under the gull, the cootstopped and held its headaloft in an apparentparrying threat at the gull overhead. In none of these casesdid the gulls succeedin capturing a coot chick during the time the observerwas in the blind. As the observer had been in the blind more than half an hour prior to theseattacks, it seemedunlikely that they were influencedparticularly by human interference. Similarparental defense of broodsby adult cootswas noted against Franklin'sGulls (Laruspipixcan), Forster'sTerns (Sterna[orsteri), Black Terns (Chlidoniasniger), Black-crownedNight Herons, Great Blue Herons, Snowy Egrets,White-faced Ibises, and a long-tailed weasel (Mustela [renata). In theseexamples, the marsh birds were usually chargedafter they approacheda coot brood which became frightenedand fled crying for cover. Crying of young cootswhen threatenedor peckedby adult cootsother than their parentsseemed to evokesimilar parental defense. In onlyone of the above-mentioned casesdid the repulsedmarsh bird seemto be definitelytrying to catcha youngcoot. Some50 minutesafter enteringthe Unit 3 blind on August2, 1956,the observersaw a parent coot splatterat a Black. ,0•,•] RYDS,Intolerance ofAmerican Cootin Utah 4•9 crownedNight Heron that wadednear the coot'syoung. During the next 20 minutes,the adult coot twicerepulsed the heron,which flew only a few yards,alighted and wadedslowly back toward the brood. Eventuallymuch splatteringand growling was heard. This time the heron flew awaywith a strugglingcoot chick in its bill. The coot continued to feed two young chicks (about one-weekold) in the samearea the remainderof the observationperiod. Coot defense threatsagainst a weaselwere observedfrom the sameblind approxi- matelyone year later. Two cootsfrom adjacentterritories were peace- fully feeding three and four young in front of the blind when one parent becamealarmed and startedgiving warning calls. One brood fled for coverimmediately, while the other seemedalert but remained near their parent. Both adultsswam toward the dike upon which the blind was located. Within a few feet of the dike they paused, "swanning"and "growling" at a weaselapparently hunting along the dike. The weaselseemed to pay lit[le attention to the coots, which swam parallel to it as it moved along the dike. In a few minutesthe weaseldisappeared from sight over the dike, and the cootsresumed feeding their respectivebroods.

INTERSPECIFIC CONFLICTS INVOLVING SPECIES OTHER THAN COOTS

It shouldnot be implied that the cootwas the only specieson the study areas which displayedinterspecific territorial intoleranceof ducks. Mallard drakes were seen to defend against Pintail drakes; Blue-wingedTeal and Cinnamon Teal drakes againstone another. A Ruddy Duck drake chaseda Yellow-headedBlackbird (Xantho- cephalusxanthocephalus) along the edgeof the WestpointNorth Pond. Pied-billedGrebes were seen charging Red-breasted Mergansers (Mergusserrator), Mallard, Redheadand Ruddy Duck adults,as well as Ruddy ducklingsand Eared Grebes. Three different timesavocets were observedpursuing Gadwalls,and once a Blue-wingedTeal. Severalinstances were noted of duckswith broodsdefending against other ducks. Interspecificterritorialism seemed rather commonamong the nesting shorebirds. Willets (Catoptrophorussemipalmatus) chased Long- billed Curlews (Numeniusamericanus); avocets chased stilts. An incubatingKilldeer periodicallydrove Spotted Sandpipers and avocets away from its nest. Various speciesof birds united to mob larger birds and mammalian predators. Black, Forster'sand Common Terns (Sterna hirundo) harassedflying herons. RedwingedBlack- birds (.4gelaiusphoeniceus) mobbed Marsh Hawks and Short-eared [- Auk 440 RYDER,Intolerance of AmericanCoot in Utah tVol.?•

Owls (Ado flammeus) and united with avocetsand Yellow-headed Blackbirdsto torment a prowling weasel. Although interspecificintolerance was apparent in severalspecies oœbirds, it wasmost oœten and consistentlydisplayed by the coot.

