Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Factors Affecting the Breeding Success of the Mute Swan Cygnus olor

Mike Birkhead, Philip J. Bacon and Peter Walter
Journal of Animal Ecology
Vol. 52, No. 3 (Oct., 1983), pp. 727-741
DOI: 10.2307/4450
Stable URL: http://www.jstor.org/stable/4450
Page Count: 15
  • Read Online (Free)
  • Download ($18.00)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Factors Affecting the Breeding Success of the Mute Swan Cygnus olor
Preview not available

Abstract

(1) This paper examines 5 years' data on the breeding biology of the mute swan Cygnus olor Gmelin., to determine what factors affect our measures of breeding success, laying date, clutch size and the number of cygnets fledged. (2) These measures of breeding success (the response variables) were examined against a number of predictor variables such as age, genotype, river types, year and mean winter temperature. (3) The data were examined in two ways. In preliminary analyses each of the response variables was tested separately against a number of relevant predictor variables. Secondly, the predictor variables were tested simultaneously against each of the response variables. (4) As adult survival was high and the same birds nested on the same territories in successive years, it was statistically invalid to combine data from all the years and then use standard linear regression. We present an alternative method for analysing data of this type. (5) Taking all the results of the restricted maximum likelihood estimations together, a causal chain was produced where; (a) female genotype, winter temperature and a pair effect significantly affected the date of laying; (b) date of laying and a pair effect significantly affected clutch size and (c) clutch size was the most significant factor determining the number of cygnets fledged. (6) Finally we considered our results in relation to a model which tries to explain the proximate regulation of laying date and clutch size.

Page Thumbnails

  • Thumbnail: Page 
727
    727
  • Thumbnail: Page 
728
    728
  • Thumbnail: Page 
729
    729
  • Thumbnail: Page 
730
    730
  • Thumbnail: Page 
731
    731
  • Thumbnail: Page 
732
    732
  • Thumbnail: Page 
733
    733
  • Thumbnail: Page 
734
    734
  • Thumbnail: Page 
735
    735
  • Thumbnail: Page 
736
    736
  • Thumbnail: Page 
737
    737
  • Thumbnail: Page 
738
    738
  • Thumbnail: Page 
739
    739
  • Thumbnail: Page 
740
    740
  • