Revised Ageing and Sexing Criteria fr the Blue-thrated Hummingbird Peter Pyle and Steve N. G. Hwell Pint Reyes Bird Observatry 4990 Shreline Highway Stinsn Beach, CA 94970 ABSTRACT Examinatin f phtgraphs and specimens cnfirms that male Blue-thrated Hummingbirds (Lamprnis clemenciae) in juvenal plumage have clse t "full" grgets, appraching thse f males in adult-basic plumage. This is unusual in Nrth American hummingbirds and has been essentially verlked in the literature. Accrdingly, we describe differences between juvenal and adultbasic plumage in males, and revise current ageing and sexing criteria fr Blue-thrated Hummingbirds. INTRODUCTION The "juvenal plumage" (that between hatching and the cmplete mlt during the first year) in male Blue-thrated Hummingbirds (Lamprnis clemenciae) has nt been described adequately. Ridgway (1911) described nly "adult"birds, presumably thse that had undergne the first cmplete mlt and gave measurement ranges fr 23 males. Bent (1940) gave a brief descriptin f the "yung" male, indicating that the blue thrat is nly "partially develped." Oberhlser (1974) mentined that he had nt seen males in "first winter" r "first nuptial" plumage but included measurements fr "adult" males and described tw unrecgnized nrthern subspecies (L. c. bessphilus, Oberhlser 1918, and L. c. phasmrus, Oberhlser 1974), pinins supprted by Brwning (1978, 1990). Hwell and Webb (1995) stated that the "immature male resembles female but with sme blue n the thrat." Based n this infrmatin, the lack f specimens f male Blue-thrated Hummingbirds in Califrnia cllectins with few blue feathers in the thrat, and apparently mis-sexed specimens (see Clench 1976) withut blue in the thrat (e.g., Mre Labratry f Zlgy [MLZ] 37499), Pyle (1997) assumed that mst r all juvenile males lacked blue in the thrat, either verlking the infrmatin presented by Bent (1940) and Hwell and Webb (1995) r assuming that they had examined ne r mre males with a few blue feathers in the thrat. Thus, Pyle (1997) nted that "mre study is needed n the acquisitin f blue in the thrat by HY/SY males; apparently, blue usually is nt acquired until March-May in SYs, althugh ccasinal HY/SYs with 1-2 blue thrat feathers may be fund in Jul-Feb." METHODS While examining phtgraphs fr an identificatin guide t Nrth American hummingbirds, Hwell nted that juvenile male Blue-thrated Hummingbirds had extensive blue feathering in the thrat, appraching that bserved in adult males. A reexaminatin f 25 male specimens at the Califrnia Academy f Sciences (CAS) and Museum f Vertebrate Zlgy (MVZ) by Pyle and Hwell indicated that 10 (38%) were juveniles, 11 (41%) were adults which had cmpleted the first-year mlt, tw were in transitinal plumage and had apparently mlted the flight feathers but nt the grget, and tw were f indeterminable age (see belw). Ages f the 23 determinable birds were cnfirmed by the extent f crrugatins n the bill (Ortiz-Cresp 1972, Yanega et al. 1997). Based n these prprtins, we suspecthat Ridgway (1911) and Oberhlser (1974) had, like Pyle, assumed that males with extensive blue n the thrats were adults, a reasnable assumptin based n patterns f grget acquisitin in males f ther Nrth American hummingbirds (Pyle 1997, Pyle et al. 1997). Page 134 Nrth American Bird Bander Vl. 25 N. 4
I RESULTS DISCUSSION Specimen examinatin indicated tw plumage criteria useful fr distinguishing juvenile frm adult male Blue-thrated Hummingbirds in the field. First, the grgets f juvenile males are, n average, less extensive than thse f adults. Cunts f thrat feathers with iridescent blue clratin revealed that 10 juveniles had 46 (MVZ101948) t 68 (MVZ137129) blue-tipped feathers (mean 58.1 +7.3 [SD]), whereas 12 adults had 76 (MVZ78798) t 118 (CAS67138) blue-tipped feathers (mean 95.9 + 13.5). In juveniles, the relative sparcity f blue-tipped feathers ften creates a gap between the grget and the dark auricular in the malar regin, which is absent r less bvius in