RESPONSES BY COOTS TO DECOYS At varioustimes, efforts were made to evokeinterspecific aggressions oœcoots against a pair of Redheaddecoys. No interspecificintolerance was noted, although most coot pairs so testeddefended against coot dummies. Live Redheadsin turn respondedto the duck decoys,but no interspecificbehavior was evoked.

CONCLUSION Most conflictsoœ coots with diving ducksseemed to involvefeeding areas and nesting and brooding platforms, while conflicts with dabbling ducksseemed concerned with loaf sites and feeding areas. This interspecificterritoriality oœcoots seems to have had ver• little effectupon duck nesting. Someducks may have been excludedfrom nestinghabitat by coots,but otherswere able to use abandonedcoot platforms and nest in open emergentswhere they otherwisecould not have done so. Cootsoccasionally disrupted duck courtshiptemporarily and, more rarely, copulation. Even the frequently attacked Cinnamon Teal drakes usually returned to loaf sites œromwhich coots had driven them. Interspecificterritorial defenseby cootswas most pronounced followinghatching. Although coots occa?ionally attacked ducks with broods,œemale ducks with young more often dominatedcoots, even within the latters'territories. Severalpredators which feed upon eggs and youngoœ both cootsand duckswere attackedby coots. These attacksagainst common enemies are believedto benefitducks nesting and rearing their young in the vicinity of territorial coots.

SUMMARY The American Coot actively defends an area centered about its nest againstducks and other vertebrates,as well as againstother coots. In all, 11 speciesof ducks, 1õ other speciesof birds, one fish, one reptile and two mammalswere seenpursued or threatened by coots. In Utah, CinnamonTeal, Redheadsand Ruddy Ducks were attackedby cootsout of proportion to their abundance,whereas Mallardswere attacked less frequently. The aggressivenessof coots is believednot to havean adverseeffect on ducknesting, for predators are kept awayand abandonedcoot platformssupply nesting sites. Oct. '1 •959 RYDER,Intolerance of AmericanCoot in Utah 441

LITERATURE CITED

ATTWOO•),A.J. 1948. One Nest, Two Species. Field (London) 191: 106. B•¾, J. 1939. The Status and Distribution of Wild Geese and Wild Duck in Scotland. Intern. Wildfowl Inquiry, Vol. II. Cambridge: Cambridge Univ. Press. 190 BL.•NCnAN,N. 1904. Birds that Hunt and are Hunted. New York: Doubleday, Page & Co. 359 pp. BRYANt,H.C. 1914. A Surveyof the Breeding Grounds of Ducks in California in 1914. Condor, 16: 217-239. BuKgII.I.,H.J. 1935. Notes on Coots. Brit. Birds, 26: 342-$47. COLLINS,J.A. 1944. Coot AttacksYoung Duck. Auk, 61: 299. C•MP, S. 1947. Notes on Territor• in the Coot. Brit. Birds, 40: 194-198. DELACOIm,j., and E. MAYR. 1946. Supplementar•Notes on the Family Anatidae. Wilson Bull., $8: 104-110. Goo•).•, J. D., A. W. Jo•Nsos, and R. A. P•n•pe•. 1951. Las Aves de Chile. Vol. 2. BuenosAires. 445 pp. GULUON,G.W. 1951. A Marker for Waterfowl. J. Wildl. Mgmt., 15: 222-223. GuerdoN,G.W. 1952. The Displaysand Calh of the American Coot. Wilson Bull., •: 8•-97. G•I.I.•oN, G. W. 1955. Territorial Behavior of the American Coot. Condor, 55: 109-186. H/•s, S.W. 195•. An EcologicalStudy of the Waterfowl of the PotholesArea, Grant County, Washington. Amer. Mid. Nat., $g: •05-•$2. H•Y•, R. 1911. OrnithologischeNotizen von den Wermsdorfer Teichen 1909. Orn. Mschr., 36: 249. Hog•/wM, H.A. 1944. The Canvasbackon a Prairie Marsh. Washington: Am. Wildl. Inst. 201 pp. HfRN, E.O. 1949. Notes on Sexual and Territorial Behavior in the Coot and on the Incidenceof Non-breedingin this Species.Brit. Birds,4g: •09-210. JEFFREY,R. G. 1•8. Notes on Waterfowl of Certain Pothole Lakes of Eastern Washington (M.S. thesis). Pullman, Wash.: State Collegeof Wash. 57 pp. Jo•, H. K. 1915. Propagationof Wild Birds. Garden City, N.Y.: Doubleday, Page& Co. 276 pp. KOR•OWSI•I,G. 1957. Beitr•igezur Ethologiedes Bl•isshuhns(Fulica atra). J. f•r Ornith., 98: $18-$55. Lm•T, W. 1926. Beobachtungenaus der Vogelwelt neum•irkischerSeen. Orn. Mschr., 51: 5-6. Low, J. B. 1940. Production of the Redhead (Nyroca americana) in Iowa. Wilson Bull., $g: 153-164. Low, J.B. 1941. Nestingof the Ruddy Duck in Iowa. Auk, 58: 506-517. MVN•O, J.A. 1919. Notes on Some Birds of the Okanagan Valley, British Co- lumbia. Auk, 36: 64-74. MON•O,J.A. 1957. Studiesof Waterfowl in the CaribooRegion, British Columbia. Condor, 39: 165-173. MUNRO,J.A. 1959. The Relation of Loons,Holboell's Grebes, and Cootsto Duck Populations. J. Wild1. Mgmt., 3: $$9-$44. NELSON,N.F. 1954. Factorsin the Developmentand Restoration of Waterfowl Habitat at Ogden Bay Refuge, Weber County, Utah. Pub. No. 6, Fed. Aid Div., Utah Fishg• Game Dept. 87 pp. 442 RYDER,Intolerance o! AmericanCoot in Utah CVol.F Auk76

