Hybridizati.on between Glossyand White-f .aced Ibises

JamesW. Arterburn and Monroe1990). Glossy and White-faced IBIS CHARACTERISTICS Ibisesare known to haveproduced hybrids in Adultand immaturePlegadis plumages are 5806East 78th Place captivity(Gray 1958, fide Terres 1980). How- adequatelydescribed in a numberof accounts Tulsa,Oklahoma 74136 ever, at breedingcolonies in Alabama, (Palmer 1962, Oberholser1974, Pratt 1976, Louisiana,and Texaswhere the two occur Crampand Simmons 1982, Kaufman 1990, together,interbreeding has not been observed Ryderand Manry 1994,Davis and Kricher (Ryder 1967, Duncanand Johnson1977; 2000,Sibley 2000, Patten and Lasley2000). JosephA.Grzybowski Hockey, pers. comm.). Pairs perform various First-basicand first-alternateplumages are CollegeofMathematics andScience courtshiprituals of allopreeningand mutual presumedsimilar to definitive-basicand waggingof nestmaterial but appearto arrive definitive-alternateplumages, respectively, UniversityofCentral Oklahoma at nestingcolonies "already mated" (Belknap with minorvariation occurring in coloration Edmond,Oklahoma 73034 1957). Surprisinglylittle is knownof the of undertail coverts bet•veen first- and defini- mechanismsof pair bonding(Davis and tive-basicplumages (Howell and de Montes and Kricher2000) or of isolatingmechanisms 1989,Patten and Lasley2000). The limited SamNoble Oklahoma Museum bet•veenspecies. Such mechanisms would amountsof whitefeatbering that surrounds presumablybe linked to species-specific the facial skin in some White-faceds is not ofNatural History plumagecharacteristics, to soft-part and eye considered(known?) to be a featureof first- UniversityofOklahoma coloration, and possiblyalso to species-spe- alternateplumage. cificdisplays. Wefocus here on coloration of theeye and Norman,Oklahoma 73072 On 30 May 2002,Arterburn was studying facialsoft parts and on the levelof white dark ibisesat the ByronFish Hatchery and leatheringimmediately surrounding the SaltPlains National Wildlife Refuge, Alfalfa facialskin, as theseform the basesfor distin- ABSTRACT County,Oklahoma. Among the White-faced guishingbetween these species. Bill andleg Up to fiveapparent hybrids between Glossy Ibisat theHatchery, he noticed two birds that color are variable,with overlapbet•veen and White-faced Ibises were discovered in he suspectedwere hybrids. The firstbird had species,and are therefore less reliable charac- AlfalfaCounty, Oklahoma during 2002. They somewhite feathering around the facebut teristics.Most obviously,aduh White-faced frequentedan area in whichWhite-faced Ibis also other characterssuggestive of Glossy Ibisin breedingcondition (in definitive-alter- had recentlyestablished breeding colonies, Ibis.The secondbird had palepink to pur- nateplumage) shows a modestto broadband and wherea few breeding-conditionGlossy plishlines forming upper and lowerborders of whitefeathers edging the barefacial skin Ibisappeared during previous breeding peri- to the bare facial skin; the facial skin was that is not presenton GlossyIbis. White- ods.Only one intermediate Plegadis individ- mainlya plum-graycolor. Along the auto- facedspast their first-winterseason have a ual had been previouslyrecognized, that tour routeat the Refuge,he foundand pho- red iris, while that of Glossiesis brown. depictedby Sibley(2000). Our Oklahoma tographeda third bird that he initially The facialskin of GlossyIbis is variously observationsdepict a spectrumof variation in thoughtwas an adultGlossy Ibis. describedas purplish black, blue-black, and characteristicsamong probable hybrids. David Sibleyand Grzybowskiexamined darkcobalt blue in breedingcondition, and is thephotos of thetwo birds from the Hatchery describedas dark blue, dull green,or dull INTRODUCTION and agreedthat both were likely hybrids. grayduring winter. There are pale blue or TheGlossy Ibis (Plegadisfalcinellus) is a cos- However,in reviewingthe photos of thethird blue-whitelines edging the upper and lower mopolitanspecies, with North American bird, both Sibleyand Grzybowskinoted bordersof facialskin from the bill to eye,but populations breeding primarily in the intermediatecharacters that suggested hybrid not extendingbehind the eye. In intense