January1984] ShortCommunications 155 HILLS, M. 1978. On ratios--a response to Atchley, nov, Cramer-Von Mises and related statistics Gaskins and Anderson. Syst. Zool. 27: 61-62. without extensive tables. J. Amer. Stat. Assoc. 69: SAS INSTITUTE.1982. SAS user's guide: basics.Cary, 730. North Carolina, SAS Institute, Inc. ZAR, J. H. 1974. Biostatisticalanalysis. Englewood SHAPIRO,S.S., & M. B. WILK. 1965. An analysis of Cliffs, New Jersey,Prentice-Hall, Inc. variance test for normality (complete samples). Biometrika 52:591-611. Received3 March 1983,accepted 6 September1983. STEPHENS,M.A. 1974. Use of the Kolmogorov-Smir- A Hybrid Red Crossbill-Pine Siskin (Loxia curvirostra x Carduelis pin us) and Speculations on the Evolution of Loxia DAN A. TALLMAN • AND RICHARD L. ZUSI 2 'Departmentof Mathematics,Natural Sciences and Health Professions, Northern State College, Aberdeen,South Dakota 57401 USA; and 2National Museum of NaturalHistory, SmithsonianInstitution, Washington, D.C. 20560 USA On the morning of 27 December1981, a strange streaksweakest on lower throat and belly and dark- finch appeared at Tallman's feeder in a residential est and best defined on flanks and crissum. backyardin Aberdeen,Brown County, South Dakota. Upperparts dusky olive streaked or spotted with Alone and in the companyof Pine Siskins,the bird dark gray. Feathersof forehead and crown dark with consumedsunflower seeds.It fed on the ground and whitish or yellowish edges, giving spotted effect. alsocracked seeds while perchedon a sunflowerhead Longer feathers of nape, neck, and back dark gray hung from a clothesline.Tallman noted that this finch, borderedwith dusky olive laterally, giving streaked when approached,did not fly with a small siskin effect. Rump contrastswith back in having feathers flock but flew alone, silently, in a straightline from with paler olive centersand yellowish lateral edges. the feeder. The bird exhibited aggressiontoward sis- Upper tail coverts uniform grayish olive without kins feeding near it. The finch was obviously not a pronounced center streaks, darker than rump but regular North American species,being most like a paler than back.Superciliary line whitish with dusky siskin but larger, less boldly streaked, and with a streaks.Auricular patch dusky grayish olive. proportionately larger bill and head. Immediately Wings sooty; median and greater wing coverts with upon recognizing the bird as an oddity, Tallman pale, olive-whitish tips (and faint brownish cast)pro- opened Potter traps and mist nets and eventually ducing two narrow wing bars--the anterior one caughtit in a Potter trap. The bird was then prepared somewhat broken and the posterior one continuous. as a museum skin and sent to the National Museum Narrow yellow edgingson all primaries, exceptout- of Natural History, SmithsonianInstitution, where er, extending distally to point of emargination.Sec- Zusi identified it as a hybrid between the Red Cross- ondaries with short yellowish outer border toward bill (Loxiacurvirostra) and Pine Siskin (Carduelispi- tip (tips bilobed), becoming broader and whiter on nus).Apparently no previous reportsof a hybrid be- inner, superficialsecondaries. Inner vanesof prima- tween Loxiaand any other genusexist (Cockrum 1952, ries and secondarieswith broad silvery yellowish in- Gray 1958). ner border that narrows distally and ends proximal The absenceof damageto the bill, feet,or plumage to tip (at point of emargination in primaries). suggeststhat the bird had not been caged.We judged Tail strongly notched; sooty with yellow outer the bird--a female--to be at leasta year old from the edges. Edges least pronounced on outer and most completely ossified skull and the shape of its rec- pronouncedon inner feathersand broadestbasally. trices. The latter are more rounded at the tip and Inner vanes edged narrowly with whitish. have broader inner vanes than those of juvenile Label data include the following: bill dark slate crossbills and siskins. We therefore compared it gray, iris dark brown, legsand feet dark brown, gape mainly with adult females taken in December and whitish, skull ossified, little to moderate fat, no molt, January. ovary tiny. The specimen(USNM 582513)may be describedas Measurements of wing, tail, tarsometatarsus,and follows (seeFig. 1). Underpartswhitish, streakedwith bill are given in Table 1. They are compared with gray.Sides and flanksshading to grayisholive. Patchy thoseof 10 specimensof Carduelispinus pinus and 10 yellowish wash on lower throat, breast,belly, and of Loxiacurvirostra sitkensis--the smallest recognized crissum. Streaks neither bold nor sharply defined, North American race of the species.If wing length formed from longitudinal center stripes on feathers; is taken as an index of body size, the hybrid is closer 156 ShortCommunications [Auk,Vol. 101 Fig.1. Photographsof a hybridLoxia curoirostra x Carduelis pinus and the parental species. From left to rightin eachphotograph: Carduelis p.pinus, female, USNM 442040; Loxia curvirostra x Carduelis pinus, female, USNM 582513;Loxia curoirostra sitkensis, female, USNM 