110 Continued timber harvesting in Literature Cited itselfmay notbeaconcern to the nesting Lumsden, H.G. 1984. The pre-settlement breeding , particularly when the operations distribution ofTrumpeter (Cygnus buccinator) take place during the winter months. and Tundra Swans (Cygnus columbianus) in eastern . Canadian Field-Naturalist 94: Disruption may occur, however, when 415-424. resource access roads are eventually Neilson. 1979. Ontario Geological Survey Maps openedfor recreational use. Boattraffic, 5106 and 5109. Ontario Ministry of Northern deposition of lead shot and accidental Development and Mines, Toronto. harassment of birds are potential Ontario Ministry ofNatural Resources. 1981. Kenora District Land Use Plan, Northwestern concerns. The forest management Region. practice of applying herbicides to Ryder, R.A. 1964. Chemical characteristics of harvested areas may affect the amount Ontario lakes with reference to a method of or suitability offorage available for the estimating fish production. Ontario Department ofLands and Forests Section Report (Fisheries) growing cygnets. No. 48.

Lillian J. Anderson, Ontario Ministry of Natural Resouces, Kenora District, Box 5080, Kenora, Ontario P9N 3X9

Harry G. Lumsden, 144 Hillview Road, Aurora, Ontario L4G 2M5

W. Bruce Ranta, Ontario Ministry of Natural Resources, Kenora District, Box 5080, Kenora, Ontario P9N 3X9

Nashville X Warbler Hybrids by Kenneth C. Parkes

Introduction Dr. Ross James ofthe Royal Ontario A wood warbler specimen identified as Museumcalled my attention to a second a hybrid between the specimen tentatively identified as a (Verlnivora ruficapilla) and the similar hybrid, and was kind enough to (V. peregrina) has send it to me for analysis. It seems been mentioned by Bledsoe (1988, cited appropriate to discuss both specimens by Morse 1989), Williams (1996), and in a single paper, and the Ontario Dickand James (1996), in each instance provenience of the second specimen based on information I supplied. The makes this journal an appropriate detailed analysis of this specimen has publication outlet. not been published, however.

ONTARIO BIRDS DECEMBER 1996 111 Materials and Methods though this series sufficed for colour The first specimen, Carnegie Museum comparisons, it was desirable to have ofNatural History (CM) no. 152341, a additional specimens to enlarge the male in first basic plumage, was netted sample for analysis ofmeasurements. I during routine -banding activity at therefore selected specimens prepared the museum's Powdermill Nature by W. E. Clyde Todd and George M. Reserve near Rector, Westmoreland Sutton and marked "im." on the label; County, Pennsylvania (the site of the both ofthese collectors were known to extinct village of Crisp, which is still me to have utilized incomplete cranial shownonsomeroadmaps)on26 August pneumatization as an ageing character 1979. It was recognized as unu~ual and for young birds. probably a hybrid Nashville X Before combining the measure­ Tennessee by bander Robert C. ments of the two samples (those with Leberman, who summoned me to and those withoutcranialdataon labels), Powdermill to examineit. Wecollected I analyzed them separately. The the bird under state and federal permits, differences between the means of the and I prepared the specimen at the two samples I considered to be trivial, Reserve. I noted testes slightly smaller and influenced by the small size of the than 1x1mID, and a craniumcompletely individual samples. Thus themean wing clear (i.e., not pneumatized). It weighed length for 6 male Nashville Warblers 8.7 g and had little fat. with cranial data was 59.2 mID, and for Thenew specimenis Royal Ontario 3 without such data 58.2 mID. For the Museum (ROM) 159630, a female, also combined series of 9 the mean was in first basic plumage. It was netted, 58.8. For the Tennessee Warbler also during bird-banding operations, at samples the match was even closer; for Porphyry Island, near Thunder Cape 8 males with cranial data the mean was Bird Observatory in Sleeping Giant 65.1 mID, and for 6 without cranial data (formerly Sibley) Provincial Park, it was 65.0 mm; for the combined series Thunder Bay District, by David Shep­ of 14 the mean was also 65.0. herd, then Managerofthe Observatory, The colours of these warblers are on 25 August 1994. The specimen and subtle, so I used vernacularcolournames its data were transmitted to the ROM by rather than those ofone ofthe available David Brewer, who suggested the colour guides. As there is sexual Nashville X Tennessee parentage. The dichromatism in both species, label indicates that the bird weighed comparisons with each other and with 8.1 g with light fat, and had an the hybrids were made sex-for-sex. unpneumatized cranium ("SNCO" = Measurements were taken to the "skull not completely ossified"). nearest 0.5 mm of the flattened wing, I made comparisons of both the tail, and the bill from the anterior specimens with series ofNashville and pointofthe nostril to the tip ofthe upper Tennessee warblers at CM, initially mandible. As measuring progressed, using only specimens on the labels of patterns becameevident such that a few which the preparator had indicated specimens could beconsideredas almost graphically or in words the extent of certainly missexed; measurement cranial pneumatization, if any. AI- discrepancies were concordant with

