Evolutionary Ecology

, Volume 19, Issue 5, pp 467–486 | Cite as

The Evolution of Reversed Sexual Size Dimorphism in Hawks, Falcons and Owls: A Comparative Study

  • Oliver KrügerEmail author
Research article


Many hypotheses have been proposed to account for the origin and maintenance of reversed size dimorphism (RSD, females being larger than males) in hawks, falcons and owls, but no consensus has been reached. I performed comparative analyses, using both cross-taxa data and phylogenetically independent contrasts, to investigate potential correlates of reversed size dimorphism. Using a similar set of explanatory variables, covering morphology, life history and ecology, I tested whether any trait coevolved with size dimorphism in all three groups and hence provided a general explanation for the evolution of RSD. For hawks, strong correlates were found in the foraging-variable complex, so RSD might have evolved in species hunting large and agile prey. This is consistent with the intersexual-competition hypothesis (sexes have evolved different sizes to lessen intersexual competition for food), but especially the small-male hypothesis (males have evolved to be smaller to be more efficient foragers). Evolutionary pathway analyses suggest that RSD evolved most likely as a precursor of changes in hunting strategy but as a consequence of high reproduction. The falcons showed a similar pattern: species with strong RSD hunted larger and more agile prey. The evolutionary pathway analysis supported the idea that RSD evolved before the specialisation on more agile and/or larger prey. Finally for owls, the results showed clear parallels. RSD increased with prey size, consistent with the small-male hypothesis. Evolutionary pathway analysis suggests that RSD in owls has most likely evolved before specialisation on large prey, so a small and more agile male might be advantageous even when hunting small prey. These results suggest that RSD in hawks, falcons and owls evolved due to natural-selection pressures rather than sexual-selection pressures.