Atlantic and Gulf coastal areas of the United status for this bird as well. breedingcondition, the loral line (upper) Statesand in the GreaterAntilles (Davis and Arterburnreturned to the Hatcheryand thickens(Figure 1). Most Glossiesshow Kricher 2000). The White-faced Ibis (Ple- Wildlife Refugeon 6-7 June and 5-6 July these lines duller and reduced in non-breed- gadischihi) breeds locally in the western 2002.He foundanother hybrid at theHatch- ing condition. UnitedStates, highlands of Mexico,and in eryon 7 Juneand yet another different bird The facialskin of breedingadult White- Gulf coastal areas of Texas and Louisiana on theRefuge 5 JulyHe alsofound one cer- facedsis describedasred, pinkish-red (Figure (Ryderand Manry1994). There is remark- tain adultGlossy Ibis on the Refugeo• the 2) to richmaroon (Figure 3), fadingto pale ably litfie variationworldwide among the Junetrip andthree to fouron theJuly trip, as pink or gray duringwinter. Some White- populationsof GlossyIbis (Davis and Kricher well asrelocating the adulthybrid on both facedsshow a thinpale loral line thatis usu- 2000). trips.Grzybowski visited the Hatcheryand allywhite or palepink. It is mostnoticeable Althoughthese two forms were considered WildlifeRefuge on 5 Julyand found two cer- duringwinter when the white leathering conspecificfor muchof theirtaxonomic his- tainadult Glossy Ibis and one of thehybrids around the facial skin is absent. In some sum- tory (Palmer1962), recent treatments have on the Refuge.He crossedpaths with Arter- merindividuals, pale pink lines form borders, elevatedWhite-faced to speciesstatus (Amer= burn at the Hatchery,where they relocated aboveand below,to the pinkish-redfacial icanOrnithologists' Union 1983, 1998; Sibley oneof thehybrids first found on 30 May skin;the palepink eyelidcan makethese

136 NORTH AMERICAN BIRDS bothspecies. The eyehas several reddish-brown,possibly a condition of •' clearlyred areas.The facialskin retardedjuvenile colon haspink, plum-purple,and gray Three o[ the five intermediates show com- tones.The linesforming the bor- binationsof redin eyes(of White-faceds) and ders of the facial skin, above and paleblue in thelines edging the facial skin (of below,are white (suggestiveof Glossies);in a fourth, the facial lines are Glossy).The upperline is thick- whitish.The mostdiagnostic feature shared ened (as in Glossy).The lower by thesehybrids is thepresence of theplum- line extendsto just behind the purplecoloranon (uncharactenstic of either eye.The paleeyelid makes these White-facedor Glossy)in the facialskin, linesappear as if theyextend and and/or toning to its pale borderlines.We meetbehind the eye (as in BirdA believeall fourof theseare hybrids. Ihe plum above). There are alsosome white tonein the eye-finesof bird E is consistent featherson thehead just above the with tones in the other birds. Ihis would Figure1. Typicaladult Glossy Ibis in breeding condition atSalt Plains loralstripe and on theside of the suggesthybrid status for thisbird as well. N.W.R.,Oklahoma 6 July 2002. The dark brown eye and blue-black facenear the gape. facialskin with borders, above and below, of bluish-whitelines are DISCUSSION characteristicofbreeding birds. Photograph byJames W.Arterburn. The eyeof BirdC (Figure7) is brown with areas of red. The bare Palmer(1962) suggested,from the occur- facialskin is a plum-purplecol- fencesof breedingrecords, that the Glossy orationwith patchesof gray.The Ibisspread to Americafrom the Old World in linesbordering the facialskin are the 1800s.Patten and Lasley(2000) dis- mostly the pale (intermediate) cussedthis historical spread into Atlantic and plum coloration, with some Gulf coastal areas of the United States. From whiter and blue-white areas. The thesedata, it wouldappear that Glossyand upper line thickenssomewhat White-facedIbises were geographically iso- (suggestiveof Glossy).Because lated for sometime, allowingreproductive the eyelidis dark (as in Glossy), isolatingmechanisms between these forms to the upperand lowerlines do not become established. appear to extend and connect Pattenand Lasley (2000) also depicted the behindthe eye. recent increase in extralimital records of Theadult hybrid in Figures8-9 