VOLUME 14 NUMBER 3 112 colourcharacters. Suchspecimens were and Corbin (1978), within the north­ not included, however, in the size eastern trio under discussion, the analyses. Tennessee Warblers are Tennessee Warbler is slightly distinctly longer-winged than differentiated from the Nashville/ Nashvilles, but tail and bill measure­ Orange-crowned pair. The latter two, it ments are virtually identical. will be noted, are characterized by an orange- or reddish-brown crown patch Results in males, although this is also an Graves (1990, 1993) has advocated a uncommon variant in adult male procedure of determining a pool of Tennessee Warblers (Dick and James possible parent species for putative 1996). Only 1 of 25 reliably sexed hybrids, followed by a process of males of V. c. celata in basic plumage character-based elimination. Fortun­ (both first and definitive) in the eM ately, this determination for the collection lacks at least a trace of a Pennsylvania and Ontario hybrids is crown patch, and it is present in 9 of25 simplicity itself. The straight, sharply females as well. Neither hybrid shows pointed bills of the hybrids are found any trace of a crown patch, strongly among North American wood warblers suggestive that one ofthe parents was a only in the genera and species lacking thepatch(i.e., Tennessee Parula; neither ofthe hybrids displays Warbler in first basic plumage), more any trace of the distinctive colour and persuasive for the male hybrid. pattern of Northern Parula (P. Several points argue against the americana). The only species of Orange-crowned Warbler as one ofthe Vermivora breeding in eastern North parents. The underparts ofboth sexes of America are the sympatric Nashville, V. c. celata in basic plumage are Tennessee, and Orange-crowned characterized by blurry olive-green Warblers (V. ruficapilla, peregrina, and streaks on a greenish yellow celata), and the Blue-winged/Golden­ background. Neither hybrid shows any winged Warbler complex (V. pinus and sign of ventral streaking. Orange­ chrysoptera), to which the presumably crowned Warblers lack any white area extinct Bachman's Warbler (V. in the lower abdomen; such an area is bachmani) appears to have been related. present in both the Tennessee and Again, the hybrids show no indication Nashville Warblers (smaller in the of the distinctive colour and pattern latter). Both hybrids have white in that characters of this latter group. The area, more in the female than in the Tennessee, Orange-crowned and male. Nashville Warblers (plus the south­ In Nashville Warblers in first basic western relatives of the latter) form a plumage, there is an area of a richer closely related group of species for concentration ofyellow, almost orange, which a new generic name will have to in the mid-breast; it is more obvious in be found, as the genus Verlnivora (type females only because of the brightness species V. pinus) as presently constituted ofthe surrounding area in males. There appears to be polyphyletic (N. Klein, is a slight suggestion of this in some pers. comm.). According to the protein female Tennessee Warblers, but it is of electrophoretic studiesofBarrowclough a much greener yellow and is wholly

ONTARIO BIRDS DECEMBER 1996 113 lacking in males. There is no trace of however, is more like that of the such a concentration of pigment in pigmented area ofthe male Tennessee, Orange-crownedWarblers. Itis present, i.e., a more greenish yellow than that of although subdued, in both hybrids. the Nashville. As mentioned earlier, For reasons outlined above, I there is an area of pigment concentra­ believe that the Orange-crowned tion on the breast that approaches the Warblercan bediscounted as apossible orange-yellow colour of this area in parent of either of the two hybrids. Nashvilles. The throat is paler and Comparisons between the two appears grayer than the posterior putative parent species and the two underparts, reminiscent of female hybrid specimens follow. All references Nashvilles.·The short throat feathers to theNashvilleandTennesseeWarblers are actually tipped with pale yellow, refer to birds in frrst basic plumage. but the overall grayerappearanceofthe throatis caused by the darkgray feather Underparts bases showing through. The undertail MaleTennessees are duller (less yellow) coverts of male Tennessees are nearly below than females, the reverse of the pure white, lightly washed with greenish situation in Nashvilles, in which the yellow; those of male Nashvilles are general yellowofmales averages some­ rich yellow. Those of the male hybrid what more intense than in females. In are fully pigmented, but with a greenish male Nashvilles, the yellow extends to yellow similar to the breast colour of the chin, whereas in females, the chin bright male Tennessees. and upper throat are more buffy. The The female hybrid has about the flanks are slightly brownish in females, sameamountofwhiteonthe underparts and there is always some white on the as female Tennessees, but it is faintly lower abdomen. In males, the yellow washed with greenish yellow. The extends to theflanks and there is a much pigment of the breast is neither as smaller whitish area in the lower greenish as in Tennessees nor as rich abdomen adjacent to the bright yellow yellow as in Nashvilles; it is more like undertail coverts. Tennessees have a the Tennessee, but duller. The chin, much larger area of white posterior to throat, and upper breast are continuous the breast, variable in extent butgreater in colour, as in the Tennessee, rather in males. In extreme male specimens than differentiated as in female (such as CM 150579, Pittsburgh, PA, 9 Nashvilles. As mentioned earlier, it has September 1975), the upper breast is the typical Nashville brighter spot in barely stained with greenish yellow, the middle of the breast. Its flanks are with the rest of the underparts (except midway between the greenish of the flanks) being white. The breast and female Tennessee and the browner flanks of females are bright greenish colour of the female Nashville. The yellow, duller and grayer in males. undertail coverts are like those of the In the male hybrid, the distribution Tennessee, white with a wash of ofpigment on the underparts is similar greenish yellow. to that of male Nashville Warblers, in that white is confined to a small area of the posteriormostabdomen; thecolour,

