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Effect of sexual dimorphism in bill length on foraging behavior: an experimental analysis of hummingbirds

Abstract

We examined whether sexual differences in trophic morphology are associated with sexual differences in foraging behavior through two laboratory experiments on rufous hummingbirds (Selasphorus rufus) designed to compare probing abilities (maximum extraction depths) and handling times of sexes at flowers. Bills of female S. rufus are about 10.5% longer than bills of males, and this difference was associated with sexual differences in foraging abilities. Maximum extraction depths of female S. rufus were significantly greater than those of males, and no overlap between the sexes was observed. Moreover, handling times of females were shorter than handling times of males at flowers having longer corollas (≥15 mm). Thus, because of their longer bills, female S. rufus have the potential to feed from longer flowers than males, and can do so more quickly. We suggest that no single mechanism is responsible for the evolution of sexual dimorphism in bill lengths of hummingbirds, but rather that the dimorphism probably reflects the combined effects of reproductive role division and intersexual food competition, and possibly, sexual selection.

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References

  • Baltosser WH (1987) Age, species, and sex determination of four North American hummingbirds. N Am Bird Bander 12: 151–166

    Google Scholar 

  • Bertin RI (1982) Floral biology, hummingbird pollination and fruit production of trumpet creeper (Campsis radicans, Bignoniaceae). Am J Bot 69: 122–134

    Google Scholar 

  • Boake CRB (1989) Repeatability: its role in evolutionary studies of mating behavior. Evol Ecol 3: 173–182

    Google Scholar 

  • Brown JH, Kodric-Brown A (1979) Convergence, competition, and mimicry in a temperate community of hummingbird-pollinated flowers. Ecology 60: 1022–1035

    Google Scholar 

  • Campbell DR, Waser NM, Price MV, Lynch EA, Mitchell RJ (1991) Components of phenotypic selection: pollen export and flower corolla width in Ipomopsis aggregata. Evolution 45: 1458–1467

    Google Scholar 

  • Colwell RK (1989) Hummingbirds of the San Juan Fernandez Islands: natural history, evolution and population status. Ibis 131: 548–566

    Google Scholar 

  • Darwin C (1871) The descent of man and selection in relation to sex. J Murray, London

    Google Scholar 

  • Ewald PW, Williams WA (1982) Function of the bill and tongue in nectar uptake by hummingbirds. Auk 99: 573–576

    Google Scholar 

  • Falconer DS (1981) Introduction to quantitative genetics, 2nd ed. Longman, New York

    Google Scholar 

  • Feinsinger P, Colwell RK (1978) Community organization among nectar-feeding birds. Am Zool 18: 779–795

    Google Scholar 

  • Gass CL (1985) Behavioral foundations of adaptation. In: Bateson PPG, Klopfer PH (eds) Perspectives in ethology, vol. 6. Plenum Press, New York, pp 63–107

    Google Scholar 

  • Gosler AG (1987) Pattern and process in bill morphology of the Great Tit Parus major. Ibis 129: 451–476

    Google Scholar 

  • Grant KA, Grant V (1968) Hummingbirds and their flowers. Columbia University Press, New York

    Google Scholar 

  • Grant V, Grant KA (1966) Records of hummingbird pollination in the western American flora. Aliso 6: 51–66

    Google Scholar 

  • Grant V, Temeles EJ (1992) Foraging ability of rufous hummingbirds on hummingbird flowers and hawkmoth flowers. Proc Natl Acad Sci 89: 9400–9404

    Google Scholar 

  • Hainsworth FR (1973) On the tongue of the hummingbird: its role in the rate and energetics of feeding. Comp Biochem Physiol 46A: 65–78

    Google Scholar 

  • Hainsworth FR, Wolf LL (1976) Nectar characteristics and food selection by hummingbirds. Oecologia 25: 101–113

    Google Scholar 

  • Hedrick AV, Temeles EJ (1989) The evolution of sexual dimorphism in animals: hypotheses and tests. Trends Ecol Evol 4: 136–138

    Google Scholar 

  • Huey RB, Dunham AE (1987) Repeatability of locomotor performance in natural populations of the lizard Sceloporus merriami. Evolution 41: 1116–1120

    Google Scholar 

  • Johnsgard PA (1983) The hummingbirds of North America. Smithsonian Institution Press, Washington, DC, USA

