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504 GeneralNotes [Auk, Vol. 85 in August,was a bird capturedin the Bay of Panama off Balboa, some8 degrees north of the equatorin 1937 (Murphy, 1938). LITERATURE CITED ALEXAI•rDER, W. B. 1928. Birds of the ocean. New York, Putnam. H^RTERT,E. 1912-21. Die VSgel der pal[tarktischenFauna, vol. 2. Berlin, Fried- lander & Sohn. J^•fESO•,W.S. 1958. The WanderingAlbatross. Londo.n,Hart-Davis. JONES,F. W. 1936. The wanderingof albatrosses.Emu, 36: 103-105. MuRr•q¾, R. C. Mus. Nat. MuurH¾, R. C. 40: 1936. Oceanic birds of South America, vol. 1. New York, Amer. Hist. 1938. The Wandering Albatross in the Bay of Panama. Condor, 126. Om;^>:DO,C. 1958. Cattura di un Albatro urlatore, Diomedea exulans exulans (Linnaeus) in Sicilia. Rivista Italiana Orn., 28: 101-113. PE^XA•;•;,D. B. 1960. Tropical records of the Wandering Albatross in the Atlantic Ocean. Ostrich, 31: 105. VAN OOaDT,G.J. 1939. Over de noordelijkste verspreidingsgrens van enkele antarctische zeevogelsoorten in den AtlantischenOceaan. Ardea, 28: 1-4. ROBERTO. PAXTOIq,Setauket, New York 11785. The genetic basis of color differences observed in the Mute Swan (Cygnus olor)L--The downyyoungof the Mute Swanappearin either of two color phases,a white or gray. The white phase was first reported in 1868 among the swans on Lake Geneva, Switzerland (Hilprecht, Hocherschwan, Singschwan, Zwergschwan, Wittenburg Lutherstadt, Die Neue Brehm-Bucherie, 1956); it is usually less common than the gray phase,but becomesmore frequentas one moveseastwardacrossEurope, and it is sometimesreferred to as the Polish variety. Cygnets with gray down have slate-gray bills and feet; the white phase birds have tan colored bills and feet. The foot color of eachphasepersistsin the otherwiseidenticalwhite-plumagedadults, and may be usedto determineits down color phase. This study was undertakento determine the geneticbasisof the color phase. Methods and materials.---In 1963 the State Division of Conservation initiated a bandingprogramto determinethe statusof the Mute Swan in Rhode Island. Nesting sites were watched and location and down color were recorded by the senior author. In the 1967 hatching season53 nestingsites were kept under observation. Cygnet data were obtained from only 36 nests; 11 were lost by flooding during adverse weather and 6 were destroyedby predation. Color phase was observed as soon as possible after hatching to reduce any effect of possibledifferential mortality. Unhatched eggs were broken and color phase determined on embryos far enough advanced to exhibit down color. Adult color phase was determined for all nesting pairs, and additional adult data were obtained from previous banding records. Resultsand dlscussion.--The1967 nestingcolor phasedata summarizedin Table 1 indicatesthat color differenceis determinedby a singlegene and that the gray allele is dominant to white. Examination of sex data indicated a preponderanceof white females. As birds follow an XO methodof sex determination,the male being homogameticXX or hayContribution number 1255 of the Rhode Island Experiment Station. July, 1968] General Notes TABLE 1967 MAT•C Typeof mating No. of adults 505 1 DAT• No. of cygnets Total Gray White Gray White individuals Gray X gray Gray X white 58 5 0 5 145 18 205 40 White X white 0 4 0 2 12 12 16 ing two sexchromosomes, and the femaleheterogametic XO or having onesexchromosome, a sex-linked recessivewould result in a greater number of visible recessives in females. Banding data from previous years included 488 swans whose sex and color phase had been recorded. Of the 288 males, 29 or 10 per cent were white phase; of the 200 females,51 or 26 per cent were white phase. If' in a random mating populationwe let the frequencyof the dominant allele (A) of an autosomalgene he p and the frequency of the recessiveallele (a) be q, then the frequencyof the three genotypesare: p2AA, 2 pq Aa and q2aa If a geneis sex-linked,the frequencyof the genotypeswithin sexeswill differ. In the caseof the male, which is homogametic(XX) the ratio of the recessivegenotypes to the total numberof individualsrepresents q2,just as if the genewere autosomal. In the caseof the female,which is heterogametic(XO), there can be no heterozygotes (Aa) and the possihlegenotypicfrequenciesare p AO and q aO and the ratio of recessives to the total numberof individualsrepresents q. 51 If the geneis sex-linked,the estimatedvalue of q basedon femalesis q•- 2OO -- .255. An estimatebasedon malesand the assumptionof random mating is q• • 2•2•8: .316. The estimates qfand q•do not differ by astatistically significa amount and matingscan be assumedto be at random. The estimatedvalue of q for the populationthen can be a weightedestimateof qf+• m .293. Further evidenceof sex-linkagewas obtained by examiningfamilies that would yield a sex-linkedresult, i.e. recessive(white) male X dominant (gray) female or the male contributingthe sex chromosomecarrying the recessiveallele to his daughters. Only two suchfamiliesappearedin the 1967 matings;theseyielded9 malesand 7 females.All male cygnetswere gray and all females(XO) were white, obtaining their sex chromosomefrom their recessive(white) sire. This clearly indicates the color phasesto he sex linked. Summary.--Examinationof bandingdata and parentsand progenyat nestingsites of the feral populationof Mute Swansin RhodeIsland indicatedthat the gray and whitecolorphasesegregating in the populationwas due to a singlesex-linkedgene. The gray wasdominantto white and the genefrequencyof the recessive allele (white) was estimated to be .293. Acknowledgements.---The authors greatly appreciatethe assistanceof the Rhode Island Departmentof National Resources, Division of Conservation,in someof the data collectionphaseof this study.--R. E. MunRo, L. T. S•a, and J. J. KuP^, University of Rhode Island, Kingston, Rhode Island 02881.