VOLUME 14 NUMBER 3 114 Upperparts this species, contrasting with the gray The upperparts of male and female of the sides of the face (browner in Tennessee Warblers, extending to the females). The lores are pale, only crown, are virtually identical in colour, slightly darker than the eyering, and an essentially uniform green, with thereis no darkpostocularline. In some occasional individuals slightly grayer. specimens there are a few palefeathers, Therump is barely perceptibly brighter mostly concealed, attheupperposterior green in mostindividuals ofboth sexes. corner of the eyering. The upperparts of Nashville Warblers In the male hybrid, the sides ofthe are not uniform. The midback is green face are nearest the Nashville in colour, (never brown as portrayed in Plate 2 of but slightly greener. The eyering is Curson et al. 1994), but darker and exactly like that ofthe Nashville, but in duller than in Tennessees, and slightly addition there is a caudad extension of brighter in males than in females. This about 5 mm from the upper edge ofthe contrasts with the crown and nape, eyering, just where the Tennessee has which are grayish brown, averaging the posterior portion ofits superciliary grayer in males (which, in addition, line. The lores are not differentiated have a reddish-brown crown patch). from thegeneral face colour, resembling The rump is distinctly brighter green the Nashville in this. The face of the than the midback; this colourresembles female hybrid is similar, but the caudad the back colour ofTennessee Warblers extension at the top of the eyering is and is brighter and more contrasting in shorter (about 4 mm). males than in females. In the male hybrid, the midback is Wings nearer the colourofthe Tennessee than InbothsexesoftheTennesseeWarbler, the Nashville, but the crown is just thegreatersecondarycoverts aretipped preceptibly darker than the midback. with greenishyellow orwhitish, forming Thecontrastbetweenmidbackandrump a usually inconspicuous wingbar; it is is slightly greater than in Tennessees, fairly obvious in some and virtually butless than inNashvilles. In thefemale, absent in others. In a very few the the crown and midback are essentially median coverts are also tipped, such the same as in the male, but the rump is that there are two quite distinct wing­ slightly paler, making the contrast with bars (cf. CM 150579, Pittsburgh, PA, 9 the midback more abrupt. September 1975, and CM 166706, Youngstown, 08, 25 September 1982, Face both male TV tower kills). A similar InTennesseeWarblers, thereis adistinct range ofvariation is found in Nashville pale gr~nish yellow superciliary line Warblers, except that the spots on the (whiter in males), bordered below by greatercoverts, ifpresent, are white and blackish lores and a short dark spots are rarely if ever found on the postocularline. Thesides ofthe face are median coverts. In the male hybrid, ofabout the samegreenish colouras the there are minute yellowish tips on the breast. There is no eyering. In the greater coverts that would quickly Nashville, theconspicuous buffy-white disappearwith wear. Theyellowish tips eyering is a well-known field mark for are more conspicuous in the female.

