FEATURED PHOTO

APPARENT HYBRIDS BETWEEN THE AMERICAN AND BLACK-NECKED IN CALIFORNIA

JOSEPH MORLAN, 1359 Solano Dr., Pacifica,California 94044 ROBIN E. DAKIN, 3305 Wilcox Avenue, San Jose, California 95118 JIM ROSSO, 2227 N LexingtonSt., Arlington,Virginia 22205

Birdsmay hybridizemore frequentlyin captivitythan in the wild becausenatural isolatingmechanisms can fail undercaptive conditions (Sibley 1994). Until recently the onlydocumented hybrid between the (Recurvirostra americana) andthe Black-neckedStilt (Himantopus mexicanus) was a birdhatched in May 1971 froma knownmixed pair heldin captivityat the San FranciscoZoo (Principe1977). We report here three similarapparent hybrids in the wild. In all cases,the presumedhybrid resembled an AmericanAvocet but showed a dark stripeup the back of the neck, a straighterbill, a dark smudgeon the face, and intermediateleg coloration.Also the whitepatch normally visible on the foldedwing of an AmericanAvocet was reduced so that onlya narrowstrip of whitefeathers was visible.All threewild hybridshad a fairlystraight bill, slightlyshorter than that of an AmericanAvocet, with a slightupturn at the tip. In addition,all threebirds appeared to have tibiaslonger than thoseof a typicalAmerican Avocet. This combinationof intermediatecharacters and the similarityof all threewild to the knowncaptive hybridsupport the hypothesisof hybridorigin rather than coincidental odd mutations. The shorterbill of the captivebird may havebeen a sexdifference. The captivebird wasthought to be a male,and males of thesespecies have shorter, straighter bills than do females. The firstapparent wild hybridwas discovered by ArnoldSmall and observedby a classfrom UCLA includingHerbert and OlgaClarke on 10 March 1994. It wasseen mid-morningin a shelteredpond at the PointMugu Naval Air WeaponsStation at Port Hueneme,Ventura County, where it was photographedby RobertE. Munsey,Jr. (Figure1). Photosof thisbird resemble those of theMoss Landing discovered only threedays later, but the hybridat PointMugu is much paler cinnamon on the headand neck,has a lesspronounced dark facepatch, more extensivewhite on the wings,a straighterbill, and pinkerlegs. The secondapparent wild hybrid was found by Rossoon 13 March 1994, whilehe led a birdingclass field trip. Rossophotographed this individualin the wetlandsof ElkhornSlough on the eastside of Highway 1 justnorth of MossLanding Harbor, MontereyCounty (see back cover).This bird was observedfor approximately20 minutesin the late afternoonabout 50 yardsfrom the road. For mostof that time it was solitary,but it alsobriefly associated with two Black-neckedStilts. Its hunting procedurewas similar to thatof the Black-neckedStilt, stabbing at possiblefood items in the cordgrass(Spartina sp.). Dakin foundthe third apparenthybrid during San FranciscoBay SnowyPlover surveysin a closedarea of saltponds in Hayward,Alameda County, California, on 29 May, 31 May, and 17 June,2003 (Gloveret al. 2003). DavidCardinal photographed thisbird on two occasions.His colorimages were publishedby Sharp(2003) and Messinger(2003), and a monochromeimage was publishedby Dakin (2003). The cinnamoncolor on the head and neck of the Haywardbird was pale and diffuse,similar to that of the PointMugu bird. The stripeof blackup the backof its neckdid not extendto the crownas it did on the MossLanding and Point Mugu

WesternBirds 35:57-59, 2004 57 FEATURED PHOTO

Figure 1. Presumedhybrid American Avocet (Recurvirostraamericana) x Black- neckedStilt (Himantopus mexicanus) near Oxnard, Ventura Co., 10 March 1994.

