Recolonization of the Flicker and Other Notes from Isla Guadalupe, Mexico

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Ornithology Program (HRC) Harry Reid Center for Environmental Studies

2001

Recolonization of the Flicker and other notes from Isla Guadalupe, Mexico

Paul R. Sweet American Museum of Natural History

George F. Barrrowclough American Museum of Natural History

John Klicka University of Nevada, Las Vegas, [email protected]

Liliana Montanez-Godoy Universidad Nacional Autonoma de Mexico

Patricia Escalante Universidad Nacional Autónoma de México

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Repository Citation Sweet, P. R., Barrrowclough, G. F., Klicka, J., Montanez-Godoy, L., Escalante, P. (2001). Recolonization of the Flicker and other notes from Isla Guadalupe, Mexico. Western Birds, 32(1), 71-80. Available at: https://digitalscholarship.unlv.edu/hrc_ornithology/34

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This Article has been accepted for inclusion in Ornithology Program (HRC) by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. RECOLONIZATION OF THE FLICKER AND OTHER NOTES FROM ISLA GUADALUPE, MEXICO

PAUL R. SWEET and GEORGE F. BARROWCLOUGH, Departmentof Ornithol- ogy, AmericanMuseum of NaturalHistory, Central Park West at 79th Street, New York, New York 10024 JOHN T. KLICKA, J. F. BellMuseum of NaturalHistory, University of Minnesota,St. Paul,Minnesota 55108 (currentaddress Barrick Museum, University of Nevada,Las Vegas,Nevada 89154) LILIANAMONTAi•IEZ-GODOY and PATRICIA ESCALANTE-PLIEGO, Instituto de Biologia, UniversidadNacional Aut6noma de M•xico, Apartado Postal 70-153, 04510 Distrito Federal, M•xico

ABSTRACT:During a visitto IslaGuadalupe from 31 May to 3 June 1996, we documentedthree speciesnew to the island,the Barn Owl, Swainson'sThrush, and HoodedOriole, and establishedfirst breeding records for the EuropeanStarling and WesternMeadowlark. Red-shafted Flickers are now breeding on the island,representing a recentrecolonization from the mainlandfollowing the extinctionof the endemic population.We investigatedthe validityof Colaptes auratus rufipileus and con- cludedthat it doesnot meet the standardfor phylogeneticspecies but differsfrom C. a. collarisat the 75% levelusually associated with subspecificrank. Damage to the cypressforest by goats continues,and all speciesdependent on these trees are threatenedby lossof habitat.

IslaGuadalupe is a volcanicoceanic island lying 260 km westof the coast of BajaCalifornia (29 ø 00' N, 118ø 20' W). It is some37 km longwith an areaof 250 km2 and reaches an elevation of 1298 m. Thehistory and status of the avifaunahave been reviewed by Howelland Cade(1954) andmore recentlyby Jehl and Everett(1985). Subsequentobservations have been reportedby Dunlap (1988), Oberbaueret al. (1989), Mellinkand Palacios (1990), Howelland Webb (1992), and Galloand Figueroa (1996). Here we reporton birdsobserved and collectedon a visitto IslaGuadalupe between 31 May and 3 June 1996. Mapsof the island,showing localities mentioned here, have been providedby Jehl and Everett(1985) and Moran (1996). Three of the specieswe recordedrepresent first records for the island;in addition,we confirmedthe breedingof two recentlycolonizing species and notedthe recolonizationof a previouslyextirpated species whose taxonomic status we reexamined.

ITINERARY

We spenta few hoursat the navalbase (Melp6mene Cove or PuntaSur) upon our arrivalon the islandand then traveledthe dirt road from there to the airstrip(Campo Pista: 29 ø01' N, 118ø 17'W), wherewe spentone night anda morningobserving and collecting.We thencontinued to the cypress grove(29 ø 07' N, 118ø 20'W, 1165m),near the highest point on the island, where we spent two nights.One night was spent at the fishingvillage (CampoTepey•c or Campo Oeste).We returnedto the naval baseby launch.

