WESTERN BIRDS Volume 21, Number 3, 1990 THE TAXONOMY, DISTRIBUTION, AND STATUS OF COASTAL CALIFORNIA CACTUS WRENS AMADEO M. REA, San Diego Natural History Museum, P. O Box 1390, San Diego, California 92112 KENNETH L. WEAVER, 1113 SenwoodWay, Fallbrook,California 92028 The southerncoastal sage scrub is a distinctiveplant communityof southernCalifornia (Munz and Keck 1959, Mooney 1977). Beginningvery narrowlyin the Santa Barbararegion, it is bestdeveloped in Ventura,Los Angeles,Orange, and San Diegocounties, and endsin northwesternBaja California,where a differentplant assemblage,the maritimedesert scrub, begins(Thorne 1976). One very prominentfeature of coastalsage scrub is thicketsof cactus,including the CoastalCholla, Opun tia prolifera, and two speciesof prickly-pears,Opuntia littoralis and O. oricola. The coastalsage scrub is the primary habitat of two birds, the California Gnatcatcher, Polioptila californica californica, and the San Diego Cactus Wren, Campylorhynchusbrunneicapillus sandiegensis, that are decliningrap- idlybecause of lossof habitatto urbanization.(For explanationof variations in the spellingof the CactusWren's scientificname, see Appendix 1). This paper hasfour goals.First, we presentthe charactersdistinguishing C. b. sandiegensisas a validsubspecies distinct from adjacentraces of Baja Californiaand the interiorcontinental deserts. The charactersare givenin sufficientdetail that anyone with a specimenin hand shouldbe able to identifyit. Second,we evaluatethe taxonomicstatus of the CactusWrens occupyingVentura, Los Angeles,and Orange counties.In the original description (Rea 1986:119), these were referred to as less typical sandiegensis,and the birdsfrom the San FernandoValley, Los Angeles Co., were called anthonyi (Phillips 1986:120). Third, we analyze the habitatrequirements of C. b. sandiegensis.And finally,we presentcensus data from the last ten years demonstratingthe rapid declineof the San Diego CactusWren due to habitatloss. TAXONOMIC BACKGROUND Taxonomistshave long recognizedthat the Cactus Wren population isolatedalong the Californiacoast is distinctive,but opinionsdiffered as to Western Birds 21:81-126, 1990 81 COASTAL CALIFORNIA CACTUS WRENS the significanceof the difference(Table 1). Debate often focusedon whetherthe wrensbelonged to a continentalor a peninsularsubspecies. The peninsularforms in Baja California(C. b. bryanti and C. b. affinis, including"C. b. purus")have the entiretail black barred with white, except for the centralbrown pair of rectrices,have little or no buff washon the flanksand abdomen, and have large spots rather uniformly distributed over the underparts.The blackthroat spots are mostlydouble on eachfeather. In contrast,the variouscontinental forms have quite a differentappearance. Their tailsare essentiallyblack except for the browncentral pair. The black feathershave a subterminalwhite bar Withadditional white barsbeing restrictedto the outerone or two pairsof rectrices.The birdshave a strong cinnamon-buffwash on the abdomenand a clusterof largeblack spots on the throat.There is usuallya singlelarge spot along the shaftof eachthroat feather.The remainingunderparts are morefinely spotted. The differencesbetween the two groupsof subspeciesare readilyap- parentin the fieldas well as in the hand.Actually the two groupslook like differentspecies. Furthermore,the two subspeciesnearest the southernCalifornia coastal populationdiffer strongly in dorsalcoloration. Carnpylorhynch us b. bryanti of northernBaja (31ø-29øN) is rather uniformdark umberbrown above, whereasC. b. anthonyi of the desertsof southernCalifornia, adjacent northeastBaja California,southern Arizona, and northwesternSonora has a brownishgray backthat contrastswith the darker,strongly rufous crown and nape (seeFigure 1 for distributions). When A. W. Anthony(1894) erectedthe subspeciesC. b. bryanti for the CactusWrens of northernBaja California(type localitySan Telmo), he referredSan Diego Countybirds to his new race. He wrote, "eastof the CuyamacaMts., ! am unableto find any indicationof either bryanti or Table 1 Historical Treatment of Coastal Cactus Wrens Author Date Disposition A. W. Anthony 1894 Racedifferent from that in Baja or desert (unnamed) E. A. Mearns 1902 bryanti H. S. Swarth 1904 coue$i R. Ridgway 1904 brpanti{not typical) in San Diegoregion; couesi in LosAngeles region F. Stephens 1904 bryanti "blendinginto couesi(or anthonyi)" J. Grinnell 1915 "Meetingground of couesiand bryanti"in samelocality, possibly without intergradation J. Grinnell 1921 couesiwith slighttendency toward bryanti G. Bancroft 1923 Distinctdisjunct subspecies (unnamed) J. Grinnell 1928 co•esi Grinnell and Miller 1944 couesi G. Bancroft 1946 Western "group" A.M. Rea 1986 Describedsubspecies sandiegensis M. R. Browning 1990 Recognizedsandiegensis 82 COASTAL CALIFORNIA CACTUS WRENS ...... :::::::<:::::!'J••: ::::::::::::::::::::::::::::::::::::::::::::::::::::::: .':':'":':':'i'•:':':':':':':':':':'•':'•'•:':':':':' ,.,.i:!:i:!:i:i:i:i:i:i:i:i:i:i:i:i:: !:i:!:i:i:i:i:i:i:i:i:i:i: 0 :':':':':';':':':':':';':':':': ,';':':':';';':':';':' ';':':':':':': __ X :::::::;: :::::::::::::::::::::::: ,,',.::•',,"•::::::::::::::::::::::: • :,:,:,:.:,:,:,:,:,:,:,:,: ,,:,:,:.:,:,:,:.:,:,:,:,:,-I-,:,:,:,:,:,: •; ,',:,;,',;,',;,:,:,:1,:,:,: :,:,:.:,:,:,:,:,:,:,:,:,:,:•:,:.:,:.:,:, • •: ::::::::::::::::::::::::::::::::', , ,•'.,,:•:::::::::::::::::::::::: •:::i:i:i:i:!:i:i:'":,•" '•>•'•:'.