Description of the Second Rectrix of Adult-plumaged Male Rufous and Allen's and Its Usefulness in Identification

Rita R. Colwell 281 Margarita Court Los Altos, CA 94022 [email protected]

ABSTRACT

Differencesin the shape of the second rectrix in adult males' R2 is "distinctlynotched." But his Rufous Hummingbirds( rufus) and illustration shows the variation in notching for Allen's Hummingbirds(S. sasin) are significant females and juvenile males. An added note to the distinguishingcharacters. Although many ref- illustrationstates that "adult males have a greater erences describe the as "notched" in notchthan is shown." Johnsgard(1997) describes RufousHummingbird, a detaileddescription of this the featheronly as "stronglynotched in males." In feather'sappearance in the adult male is lacking. Williamson's(2001) account,she states My studydescribes the typicalnotching of the inner that adult male Rufous Hummingbirdshave "R2 web and emarginationof the outer web of the distinctly notched on inner web near tip" and providesa photographshowing a strongnotch on secondrectrix of the adult-plumagedmale Rufous the inner web and an additional emarginationon Hummingbirdthat is lackingin the adultmaleAllen's the outer web. Howell (2002) writes that in the Hum-mingbird.I examined135 ,of which62 adult males "a stronglyemarginated notch on the had characteristicstypical of RufousHummingbird, outerweb of R2 is diagnostic."However, the plate and 70 which showed characteristics of Allen's referenceshows an adult male RufousHumming- . This rectrix in three birds had with a strong notch on the oppositeweb than abnormal features and the individuals had stated. •nconsistent measurements that may indicate hybridization. Thesedisparate descriptions create confusion over what is normal and what is abnormal in the feather's INTRODUCTION structure.The purposesof this paperare to clarify the typical R2 appearance in adult male Rufous In-hand separation of adult male Rufous Hum- and Allen'shummingbirds, describe three abnormal mingbirds (Selasphorus rufus) from Allen's individuals,and presentthe hypothesisthat these Hummingbirds(S. sasin)is accom-plishedby using birdswere interspecifichybrids. a combinationof plumageappearance and rectrix measurements (Pyle 1997, Mitchell 2000, Stiles METHODS 1972). Notchingof the second rectrix(R2) has been stated as an important identification I examined mist-netted adult-plumaged male characteristicof Rufous Hum-mingbirds,and the Rufousand Allen'shummingbirds at a site 10 miles lack of notching on R2 indicates an Allen's northeast of San Jose, , and at the Hummingbird(Stiles 1972, Pyle 1997, Mitchell Arboretumof the Universityof CalifornialSanta 2000, Williamson 2001, Howell 2002). These Cruz, California. Museum specimens were accounts,however, vary greatly and most do not examined at the CaliforniaAcademy of Science describeadequately the appearanceof the feather. (CAS), San Francisco, California;at the Museum of VertebrateZoology (MVZ), Berkeley,California; Stiles(1972) statesthat the "tipof secondrectrix and at the Universityof , Fairbanks,Alaska [is] deeplyemarginated." Pyle (1997) maintains (UAF). Livebirds were examined during February, Jan - Mar 2005 NorthAmencan Bird Bander Page21 March,and April and all of the museumspecimens RESULTS examinedwere collectedduring February through July. Becauseof the area where mist-netting The samplesize of adult-plumagedmales was 135. occurredand the collectingsites for specimens, Sixty-two birds were classified as Rufous Hum- all Allen's Hummingbirds encountered were mingbirdon the basis of wing chordrange given assumed to be the nominate race S.s. sasin. by Stiles (1972) and R5 width measurementsin Measurementstaken were wing chord and width range given by Pyle (1997)for adult males (Table of rectrix5 (R5). Thesefeatures were measured 1). R2 patternsof these birds showed a strong accordingto Baltosser(1987). R2 notchand notchon the innerweb and a distinctemargination emarginationwere taken on individualswith onthe outer web (Figure 2A). The m•asurements measurabledimensions. The wingchord measure- of the notch and emarginationfor these 62 birds mentwas takenusing a thinplastic rule. R5 width are shown in Table 2. and R2 notch dimensions were measured to the nearest 0.1 mm usinga digitalcaliper. Seventy birds identifiedas Allen's Hummingbirds showedno notchingor emarginationon eitherweb Notchingon the innerweb of R2 was measuredby of R2 (Figure 2B). These birds had wing chord quantifyingthe distance of the notch from the range given by Stiles (1972) and R5 width feathertip andthe depthof notchfrom the margin. measurementsin range given by Pyle (1997) for The emarginationon the outerweb was measured adult males (Table 1). in a similarmanner (Figure 1). Forall birds,feather tip wear was negligible. Table 3 shows measurements and characteristics of three birdsdemonstrating inconsistencies which I included an estimate of the amount of green preventedtheir identificationas to species. One presentdorsally on all individualsof both species was a mist-netted bird and the other two were that I examined. The area used for the estimate is specimensat CAS. The live bird, band number describedin AIddch(1956) as the "dorsalregion" 3000-07475 (Figure3A), and specimenCAS 46047 and extendsfrom the posteriormargin of the nape (Figure3B) had notchingon R2, but in bothcases to the uppertail coverts, shoulder to shoulder(wing the innerweb notchand the outerweb emargination bases) on the upper back, and laterally on the were not so strongand distinctas those foundon lower back sides down to the abdominal tract typicalRufous Hummingbirds and the R5 widthwas region. in range of Allen's Hummingbirds.