    Google Scholar 

  • Kodric-Brown A, Brown JH (1978) Influence of economics, interspecific competition, and sexual dimorphism on territoriality of migrant rufous hummingbirds. Ecology 59: 285–296

    Google Scholar 

  • Lessels CM, Boag PT (1987) Unrepeatable repeatabilities: a common mistake. Auk 104: 116–121

    Google Scholar 

  • Lewin R (1985) Why are male hawks so small? Science 228: 1299–1300

    Google Scholar 

  • Martindale S (1982) Nest defense and central place foraging: a model and experiment. Behav Ecol Sociobiol 10: 85–89

    Google Scholar 

  • Montgomeric RD (1984) Nectar extraction by hummingbirds: response to different floral characters. Oecologia 63: 229–236

    Google Scholar 

  • Morse DH (1980) Behavioral mechanisms in ecology. Harvard University Press, Cambridge, Mass

    Google Scholar 

  • Morton ES (1990) Habitat segregation by sex in the hooded warbler: experiments on proximate causation and discussion of its evolution. Am Nat 135: 319–333

    Google Scholar 

  • Munz PA (1974) A flora of southern California. University of California Press, Berkeley

    Google Scholar 

  • O'Brien RG, Kaiser MG (1985) MANOVA method for analyzing repeated measures designs: an extensive primer. Psychol Bull 97: 316–333

    Google Scholar 

  • Paton DC, Collins BG (1989) Bills and tongues of nectar-feeding birds: a review of morphology, function and performance, with intercontinental comparisons. Austr J Ecol 14: 473–506

    Google Scholar 

  • Peters WD, Grubb TC, Jr (1983) An experimental analysis of sex-specific foraging in the Downy Woodpecker, Picoides pubescens. Ecology 64: 1437–1443

    Google Scholar 

  • Roberts WM (1992) Hummingbirds' concentration preferences and the energetics of nectar-feeding: predictions, tests, and implications for optimal foraging theory and pollination biology. M. Sci. thesis, University of British Columbia, Vancouver

  • Rosenzweig ML, Sterner PW (1970) Population ecology of desert rodents: body size and seed-husking as bases for heteromyid coexistence. Ecology 51: 217–224

    Google Scholar 

  • Ryan BF, Joiner BL, Ryan TA, Jr (1985) Minitab handbook, 2nd ed. Duxbury Press, Boston

    Google Scholar 

  • SAS Institute Inc. (1988) SAS/STAT User's guide, release 6.03 edition. Cary, North Carolina

  • Selander RK (1972) Sexual selection and dimorphism in birds. In: Campbell B (ed) Sexual selection and the descent of man 1871–1971. Aldine Publ Co, Chicago, pp 180–230

    Google Scholar 

  • Shine R (1989) Ecological causes for the evolution of sexual dimorphism: a review of the evidence. Q Rev Biol 64: 419–461

    Google Scholar 

  • Slatkin M (1984) Ecological causes of sexual dimorphism. Evolution 38: 622–630

    Google Scholar 

  • Snow DW, Snow BK (1980) Relationships between hummingbirds and flowers in the Andes of Columbia. Bull Brit Mus Nat Hist (Zool) 38: 105–139

    Google Scholar 

  • Tamm S (1987) Tracking varying environments: sampling by hummingbirds. Anim Behav 35: 1725–1734

    Google Scholar 

  • Temeles EJ (1985) Sexual size dimorphism of bird-eating hawks: the effect of prey vulnerability. Am Nat 125: 485–499

    Google Scholar 

  • Vaudry R, Raymond M, Robitaille J-F (1990) The capture of voles and shrews by male and female ermine Mustela erminea in captivity. Holarct Ecol 13: 265–268

    Google Scholar 

  • Vickery RK (1990) Pollination experiments in the Mimulus cardinalis — M. lewisii complex. Great Basin Nat 50: 155–159

    Google Scholar 

  • Weisberg S (1980) Applied linear regression. Wiley and Sons, New York

    Google Scholar 

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Temeles, E.J., Roberts, W.M. Effect of sexual dimorphism in bill length on foraging behavior: an experimental analysis of hummingbirds. Oecologia 94, 87–94 (1993). https://doi.org/10.1007/BF00317307

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  • DOI: https://doi.org/10.1007/BF00317307

Key words

  • Sexual dimorphism
  • Foraging behavior
  • Plant-pollinator interactions
  • Hummingbirds
  • Trochilidae