Western Birds 32:71-80, 2001 71 NOTES FROM ISLA GUADALUPE

CONSERVATION

Unfortunatelythe decimationof the island'svegetation by feral goatsis continuing;we saw large numbersof goatsthroughout the island.They appearedto be most numerousin the centraland northernportions of the island,nearer the major sourceof freshwater. Moran (1996) reviewedthe historyof goat damage to the flora of the islandand estimatedthat the youngestof the endemicGuadalupe Cypress (Cupressus guadalupensis) were well over 100 yearsold. Apparently,in excessof 20,000 goatswere removedfrom the islandin 1971, reportedlyleaving only 239 animalsat that time (AgrazGarcia 1978). Moran (1996) estimatedthat the population had reboundedto at least7000 in 1994. Low-intensityhunting by fisher- men and marineshas had littleimpact on the populationin recentyears. In addition,attempts at protectingthe remainingcypress forest fragment with a wire fence have failed.The fenceis breachedin many places,and a gate is missing;large herds of goats were observedtrooping through the cypressesat all hours,leaving virtually no vegetationof consequencewithin the understoryof the grove(Figures 1 and 2). In addition,the bark of many of the treesshowed evidence of damageby goats.Clearly only the complete removalof goatsfrom the islandor a securefence with a full-timewarden will guaranteelong-term survival of the cypressesand the birdsdependent on them. We also saw feral dogs and cats on the island,but only in small numbers.

ANNOTATED LIST

LaysanAlbatross (Phoebastria immutabilis). First recordedbreeding on IslaGuadalupe in 1986 (Dunlap1988). Its statusup to 1992 was reviewed by Gallo and Figueroa(1996). We brieflysurveyed the rockyplateau above the naval base and observedsix full-grownchicks and one adultbird. The youngbirds were closeto fledgingwith down remainingonly on the head and neck. Brandt'sCormorant (Phalacrocorax pencillatus). A pair was seenflying past IsloteZapato at the southanchorage. American Kestrel (Falco sparverius). Fairly common and observed throughoutthe island. Western Gull (Larus occidentalis).A few were seen along the coast between Campo Tepeyficand Melp6mene Cove. Mourning Dove (Zenaida macroura). Common throughoutthe island. Many were observedcoming to drink at the freshwater springbelow the north end of the cypressgrove. Barn Owl (Tyto alba). A singleflank feather(Colecci6n Nacional de Aves 25550) found near the airstrip providesthe first documentationof the occurrenceof this specieson the island,although we saw or heard none. There have been severalanecdotal reports of large owlson the island,and previousauthors assumed that theserefer to the Great Horned Owl (Bubo virginianus). DuringEdward Palmer's initial study of the avifaunaof the island(Ridgway 1876), two unidentifiedspecies of owls were observedbut not collected.

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Accountsof B. virginianuson the islandappear to originatewith Palmer's assistant(Bryant 1887) who reporteda "HornedOwl (Bubo)"and that "the Mexicans"reported a "largeowl ("Tecolote")."It is possiblethis represents a misunderstandingon behalfof the assistant:tecolote in MexicanSpanish couldrefer to any smallowl, buho (interpretedas Bubo?)to any large owl. Presumablythe tecoloteis the BurrowingOwl, and Bryant(1887) assumed that the largeowl wasa Great Horned. However,it now appearsplausible that theseearly reports refer to the Barn Owl, a speciesthat is knownfor its abilityto colonizeislands, including Isla Socorro some 500 km from the southerntip of Baja California.No Great Horned Owlswere heardduring our visit. BurrowingOwl (Athene cunicularia).Fairly common; several pairs were seenbetween the southend and the cypressgrove. Anna'sHummingbird (Calypte anna). Commonin the cypressgrove. Northern Flicker(Colaptes auratus [cafergroupl). Fairly common in the cypressgrove; we foundseveral active nests and collectedtwo birds.A male (CNAV 24795) had enlargedtestes and a female(CNAV 24794) had yolking eggs.The endemicform, C. a. rufipileus,has not beencollected since 1906 and has been considered extinct. We believe the birds we saw and collected were mainland Red-shaftedFlickers and that Isla Guadalupehas been successfullyrecolonized by flickersfollowing the extirpationof the endemic subspecies(see below). RockWren ($alpinctesobsoletus). Abundant from the beachesup to the cypressforest. Swainson's Thrush (Catharus ustulatus). We collected a male with moderatelyenlarged testes (CNAV 24746) in the cypressgrove; no other individualswere seenor heard.This is the firstrecord of thisspecies on Isla Guadalupe.Presumably it representsa vagrant;Swainson's Thrush occurs throughoutBaja Californiaas a migrant(Howell and Webb 1995) and has been recordedand presumedto be migratingin the mountainsof Baja Californiaas late as early June (Wilbur1987). Escalante-Pliegocompared the specimento seriesat CNAV and tentativelyidentified it as nominateC. u. ustulatus,common in migrationon the nearbymainland. Northern Mockingbird(/•/im us polyglottos).We saw two togetherin an openarea near the cypressgrove but could not determineif theywere a pair. Bryant (1887) observedtwo birdsin 1886, and subsequentlyindividuals were seennear the airstripin January1988 (Howelland Webb 1992) and November 1989 (Mellink and Palacios1990). EuropeanStarling ($tu rnus vulgaris).This species is now commonon Isla Guadalupe.We saw a flock of over 100 birdsnear the springbelow the cypressgrove. Previousauthors noted a few starlingson the islandbut suspectedthat they might representonly wintervisitors (Howell and Webb 1992). However,we confirmednesting in tree cavitiesin the cypressgrove and collectedone juvenile(CNAV 24826). GuadalupeJunco (Junco insularis).This distinctive,endemic taxon has beenrecognized as a speciesin recenttreatments (Howell and Webb 1995). We foundit commonwithin the cypressgrove but did not see it anywhere else on the island.At the time of our visit, fledglingsin streakyjuvenal plumagewere abundantand somemales were stillsinging. Although other