c a

Figure 1. Dimensionsof notchand emarginationon secondrectrix of an adult male .The innerweb of the feather is on the right.The distanceof the notchfrom the tipon the innerweb is (ab); the distanceof emarginationon the outerweb is (cd). The depth of the notchon the innerweb is (e) and the depthof emarginationon the outerweb is (f).

Page 22 North American Bird Bander Vol 30 No 1 Table '1. Measurementsof adult male Rufousand Allen'shummingbirds with typical R2.

This study Reference Mean SD Mean SD Wing (mm) Rufous 40.88 0.88 40.32 (Stiles) 0.87 Allen's 38.33 0.99 38.08 (Stiles) 0.84

1:{5width (mm) Rufous 2.39 0.18 Range 2.0 - 2.7 (62) 1.8 - 2.6 (Pyle) Allen's 1.44 0.22 Range 0.9 - 1.9 (70) 1.2- 1.9 (Pyle)

Table 2. Adult male Rufous HummingbirdR2 notch and emarginationmeasurements (mm) for 62 individualsdesignated as typical.

Inner web Outer web Down from tip In from margin Down from tip In from margin (depth) (depth)

Range 4.0 - 6.0 0.6 - 2.0 3.0 - 4.7 0.2 - 0.9 Mean 4.98 1.27 3.75 0.57 SD 0.46 0.32 0.39 0.16

Table 3. Three hummingbirdswith inconsistentmeasurements and atypicalappearing R2.

3000-07475 CAS 46047 CAS 75817 Wing chord (mm) 38 40 40 possiblespecies Allen's or Rufous Rufous Rufous Width 1:{5(mm) 1.6 1.6 2.1 possiblespecies Allen's Allen's Rufous 1:{2appearance atypicalnotching atypicalnotching sl. concavemargins % Green back 100 80 95