Photo by Robert E. Nlunsey Jr.

hybrids.In this respectit resembledthe captivehybrid at the San FranciscoZoo. A patch of gray feathersaround the eye and coveringthe crown suggestedthe facial markingsof a Black-neckedStilt, but these markingswere paler on than the Moss Landingbird. The white area on the foldedwings was even more reducedin this individualso that the wings, at times, appearedalmost entirely black. The head and bodyshape of the Haywardhybrid was similarto that of an AmericanAvocet. This bird was also heard to give intermediate vocalizations,but no recordingswere obtained. The copulatorybehavior of these two speciesis almostidentical (Sordahl 2001), and attemptedcopulation with inanimateobjects has been reportedfor at leastsix of the ten speciesof recurvirostrids,including both the AmericanAvocet and Black- neckedStilt (Hamilton 1975). Such similarityin copulatorybehavior, combined with the reportedlack of discrimination,provides additional support for the hypothesisof wild hybridizationin thesespecies. Within the genus Himantopus, hybridizationin the wild has been reported frequentlyin New Zealandbetween the highlylocalized. critically endangered Black Stilt (H. novaezelandiae)and the widespreadBlack-winged Stilt (H. himantopus) (Reedet a11993, Pierce 1984, Pierce 1996, Greene 1999, MacAvoyand Chambers 1999). Thus intrageneric hybrids have been reported more often in the Recurvirostridaethan intergenerichybrids. An analysisof the distributionof hybridsin thisfamily, however, suggests that breedingsympatry may be at leastas importantas geneticsimilarity in predictingwhich hybridcombinations are likelyto occur. As thisarticle was in preparationwe learnedof a possiblehybrid between the Pied Avocet(R. avosetta)and Black-winged Stilt, photographed2 May 2004 by GerritJan Klop at Culemborg,Netherlands. Photos of the bird on the World Wide Web (http:/

58 FEATURED PHOTO

/members.lycos.nl/digivogels/klutigl.jpgetc.) show its strongresemblance to the PiedAvocet, but it alsohas a whiteforehead, pinkish legs, and an almoststraight bill, suggestingthe Black-wingedStilt. We are unawareof any hybridspreviously docu- mentedbetween these two species.A redband above the intertarsaljoint on the right leg of thisindividual adds to the mysterysurrounding its originand identity. We thank RobertE. Munsey,Jr., WilliamPrincipe, and KimballGarrett for helpful informationon the Point Mugu hybrid. Kimball Garrett revieweda draft of this manuscriptand providedcomments which improved it substantially.The San Fran- ciscoBay Bird Observatoryand the U.S. Fishand WildlifeService provided funding and logisticsupport for Dakin duringher surveys.

LITERATURE CITED

Dakin, R. 2003. Serendipityand stavocets.The Stilt (SFBBONewsletter), summer, p. 5 Glover,S. A., Cole, L. W., Terrill, S. B., and Rogers,M. M. 2003. The spring migration:Middle Pacific Coast region. N. Am. Birds57:398-401. Greene, B. 1999. Geneticvariation and hybridizationof BlackStilts (Himantopus novaezelandiae)and Pied (H. h. leucocephalus),order . New Zealand J. Zool. 26:271-277. Hamilton,R. B. 1975. Comparativebehavior of the AmericanAvocet and the Black- neckedStilt ().Ornithol. Monogr. 17. MacAvoy,E. S., and Chambers,G. K. 1999. Part 2. MitochondrialDNA sequence from Blackand PiedStilts. Science for Conservation(Wellington) 105:15-29. Messinger,L. 2003. Ear to the ground.Bay Nature 3(4):42 Pierce, R. J. 1984. Plumagemorphology and hybridizationof New Zealandstilts Hima ntopus spp. Notornis31:106-130. Pierce, R. J. 1996. Ecologyand managementof the Black Stilt Himantopus novaezelandiae. Bird Cons. Int. 6:81-88. Principe,W. L., Jr. 1977. A hybridAmerican Avocet x Black-neckedStilt. Condor 79:128-129. Reed, C. E. M., Nilsson,R. J., and Murray, D. P. 1993. Cross-fosteringNew Zealand'sBlack Stilt. J. WildlifeMgmt. 57:608-611. Sibley,D. 1994. A guideto findingand identifying hybrid birds. Birding 26:163-177. Sharp, M. F. (ed.).2003. Pictorialhighlights. N. Am. Birds57:432. Sordahl,T. A. 2001. Copulatorybehavior of AmericanAvocets and Black-necked Stilts. Auk 118:1072-1076.

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PublishedSeptember 1, 2004 ISSN 0045-3897