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BROWER,L. P., B. S. ALPERT,AND S. C. GLAZIER. 1970. sonia), p. 133-154. In A. C. Bent, Life histories of Observational learning in feeding behavior of Blue North American jays, crows, and titmice. U.S. Natl. Jays (Cyanocittacristata). Am. Zool. 10:475-476. Mus. Bull. 191. (Dover reprint, 1964). DINSMORE,J. J. 1973. successof Cattle Egrets, MACKWORTH-PRAED, C. W., AND C. H. B. GRANT. 1955. Bubulcusibis. Am. Midl. Nat. 891242-246. Birds of eastern and northeastern Africa. Vol. II. DIXON, J. S. 1944. California jay picks ticks from mule Longmans Green and Co., London. deer. Condor 46:204. SCHULZ, T. A., AND P. D. BUDWISER. 1970. Scrub Jay HEATWOLE,H. 1965. Some aspectsof the associationof possiblyfeeding on ectoparasitesof a black-taileddeer. Cattle Egretswith cattle. Anim. Behav. 20:42 l-424. Calif. Dept. Fish Game Bull. 56 (January). HOWELL,T. R. 1979. Breeding biology of the Egyptian SKEAD, C. J. 1951. Notes on honeyguidesin southeastern Plover, Pluvianusaegyptius. Univ. Calif. Publ. Zool. Cape province, South Africa. Auk 68:52-62. 113. LINSDALE,J. M. 1937. Natural history ofMagpies. Pacific Point ReyesBird Observatory,4990 ShorelineHighway, Coast Avifauna 25. Stinson Beach, California 94970. Received 13 January LINSDALE,J. M. 1946. American Magpie (Picapica hud- 1984. Final acceptance7 November 1984.

The Condor87:147-148 24 l-242, 1971) describeda similar instanceof feeding by 0 The CooperOrnithological Society 1985 Pied-billed Grebes and Snowy Egrets (Egretta thula) in which the grebeswere chasingsmall fish into shallowwater A MUTUALISTIC FEEDING where they were capturedby both species,the grebesben- efitting by the herons “chasing” fish from their refuge in ASSOCIATION BETWEEN vegetation. Mueller et al. (Auk 89:190, 1972) reported BOAT-TAILED GRACKLES similar interactions between Pied-billed Grebes, a Tri- AND PIED-BILLED GREBES colored Heron (E. tricolor),and a Snowy Egret. Paulson (Auk 86:759, 1969) reviewed examples of feeding asso- ciations between other grebe species and other aquatic JEROME A. JACKSON birds. The observation reported here is novel in that it involved interaction with a terrestrial bird species, and unusualprey for the grebes. Similar involvement of multiple individuals of two bird At noon on 25 December 1978, I observed a feeding as- specieswas described by Clark (Fla. Field Nat. 6:45-46, sociation between Pied-billed Grebes (Podilymbuspodi- 1978) for a feeding associationof American White Peli- ceps)and female Boat-tailed Grackles (Quiscalusmajor) on Horn Island, approximately 10 km south of Ocean cans (Pelecanuserythrorhynchos) and Wood Storks (Myc- teria americana), and by Rodgers (Fla. Field Nat. 6:44- Springs, Jackson County, Mississippi. My attention was drawn to the birds becauseof their numbers, proximity 45, 1978) for Brown Pelicans(Pelecanus occidentalis) and Wood Storks.Both ofthesecases also recognized one species to one another, and their frenzied behavior. Observations were made with a 20 x spotting scopefrom 30 m away at (the Wood Stork) as the primary beneficiary of the asso- ciation. Those associationsmight also have been mutu- a ca. l-ha freshwaterpond fringed with yaupon (Ilex vom- alistic, however, becausefish that escapedthe Wood Storks itoria) and low (~0.3 m) grassesand herbaceousvegeta- tion. When first seen,two grebeswere feeding within 1 m were probably often herded back into the path of the pel- of one another and within 0.3 m of a grassy shoreline. ican assemblages. Suchinteractions involving multiple individuals of each Water depth did not exceed 0.2 m and the grebes were predatorspecies herding multiple prey individualsare likely capturing prey from the surface. A tight group of eight to be mutualistic. Various authors have referred to such female Boat-tailed Grackles was clustered at the water’s associationsas “cooperative” (e.g., Leek 1971) or “com- edgenear (often within 0.1 m) the grebes.The mixed group mensal” (e.g., Paulson 1969, Clark 1978, Rodgers 1978). moved steadily along the shore at about 1 m/10 s. None of the interspecificassociations there describedsug- As the grackles worked their way through the grass, gested that the relationship resulted from active associa- climbing, hopping, and flying, I sawnumerous grasshopper tion by both species.Rather it appearsthat one, the grebe nymphs jumping in front of them. Some were captured or the Wood Stork in the casesdescribed above, was at- by the grackles,others escapedto the water where many tracted to the feeding activities