A NEW HYBRID HUMMINGBIRD, 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 hummingbirds at Courtland, Sacramento closely similar to those of the specimen that County, California. We had been informed of was preserved. the presence of these birds 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 species of North American humming- characters, the specimen appears to be inter- bird. 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 Rufous Hummingbird (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.