Jan. - Mar. 2005 NorthAmerican Bird Bander Page 23 SpecimenCAS 46047 had been identified originally study,this measurement showed no overlapeither, as RufousHummingbird, but later L.C. Baptista whichsupports this feature as a reliablecharacter added the commentthat it was possiblya S. rufus for separatingthe species. x S. sasinhybrid. The thirdbird, specimen CAS 75817 (Figure30), labeledS. sasin, had wider The 62 Rufous Hummingbirds determined as appearingrectrices than other Allen's Hum- typicalshowed a wide range of green on the back. mingbird.Rectrix 2 appearedblunt-tipped rather Seventeen birds had totally rufousbacks; 40 had than slimmingto a sharp point as is typicalfor 1-50% green; four had 51-75% green; none had Allen'sHummingbird and was not notched. Both 76-94% green and one had 95-100% green. webs of the feather had a slightatypical concavity McKenzieand Robbins(1999), in a sampleof 125 to the marginsclose to the tip. Significantly,the birds,had resultsshowing six birdswith backs50- measured R5 width was within range of Rufous 74% green; five with backs of 75-94% green; and Hummingbird. five with backs95-100% green, three of these birds in this range were consideredpossible hybrid S. Measurementsof the R2 notch and emargination rufus x S. sasin. of the 62 typicalRufous Hummingbirds (Table 2) show that the inner web notch is strong and deep, My sampleof 70 Allen's Hummingbirdshad backs and itsdistance from the tip of the featheris usually rangingfrom 80 to 100%, a percent lower than greater than the emarginationon the outer web. McKenzie and Robbins (1999). The difference The less distinctemargination on the outerweb of between my findingsand theirs may be due to the birds classified as Rufous Hummingbird was particular area of the back I used to estimate slighter,placed closer to the tip, and not as deep coloration.My estimatearea includedthe sidesof as the strong notch on the inner web. The the lower back which is the area where the rufous emarginationon the outerweb was presenton all feathering,if present,was consistentlyfound. In birds classifiedas typical Rufous Hummingbirds. the Rufous HummingbirdsI examined, if the bird All typical Allen's Hummingbirds showed no or specimen had significant amount of green notching or emargination on either web of the feathering (>50%), it was concentratedon the second rectrix. upperand mid-backarea with the rufousfeathering appearingon the upper rumpand lowerback sides. The individualsdetermined to be typical for each This patternwas similar in Allen's Hummingbirds of the speciesdemonstrated no overlap in the R5 when they showed green featheringof less than width. In the McKenzie and Robbins (1999) 100%.

Figure2. The secondrectrix of (A) a typicaladult male Rufous Hummingbird and (B) a typicaladult male Allen's Hummingbird. The innerwebs of the feathersare on the rightfor both illustrations.

Page 24 NorthAmerican Bird Bander Vol. 30 No. 1 A B C

Figure 3. Three unusualsecond rectrices showing abnormal notching and emargination. The inner webs of the feathersare on the rightfor all illustrations.A, 3000-07475. B, CAS46047. C, CAS75817.

