30 ROBERTE. RICKLEFS [Auk, Vol. 96 ß 1969a. Preliminary models for growth rates of altricial birds. Ecology 50: 1031-1039. ß 1969b. An analysisof nestingmortality in birds. Smithson. Contrib. Zool. 9: 1•[8. 1973. Patterns of growth in birds. II. Growth rate and mode of development. Ibis 115: 177- 201. ß 1975. Patterns of growth in birds. III. Growth and developmentof the Cactus Wren. Condor 77: 3445. ß 1976. Growth rates of birds in the humid New World tropics. Ibis 118: 179-207. , & F. R. HAINSWORTH. 1968 Temperature regulation in nestling Cactus Wrens: the development of homeothermy. Condor 70: 121-127. SACHER,G. A., & m. F. STAFFELDT. 1974. Relation of gestation time to brain weight for placental mammals: implications for the theory of vertebrate growth. Amer. Natur. 108: 593-615. SPIERS,D. E., R. A. MCNABB, & F. M. A. McNABB. 1974. Development of thermoregulatory ability, heat seekingactivities, and thyroidfunction in hatchingJapanese Quail (Coturnixcoturnix japonica). J. Comp. Physiol. 89: 159-174. STEGEMAN,C. C. 1954. Variation in a flock of the European Starling. Auk 71: 179-185. SUTTER,m. 1943. f•ber dasembryonale und postembryonaleHirnwachstum bie Hiihnernund Sper- lingsviSgeln.Mem. Soc. Helv. Sci. Nat. 75: 1-110. TAYLOR, ST. C. S. 1968. Time taken to mature in relation to mature weight for sexes,strains, and speciesof domesticatedmammals and birds. Anim. Prod. 10: 157-169. WEST, G. C. 1965. Shivering and heat productionin wild birds. Physiol. Zool. 38: 111-120. WETHERBEE,D. K. 1961. Investigationsin the life history of the Common Coturnix. Wilson Bull. 65: 168-186. , & N. S. WETHERBEE. 1961. Artificial incubation of eggs of various bird speciesand some attributes of neonates. Bird-Banding 32: 141-159. THE WILSON ORNITHOLOGICAL SOCIETY ANNOUNCES PAUL A. STEWART AWARDS The Paul A. Stewart Fund for Ornithological Researchhas been establishedby donationsfrom Paul A. Stewart. Income from this endowment will be awarded annually to support researchin ornithology, especiallystudies of bird movementsbased on banding and analysesof recoveriesand returns and investigationspertaining to economic ornithology. Several Stewart Awards in the amount of $200 each will be available each year. Stewart Awards will be equally available to students,amateurs, and professionals. Louis AGASSIZ FUERTES AND MARGARET MORSE NICE AWARDS Fuertes Awards are devoted to the encouragementand stimulation of young ornithologists.One par- ticOar desire is the developmentof researchinterests among amateur ornithologistsand students.Any kind of ornithologicalresearch may be aided. Recipientsof grants need not be associatedwith academic institutions.Each proposalis consideredprimarily on the basisof possiblecontributions to ornithological knowledge.Although granteesare not required to publish their studiesin The Wilson Bulletin, it is hoped that they will submit their manuscriptsto the editor of The Wilson Bulletin for consideration. Most statementsapplicable to the Fuertes Awards also are applicable to the Nice Award. However, the Nice Award is limited to applicants not associatedwith a college or university. It is intended to encouragethe independentresearcher without accessto funds and facilities generallyavailable at the colleges.High schoolstudents are eligible. In some years 2 Fuertes Awards of $200 each have been made, in someyears, one. One Nice Award is made annually in the amount of $200. Personsinterested in thoseawards may write to Clait E. Braun, Wildlife Research Center, P.O. Box 2287, Fort Collins, Colorado 80522. Completed applicationsmust be receivedby 1 March 1979. Final decisionswill be made by the Council of The Wilson Ornithological Society at the annual meeting of the Society, 12-15 April 1979. INDIVIDUAL AUDITORY RECOGNITION IN THE LEAST TERN (STERNA ALBIFRONS) LYNN J. MOSELEY• Department of Zoology, University of North Carolina, Chapel Hill, North Carolina 27514 USA ABST•CT.--Playback experiments performed in a colony of Least Terns near Fort Macon, North Carolina, demonstrated that adults can distinguish the call of their mate from that of a stranger. Sonagram analysis of the "Purrit-tit-tit" call, the most common vocalization used when an adult approachesits mate, revealed that both temporal and spectral characteristicsof the first note of the call varied significantly among individuals, whereas all measured features of the second note were not significantlydifferent for different birds. Presumably the first note is used to convey an individual's identity, while the secondnote indicates a tendency to approach the mate and perform certain courtship behaviors. Received 17 January 1978, accepted26 March 1978. IN his review of individual auditory recognition in birds, Beer (1970a) stated that the best evidence for the