A NEW HYBRID , ARCHILOCHUS ALEXANDRI X SELASPHORUS SASlN

JAMES F. LYNCH

AND PETER L. AMES1 Museum of Vertebrate Zoology University of California Berkeley,California 94720

On 16 May 1968 we observed two unusual characters of this individual appeared to be male at Courtland, Sacramento closely similar to those of the specimen that County, California. We had been informed of was preserved. the presence of these by Mr. and Mrs. The specimen is an adult male in breed- Arvil Parker, whose yard had been visited ing condition (left testis 2.5 x 2.0 mm) and regularly by the two hummingbirds since 28 weighed 3.2 g at the time of capture (the April 1968. It was immediately apparent that other hybrid weighed 3.3 g). On the basis these individuals were not referable to any of coloration, pattern, and certain mensural known of North American humming- characters, the specimen appears to be inter- . Although they resembled the locally mediate between A. alexandri and either Selas- abundant Black-chinned Hummingbird (AT- phorus sasin or S. rufus. The fact that the chilochus abxandri), they also showed un- outermost rectrices of the hybrid are slightly mistakable influence of Selasphorus through wider than those of S. sasin but are narrower the presence of abundant rufous pigmentation than those of either S. rufus or A. alexandri on the tail, flanks, and back. Perhaps the most suggests that S. sa.sin is involved in the cross. distinctive field mark of the hybrids was the This conclusion is supported by the absence gorget, which was different in color and form in the hybrid of rufous pigment in the mid- from that of Archilochus and the two species dorsal region. The zoogeographical relation- of Selmphorus that occur in central California. ships of the two species of Selasphorm also Both of the hybrids were captured alive, indicate S. sasin as the most likely parent. The together with seven A. abxandti and one male (S. rufus)occurs as a Allen Hummingbird (Selusphorus win). In migrant in most of California. The only reliable accordance with the wishes of the Parkers, one breeding records for this species in the state of the hybrids was released after we had are in the mountains of Trinity County, more carefully observed its plumage and removed than 150 mi. NW of Courtland (Talmadge an outer rectrix for later comparison with 1953). The Allen Hummingbird, on the other study skins. The second hybrid was main- hand, is a common breeding bird in the coastal tained at Berkeley in a large aviary where its hills 45 mi. W of the locality where the hybrid behavior was observed and compared with was taken ( Grinnell and Miller 1944), and in that of examples of A. alexandri and S. sasin. recent years it has been observed to remain in (These observations will be included in a the Courtland area throughout the breeding behavioral study of hummingbirds to be pub- season (A. Parker, pers. comm. ) . We observed lished by Fernando Ortiz-Crespo. ) On 22 at least two adult males and an immature bird May 1968 the hybrid died and the skin was of this species in the same locality where the deposited in the Museum of Vertebrate Zool- hybrids were taken. It thus seems very likely ogy (No. 158783). Samples of blood, pectoral that the two hybrid hummingbirds represent muscle, and testis tissue were taken for bio- crosses (or a single cross) between A. alex- chemical and karyological tests. andri and S. s&n.

ACCOUNT OF THE HYBRID DESCRIPTION The following description is based upon data Adult males of the presumed parental species gathered from the second hybrid. While it were used in all comparisons. was impossible to make comparably detailed Capital tract. The crown feathers of A. observations on the bird that was released after alexandri appear dark green and dusky gray. brief examination in the hand, the plumage The corresponding feathers in S. susin lack the extensive dusky color and have much 1 Presentaddress: Encyclopaedia Britannica, 425 North Mich- igan Avenue, Chicago, Illinois 60611. rufous mixed with the green. In the hybrid 12091 The Condor,72:209-212, 1970 210 JAMES F. LYNCH AND PETER L. AMES