GlossyIbis into the westernreaches of the (BirdD) looksmost like a Glossy UnitedStates beginrang in the 1980sand Figure2. AdultWhite-faced I• inbreeding condition atSalt Ibis. However, it has several showingan especiallypronounced increase PlainsN.W.R. 5 July 2002. White feathers surround the facial skinand red eye. The fadal skin appears pinkish-red. Note clearlyred areasin the eye.The beginningin 1998.This is consistent with the thepale eyelid. Photograph byJames W.Arterburn. facialskin is largelya plum-purple recentincrease in GlossyIbis sightings for the toneapproaching, but essentially southernGreat Plains. A bird foundby Jo linesappear to circlebehind the eye and con- duller than, the maroon tones on the bare- Loydand Pat Seibertand photographedby nect(Grzybowski, pets. obs.). In bothcases, skinareas of theWhite-faced Ibis in Figure3. SteveMetz in TulsaCounty, Oklahoma in thepinkish, red or maroonfacial skin readily The linesforming the bordersof the facial October1991 was only the secondGlossy distinguishesthese birds as White-faceds. skinare pale blue and appear very much like Ibisdocumented for Oklahoma(Grzybowski thoseof a GlossyIbis, the upperthickening 1992).The next to appearwere in thespring HYBRIDDESCRIPTIONS somewhat.The eyelid is dark.There is white of 1999, when at least three were noted in the The five birds with intermediate characters in someof thefeathers on topof thehead just SouthernGreat PlainsRegion of Nebraska, describedbelow show a spectrumof variation abovethe loral stripe and on theside of the Kansas,and Oklahoma(Grzybowski 1999). froma bird veryclosely resembling an adult facenear the gape. In 2000, Arterburn discoveredseveral adult GlossyIbis to one appearingas an off-tone BirdE (Figure10) maybe a hybridor pos- GlossyIbis in countiesnear the Salt Plains White-faced.Ibe lattermay indeed be a vari- siblya variantWhite-faced in retardedfirst- (Kingfisherand Major Counties, Oklahoma) ant White-faced. alternateplumage. The featbering Ihree birdsdepicting clearly intermediate on the anteriorportions of the charactersare thosein Figures4-7. These head shows a few white streaks birdsmay be subadults in theirfirst-alternate thatmay be remnants of first-basic plumage.Bird A (Figures4-5) hasa brownto plumage.The facial skin is largely brownish-redeye. The barefacial skin has plum-gray,with a few brighter patchesof bothdark gray and a plum-purple areasof plum colorationcharac- coloration,the latter intermediatebetween teristic of the intermediates above. thatfound in Glossyand White-faced Ibises. The linesforming the bordersof The line formingthe upperborder to the the facialskin are a paleplum or facialskin is mostlypale blue (as in Glossy), pale maroon(the intermediate whilethat forming the lower border contains tone).The upper line thickens(as a paleplum cast (an intermediate coloration). in Glossy)and is palerthan the The eyelidis pale, of similartones to the lower.The eyelidis plumposteri- faciallines. There is somewhite leathering orly,matching the lowerborder- just abovethe loralstripe and on theside of line,but grayanteriorly. The eye Figure3. Anotheradult White-faced Ibis in breeding condition atSalt is brownbut, upon closeinspec- PlainsN.W.R. 7June 2002. Note the bright red eye and rich maroon the[ace near the gape (as in White-faced). facialskin of this bird. Photo9raph byJames ß Afterburn. BirdB (Figure6) alsohas characteristics of tion, vermiculatedslightly with

VOLUME 57 (2003) NUMBER I 137 (Balknap1957, Duncan and John- rarerelative to thetotal populations, making son 1977). In Iexas, GlossyIbis them less likely to be detected.Several was first foundnesting at Sun- authorshave suggested that the situation•n down Island in MatagordaBay Gulf coastalcolonies needs more study • during1998 by PetraHockey (Ryderand Manry1994, Patton and kasley (pers. comm.) and Brush Free- 2000). man. In surveyingibis colonies Pattenand kasley (2000) anticipatedthat during 2002 on MatagordaBay with the expansionof bothWhite-faced and islands,Hockey found approxi- GlossyIbises, hybrids would be found. mately23 GlossyIbises on nests Whetherthis will be a patternoccurring in amongthose of White-faced broadlyor oneof occasionallocal occurrence