Some Observations of Birds on the Central Mexican Plateau

SOME OBSERVATIONS OF BIRDS ON THE CENTRAL MEXICAN PLATEAU

TONY LEUKERING and JIM BRADLEY, Colorado Bird Observatory, 1340I PiccadillyRoad, Brighton,Colorado 8060I

Phillips(I977) describedthe avifaunaof the ChihuahuanDesert region as ranking among the least known bird communitiesof North America. In the intervening nineteenyears, little has happened to alterthat assessment.In Januaryand February I996, the Colorado Bird Observatorystudied the winter distributionand habitat associationsof prairie-breedingbirds in the northern Central Mexican Plateau (definedas that area boundedby the internationalborder to the north, the Sierra Madre Occidental to the west, the Sierra Madre Oriental to the east, and the TransvolcanicBelt to the south;hereafter Central Mexican Plateau). We surveyeda varietyof grasslandtypes and madeancillary observations of birdsin otherhabitats. Observationsreported here were made while traveling between study sites and at daily campsites,all within 10 km of major state and federalhighways between Janos, Chihuahua,and Durango,Durango. We notedrecords of interestfor elevenspecies, mosfiyof individualsoutside the winter rangesas mapped by Howell and Webb (I995). Our observationswere primarilyat the followingsites: FI Palmito, a smalltown at the westernterminus of Mexico Route 30 on the east sideof L•zaro CardenasReservoir in north-centralDurango. The siteis at approxi- mately25 ø 34' N, 104 ø 56'W, 10 km northeastof [] Palmito,and 1.5 km southof MexicoRoute 30 on the road to Los Zarquefios. La Concel•i6n, a smalltown in centralChihuahua off MexicoRoute 45, about 20 roadkm southof Palomasand about 60 km SSW of ChihuahuaCity at 28 ø 10' N, I06 ø I3'W. The siteis alongthe Rio SantaIsabel just east of town. Ricardo Flores Maõ6n, an ejido (collectivefarm) on ChihuahuaRoute 10, halfwaybetween Chihuahua Route 23 and MexicoRoute 45 in centralChihuahua, at 29 ø 57' N, 106 ø 58'W. Rio Nazas, a large river flowingthrough north-central Durango. The site is the MexicoRoute 45 crossingabout I70 km north of DurangoCity at 25 ø I8' N, I04 ø 38'W. Villa de Nieves, a smalltown alongMexico Route 45 in extremenorth-central Durangoabout 20 roadkm southof the Chihuahuaborder at 26 ø 25' N, 105 ø 26'W. Golden-frontedWoodpecker (Melanerpes aurifrons). We found this speciesin mostlocations having suitable habitat. The northernmostindividual found was a male in riparianhabitat near La Concepci6non 26 January.We foundGolden-fronted Woodpeckersat four otherlocations, all in Durango,with a maximumof five(three malesand two females)at the Rio Nazason 29 January.All birdsseen well appeared to be of the nominaterace, whichis the expectedone as it is the form in the United Statesand in northeasternMexico. It is distinguishedby a nearlyall-black tail, wide barringon the back,and, in males,the crownpatch is separated from the napepatch (connectedin the Pacificslope polygrannnn us). No speciesof "Centurus"woodpecker is mappedby Howelland Webb (1995) as occurringin the heartsof eitherChihuahua or Durango;the westernrange limit for Golden-frontedWoodpeckers is drawnas roughlyparalleling the easternborders of the two states,whereas, the easternedge of the rangeof the similarGila Woodpecker (M. uropygialis)is drawnas roughlyparalleling the westernedge of the two states. These recordsof suchan obviousspecies reflect on how little is known about the CentralMexican Plateau avifauna and how littleornithological investigation has been conducted there.