of the other. Thus “co- were caught by the grebes, and still others escapedback operative” seemsan inappropriate descriptor.In all of the to land either to be eaten by waiting grackles or to be casesdescribed here, however, both speciesprobably ben- chasedback to the water. Becauseof the rapid movement, efitted from the activity, albeit the grebesand storks per- the number of birds, and the partially obscuringvegeta- haps more so. Thus, the associationsare more than “com- tion, it was difficult to determine capture rates. For brief mensal.” It seemssignificant that in none of the caseswas periods when I was able to keep one bird in view, grackles interspecificevasive or aggressiveactions observed. This caught grasshoppersat an average rate of one every 9 s (range 5-17 s, n = 11) and grebescaught grasshoppersat supportsthe notion that the associationswere mutualistic. a rate of one every 11 s (range = 5-23 s, n = 14). These It is easy to imagine, however, that under circumstances of more distant or closer associationand/or decreasedor peak rates were for individuals closestto the water’s edge, increased numbers of grebes, the relationship might be- capture rates seemed slower for birds more distant. This come one of or , respec- feeding frenzy continued for nearly 20 min, at which time tively. Interspecificfeeding associations thus seemto form the group arrived at a densecattail (Typha latifolia) stand. a gradedseries from commensalismto to klep- The gracklesthen flew off as a group and the grebesdis- toparasitism, depending on the closenessof the birds and appearedinto the cattails. the numbers of the “benefitted” species. Although the grebeswere the primary beneficiaryof the feedingassociation, the observedbehavior was mutualistic I acknowledgeboth logistic and financial support from rather than merely commensal. Most captures by both the U.S. National Park Service,GulfIslands National Sea- speciesresulted from flushingof the insectsback and forth shore, for my studies on the National Seashoreislands. between the land and the water. Leek (Am. Midl. Nat. 86: Stephen Cofer-Shabica, Jim Ray, and numerous park 148 SHORT COMMUNICATIONS rangers have facilitated my work. Ron Mumme and an Departmentof BiologicalSciences, Box Z, MississippiState anonymousreviewer made helpful comments on an earlier University,Mississippi State, Mississippi39742. Received draft of the manuscript. 1 March 1984. Final acceptance26 July 1984.

The Condor87:148-150 The major color differencesbetween C. sordidusand C. 0 The Cooper Ornithological Society 1985 latirostrisare as follows (C. latirostrisin parentheses):(1) throat dull sootv-arav.,._. ,, each feather with a concealeddark- RE-EVALUATION OF THE er gray subterminal area (strongly glittering bluish-green to purplish-blue); (2) midbreast sooty-gray(metallic, i.e., “HYBRID” HUMMINGBIRD shiny but not stronglyglittering, yellow-green,green, blue- CYNANTHUS SORDIDUS x green or blue); (3) abdomen dull pale gray (metallic yel- C. LATIROSTRIS lowish-greento blue-green),(4) long undertail coverts pale bulfy-gray (white, mostly white or, in doubledayi,glossy FROM MEXICO bluish-black); (5) dorsal surfaceof central rectrices olive- green, basal one-third orange-green(glossy bluish-black, LAURENCE C. BINFORD tipped gray); and (6) forehead and crown metallic yellow- ish-green(similar, exceptstrongly glittering green to bluish- green in doubledayz]. Friedmann et al. (1950) reported a “hybrid” between the The “hybrids” were identical to C. sordidusin all re- Dusky Hummingbird (Cynanthussordidus) and the nom- spects except throat color, which, presumably, was the inate race of Broad-billed Hummingbird (C. latirostris). characternoted by Friedmann et al. (1950). The throat of Gray (1958) did not list this hybrid combination in her “hybrids” had a variable number (from 1 to many) of extensive survey, but Short and Phillips (1966) and Mayr featherswith a single, metallic, green-to-blue subterminal and Short (1970) mentioned its existence.Here I present disc that was only partially concealed.I judged the color evidence that the purported hybrid, as well as 14 similar of thesespots by eye, employing an evenly graded spectral specimens,are simply plumage variants of C. sordidus. scale from green to blue, as follows: 1, green; 2, bluish- While studying the avifauna of the Mexican state of green; 3, blue-green;4, greenish-blue;and 5, blue. Of the Oaxaca, I examined the hybrid specimenin question,No. 15 “hybrids” that I examined, 1 had greenspots, 5 bluish- 37930 in the Moore Laboratory