Key words

intersexual-competition hypothesis natural selection reversed size dimorphism sexual selection small-male hypothesis 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Amadon, D. 1975Why are female birds of prey larger than males?J. Raptor Res.9111Google Scholar
  2. Andersson, M. 1994Sexual SelectionPrinceton University PressPrinceton, NJGoogle Scholar
  3. Andersson, M., Norberg, R.A. 1981Evolution of reversed sexual size dimorphism and role partitioning among predatory birds, with a size scaling of flight performanceBiol. J. Linn. Soc.15105130Google Scholar
  4. Arak, A. 1988Sexual dimorphism in body size: a model and a testEvolution42820825Google Scholar
  5. Balgooyen, T.G. 1976Behaviour and ecology of the American kestrel (Falco sparverius) in the Sierra Nevada of CaliforniaUniv. Cal. Publ. (Zoology)103183Google Scholar
  6. Barraclough, T.G., Harvey, P.H., Nee, S. 1995Sexual selection and taxonomic diversity in passerine birdsProc. R. Soc. Lond. B259211215Google Scholar
  7. Cade, T.J. 1982The Falcons of the WorldCornell University PressIthaca NYGoogle Scholar
  8. Catry, P., Phillips, R.A., Furness, R.W. 1999Evolution of reversed sexual size dimorphism in skuas and jaegersAuk116158168Google Scholar
  9. Cezilly, F., Dubois, F., Pagel, M. 2000Is mate fidelity related to site fidelity? A comparative analysis in CiconiiformsAnim. Behav.5911431152CrossRefPubMedGoogle Scholar
  10. Colwell, R.K. 2000Rensch’s rule crosses the line: convergent allometry of sexual size dimorphism in hummingbirds and flower mitesAm. Nat.156495510CrossRefGoogle Scholar
  11. Darwin, C. 1871The Descent of Man, and Selection in Relation to SexJohn MurrayLondonGoogle Scholar
  12. Fairbairn, D.J. 1997Allometry for sexual size dimorphism: pattern and process in the coevolution of body size in males and femalesAnn. Rev. Ecol. Syst.28659687CrossRefGoogle Scholar
  13. Felsenstein, J. 1985Phylogenies and the comparative methodAm. Nat.125115CrossRefGoogle Scholar
  14. Ferguson-Lees, J., Christie, D.A. 2001Raptors of the WorldChristopher HelmLondonGoogle Scholar
  15. Figuerola, J. 1999A comparative study on the evolution of reversed size dimorphism in monogamous wadersBiol. J. Linn Soc.67118CrossRefGoogle Scholar
  16. Fowlie, M.K., Krüger, O. 2003The evolution of plumage polymorphism in birds of prey and owls: the apostatic selection hypothesis revisitedJ. Evol. Biol.16577583CrossRefPubMedGoogle Scholar
  17. Hair, J.F., Anderson, R.E., Tatham, R.L. and Black, W.C. (1995) Multivariate data analysis with readings. 4th edn. Prentice Hall, Englewood Cliffs, NJGoogle Scholar
  18. Hakkarainen, H., Korpimäki, E. 1991Reversed sexual size dimorphism in Tengmalm’s owl: is small male size adaptive?Oikos61337346Google Scholar
  19. Hakkarainen, H., Korpimäki, E. 1993The effect of female body size on clutch volume of Tengmalm’s owls (Aegolius funereus) in varying food conditionsOrn. Fenn.70189195Google Scholar
  20. Hakkarainen, H., Korpimäki, E. 1995Contrasting phenotypic correlations in food provision of male Tengmalm’s owls (Aegolius funereus) in a temporally heterogeneous environmentEvol. Ecol.93037CrossRefGoogle Scholar
  21. Hakkarainen, H., Huhta, E., Lahti, K., Lundvall, P., Mappes, T., Tolonen, P., Wiehn, J. 1996A test of male mating and hunting success in the kestrel: the advantages of smallness?Behav. Ecol. Sociobiol.39375380CrossRefGoogle Scholar
  22. Harvey, P.H., Pagel, M. 1991The Comparative Method in Evolutionary BiologyOxford University PressOxfordGoogle Scholar
  23. Harvey, P.H., Rambaut, A. 2000Comparative analyses for adaptive radiationsPhil. Trans. R. Soc. Lond. B35515991605CrossRefGoogle Scholar
  24. Holdaway, R.N. 1994An exploratory phylogenetic analysis of the genera of the Accipitridae, with notes on the biogeography of the familyMeyburg, B.U.Chancellor, R.D. eds. Raptor Conservation TodayPica PressBerlin601647Google Scholar
  25. Hoyt, D.F. 1979Practical methods of estimating volume and fresh weight of bird eggsAuk967377Google Scholar
  26. James, F.C., McCulloch, C.E. 1990Multivariate analysis in ecology and systematics: Panacea or Pandora´s box?Ann. Rev. Ecol. Syst.21129166Google Scholar
  27. Jehl, J.R., Murray, B.G. 1986The evolution of normal and reverse sexual size dimorphism in shorebirds and other birdsCurr. Ornithol.3186Google Scholar
  28. Kissner, K.J., Weatherhead, P.J., Francis, C.M. 2003Sexual size dimorphism and timing of spring migration in birdsJ. Evol. Biol.16154162CrossRefPubMedGoogle Scholar
  29. König, C., Weick, F., Becking, J.H. 1999Owls: A Guide to the Owls of the WorldPica PressEast SussexGoogle Scholar
  30. Krüger, O. 2000Correlates of population density and body weight of raptors in the family Accipitridae: a comparative studyJ. Zool. Lond.250185192Google Scholar
  31. Krüger, O., Davies, N.B. 2002The evolution of cuckoo parasitism: a comparative analysisProc. R. Soc. Lond. B269375381CrossRefGoogle Scholar
  32. Lindenfors, P., Szekely, T., Reynolds, J.D. 2003Directional change in sexual size dimorphism in shorebirds, gulls and alcidsJ. Evol. Biol.16930938CrossRefPubMedGoogle Scholar
  33. Massemin, S., Korpimäki, E., Wiehn, J. 2000Reversed sexual size dimorphism in raptors: evaluation of the hypotheses in kestrels breeding in a temporally changing environmentOecologia1242632CrossRefGoogle Scholar
  34. McArdle, B.H. 1988The structural relationship: regression in biologyCan. J. Zool.6623292339Google Scholar
  35. Mueller, H.C. 1986The evolution of reversed sexual dimorphism in owls: an empirical analysis of possible selective factorsWilson Bull.98387406Google Scholar
  36. Mueller, H.C. 1990The evolution of reversed sexual dimorphism in size in monogamous species of birdsBiol. Rev.65553585Google Scholar