73 NOTES FROM ISLA GUADALUPE authorshave found juncos down to sealevel outside of the nestingseason, we sawthem only in the remnantstand of cypress. WesternMeadowlark ($turnella neglecta).Jehl and Everett(1985) re- portedonly a recordfrom 1886, but Howell and Webb (1992) saw 35-40 near the airstripin January1988 and suggestedthat the speciesmight breed. Mellink and Palacios(1990) alsoobserved it in November 1989. We foundthis species to be commonthroughout the island,particularly in the extensivegrasslands of the centralplateau, with flocksof up to 50 birds. Maleswere singing from prominentperches. We collectedtwo birds,a male with enlargedtestes (CNAV 24798) and a femalewith a regressingbrood patch(CNAV 24836). Evidentlythis species has successfully colonized the island. HoodedOriole (Icterus cucullatus). We sawand collected a singlemale, whichhad slightlyenlarged testes, in a solitaryeucalyptus tree at Campo Pista (CNAV 24756). This is the first islandrecord and presumablya vagrant;however, we were unableto reachthe palm groveon the north slope of the island(Moran 1996), which perhapscould harbor a small breedingpopulation. House Finch (Carpodacusmexicanus). Common from sea level to the cypressgrove. Recently fledged young were abundantduring our visitand maleswere singing.

SYSTEMATIC STATUS OF THE FLICKERS OF ISLA GUADALUPE

Ridgway(1876) originallydescribed the subspeciesof the Red-shafted Flickerfrom Isla Guadalupe,emphasizing the "brighttawny forehead"-- hencethe namerufipileus--as the diagnostic character. He suggestedrump color,bill length,wing length,tail length,and the amountof blackon the undersideof the tail as additionalcharacters. Bryant (1886) treatedthe flickersof IslaGuadalupe as a full species. Here we reevaluate the taxonomic status and characteristics of the GuadalupeFlicker in orderto determinethe provenanceof the flickerswe observedon the island.A seriesof C. a. rufipileus is availablein the ornithologicalcollections of theAmerican Museum of NaturalHistory; these birdswere collectedin the monthsof May, July,and August. For compara- tive materialof mainlandflickers that might representthe sourcefor a possiblerecolonizing population, we borrowedspecimens from a numberof museums(see Acknowledgments). To ensurethat we were workingwith individualsfrom breedingpopulations, and not migrants,we usedadult specimensof both sexesfrom late spring and summerfrom mainland breedinglocalities. Few specimenswere availablefrom any one localityfor the breedingseason; therefore, our mainland sample was composed of Red- shaftedFlickers from the mountainsof northern Baja California,the southernCalifornia ranges from San Diego north to the San Bernardinos, the coastalranges north to Monterey,and a few birdsfrom the Sierra Nevada. These samplesrepresent C. a. collaris, a form with a range proximalto and a phenotypesimilar to the recent Guadalupebirds (a comparisonof extremesof C. a. collaris and the paler C. a. canescens,

