Hybridization Between Glossy and White-Faced Ibises
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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,