ONTARIO BIRDS DECEMBER 1996 115 Measurements in millimetres Nashville Warbler: Males (9) Females (13) wing 57.5 - 60.5 (58.8) sd 0.968 53.5 - 59.5 (56.9) sd 1.635 tail 40.5 - 46.5 (43.2) sd 2.151 37.0 - 44.5 (41.0) sd 1.952 (n=8) bill 7.5 - 10.0 (8.6) sd 0.678 7.5 - 8.5 (8.1) sd 0.300

Tennessee Warbler: Males (14) Females (22) wing 62.5 - 67.0 (65.0) sd 0.865 59.0 - 64.5 (61.6) sd 1.449 tail 42.0 - 45.0 (43.3) sd 0.935 39.5 - 43.5 (41.4) sd 1.158 (n=13) bill 8.0 - 9.5 (8.6) sd 0.463 7.5 - 9.5 (8.6) sd 0.549

Hybrids: Male: wing 61.0, tai143.0, bill 8.0 Female: wing 59.0, tail 39.0, bill 8.5

The marginal wing coverts, Its tail is 0.5 nun shorter than any underwing coverts, and axillars are Tennessee measured, and 2 mm longer nearly pure white in most Tennessee than the shortest Nashville, but still 2 Warblers (washed with greenish yellow mID less than the mean for Nashvilles. in some). In the Nashville Warbler, Its bill is near the mean for Tennessees these feathers are bright yellow. In both and the same size as the largest hybrid birds, these feathers are pale Nashville. yellow, whiter in the female. The wing of the male hybrid is Discussion intermediate - shorter than the shortest In a series of papers on avian hybrids, Tennessee, longer than the longest Graves (1996 and papers cited therein) Nashville. The mean tail length for has performed rather elaborate statis­ males ofthetwo paternal species differs tical treatments of measurement data by only 0.1 mm, and the tail of the ("bivariate plots offactor scores from a hybrid is thus 0.3 mm shorter than the principal componentsanalysis"). These mean for Tennessees and 0.2 shorter are undoubtedly useful when the than the meanfor Nashvilles. Themeans parentage is controversial (as in Graves for male bill length are identical for the 1988), butinotherinstances, they simply two species~ the male hybrid is 0.6 mm confirm what was already obviousfrom shorter than this mean of 8.6; equal to plumage characters as well as raw the smallest Tennessee and 0.5 mID measurement data. I believe the case longer than the smallest Nashville. for the parentage postulated for the two The wing of the female is also specimens reported herein is strong essentially intermediate; equal in size enough not to warrant devoting the to theshortestTennessee(59) and within time and space for the additional 0.5 mID ofthe longest Nashville (59.5). analytical procedures.

VOLUME 14 NUMBER 3 116 These specimens apparently Curson, l., D. Quinn, andD. Beadle. 1994. Warblers constitute the first intrageneric hybrids ofthe Americas. Houghton Mifflin, Boston and . within Vermivora as that genus is Dick, l.A. and R.D. lames. 1996. Rufous crown presently constituted, other than those feathers in adult male Tennessee Warblers. between the Blue-winged and Golden­ Wilson Bulletin 108: 181-182. winged Warblers. There are no other Graves, G.R. 1988. Evaluation of Vermivora X hybrids known in which the Tennessee Oporornis hybrid wood-warblers. Wilson Bulletin 100: 285-289. Warbler is one of the parents; the Graves, G.R. 1990. Systematics of the "green­ NashvilleWarbleris oneofthe putative throated sunangels" (Aves: Trochilidae): valid parents in the first known "Vermivora" taxa or hybrids? Proceedings of the Biological X Dendroica hybrid (Parkes, in prep.). Society of Washington 103: 6-25. Graves, G.R. 1993. A new intergeneric wood warbler hybrid (Parula american{~ X Dendroica Acknowledgements coronala) (Aves: Fringillidae). Proceedings of I am indebted to Ross James for calling the Biological Society of Washington 106: my attention to the Ontario specimen 402-409. Graves, G.R. 1996. Hybrid wood warblers, and arranging for me to borrow it and to Dendroica striataX Dendroicacastanea(Aves: study itfor publication. He read the first Fringillidae: Tribe Parulini) and the diagnostic draft of this paper, and had several predictability of avian hybrid phenotypes. useful suggestions for its improvement. Proceedings of the Biological Society of Washington 109: 373-390. Morse, D.H. 1989. American Warblers. Harvard Literature Cited University Press, Cambridge, Massachusetts. Barrowclough, G.F., and K. W. Corbin. 1978. Williams,l.M. 1996. NashvilleWarbler(Vermivora Genetic variation and differentiation in the ruficapilla). In The Birds of , Parulidae. Auk 95: 691-702. No. 205 (A. Poole and F. Gill, editors). Bledsoe, A.H. 1988. A hybrid Oporornis Academy of Natural Sciences, Philadelphia, philadelphia X Geothlypis trichas, with and American Ornithologists' Union, comments on the taxonomic interpretation and Washington, D.C. evolutionary significance of intergeneric hybridization. Wilson Bulletin 100: 1-8.

Kenneth C. Parkes, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213 USA

ONTARIO BIRDS DECEMBER 1996