74 NOTES FROM ISLA GUADALUPE courtesyP. Unitt,indicates that the two recentisland birds are nottypical of the highlymigratory canescens). In all, our final sampleconsisted of one recentmale and one recent female flickerfrom Isla Guadalupe,which we treatedas of unknownorigin, 11 malesand 13 femalesfrom Isla Guadalupe from the late 19th and early 20th centuries,representing C. a. rufipileus, and 13 male and 15 female specimensfrom Baja California and southern California, representingC. a. collaris. Sweet and Barrowcloughindependently measured, for all specimens, culmenlength (from base of skull),wing chord (bendof wing to longest primary),tail length (to tip of longestcentral rectrix), and width of the terminal black band on the ventral surface of one of the central rectrices; some measurements could not be taken because of molt or broken feathers or bill. In addition,we independentlyarranged the specimensinto graded seriesof crown/foreheadcolor, by sex,from most to leastrulescent; we then assignedthe valueof one to the mostreddish bird, the valuetwo to the next birdin the series,etc. (R. W. Dickerman,pers. comm. suggested that foxing was not a significantproblem in flickers).In this way, we obtainedtwo estimates for each of four mensural characters and a color character for the Guadalupe,mainland, and two new flickers.We averagedthe two values, reducingmeasurement sampling error. We usedthe computerpackage SAS (Windowsversion 6.12: procedure univariate; SAS Inst. 1988) to produce box plots for the crown color estimates.Because the colorscores we assignedthe birdsare on an arbitrary scale,which is undoubtedlynonlinear, we useda nonparametric,descriptive techniquefor analyzingthose data. Box plots simply encodefrequency informationand requireno assumptionsabout the underlyingdistribution: the heavyvertical lines indicate the range,the solidlower and upper edges of the box correspondto the 25th and 75th percentilesof the distribution, the dashedline is the 50th percentile(median), and the crossis the mean of the distribution(Figure 3). Crown color,the principalcharacter originally usedto diagnosethe GuadalupeFlicker, clearly varies substantially between the mainlandand the islandfor both sexes.The two new specimens,a male and a female, both have scoresunequivocally placing them with the mainland series. Ridgway(1876) alsomentioned a pink washon the rump as a character for the islandrace, but we were unableto finda consistentdifference in rump colorand did not investigatethat trait further.In the four measurements,the islandand mainland forms completely overlapped in culmenand tail length. In wing lengthand widthof the blacktail bar, the meansof the two samples for males and females differed, though with substantialoverlap in the distributions(box plots not shownhere). However, neither measurement had as great a power for discriminationas the crowncolor. Because these four measurementsshowed varying patterns of correlation(Table 1), we useda principal-component(PC) analysis to determinewhether there was a linear combinationof measurementsthat, independentof crowncolor, yielded a segregationof the islandbirds. We adopteda PC ratherthan a discriminant- functionanalysis (DFA) because our samplesizes were smalland PC analysis identifiesthe "natural" combinationsof the measurementsrepresenting

75 NOTES FROM ISLA GUADALUPE

Figure1. View northwestfrom remainingcypress grove. Young trees do not existand oldertrees (such as the one in foreground)have had piecesof barkstripped by goats. Photo by Paul R. Sweet

...

Figure2 View into remnantsof cypressgrove, showing lack of understory. Photo by Paul R. Sweet

76 NOTES FROM ISLA GUADALUPE

30- o 99

20-

Guadalupe Mainland Guadalupe Mainland

Fiõure3. Box plotsfor crown color scoresfor male and femalespecimens of Red- shaftedFlickers from ]slaGuadalupe (historical sample), the southwesternmainland, and two recent]sla Guadalupe specimens, (tdanõles). mostof the variationin a setof data;in DFA, desiredgroupings are madeon an a priori basisand high discriminationamong groupsthat representsa verysmall fraction of the actualtotal variation is sometimesfound. Using the matrix of charactercorrelations, we foundPC axes,separately for the two sexes, that summarizedmost of the variation in measurementswith two vectors(SAS Inst. 1988: procedureprincomp). For males,the firsttwo PC axesexplain 45% and 27% of the totalvariation, respectively; for females, the correspondingvalues are 41% and 38%. The characterloadings on the firsttwo PC axesare availablefrom the authors.In Figure4 we haveplotted

Table I Matrix of Correlation Coefficients between MensuralMeasurements of Isla Guadalupeand Main- land Red-shafted Flickers a

Culmen Wing Tail Tail Tip

Culmen -- -0.076 -0.031 0.292 Wing -0.182 -- 0.091 -0.640 Tail 0.276 0.515 -- 0.372 Tail Tip 0.409 -0.321 0.198 --

aMalesabove and femalesbelow diagonal.

