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Proc Biol Sci. 2003 Sep 7; 270(1526): 1785–1791.
PMCID: PMC1691437

Degree of mutual ornamentation in birds is related to divorce rate.


Many bird species have ornaments that are expressed equally in both sexes. I use comparative analysis to investigate why some monomorphic birds are highly ornamented, whereas others are drab. The results show a significant positive association between the degree of mutual ornamentation and divorce rate. This result is robust to the removal of the effects of phylogeny, site fidelity, residency, coloniality, nest type, mortality, body size and body-size dimorphism. The level of extra-pair paternity was not related to the degree of mutual ornamentation. I argue that these results are compatible with a process of mutual sexual selection, in which both sexes compete for access to mates. The coupled evolution of ornamentation and divorce rate, from the probable ancestral state of a high degree of ornamentation and a low divorce rate, appears to result mainly from a loss of ornamentation under mate fidelity.

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Selected References

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  • Amundsen T. Why are female birds ornamented? Trends Ecol Evol. 2000 Apr;15(4):149–155. [PubMed]
  • Braun MJ, Brumfield RT. Enigmatic phylogeny of skuas: an alternative hypothesis. Proc Biol Sci. 1998 Jun 7;265(1400):995–999. [PMC free article]
  • Cézilly F, Dubois F, Pagel M. Is mate fidelity related to site fidelity? A comparative analysis in Ciconiiforms. Anim Behav. 2000 Jun;59(6):1143–1152. [PubMed]
  • Dunn PO, Whittingham LA, Pitcher TE. Mating systems, sperm competition, and the evolution of sexual dimorphism in birds. Evolution. 2001 Jan;55(1):161–175. [PubMed]
  • Grafen A. The phylogenetic regression. Philos Trans R Soc Lond B Biol Sci. 1989 Dec 21;326(1233):119–157. [PubMed]
  • Hunt S, Bennett ATD, Cuthill IC, Griffiths R. Blue tits are ultraviolet tits. Proc Biol Sci. 1998 Mar 22;265(1395):451–455. [PMC free article]
  • Jones IL, Hunter FM. Experimental evidence for mutual inter- and intrasexual selection favouring a crested auklet ornament. Anim Behav. 1999 Mar;57(3):521–528. [PubMed]
  • Lande R, Arnold SJ. Evolution of mating preference and sexual dimorphism. J Theor Biol. 1985 Dec 21;117(4):651–664. [PubMed]
  • Owens IPF, Hartley IR. Sexual dimorphism in birds: why are there so many different forms of dimorphism? Proc Biol Sci. 1998 Mar 7;265(1394):397–407. [PMC free article]
  • Pagel M. Inferring the historical patterns of biological evolution. Nature. 1999 Oct 28;401(6756):877–884. [PubMed]
  • Purvis A, Rambaut A. Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data. Comput Appl Biosci. 1995 Jun;11(3):247–251. [PubMed]
  • Saunders MA, Edwards SV. Dynamics and phylogenetic implications of MtDNA control region sequences in New World Jays (Aves: Corvidae). J Mol Evol. 2000 Aug;51(2):97–109. [PubMed]
  • Sheldon FH, Jones CE, McCracken KG. Relative patterns and rates of evolution in heron nuclear and mitochondrial DNA. Mol Biol Evol. 2000 Mar;17(3):437–450. [PubMed]
  • Zahavi A. Mate selection-a selection for a handicap. J Theor Biol. 1975 Sep;53(1):205–214. [PubMed]

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