adults. The width f this gap was generally > 2 mm in juveniles and < 2 mm in adults, althugh there was sme verlap and a standardized measurement was difficult btain frm specimens. In additin, the extent f blue n each feather is reduced in the juvenile relative t the adult. Thus, the gray bases f these feathers shw thrugh in the juvenile, giving the grget an "incmplete" r less "full" appearance, as described by Pyle et al. (1997) fr sme males f ther hummingbird species in firstbasic plumage (see als Figure 99F and G in Pyle 1997). Secnd, in juvenile males (as in females), r3, the third rectrix frm the inside (and utside), has a distinct white tip which bradens tward the tip (Figure 1A-B), whereas in adult males the white n r3 is usually reduced t a small shaft-streak r diamnd-shaped mark alng the shaft (Figure 1C- D). In additin, the rectrices are slightly narrwer and usually shw mre wear, mnth-t-mnth, in juveniles than in adults. Fig. 1. Age-specific variatin in the amunt f white in r3 (the third rectrix frm the inside r utside) f male Bluethrated Hummingbirds. A-B represent variatin in juvenal rectrices, and C-D represent variatin in adult rectrices. We believe that there is little verlap between juvenile and adult males in plumage, at least in nrthern ppulatins (see belw); althugh the juvenile with the fullest grget (see abve) apprached in appearance the adult with the least full grget, and the plumage f the juvenile with the least amunt f white n r3 (MVZ137129; Figure lb) apprached that f the adult with the greatest amunt f white n r3 (MVZ129682; Figure 1C). Based n 95% cnfidence intervals frm ur data, the number f blue-tipped feathers in the thrat shuld range frm 43-73 in juvenile males and 70-122 in adult males, indicating slight verlap. Sme (5-15%) bill crrugatin (see Yanega et al. 1997) n adults with fewer blue-tipped feathers and larger amunts f white in the tail (e.g., 119402, 129684, 129685, and 129682 at MVZ) suggests that they were in first-basic plumage, althugh the reliability f identifying males in this plumage needs t be researched further. Tw specimens f the nminate subspecies cllected in Veracruz, Mexic, in early July 1965 (CAS87712 and CAS87713) were in indeterminable plumage. Respectively, these had 5% and 15% bill crrugatins, 73 and 70 blue-tipped feathers in the thrat, and white patches n r3 resembling Figure lb but n rectrices that were very brad, fresh, and adult-like in appearance. It is pssible that these tw birds were in first-basic plumage and/r that males f the trpical, nminate subspecies (which culd breed at varying times f the year; cf. Hwell and Webb 1995) are mre difficult t age by plumage. Examinatin f 18 male Amesthyst-thrated Hummingbirds (L. arnethystinus) by Pyle at MVZ, aged by bill crrugatins, indicates that juvenile and adult males f this cngener are virtually indistinguishable by plumage. Based n the tw plumage differences described abve, we present revised criteria and bar graph fr ageing and sexing Blue-thrated Hummingbirds f nrthern (including Texas and Arizna) ppulatins (Appendix). a B C D Sep. - Dec. 2000 Nrth American Bird Bander Page 135
ACKNOWLEDGMENTS We thank the late Luis Baptista and Duglas J. Lng at CAS and Ned Jhnsn and Carla Cicer at MVZ fr allwing us frequent access t their specimen cllectins; James R. Nrthern (MLZ), Rene Crad (Western Fundatin f Vertebrate Zlgy), Philip Unitt (San Dieg Natural Histry Museum), and Kimball L. Garrett (Natural Histry Museum f Ls Angeles Cunty) fr infrmatin n Blue-thrated Hummingbird specimens in their cllectins; Priscilla Ycm fr typesetting the appendix; and Brian Small fr phtgraphs f yung male Blue-thrated Hummingbirds. Cmments by Dr. Dnald Pwers and Kay Lughman imprved the manuscript. This is cntributin # 929 f the Pint Reyes Bird Observatry. LITERATURE CITED Bent, A.C. 1940. Life histries f Nrth American cucks, gatsuckers, hummingbirds, and their allies. U.S. Natl. Mus. Bull. 176. Ortiz-Cresp, F.I. 1972. A new methd t separate immature and adult hummingbirds. Auk 89:851-857. Pyle, P. 1997. Identificatin guide t Nrth American birds. Part 1. Slate Creek Press, Blinas, CA. Pyle, P., S.N.G. Hwell, and G.M. Yanega. 