77 NOTES FROM ISLA GUADALUPE

o o 3 99 o

o ß o o ß o• i o Oo o 0 o ¸ ß O0 O0 ß

o ß I I I I I -1 0 1 2 3 -3 -2 -1 0 1 2 3 PC1 Figure4. Scoresof Isla Guadalupe(solid circles) and mainland(open circles)Red- shaftedFlickers on firsttwo PC axesbased on measurementsonly. The recentfemale from Isla Guadalupeis indicatedby a triangle;the recent male specimenwas incompleteand so cannot be included.

the PC scoresfor the IslaGuadalupe, mainland, and recentflickers for which a full set of measurementswere available.Unfortunately, some birds, includingone of the recent specimensfrom Isla Guadalupe,had missing valuesand couldnot be includedin the PC analysis. For both sexes,the firstPC axisyielded a good,but not perfectdiscrimi- nationbetween the islandand mainlandspecimens. In both casesthe island birdshave greater average PC1 scoresthan do the mainlandspecimens. The pattern of characterloadings indicates that for both sexesthe PC1 axisis largelya contrastof wing lengthvs. tail tip. For the males,sample location appears to be independentof the secondPC axis; for females, island spedmenshave somewhat lower average scores on PC2 thando thosefrom the mainland.The patternof characterloadings indicates that PC2 is at least in part a winglength plus tail lengthaxis. The recentisland female is clearly associatedwith the mainlandspecimens. Our analysisof crowncolor plus four measurements indicates that the two recentflickers collected on IslaGuadalupe have characteristics placing them with mainlandflickers rather than with the historicalpopulation. Greenway (1967) summarizedthe historicalstatus of the GuadalupeFlicker; it was last collectedin June 1906. None were recordedafter that in spiteof a number of expeditionsand searches.However, Jehl and Everett (1985) reportedthat in late 1972 flickerswere once againseen on the island;such observations have continued(e.g., Howell and Webb 1992), but the subspecificstatus of the recently observedbirds was in doubt. The long historicalgap in observationsof flickersbetween 1906 and 1972, the continuingpresence of flickerssince then, andour character analysis, taken together, suggest that IslaGuadalupe was recolonized by mainlandRed-shafted Flickers in the late 1960s or early 1970s and that the endemicsubspecies is extinct.

78 NOTES FROM ISLA GUADALUPE

Like mostbirds, the GuadalupeFlicker was described before the invention of statisticaltests and quantitative studies of populationvariability. In partour detailedanalysis of these flickerswas basedon an interestin ascertaining whether the subspeciesC. c. rufipileus actuallydesignates a distinctive endemicpopulation (e.g., Barrowclough1982). One modern, statistical standardfor the recognitionof subspeciesis the "75% rule" (e.g., Mayr 1969). One interpretationof this rule is that subspecificrecognition is warrantedif 90% of one subspeciescan be distinguishedfrom 90% of the second(this is the 75% rule for symmetricaldistributions). For crowncolor, the box plotsindicate that femalesmeet this standard, but males do not. For the PC analysis,based on measurementsalone, the resultsare even less conclusive;no singlePC axiscan separatethe islandand mainlandbirds in accordwith the 75% rule for either sex. For the females,a linear combina- tion of PC1 and PC2 can do so, but the pattern of Figure4 is suchthat it appearsthis wouldnot hold up with an increasedsample size. With the specimenscurrently available--that is, with few specimensfrom Isla Guadalupein fresh(recently molted) plumage--the now extinctGuadalupe Flickerdoes not approachthe 100% diagnosablydifferent status required for recognitionof a phylogeneticspecies (e.g., McKitrickand Zink 1988). However, femalesmeet the 75% standardfor subspecies.We therefore believethat subspeciesstatus is (was?)warranted for this islandform. It is clearthat the flickersof IslaGuadalupe differed on averagefrom thoseof the mainland;however, we did not find the degree of differentiationto be extensive.There may havebeen sufficient continuing gene flow to prevent completeisolation. An alternativepossibility is that a seriesof freshAugust or Septemberspecimens would have been largelydiagnosable. Molecular methodsmay somedayhave the power to addresssuch questions.