•', .... .i" .:..':'::'"''' ':i:i:i:i:i:i :::::, .'.','.'.:,::::: :::::::::::::::::::::::::: .,,.. :.,,-,, o .:':'::i:i:i::.:.,'i.::i:!:!:!,:i:i'!O:!:i:i:i:::::i:i:i:i:' '""'::i:i:i:i:i:i:i:i:i:i:,Oi:i:i:i:i:i:i:i:i" ..• ß :::::::::::::::::::::::::::::::::: 113 "!:!:!:i:!:i:!,:i:i:i:.•::• - •_ _;•'•..- .......... •i!•i:•ii••?: :.•!i:: ...:...-,:..... 83 COASTAL CALIFORNIA CACTUS WRENS affinis," notingthat birdsfrom the interioror desertportion of the county are unlikethose of BajaCalifornia but the sameas those from the restof the Sonoran Desert of southernCalifornia, Arizona, and New Mexico. He also noted that the rufouswash of the underparts"is not so pronouncedin westernSan Diego County skinsas those from San BernardinoCounty (Cal.),Arizona, and New Mexico."In an addendumAnthony noted, "Owing to the lackof material,I am unableto makea satisfactorydisposition of the CactusWren from northof the boundary.The seriesat handpoints toward a raceinhabiting the southwesternpart of California,differing from the bird of Arizona,New Mexico,and Texas."Also in 1894, Anthonycollected four specimens(now in the Carnegie Museum, Pittsburgh)from Valle de las Palmasand Carrizo Valley, a bit southeastof Tijuana in Baja California. These alsoshow the San Diego combinationof characters. The CactusWren as a specieshad beendescribed originally by Lafresnaye in 1835 from "Californie."Edgar A. Mearns(1902) attemptedto determine where, in what was broadlyconceived in the 1830s as constitutingCali- fornia, the originalspecimen might have been taken because,as Mearns explained,"the CactusWren of the portion of Californiawest of the Coast Range Mountainsis different from that of east." At his request,Robert Ridgwayat the SmithsonianInstitution examined the type specimenpre- servedat the BostonSociety of NaturalHistory. He concludedthat it best matched material from Guaymas,Sonora, thus fixing this as the type locality.Mearns then describedthe subspeciesC. b. anthonyi with type localitynear Tacna,Yuma County,Arizona, and gaveits rangeas "interior desertsof the southwesternUnited States, south into the Mexican statesof Chihuahua,Sonora, and northeasternLower California (eastof the Coast Range)." He retained the populationwest of the PeninsularRanges in bryanti. Swarth (1904) took exceptionto Mearns' treatment, consideringC. b. anthonyi and C. b. bryanti (at leastas representedin southernCalifornia) both synonymsof C. b. couesi(type localityLaredo, lower Rio Grande, Texas).Swarth conceded that bryanti might be a validrace from the Baja Californiaarea Anthonyascribed to it. Swarth'sinability to see more than one subspeciesis hardlysurprising because his specimens were all fromthe rangeof anthonyi as we defineit here. The same year Ridgway (1904) completed the third volume of his monumentalBirds of North and MiddleAmerica. He treatedC. b. anthonyi as a synonymof C. b. couesiof the lower Rio Grande, rangingwest to Orange, Los Angeles,and interior San Diego counties,and includedthe "coast district of San Diego County" in the range of C. b. bryanti of northernBaja California. Before the volumewas issued,Ridgway received Swarth's publication and noted in an addendum(Ridgway 1904:753-754) that he agreedwith Swarth in synonymizinganthonyi but not with Swarth's treatment of bryanti: "Mr. Swarth's California material apparentlydid not contain a specimenfrom the coast district(or any other portion?)of San Diego County, to which H. b. bryanti (not typical,however) is restrictedin its California range." The third edition of the A.O.U. Check-list(1910) es- sentiallyfollowed Ridgway's (1904) treatment. 84 COASTAL CALIFORNIA CACTUS WRENS Frank Stephens(1904) likewiseresponded to Swarth'spaper. Stephens gavean excellentanalysis of the northwestcontinental and the two penin- sularraces. On the basisof a "hastystudy" of A. W. Anthony'sspecimens, Stephensassigned two skinsfrom San Diegoto bryanti, notedthe differ- encein crowncolor between the birdsof coastalSan Diego and the interior, but concludedthere were "morecones/[or anthonyi, if distinct]south of the borderthan bryantinorth of it." He did not specifywhether