Ibisand other herons and egrets. dependspresumably in largemeasure on the She scrutinized each dark ibis for effectivenessof currentisolating mecha- •' signsof possible hybridization but nisms.Given that hybridshave been rare to did notfind a singleodd ibis. dateeven when looked for, isolating mecha- DavidSibley (pets. comm.) also nismsbetween these species may be effective. studied ibises in the Iexas coastal We would, thus, predict frequenciesof areasand found only one sus- hybridizationsimilar to thosefor waterfowl, pected intermediate, a bird occurringonly occasionallywhere vagrants depictedin his recentidentifica- in breedingcondition encounter localized tionguide (Sibley 2000). It shows breedingpopulations of the regionally the sameplum castto the facial expectedspecies. skin and lines as the Alfalfa County birds. No other potential hybrids have been reportedto datein the wild. Why wouldhybrid- ization occur at the Salt Plainsbut not appar- Figures4 & $. HybridPlegadis (possibly subadult) near Salt Plains ently on the ¾exas N.W.ROklahoma •0 May 2002. Notice the brown to brownish-red coast?With isolating eye;facial skin that has pink, plum-purple, andgray patches mechanismsin place, andpale blue-line borders; and white feathers above the Ioral stripeand near the gape. Photographs byJames W.Afterburn. hybridization should rarelyoccur. However, duringthe breeding season. withlittle knowledge on courtship White-facedIbis breedsvery locallyat andpossible behavioral cues, little scattered localities in the Great Plains and but speculationcan be offered. Figure6. HybridPlegadis (possibly subadult) near Salt Plains N.W.R MountainWest (Ryderand Manry 1994). Many waterfowlare genetically 6 June2002. The eye is mostly red, and the facial skin has pink, plum-purple, Ihe specieshas long been noted nesting at compatible,yet comparauvelyfew andgray coloration. The lines forming the borders ofthe facial skin are CheyenneBottoms Wildlife Management individualshybridize because of white,the upper line thickening; the pale eyelid makes them appear Areaand Quivira National Wildlife Refuge in toconnect behind the eye. Also note white feathers above the Ioral detailedand stereotypeddisplays stripeand near the gape. Photograph byJames W.Arterhurn. centralKansas (Ihompson and Ely 1989), and very discretemale plumages withone recently documented nesting colony (Mayr1965). Hybridization at the in MeadeCounty, Kansas during 1998 (l:1ow- SaltPlains may be a localphenom- ers 1998). enoninduced by therelative rarity Concomitantwith the•ncreas•ng extralim- of GlossyIbis: an adult Glossy Ibis ital appearancesof GlossyIbis has been the in Oklahoma would have had few southwardexpansion in breedingof the choices other than a White-faced White-facedIbis into Oklahoma.The species fora mate.Such is thetypical con- wasfirst noted breeding on RalstonIsland, dition deducedby Mayr (1965): SaltPlains National Wildlife Refuge, north- hybridization between bird centralOklahoma in 1995,although several species with species-specific wereobserved annually during summer on courtshipdisplays and extended thisisland since 1992 (Shepperd 1996). Dur- pair bondswould be morelikely ing 2000 and 2001, several temporary in a situationof same-species mate colonieswere observedin Kingfisherand scarcity.In Gulf coastalcolonies Beaver Counties of northwestern Oklahoma whereboth speciesnest, hybrids (Arterburn,pers. obs.) and as far southas have not been found (or recog- ¾illmanCounty in southwesternOklahoma Figure7. Hybrid Plegadis (possibly subadult) atSalt Plains N.W.R nized)to date.Ihis maybe due to 6 July2002. The eye is brown with patches ofred, and the facial skin (l:azio,Grzybowski, pers. obs.). highernumbers of eachspecies hasplum-purple and gray coloration. The lines forming the borders of Hybridizationin the wild betweenthese there,making it easierto find a thefacial skin are mostly plum-purple, with some areas of blue-white Plegadisibises has not been observed in sew mate of the sametype. Alterna- (upper)and white (Iower),the upper line thickening. Note the eral Gulf Coast colonies where both occur tivelb hybridsmay be presentbut eyelidsof this bird ore da•k. Photograph byJames W.Arterburn.