ACKNOWLEDGMENTS

Our trip to IslaGuadalupe would not havebeen possible without the assistanceof the Armada de M•xico, which providedtransport to and from Isla Guadalupe;we particularlythank Commandante Francisco P•rez-Rico and the officersand crewof C-81 Zarcofor theirhospitality while we were at sea.The fishermenof Cooperativa de Langosterosy Abulonerosde Ensenadaprovided much needed logistic support on the islandand taught us the nobleart of "chivo"hunting. We thankthe curatorialstaffs of the U.S. National Museum of Natural History (Philip Angle), the Los Angeles CountyMuseum of NaturalHistory (Kimball Garrett), the CalifomiaAcademy of Sciences(Karen Cebra),and the Museumof VertebrateZoology (Carla Cicero)for providingloans of flickersunder their care. We thank the Secretariadel Medio Ambiente,Recursos Naturales y Pesca,for providingpermits. We are gratefulto JeffreyGroth for preparingtwo figuresand to PhilipUnitt, WilliamEverett, and an anonymousreviewer for helpfulcomments on an earlierversion of thispaper. This researchwas supported in part by the LeonardJ. SanfordTrust.

LITERATURE CITED

AgrazGarcia, A. A. 1978. La cabracimarrona (Capra hircus) en la Islade Guadalupe, B.C. Ganadero 3:35-49. Barrowclough,G. E 1982. Geographicvariation, predictiveness, and subspecies. Auk 99:601-603.

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Bryant, W. E. 1887. Additionsto the ornithologyof GuadalupeIsland. Bull. Calif. Acad. Sci. 2:269-318. Dunlap,E. 1988. LaysanAlbatross nesting on GuadalupeIsland, Mexico. Am. Birds 42:180-181. Gallo-Reynoso,J.-P., and Figueroa-Carranza,A.-L. 1996. The breedingcolony of LaysanAlbatrosses on Islade Guadalupe,Mexico. W. Birds27:70-76. Greenway,J. C., Jr. 1967. Extinctand VanishingBirds of the World, 2nd ed. Dover Publ., New York. Howell, S. N. G., and Webb, S. 1992. Observationsof birdsfrom Isla Guadalupe, M•xico. Euphonia 1:1-6. Howell, S. N. G., and Webb, S. 1995. A Guideto the Birdsof Mexicoand Northern CentralAmerica. Oxford Univ. Press,Oxford, England. Howell, T. R., and Cade,T. J. 1954. The birdsof GuadalupeIsland in 1953. Condor 56:283-294. Jehl, J. R., and Everett, W. T. 1985. History and statusof the avifaunaof Isla Guadalupe,Mexico. Trans. San DiegoSoc. Nat. Hist. 20:313-336. Mayr, E. 1969. Principlesof SystematicZoology. McGraw-Hill, New York. McKitrick,M. C., and Zink, R. M. 1988. Speciesconcepts in ornithology.Condor 90:1-14. Mellink, E., and Palacios,E. 1990. Observationson Isla Guadalupein November 1989. W. Birds 21:177-180. Moran,R. 1996. The Floraof GuadalupeIsland, Mexico. Memoirs Calif. Acad. Sci. 19. Oberbauer,T. A., Cibit, C., and Lichtwardt,E. 1989. Notesfrom Isla Guadalupe. W. Birds 20:89-90. Ridgway,R. 1876. Ornithologyof GuadalupeIsland, based on notesand collections madeby Dr. EdwardPalmer. Bull. U.S. Geol. Geogr.Surv. Terr. 2:183-195. SAS InstituteInc., 1988. SAS LanguageGuide for PersonalComputers, release 6.03 ed. SAS Inst., Cary, NC. Wilbur,S. R. 1987. Birdsof BajaCalifornia. Univ. Calif.Press, Berkeley.

Accepted 30 October 2000