WesternBirds 28:177-180, 1997 177 SOME OBSERVATIONS OF BIRDS ON THE CENTRAL MEXICAN PLATEAU

DuskyFlycatcher (Empiclonax oberholseri). We foundtwo individualsin riparian habitat along the Rio Nazas on 29 January. The birds were separatedfrom Hammond'sFlycatcher by their longbills, long tails, and shortprimary extensions. Also, one of them was heard to give a soft "wit" call a few times; the call of Hammond'sis a sharper"peek." This site appearsto lie at the edgeof the winter rangemapped for thisspecies by Howell and Webb(1995). Cassin'sKingbird (Tyrannus vociferans).We found this speciesin numerous locationsin Durangoin lateJanuary. The northernmostlocation was Villa de Nieves on 28 January,about 260 km northof the winterrange limit depicted by Howelland Webb(1995), whomapped it aswintering in Durangoonly in the extremewest and south. Phillips(1994) seemedto suggestthat this specieswinters on the Central Mexican Plateau, contra Howell and Webb (1995), but his statementis somewhat ambiguous:"It does winter in northernMexico (American Ornithologists' Union 1983), but eastof the Pacificslope and northof the highlandsof southernNuevo Le6n (A.M. Sadapers. comm.) it isthen hardly more regular than in Texas,where the variouswinter reports are generallyconsidered dubious." Tree Swallow(Tachycineta bicolor). Bradley saw one flying at RicardoFlores Mag6n on 25 January.This siteis more than 300 km NNW of the northernlimit of the winterrange in Chihuahuamapped by Howelland Webb(1995). Phillips(1991) statedthat "winteringin N Chihuahua(Oberholser) is dubious." Northern Rough-wingedSwallow ($telgiclopteryx serripennis). We found this speciesnumerous (>20 individuals)along the Rio Nazason 29 Januaryand one or two at two otherlocations farther south in Durangoon subsequentdays. Howell and Webb (1995) depictedthis speciesas winteringin extremewestern Durango and not at all on the CentralMexican Plateau. Phillips (1991) reportedsome birds "returning N by mid- or late January,"so there is some questionas to the migratorystatus of the individuals we saw. CaveSwallow (Hirunclo fulva). We sawtwo CaveSwallows among the Northern Rough-wingedSwallows at the Rio Nazason 29 January.The Rio Nazassite is within the rangeof permanentresidency depicted by Howelland Webb(1995); however, until recenfiy,little was known of the whereaboutsof this speciesduring the nonbreedingseason. The fewdata available suggested that some or mostindividuals migratedout of Mexicofor the winter and/or that wintering in numberson theCentral Mexican Plateauis recent (Howell and Webb 1995, Petersonand Chalif 1973). This haschanged with the reportby Komar(1997) of in excessof 10,000 CaveSwallows winteringin E1Salvador. Anotherproblem posed is determining the winteringstatus of individualsseen after December.Phillips (1991) statedthat the speciesmay returnto Texasas earlyas 6 February.This suggeststhat individualsin Durangoin late Januarycould be on migration(as in the NorthernRough-winged Swallow). However, Leukering (pers. obs.)has seenthe speciesover the Rio Grandeat Bentsen-RioGrande Valley State Park, Texas,in earlyJanuary. EuropeanStarling ($turnus vulgaris).Leukering saw two flying over Janos, Chihuahua,on 24 January. Howell and Webb (1995) depictedthis speciesas occuringin Mexicoonly in the northwesterncorner of the country.Janos is on the southernedge of thisspecies' range in Mexico. Gray Vireo (Vireo vicinior).While casuallybirding around our campsitenear [] Palmito,Durango, on the morningof 30 January,L. Dombroskifound, and the whole fieldcrew observed, a singleGray Vireo foragingin desertscrub. The bird wasgray aboveand whitish below, with a decidedresemblance to a gnatcatcher(Polioptila) in both plumageand habits. Its bill was typical of Vireo, beingdeep and hooked,despite the bird'ssmall size, not thin, long, and pointed as a gnatcatcher's.Its eye ring was less pronouncedthan that on a PlumbeousSolitary Vireo (V. solitarius plumbeus), and its actionswere more energeticthan thoseof a SolitaryVireo, thoughnot as freneticas