of Zoology ([MLZ] Oc- green, 6 blue-green, 1 greenish-blueand 2 blue. The av- cidental College, Los Angeles). It was an adult male col- erage value was 2.9, or approximately blue-green. If the lected by C. C. Lamb on 9 July 1943 at 1,829 m elevation spotted-throat birds were true hybrids, I would have ex- at “Tamazulapam” (=Tamazulapan de1Progreso), a town pected more similarities in plumage color between them located in the interior highlandsof extreme northwestern and C. latirostris,especially in view of the great differences Oaxaca, not far from the Puebla border. My field com- between the species. panions took two similar specimensin Oaxaca, and my Simon (192 1) long ago noted that certain “very old” search of museums disclosedan additional 12 from var- adult males of sordidushave colored spotson the “chest.” ious Mexican states,as follows: MICHOACAN: Tafetan, This charactermight be the result of older agebut I cannot 1,410 m elevation, 31 July 1939 (MLZ 24159); DISTRI- think of any way to test this possibility short of raising TO FEDERAL: no locality, 14 March 1943 (MLZ 36007); birds in captivity. The “hybrid” spotsare similar in shape MORELOS: 3 mi S Cuemavaca, 1,433 m elevation, 3 and position to the concealeddark gray subterminal areas November 1946 (MLZ 44491); 12 mi E Cuemavaca, 1 of typical sordidus,differing only in extent, color, and March 1970 (F. G. Stiles 249); PUEBLA: no locality, July iridescence,which suggeststhat the two are merely vari- 1928 (MLZ 641); 4 mi N Izticar de Matamoros, 1,326 m ations on a single theme. elevation, 28 July 1957 (Western Foundation of Verte- The racesC. 1.latirostris, magicus, and doubledayiwere brateZoology [WFVZ] No. 4407) and 29 July 1957 (WFVZ smaller than C. sordidusin wing, tail and culmen lengths, 4408); OAXACA: Ranch0 Las Animas, 2 mi W Nejapa, outer rectrix width, and weight (Table 1). The depth of 9 15 m elevation, 8 July 1957 (WFVZ 4402), 11 July 1957 the tail fork was greater in magicusand doubledayithan (WFVZ 4403), and 25 September 1952 (MLZ 54436); 9 in sordidusbut about the same in nominate latirostris.In mi E El Tule (=Santa Maria de1Tule), 9 May 1961 (Lou- size, propinquusis similar to nominate latirostris(Moore isiana StateUniversity Museum of Zoology lLSUMZ1 No. 1939) while toroi is intermediate between latirostrisand 24339); 18 mi SE Matatlan [=Santiago Matatlan], 976 m doubledayi(Berlioz 1937). elevation. 30 Mav 1964 (LSUMZ 33086): 10 mi SE Oa- All available measurementsfor the reported “hybrid’ xaca, 1,585 m elevation, 28 November 1964 (WFVZ (MLZ 37930) were similar to the means for sordidus;com- 2 1269); 15 mi SE Oaxaca, 1,585 m elevation, 30 Novem- pared to C. latirostris,they were outside the range of vari- ber 1964 (WFVZ 21268). ation in outer rectrix width and near the upper extremes The purported hybrid has never been described.I com- in tail and culmen lengths. The means for the other “hy- pared it and the other “hybrids” for size and plumage brids” were virtually identical to thosefor typical sordidus, color to typical examples of C. sordidusand all races of except in tail fork depth, and were appreciablylarger than C. latirostris (ma&us, prouinquus,latirostris, toroi and those for C. latirostris.Compared to doubledayi,the “hy- doubledayz].A. R-Phillips (in l&t.) and I both agreewith brids” exceeded the range of variation in weight, wing Salvin and Godman (1888-1904), Ridgway (1911) and length, and culmen length, and matched the largest ex- others that C. 1. nitida (Salvin and Godman). acceptedas tremes for tail length and outer rectrix width. Only in the a distinct race by Friedmann et al. (1950), ib a synonym depth of the tail fork were the “hybrids” clearly inter- of C. 1. doubledayi(Bourcier), the described differences mediate between the two species. If the spotted-throat being attributable to age, wear, or individual variation. birds were hybrids, I would have expected more of their All of the “hybrids” were adult males as determined from measurementsto be intermediate (or perhaps larger than the labeled sex, plumage characters,and absence of the sordidusif hybrid vigor were involved). strongbill corregationsof immatures (Ortiz-Crespo 1972). The known ranges of the two presumed parents also Of the many females and 14 immature males that I ex- argue against, if not preclude, hybridization. C. sordidus amined, none possessedintermediate characters.Hence, occursin Jalisco,Michoacan, Guerrero, Oaxaca, Hidalgo, here I deal with only adult males. Distrito Federal, Morelos, and Puebla, while C. latirostris