hybrid ;J JeZasph0ru.s sasin

FIGURE 1. Comparison of gorgei ring, and tail shapes in the hybrid and two parental species. In the large drawings of the tail, heavy stipple green, light stipple = rufous, hatching = black. these feathers are similar to ’ those of A. aler- feathers extend farther posteriorly in the Allen andri, but traces of rufous pigment are present. Hummingbird than in the Black-chinned Hum- The frontal and loral regions are sooty mingbird (fig. 1). The hybrid is intermediate greenish in the Black-chinned Hummingbird in this respect. In S. sasin the entire gorget is and mixed rufous and green in the Allen brilliant orange-red. All the gorget feathers Hummingbird. The hybrid is intermediate, have rufous bases. In A. alexandri the poste- but clo~serto the former species, showing a rior half of the gorget is deep purple. The gray-green color with a trace of rufous. Both feathers in this region have sooty gray bases parental species and the hybrid have white separated from the purple tips by an iridescent postorbital spots. greenish stripe. The anterior half of the gorget Spinal tract. In both species the dorsum is dull black. In the hybrid, the posterior two- appears bronze-green, but in S. sasin consider- thirds of the gorget is composed of feathers able rufous is admixed, especially in the dorso- that have sooty bases and red-purple tips that lateral region. The hybrid is intermediate, become deeper purple along the extreme distal showing traces of rufous in the dorsolateral margin. The iridescent green stripe charac- region. teristic of Archiluchus is present, but reduced VentvaZ tract. Feathers of the malas and in the hybrid. The anterior third of the gorget auricular regions are uniformly blackish in of the hybrid is composed of feathers with A. alexan& and rufous in S. s&n. In the brownish bases and sooty tips. hybrid these feathers are gray-black with fine The sternal and abdominal regions are brownish flecks. smoothly blended rufous and white in S. s&n, .The gorgets of the two species are similar while in A. alexandri these areas are faintly in general form, except that the iridescent barred greenish and gray with no trace of A NEW HYBRID HUMMINGBIRD 211

m Selosphorus sasin •i- hybrid m Archilochus alexanari’

Length of fourth rectrix Length of exposed culmen

-=- (N=l9) -@@-- (N=201

-&- (N-19) (N =18) -&

I I I I I I I I I I I I I I 20 22 24 26 28 16 18

Length of Wing length central rectrix

(N=l9) -e + (N=l9)

-acEt-_- ,,=:I (N=IE)

I I I I I I I I I I I I I I 1 22 24 26 28 38 40 42 44 mm FIGURE 2. Comparison of mensural characters in the hybrid and representative series of the parental species. Horizontal lines show the range of measurements, vertical lines indicate the mean. The open rectangles mark the standard deviation of the samples. The black and patterned rectangles indicate the 95 per cent confidence limits for the mean. rufous. The hybrid is close to the latter species The individual rectrices are narrower in S. in the overall appearance of the ventral region, sa.vinthan in A. alexandri, especially in the but some rufous is present, especially on the cases of pairs 4-4 and 5-5. In the hybrid these flanks and lower abdomen. feathers are intermediate in shape and width. Alar truct. The small feathers of the leading The pigmentation of the rectrices of the edge of the wing distal to the wrist are rufous parental species is strikingly different. Viewed in the Allen Hummingbird, while in the Black- dorsally, the rectrices of S. susin are rufous chinned Hummingbird they are sooty with a with varying amounts of black on the feather white margin and brownish tips. The hybrid tips and margins. In A. alexundri rectrices l-l is intermediate, having both sooty and rufous are iridescent green, while the others are in these feathers but lacking white. purple-black with faintly greenish tips. The Primaries 9 and 10 of male Allen Humming- hybrid is clearly intermediate, exhibiting birds are narrow and pointed, while in the rufous, green, and blackish coloration. B!ack-chinned Hummingbird these feathers are wider and well-rounded. As can be seen MENSURAL CHARACTERS from figure 1, the outer primaries of the hybrid The parental species are similar in overall are intermediate in form. body size, as measured by body weight (mean In A. alexandri primaries 3-7 are angular in = 3.3 g for S. se.& vs. 3.1 for A. alexandri). outline and possess a peculiar notch on the The two hybrids (3.2 and 3.3 g) are well trailing edge. In S. sasin these feathers are within the range of variation of both species. much more rounded and lack the notches. In Despite the similarity between the parental the hybrid the notches are missing, but the species in body weight, there is essentially no feathers are angular in outline. overlap in wing length, length of culmen, Caudal tract. In S. sasin rectrices l-l (the length of central rectrix, and length of fourth central pair) are longest, and 5-5 shortest, rectrix (fig. 2). In all these characters the the result being a pointed tail shape. In A. hybrid falls between the means of the two alexundri rectrices l-l are shortest, while 4-4 species. It is impossible, however, to separate are longest, producing a forked configuration the hybrid from the parental species on reli- of the tail. In the hybrid, rectrices 2-2 and able statistical grounds, since in every case 3-3 are longer than the others, and the tail is the hybrids measurements fall within the ob- thus intermediate in shape between the paren- served limits of variation of one or the other tal species (fig. 1) . parental distribution. 212 JAMES F. LYNCH AND PETER L. AMES