178 SOME OBSERVATIONS OF BIRDS ON THE CENTRAL MEXICAN PLATEAU thoseof a gnatcatcher.The outerwebs of the outerrectrices were contrastinglypale (anothergnatcatchefiike feature); however, the bird'stail was not aslong, relatively, as in a Blue-grayGnatcatcher (P. caerulea).Dombroski heard it twicegive the short, harshrattle call described by Bates(1992). The vireoforaged from nearthe groundto near the tops of variousshrubs ranging to 3.5 m. Dominant plant speciesof the habitatwere Desert Hackberry(Celtis pallida) and Ocotillo(Fouquieria splendens) with numerousother shruband ground-coverspecies present. Thisrecord is apparenfiythe secondfor thisspecies in Durango;the firstwas of an individualcollected at Inde on 13 August 1898 (Fry et al. 1996; this record not depictedby Howelland Webb 1995), now in the Smithsonian.Even though Phillips (1991) describedthe specimenas "hopelesslyworn," he suggestedthat it represented an undescribedsubspecies. The mostinteresting aspect of this recordis that Inde is lessthan 35 km northwestof the El Palmitosite. Except for a veryfew reports[Barlow and Wauer 1971 (BigBend NationalPark), Fry et al. 1996 (San LuisPotosi), and, possibly,Howell and Webb 1995 (Coahuila)],the speciesis not known to winter outsideof Baja California,Sonora, and extreme southernArizona, though these suggestthat this speciesmay be distributedmore widely acrossnorthern Mexico duringthe nonbreedingseason than is currenfiyrecognized. Wilson'sWarbler (Wilsonia pusilla). We founda malein riparianvegetation at the Rio Nazassite on 29 January,at least200 km north of the mappedwinter rangein extremewestern and southernDurango (Howell and Webb 1995). B. Howe and D. Hawksworthreported to us a male Wilson'sWarbler on 12 Januaryalong the Rio CasasGrandes, just west of the cityof NuevoCasas Grandes in northernChihuahua. Thissite is only120 km south-southeastof the southeasterncorner of the bootheelof New Mexico. BlueGrosbeak (Guiraca caerulea). On 28 January,we foundtwo, one adultmale and one brown-plumagedbird, just south of the town of GuadalupeAguilera, Durango.This site is at least 200 km north or 150 km east of the winter range mappedby Howelland Webb(1995) in extremewestern Durango. Clay-coloredSparrow (Spizella pallida). We foundthis species fairly common at manylocalities from La Concepci6nsouth. The La Concepci6nsite had a largeflock of $pizella (•75 individuals)on 27 January,with Brewer's and Clay-colored sparrows in a ratio of about2 or 3:1. This siteis 75 km north of thisspecies' winter rangeas mappedby Howell and Webb (1995). Baird's Sparrow (Ammodramus bairdii). We recorded a total of 53 Baird's Sparrowson 18 of 99 studyplots, as well asmore than 25 individualsin an extensive grassypasture at RicardoFlores Mag6n, Chihuahua.Generally, areas with denser, tallergrass and patchesof bare groundcontained Baird's Sparrows. We foundthe speciesin mostpatches of suitablehabitat from Janos, Chihuahua, in the north,to just north of Durangoin the south.Baird's Sparrows occurred with GrasshopperSpar- rows(A. sauannarum)in manyplaces, and the RicardoFlores Mag6n site held about equal numbersof the two species. Concertedefforts to studythe avifaunaof the CentralMexican Plateau will continue to providemuch new information.We were able, with little effort, to recordeight speciesat least 75 km outside of their mapped ranges, with most records of "extralimital"individuals being at leasttwice that distancefrom their knownranges. Moreover,many of our recordsappear to representresident or regularwintering populations,rather than vagrantsor oddindividuals. We thank the members of Colorado Bird Observatoryfor their support in our researchand conservationendeavors, and for providingsome of this project's funding.We also thank Howard Ness of the U.S. National Park Service(Mexico Affairs Office) for additionalfunding. Thanks also go to Carol Beidleman,Cory Counard,Beth Dillon,Louie Dombroski, Joe Kaplan,and Mary Teesdalefor volun- teeringtheir time and expertisein the field. We also appreciatelogistical advice

179 SOME OBSERVATIONS OF BIRDS ON THE CENTRAL MEXICAN PLATEAU offeredby Bill Howe and CynthiaMelcher and assistancewith translationby Carol Beidlemanand Beth Dillon. Thanks to Chuck Aid, Mike Carter, Scott Gillihan, Bill Howe, andA. TownsendPeterson for reviewingprevious drafts of the manuscriptand providinginsightful comments thereon. We trulyappreciate, and wereconstantly amazed by, the unfettereduse of private (grazingand agricultural)lands for surveysand/or campingoffered us by Mexican landowners,relative to thatin the U.S. Their livelyconversation and friendly support of our projectwere eye-openersfor everymember of our projectteam. We would particularlylike to singleout Jorge Chavez-Vegaof RicardoFlores Mag6n in this respect;his land held the best grasslandhabitat we saw and the huge flock of Ammodramus mentioned above.

LITERATURE CITED

AmericanOrnithologists' Union. 1983. Check-listof NorthAmerican Birds, 6th ed. American Ornithol. Union, Lawrence, KS. Barlow,J. C., and Wauer,R. H. 1971. The GrayVireo (Vireo viciniorCoues, Aves: Vireonidae)wintering in the BigBend region, west Texas. Can. J. Zool.49:953- 955. Bates,J. M. 1992. Frugivoryon Bursera microphylla(Burseraceae) by wintering GrayVireos (Vireo vicinior,Vireonidae) in the coastaldeserts of Sonora,Mexico. Southwest Naturalist 37: 252-258. Fry, A. J., Rojas-Soto,O. R., andNavarro S., A. G. 1996. A winterrecord of the Gray Vireo from San Luis Potosi, Mexico. W. Birds 27:54-55. Howell, S. N. G., and Webb, S. 1995. A Guideto the Birdsof Mexicoand Northern CentralAmerica. Oxford Univ. Press,Oxford, England. Komar,O. 1997. Communalroosting behavior of the CaveSwallow in [] Salvador. WilsonBull. 109: In press. Peterson,R. T., and Chalif, E. L. 1973. A FieldGuide to MexicanBirds. Houghton Mifflin, Boston. Phillips,A. R. 1971. Summaryof avianresources of the ChihuahuanDesert region, in Transactionsof the symposiumon the biologicalresources of the Chihuahuan Desertregion, United States and Mexico(R. H. Wauerand D. H. Riskind,eds.). Sul RossState Univ.; U.S. Dept. Interior Nafi. Park ServiceTrans. Proc. Ser. 3. Phillips,A. R. 1991. The KnownBirds of North and MiddleAmerica, part 2. A. R. Phillips,Denver. Phillips,A. R. 1994. A tentativekey to the speciesof kingbirds,with distributional notes. J. Field Ornithol. 65:295-306.

Accepted2 April 1997

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