DISCUSSION Allen's and Rufous hummingbirds.The authors providecomments about the shape of R2 on two The appearance of the second rectrix in the adult of these specimens. One had the tip "slightly male Rufous and Allen's hummingbirdcan serve emarginated"and the other specimenthey found as a distinguishingidentification feature. The had been annotatedas "an Allen's Hummingbird notchingand emarginationpattern found on R2 of with an anomalouslyemarginated R2." Though all adult male Rufous Hummingbirdsshould have McKenzieand Robbins(1999) furnisha photograph typical,measurable dimensions with the outerweb showingthe tails of typicaladult male Allen'sand showinga distinctemargination and the innerweb Rufous hummingbird, they do not provide a a dramatic notch. Three birds encountered in this comprehensivecomparison of the typicaland the studyshowed atypical looking R2s. Twoindividuals' atypicalR2s they found. measurementscould allow for speciation,#3000- 07475 and specimenCAS 46017, but the appear- BecauseRufous and Allen'shummingbirds exhibit ance of their R2s did not match the measurements. a narrowregion of overlapin their breedingranges The third individual,CAS 46047, had conflicting (Grinnelland Miller1944; Gilliganet al. 1994), they measurementsnot allowingspeciation. Table 3 are likelycandidates for hybridization.While other shows the comparisons. The reason for this knownhummingbird hybrids show unusual physical appearancesin their plumagethat are unlikeeither variability is uncertain but may indicate hybrid individuals. parent(Williamson 2001, Howell2002, Heindeland Howell2000, Williamson 1957, Banks and Johnson 1961), hybrids between Rufous and Allen's That hummingbirdshybridize has been supported hummingbirdsmight not be recognizedas such by numerousexamples (Banks and Johnson1961, because the two species are so similar in Williamson1957,Lynch and Ames 1970, Heindel appearance. The distinctR2 patternof the adult- and Howell2000). Hybridizationbetween Rufous plumagemale RufousHummingbird is a physical and Allen'shummingbirds has been suggestedin characteristicwhich, if affected,might identify the the past (Newfield 1983; McKenzie and Robbins individualsas hybrids. 1999), but has not been confirmed (Pyle 1997). Newfield(1983) examinedspecimens of an adult- In the adult-plumagedmales of thesetwo species, plumagedmale, an immaturefemale, and a juvenile a combinationof a typical appearingR2 for that male which she described as unusual. The adult- species and measurements,especially the width plumagedmale showed measurementswithin the of R5, is the most effectiveway of distinguishing range of Allen'sHummingbird, but had a "strongly these two hummingbirdsspecies. When atypical emarginated" second rectrix. McKenzie and or anomalous, those criteria may also serve to Robbins(1999) describefive specimensof adult- identify hybrids of Rufous and Allen's hum- plumaged males with mixed measurements of mingbirds. Jan. - Mar 2005 NorthAmerican Bird Bander Page25 ACKNOWLEDGMENTS McKenzie, P.M. and M. B. Robbins. 1999. Identification of male Rufous and Allen's I am gratefulto the followingindividuals for their hummingbirds,with specificcomments on assistanceduring banding:Joyce Bartlett, Gina dorsal coloration. W. Birds 30:86-93. Barton,Irene Beardsley,Barbara Cadson, Maryann Mitchell,D. E. 2000. Allen's Hummingbird Danielson,Sherry Hudson, Kay Loughman,and (Selasphorussasin). In The Birdsof North Ruth Yoder. Examinationof museum specimens Amedca, No. 501 (A. Poole and F. Gill, was facilitated by Douglas Long (CAS), Carla eds.). The Birdsof NorthAmedca, Inc., Cicero (MVZ), and Dan Gibson (UAF). Mr. and Philadelphia,PA. Mrs. John C. Fell generouslyallowed access to Newfield, N. L. 1983. Records of Allen's their propertyfor banding. Daniel Harderand the Hummingbirdin Louisianaand possible staff of the Universityof California, Santa Cruz RufousxAllen's hybrids. Condor85:253- Arboretum granted permission to band hum- 254 mingbirdsat thissite. BarbaraA. Carlson,Rosalie Pyle, P. 1997. Identificationguide to North Lefkowitz,David L. Pearson, Stephen M. Russell, American birds. Part I. Slate Creek Press, GeorgeWest, and SusanM. Wethingtoncritiqued Bolinas, CA. earlierdrafts of this paper. I am appreciativeof Bill Stiles, F. G. 1972. Age and sex determinationin Loughman'seditorial perspective in preparingthe Rufous and Allen's hummingbirds. current versionof this paper. Condor 74:25-32. Williamson,F. S. L. 1957. Hybridsof Anna and Allen LITERATURE CITED hummingbirds.Condor 59:118-123. Williamson, S. L. 2001. A field guide to Alddch,E. C. 1956. Pterylographyand moltof the hummingbirdsof NorthAmedca. Houghton Allen'sHummingbird. Condor 8:121-133. Mifflin Co., Boston/New York. Baltosser,W. H. 1987. Age, species, and sex determination of four North American hummingbirds.N. Am. BirdBander 12:151- 166. Banks, R. C. and N. K. Johnson. 1961. A review of NorthAmerican hybrid hummingbirds. Condor 63:1-28. GilliganJ., D. Rodgers,M. Smith,A. Contraras, eds. 1994. Birds of : status and distribution.Cinclus Publ., McMinnville, OR. Grinnell, J. and A. H. Miller. 1944. The distribution of the birds of California. Pac. Coast Avifauna 27. Heindel, M. and S. N. G. Howell. 2000. A hybrid hummingbirdin southeastArizona. VV. Birds 31:265-266. Howell, S. N. G. 2002. Hummingbirdsof North Amedca- the photographicguide. San • RufousHummingbird (gray scale) by George West Diego, CA. Academic Press Johnsgard,P.A. 1997. Hummingbirdsof North Amedca. Second Edition.Washington, D.C. Smithsonian Institution Press. Lynch,J. and P. L. Ames. 1970. A new hybdd hummingbird,Archilochus alexandri x Selasphorussasin. Condor72: 209-212.

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