269830. in size to the smallest crossbill than to the siskin. edgeof the uppermandible is smoothlyconcave from Thetail of thehybrid is longer in proportionto wing baseto tip; the left edgeis somewhatangled near the length than that of the crossbilland similar to that middle of the bill. In the lower mandible the left side of the siskin.Tarsal length of the hybridand of the is smoothlyconcave and the right sideangled. The crossbillis relatively shorter than that of the siskin. tip of the uppermandible is deflectedslightly to the The lengthof the bill of the hybridis greaterthan right and the tip of the lower mandibleslightly to that of siskinsand is alsogreater in proportionto the left. These features are similar to those seen in wing length (13.6%in hybrid, 12.3%in siskin).Com- exaggeratedform in right-crossedcrossbills. Other parable measurements of the bill in Loxia could not crossbillfeatures are the dark auricularpatch, yel- be made. lowish rump, and spottedpattern on the forehead Several features indicate that Loxia is one of the and crown. parentsof the hybrid. On casualinspection, the bill The White-wingedCrossbill (Loxia leucoptera) is showsnone of the asymmetryof a crossbilland re- unlikely as a parent,because the wing barsof the semblesthe conicalbill of a siskin.Under magnifi- hybrid are narrower, not broader, than those of a cationof a dissectingmicroscope, however, the right siskin,and the uppertail covertsare olive ratherthan and left tomial edgesof each mandibleare different- blackish. ly shapedin dorsalor ventralview (Fig. 2). The right Charactersof the hybridthat indicateCarduelis pi- TABLE1. Measurements(mm)of adult female Carduelis p.pinus, Loxia curvirostra sitkensis, andthe hybrid Loxia curvirostrax Carduelispinus. Carduelisp. pinus Loxiac. sitkensis (n = 10) (n = 10) Measurements Mean SE Hybrid Mean SE Wing length 70.8 0.42 78.5 81.4 0.43 Tail length Inner rectrix 32.4 0.43 36.5 37.2 0.57 Outer rectrix 39.4 0.37 43.3 42.6 0.42 Tarsometatarsallength 14.2 0.05 15.1 15.5 0.19 Bill length from nostril 8.7 0.12 10.7 -- -- January1984] ShortCommunications 157 are noted among carduelinesfor their habit of feed- ing in a variety of positions,often head down or back down, and for holding conesor other food sources with one foot while extracting seeds with the bill (Newton 1967, Palmer 1968). The bills of Carduelis pinus,C. spinus(Siskin), C. carduelis(European Gold- finch), Loxia curvirostra,and L. leucopteraare laterally compressedfor much of their length and are provid- ed with fine, sharp points on both mandibles. Their bills differ from the thicker bills of most other species of the Carduelinae. The tweezer-like bills of the three speciesof Carduelismentioned above are used in part to extract seeds from cones and cone-like structures, in which scalesmay be forced apart by gaping. The depressor mandibulae muscle and the retroarticular processof the lower jaw are enlarged in C. carduelis, C. spinus,and C. pinusas part of an adaptive complex for gaping, but this is not true of other speciesof Carduelis,in which gaping does not occur (Newton a b 1967). These anatomical features are also found in Fig. 2. Outline drawingsof mandiblesof a hybrid Loxia,where they serve in a variety of forceful move- Loxia curvirostrax Carduelispinus (USNM 582513). a, ments of the lower jaw. Thus, these three speciesof upper mandible in dorsal view; b, lower mandible Carduelisappear to be preadapted for opening cone in dorsal view. Dotted median lines added to em- scalesby methods other than gaping and for opening phasize asymmetry. tougher and larger cones. In an ancestral form, lat- eral prying, as suggestedfor the hybrid, might favor the evolution of asymmetrical mandibles and jaw musclesand the further specializations of structure nus to be one of the parents are the extensively found in crossbills.An increase in bill and body size streaked,whitish underparts,the narrow (and faintly would probably have accompanieda shift to feeding brownish) wingbars, yellow outer edges to the bases on larger cones, as it has apparently in Palearctic of the primaries and toward the tips of the second- speciesand races of Loxia (Lack 1944a, b). The North aries, the broad whitish outer edgings on the inner- American races of Loxia curvirostra show more of a most secondaries,and the yellowish inner vanes of difference in body size than existsbetween the Pine the primaries and secondaries. Siskin and the smallest of the races of Loxia curvirostra The pattern of wear on the bill tips of the hybrid (compare Table 1 with measurements in Griscom is intriguing. Under magnification,the tips of both 1937), and a correlation with cone size is probable, mandibles were noted to be smoothly rounded by although it has not been thoroughly documented. wear, and the gonys and left surfacenear the tip of The feeding adaptationstypified in Carduelispinus the lower mandible showed wear in the form of a may have evolved more than once within the car- slight depression with irregular longitudinal stria- duelines, but among living speciesthey are known tions.