existenceof vocal recognition comeseither from colonial species, for which the omnidirectional properties of sound far exceed those of visual signals in a crowded colony, or from speciesthat inhabit thick vegetation, as foliage obstructsvision but doesnot greatly hinder sound transmission. This study examines vocal recognition between mates in the Least Tern (Sterna albifrons), a colonially- nesting larid. Individual recognition by voice has been hypothesized for several speciesof co- lonial birds and documentedfor a few. Most investigationsdeal with auditory com- munication between members of a mated pair or between parent birds and their young. According to Beer, investigators have used three approachesin the study of vocal recognition in birds: field observation, sound analysis, and playback experi- ments. Field observation has provided circumstantial evidence for the existence of auditory recognition between mates in several colonial species(e.g. Sterna hirundo, Tinbergen 193! and Palmer 194!; Larus argentatus, Tinbergen !953) and between parents and offspring (e.g.S. fuscata, Watson and Lashley 1915; L. argentatus, Goethe 1937; S. sandvicensis, Hutchinson et al. 1968). However, some method of experimentation is usually necessaryto eliminate the possibility that a bird is actually respondingto visual rather than auditory stimuli, as in most casescolonial birds can see as well as hear one another (Beer 1970a). Several investigators have performed experiments to test the ability of parent birds to recognizetheir own chicks. Although individual recognitionof chicks has been demonstratedfor several speciesof colonial nesters(e.g. Anous stolidus and S. fuscata, Lashley 1913; S. bergii, Davies and Carrick 1962; S. maxima, Buckley and Buckley 1972), such experiments usually do not reveal the relative importance of visual and auditory modalitiesfor suchrecognition. However, Miller and Emlen's (1974) study of the effect of altering a chick'svoice and appearanceon the recognition of young by their parents in the Ring-billed Gull (Larus delawarensis)revealed that vocally impaired chicks 12 to 20 days old were accepted whereas visually altered chicks were not. In some species, at least, visual rather than auditory stimuli are important for the development of chick recognition. Experiments involving the recognitionof parents' voices by chicks have met with somewhat more successdue to the ease with which chicks can be manipulated. Presentaddress: Department of Biology,Guilford College, Greensboro, North Carolina27410 USA. 31 The Auk 96: 31-39. January 1979 32 LYNN J. MOSELEY [Auk, Vol. 96 Controlled playback experiments, performed under both natural and laboratory conditions, demonstrate that in most cases chicks of colonial species clearly distin- guish between the voice of a parent and the voice of a strange adult (Uria aalge, Tschanz 1968; L. atricilla, Beer 1969, 1970b; S. hirundo, Stevenson et. al. 1970). White (1971) reported that chicks of the Gannet (Sula bassana) seem to have the ability to recognize the voice of a parent in a playback test, but do not always do so. Presumably in this speciesthere is no particular advantage for vocal recognition between parents and young since, unlike the specieslisted above, Gannet chicks are not mobile and remain on the nest until fledging. Investigators have also studied the ability of adult birds to discriminate the call of the mate from that of other adults in the colony. Hutchinson et. al. (1968) recorded "fish calls" from 40 adult Sandwich Terns (S. sandvicensis) and analyzed various temporal and spectral parameters of sonagramsof these calls. They concludedthat the general "patterning" of the call was always characteristic for each individual. However, they were unable to perform playback experiments to test whether the adults did, in fact, use such characteristicsto identify their mates by voice. They were also unable to record more than one sequence of vocalizations from each individual. Intra-individual variation is probably greater among calls from different sequencesthan among calls in the same sequence(see below). In a more conclusive investigation, playbacks showedthat adult Gannets recognizevocalizations of their mates (White 1971). Sonagram analysis of landing calls of individual Gannets sug- gested that recognition resulted from individually consistent temporal changes in amplitude (White and White 1970). To demonstrate individual auditory recognition, playback experiments must show that test birds respond selectivelyto vocalizationsfrom different individuals. Anal- ysis of physical characteristicsof the vocalization should reveal one or more sources of interindividual variation. Using this procedure, I investigated auditory recogni- tion between mates in Least Terns.