138 NORTH AMERICAN BIRDS existenceof apparent hybrids NationalGeographic Society. 1998. Field raises cautions for identification of Guideto theBirds of North America, extralimitalPlegadis ibises. 3rd. ed.National Geographic Society, Washington,D.C. Acknowledgments Oberholser,H.C. 1974.The Bird Life of We thankDavid Sibley for careful Texas,vol. 1. Universityof Texas reviewof the initialphotographs Press,Austin. andsubsequent discussion. Palmer,R.S., ed. 1962.Handbook of North AmericanBirds, vol. 1. YaleUniversity Literature cited Press,New Haven, Connecticut. .• AmericanOrnithologists' Union. Patten,M.A., and G.W. Laslcy. 2000. Range 1983.Check-list of North Expansionof theGlossy Ibis in North AmericanBirds, 6th ed. America. North American Birds 54: AmericanOrnithologists' 241-247. Union,Washington, D.C. Pratt, H.D. 1976. Field identificationof AmericanOrnithologists' Union. White-facedand Glossy Ibis. Birding 8:1-5. 1998.Check-list of North Ryder,R.A. 1967. Distribution, migration AmericanB•rds, 7th ed. andmortality of theWhite-faced Ibis AmericanOrnithologists' (Plegadischihi) in NorthAmerica. Bird Union.Washington, D.C. Banding38: 257-277. Belknap,H.W. 1957. Observa- Ryder,R.A., and D.E. Manry. 1994. White- tions on the White-faced Ibis facedIbis (Plegadis chihi). In TheBirds (Plegudischihi) in Louisiana. of North America,No. 130. (A. Poole MastersThesis, Louisiana State andF Gill,Eds.). Philadelphia: The University,Baton Rouge. Academyof NaturalSciences; Wash- Cramp,S., and K.E.L. Simmons, ington,D.C.: The American Ornitholo- eds.1982. Birds of theWestern gists'Union. Palearctic,vol. 1. Oxford Shepperd,R. 1996.White-faced Ibises nest UniversityPress, Oxford. at SaltPlains National Wildlife Refuge, Davis,W.E., Jr., andJ. Kricher. Oklahoma.Bulletin Oklahoma Ornithologi- 2000.Glossy Ibis (Plegudis calSociety 29: 1-2. Figures8 & 9. Adult breeding-condition Plegadis hybrid a• Salt Plains falcinellus).In TheBirds of Sibley,C.G., and B.L. Monroe. 1990. Distrib- N.W.R30 May 2002. This bird looks like a Glossya•a distance,but notice North America,No. 545 (A. utionand Taxonomy ofBirds of the World. Yale thered in the eye, some white feathers above the Ioral stripe and near Pooleand E Gill, eds.).The UniversityPress, New Haven, Connecticut. thegape, the dearly blue lines forming the borders ofthe bare facial Birdsof North America,Inc., Sibley,D.A. 2000. The Sibley Guide to Birds. skin(upper thickening), and the largely plum-purple tone to the remainingfacial skin. Photographs byJames W.Arterburn. Philadelphia,PA. RandomHouse, New York. Duncan,C.D., and P.G.Johnson. Terres,J.K. 1980.The Audubon Society Nonetheless,the occurrenceof theseinter- 1977.First breeding record of White-faced EncyclopediaofNorth American Birds. mediates adds a new consideration to identi- Ibis for Alabama and a new area of AlfredA. Knopf,New York. ficationissues for extrafimital Plegadis ibises. Plegadisphilopatry. Alabama Birdlife Thompson,M.C. and C. Ely.1989. Birds Althoughhybrids would not be expectedin 25: 16. in Kansas,vol. 1. Universityof Kansas the firstwave of extrafimitals,the vagrancies Flowers,T. 1998.Playa lake nest- MuseumofNatural History, Lawrence. • in thesespecies now includemuch of the ingrecords. Rookery in Meade contiguousUnited States where one of the County,Kansas. Bulletin Kansas cohortspecies is very rare relativeto the OrnithologicalSociety 49: 33-38. other.Hybrids should be considered carefully Gray,A.P. 1958. Bird Hybrids • in eachinstance of potentialvagrancy. Docu- CommonwealthAgricultural mentationis stillcritical in assessingbiologi- Bureau,Technical Communica- cally meaningfuldistributional patterns of tion No. 13. London. thesespecies. Grzybowski,J.A. 1992. Southern GreatPlains Region (Fall 1991). CONCLUSIONS American Birds 46:113-117. Plegadisibises with charactersintermediate --1999. Southern Great Plains betweenGlossy and White-facedsuggest Region(Spring 1999). North hybridizationevents between these species in American Birds 53: 403-405. a circumstancein which Glossy Ibis is very Howell, S.N.G., and B.M. de rare relative to White-faced Ibis. The extent Montes. 1989. Status of the • of hybridizationexpected in otherareas is GlossyIbis in Mexico. uncertain, as so little is known about American Birds 43: 43-45. courtshipand the influenceof isolating Kaufman,K. 1990. A Field Guide Figure10.Apparent subadult Plegadis hybrid or variant White-faced Ibisnear Salt Plains N.W.R 30 May 2002.This bird may be a White-faced mechanismsin this group,or the extentto toAdvanced Birding. Houghton inretarded juvenile color (see text). The brown eye has slight flecks of whichit maybe occurring where both species Mifflin. Boston. red.But notke the largely plum-gray facial skin with brighter patch are more common. Nonetheless,with the Mayr,E. 1965.Animal Species anteriorly,aswell as the pale plum or maroon lines forming the currentexpansion of vagrantsof bothspecies andEvolution. Belknap Press, bordersof the facial skin, tones characteristic of the other into the breedingranges of the other,the Cambridge,Massachusetts intermediates.Photograph byJames W.Arterburn.

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