  37. Mueller, H.C., Meyer, K. 1985The evolution of reversed sexual dimorphism in size: a comparative analysis of the Falconiformes of the Western PalearcticCurr. Ornithol.265101Google Scholar
  38. Myers, J.H. 1978Sex-ratio adjustment under food stress: maximisation of quality or numbers of offspringAm. Nat.112381388CrossRefGoogle Scholar
  39. Newton, I. 1979Population Ecology of RaptorsT. & A.D. PoyserLondonGoogle Scholar
  40. Norberg, R. 1987Evolution, structure and ecology of northern forest owlsNero, R.W. eds. Biology and Conservation of Northern Forest OwlsUSDAFort CollinsGoogle Scholar
  41. Olsen, P., Cockburn, A. 1993Do large females lay small eggs? Sexual dimorphism and the allometry of egg and clutch volumeOikos66447453Google Scholar
  42. Olsen, P., Olsen, J. 1984Book review: the falcons of the worldAustral. Wildl. Res.11205206CrossRefGoogle Scholar
  43. Olsen, P., Olsen, J. 1987Sexual size dimorphism in raptors: intrasexual competition in the larger sex for a scarce breeding resource, the smaller sexEmu875962Google Scholar
  44. Owens, I.P.F., Hartley, I.R. 1998Sexual dimorphism in birds: why are there so many different forms of dimorphism?Proc. R. Soc. Lond. B265397407CrossRefGoogle Scholar
  45. Pagel, M. 1994Detecting correlated evolution on phylogenies: a general method for the comparative analysis of discrete charactersProc. R. Soc. Lond. B2553745Google Scholar
  46. Pagel, M. 1999Inferring the historical patterns of biological evolutionNature401877884CrossRefPubMedGoogle Scholar
  47. Parker, G.A., Partridge, L. 1998Sexual conflict and speciationPhil. Trans. R. Soc. Lond. B353261274CrossRefGoogle Scholar
  48. Paton, P.W.C., Messina, F.J., Griffin, C.R. 1994A phylogenetic approach to reversed size dimorphism in diurnal raptorsOikos71492498Google Scholar
  49. Phillips, R.A., Dawson, D.A., Ross, D.J. 2002Mating patterns and reversed size dimorphism in Southern skuas (Stercorarius skua lonnbergi)Auk119858863Google Scholar
  50. Pleasants, J., Pleasants, B.Y.M. 1988Reversed size dimorphism in raptors: evidence for how it evolvedOikos52129135Google Scholar
  51. Price, T. 1997Correlated evolution and independent contrastsPhil. Trans. R. Soc. Lond. B352519529CrossRefGoogle Scholar
  52. Purvis, A., Rambaut, A. 1995Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative dataComp. Appl. Biosciences11247251Google Scholar
  53. Ralls, K. 1976Mammals in which females are larger than malesQuart. R. Biol.51245276CrossRefGoogle Scholar
  54. Ranta, E., Laurila, A., Elmberg, J. 1994Reinventing the wheel: analysis of sexual dimorphism in body sizeOikos70313321Google Scholar
  55. Reichle, D.E. 1970Analysis of Temperate Forest EcosystemsSpringer-VerlagNew YorkGoogle Scholar
  56. Reynolds, RT. 1972Sexual dimorphism in accipiter hawks: a new hypothesisCondor74191197Google Scholar
  57. Rolland, C., Danchin, E., Fraipont, M. (1998) The evolution of coloniality in birds in relation to food, habitat, predation, and life history traits: a comparative analysisAm. Nat.151514529Google Scholar
  58. Schantz, T., Nilsson, N.I. 1981The reversed size dimorphism in birds of prey: a new hypothesisOikos36129132Google Scholar
  59. Schönwetter, M. 1967–1992Handbuch der OologieAkademie-VerlagBerlinGoogle Scholar
  60. Selander, R.K. 1972Sexual selection and dimorphism in birdsCampbell, B. eds. Sexual Selection and the Descent of Man 1871–1971Aldine PressChicago180230Google Scholar
  61. Sibley, C.G., Ahlquist, J.E. 1990Phylogeny and Classification of BirdsYale University PressNew HavenGoogle Scholar
  62. Sigurjónsdóttir, H. 1981The evolution of sexual size dimorphism in gamebirds, waterfowl and raptorsOrn. Scand12249260Google Scholar
  63. Snyder, N.F.R. and Wiley, J.W. (1976) Sexual size dimorphism in hawks and owls of North America. Ornithological Monograph 30, American Ornithologist’s UnionGoogle Scholar
  64. Storer, R.W. 1966Sexual dimorphism and food habits in three North American accipitersAuk83423436Google Scholar
  65. Székely, T., Reynolds, J.D., Figuerola, J. 2000Sexual size dimorphism in shorebirds, gulls, and alcids: the influence of sexual and natural selectionEvolution5414041413PubMedGoogle Scholar
  66. Temeles, E.J. 1985Sexual size dimorphism of bird-eating hawks: the effect of prey vulnerabilityAm. Nat.125485499CrossRefGoogle Scholar
  67. Thiollay, J.M. 1994Family AccipitridaeHoyo, J.Elliott, J.Sargatal, J. eds. Handbook of the Birds of the WorldLynx EdicionsBarcelona52205Google Scholar
  68. Tornberg, R., Mönkkönen, M., Pahkala, M. 1999Changes in diet and morphology of Finnish goshawks from 1960s to 1990sOecologia121369376CrossRefGoogle Scholar
  69. Noordwijk, A.J. 2002The tale of the parasitic cuckoosNature416687690CrossRefPubMedGoogle Scholar
  70. Walter, H. 1979Eleonora’s Falcon: Adaptations to Prey and Habitat in a Social RaptorChicago University PressChicagoGoogle Scholar
  71. Weatherhead, P.J., Teather, K.L. 1994Sexual size dimorphism and egg-size allometry in birdsEvolution48671678Google Scholar
  72. Webster, M.S. 1992Sexual dimorphism, mating system and body size in New World blackbirds (Icterinae)Evolution4616211641Google Scholar
  73. Wink, M., Heidrich, P. 1999Molecular evolution and systematics of owls (Strigiformes)König, C.Weick, F.Becking, J.H. eds. Owls: A Guide to the Owls of the WorldPica PressEast Sussex3957Google Scholar
  74. Wink, M., Sauer-Gürth, H. 2000Advances in the molecular systematics of African raptorsChancellor, R.D.Meyburg, B.U. eds. Raptors at RiskHancock House PublishersSurrey B.C135147Google Scholar
  75. Ydenberg, R.C., Forbes, L.S. 1991The survival-reproduction selection equilibrium and reversed size dimorphism in raptorsOikos60115120Google Scholar

Copyright information

© Springer 2005

Authors and Affiliations

  1. 1.Department of ZoologyUniversity of CambridgeCambridgeUK

Personalised recommendations