NYLU•D, P. 1945. Bidrag till kannedomenom soth/Jnansbiologi. Ornis. Fenn., 9.2: 100-121. SMrrH, A. G. 1956. The Coot on the Lousana Waterfowl Area, 1953-1955. (Appendix to ProgressRept. on the LousanaWaterfowl Study Area, 1953-1955, Lousana, Alberta, Canada.) pp. 90-109. (Mimeo.) SMrrH, R.I. 1955. The Breeding Territory and its Relationship to Waterfowl Productivityat Ogden Bay Bird Refuge. (M.S. thesis)Logan, Utah: Utah State Agr. College. 46 pp. SoomzR, C.A. 1945. Relations of the American Coot with Other Waterfowl. J. Wildl. Mgmt., 9: 96-99. Smzvz•s,W.E. 1947. Diving Duck Productionat Barringer'sSlough, Clay County, Iowa (M.S. thesis). Ames, Iowa: Iowa State College. 82 pp. STUARm-BAx•a•R,E.C. 1929. The Fauna of British India: Bird. Vol. 6. London: Taylor & Francis. 499 pp. Wz•zR, M.W. 1956. Parasitic Egg Laying in the Redhead (Aythya americana) and Other North American Anatidae (Ph.D. thesis). Columbia, Mo.: Univ. of Mo. 160 pp. WZmMORZ, A. 1920. Observations on the Habits of Birds at Lake Burford, New Mexico. Auk, 37: 221-247; 393-412. WITHERBY,H. F., F. C. R. JOURDAIN,N. F. TICEHURSTand B. W. Tuc•R. 1949. The Handbook of British Birds, Vol. V. London: H. F. & G. Witherby Ltd. pp. 2O4-2O5. Utah CooperativeWildlife ResearchUnit, Utah State University, Logan, Utah.

PINK-HEADED DUCK--INFORMATION WANTED Our CorrespondingFellow, S•lim Ali, of the BombayNatural History Society, 91 WalkeshwarRoad, Bombay 6, India, wishesinformation on any specimens existingin public or private museumsof the probablyextinct Pink-headed Duck (Bhodonessacaryophyllacea). The provenanceof specimensand any other data on the original labels will be welcome.