1997. Mlt, retained flight feathers and age in Nrth American hummingbirds. Pp. 155-166 in R.W. Dickerman, cmp., The era f Allan Phillips: A Festschrift. R.W. Dickerman, Albuquerque, NM. Ridgway, R. 1911. The birds f Middle and Nrth America. Part V. Bull. U.S. Natl. Mus. 50. Yanega, G.M., P. Pyle, and G.R. Geupel. 1997. The timing and reliability f bill crrugatins fr ageing hummingbirds. Western Birds 28:13-18. Brwning, M.R. 1978. An evaluatin f the new species and subspecies prpsed in Oberhlser's bird life f Texas. Prc. Bil. Sc. Washingtn 91:85-122. Brwning, M.R. 1990. Taxa f Nrth American birds described frm 1957 t 1987. Prc. Bil. Sc. Washingtn 103:432-451. Clench, M.H. 1976. Pssible pitfalls in museum specimen data. N. Am. Bird Bander 1:20-21. Hwell, S. N. G. and S. Webb. 1995. A guide t the birds f Mexic and nrthern Central America. Oxfrd University Press, Oxfrd, UK. The next page is the appendix t this ms. It is perfrated n the left margin and can be remved and trimmed t fit Peter Pyle's Identificatin Guide t Nrth American Birds. Part I, 1997, replacing page 129. Oberhlser, H.C. 1918. Descriptin f a new subspecies f Cyanlaemus clemenciae. Cndr20:181-182. Oberhlser, H.C. 1974. The bird life f Texas. Vl. 1. University f Texas Press, Austin. Page 136 Nrth American Bird Bander Vl. 25 N. 4
TR OCHILIDAE 129 HY/SYs; the grget feathers f SY c prbably are the last feathers t be replaced. The timing f breeding and mlt may differ in ppulatins f Mex. Lk fr SY/TYs rarely t retain a few flight feathers until the 2nd PB, as in ther hummingbirds. SkullsExperience by species is required fr the use f pneumaticizatin in ageing (see Family accunt). Age/Sex--Juv (May-Nv) has a sft and crrugated bill (Fig. 92A), feathers f the upperparts tinged glden and distinctly edged pale gray, and mandible flesh-clred r pink at the base; sexes are readily distinguished by lack ( x2) r presence (83) f blue in the thrat. CP and BP apparently are nt well develped. Measurements (especially tl) are useful:? wg(n21) 67.1-74.1, tl(n20) 40.4-45.5; c wg(n30) 71.9-78.5, tl(n30) 43.5-51.1. Juv-HY/SY?(Jun-Mar): Bill sft (thrugh Jul-Sep) with deep t shallw crrugatins cvering > 10% f culmen (Fig. 92A-B; thrugh Dec-Mar); thrat brwnish-gray withut iridescent blue feathers (Fig. 99A); mandible pinkish at base (thrugh Nv?). AHY/ASY?(Feb-Jan): Bill hard with shallw t n crrugatins cvering < 10% f culmen (Fig. 92C-D); thrat gray, withut iridescent blue (Fig 99A) r (ccasinally) with 1-2 blue feathers; mandible dark at base. Nte: Lk fr retained flight feathers n ccasinal SY/TYs (see AHY/ASY d). Juv-HY/SY d [jun-mar): Bill as in Juv-HY/SY ; thrat with blue feathers Ixg grget incmplete (Fig. 99F-G), with 43-73 blue-tpped feathe and distance between the dsest blue4ipped feather and the auricular usually > 2 mm; r3 with brad, triar, white terminal patch (Fig. 94.SA-B): mandible pinkish at base (thrugh blue feathe (but nt a cmplete AHY/ASY c (Mar-Feb): Billas in AHY/ASY 9; thrat unifrmly iridescent blue (cf Fig. 99H), with 70-122 blue-tipped feathers A B C D FIGURE 94.5. auricular usually < 2 mm: r3 with a small the shaft (F' 94.5C-D); mandible dark Blue-thmal d Hummingb d Juv-.v i I I caate gatget m' r3 m- with AHY E ; Hybrids reprted--prbably with Anna's Hummingbird. Pssibly with Black-chinned Hummingbird. la > = 2 m 25, 5 i See Fig. 24 References--Ridgway (1911), Bent (1940), Wagner (1957), Phillips et al. (1964, 1984), Oberhlser (1974), Phillips & Chase (1982), Baldridget al (1983). c MAGNIFICENT Eugenes fulgens HUMMINGBIRD MAHU Species # 4260 Band size: X-0A Species--Frm mst hummingbirds f N.Am by large size (wg 66.1-77.5, tl 37.4-51.1; see Age/Sex); bill black withut red. 9 frm 9 Blue-thrated Hummingbird by nares cvered