DISCUSSION preliminary attempts along these lines have It seems certain that the attainment of local not been successful. Fred McCollum exam- sympatry between S. sasin and A. alexandri in ined extracts from pectoral muscle and blood the Sacramento Valley has occurred very by means of starch gel electrophoresis. Spe- recently. In this case, as in so many others, cific stains for lactate dehydrogenase (LDH) the spread of a species (S. sasin) has probably and hemoglobin revealed no significant differ- been made possible by human alteration of ences among the parental species and the the original habitats of the region. Specifi- hybrid in the electrophoretic mobility of either cally, the ecological and microclimatic aspects of these proteins. Further work, now in prog- of the Sacramento Valley have been drastically ress, may reveal the existence of suitably changed by the introduction of irrigated sensitive biochemical taxonomic characters. orchard and ornamental trees and by the SUMMARY planting of flowering forbs and shrubs. These Two adult male hummingbirds of the hybrid changes have evidently been sufficient to allow combination Archilochus alexandri x Selas- S. satin, a species normally restricted as a phows sasin were observed in Courtland, breeding bird to the relatively sheltered and Sacramento County, California, in late spring, moist conditions of the coastal chaparral belt 1968. Both birds were examined in the hand; ( Miller 1951)) to invade an area that was one was collected and is described in detail. formerly unsuitable. In California, A. alexan- This new hybrid combination raises to at least dri is a typical species of the warm, relatively 10 the number of intergeneric hybrid hum- dry interior valley, and has been able to mingbird crosses reported from North Amer- adjust quite well to human influence, such ica. The hybridization is viewed as one result that it is extremely common in many agricul- of the recent attainment of sympatry of the tural and residential areas (including Court- parental species in the Sacramento Valley, land). Whether or not future observations California. indicate that frequent hybridization between the two species, reflecting a chronic break- ACKNOWLEDGMENTS down of ecological and/or behavioral isolating We wish to thank Mr. and Mrs. A. Parker, whose keen mechanisms, is an integral part of this newly observation led to our recognition of the hybrids. F. attained sympatry, the situation is of consider- Ortiz-Crespo and W. Davis provided valuable logistic support, without which the birds might not have been able ecological and zoogeographical interest. captured alive. F. McCollum kindly performed the The question of hybrid fitness is, of course, electrophoretic tests on extracts from the blood and an important one. As judged by size, apparent pectoral muscle of the hybrid specimen and examples physical condition, and aggressive behavior of both parental species. N. K. Johnson read the toward other hummingbirds, the somatic fit- manuscript and offered critical advice and stimulating discussion on problems concerning hummingbird hy- ness of the hybrids did not appear unusually bridization. Gene M. Christman prepared the illustra- high or low, relative to the local examples tions. of the parental species. The fact that both LITERATURE CITED hybrids had survived for at least a year and BANKS, R. C., AND N. K. JOHNSON. 1961. A review had presumably undergone a round-trip mi- of North American hybrid hummingbirds. Condor gration to Mexico indicates a lack of gross 63: 3-28. somatic defects. While direct evidence of GRINNELL, J., AND A. H. MILLER. 1944. The dis- reproductive viability is lacking, the specimen tribution of the birds of California. Pacific Coast collected did have normally enlarged testes Avifauna, no. 27: l-668. MILLER, A. H. 1951. An analysis of the distribution and abundant spermatocytes in the testicular of the birds of California. Univ. California Publ. lumina. Zool. 50:531-644. The discovery of this new intergeneric SHORT, L. L., AND A. R. PHILLIPS. 1966. More North American hybrid hummingbird com- hybrid hummingbirds from the United States. bination, bringing the total number of such Auk 83:253-265. SIBLEY, C. G. 1957. The evolutionary and taxonomic combinations to at least 10 (see Banks and significance of sexual dimorphism in birds. Con- Johnson 1961; Short and Phillips 1966), lends dor 59: 166-191. additional support to the oft-expressed view TALMAIXZE, R. R. 1953. Rufous Hummingbird nest- (Taylor 1909; Sibley 1957; Williamson 1957; ing in- California. Condor 55: 155-156.- Banks and Johnson 1961; Short and Phillips TAYLOR. W. P. 1999. An instance of hvbridization in hummingbirds, with remarks on the weight of 1966) that the time is ripe for a thorough generic characters in the Trochilidae. Auk 26: study of the generic limits within the Trochi- 291-293. lidae. Biochemical methods promise to pro- WILLIAMSON, F. S. L. 1957. Hybrids of the Anna vide some of the new kinds of characters that and Allen Hummingbirds. Condor 59: 118-123. will be required in such a study. Our own Accepted for publication 12 December 1968.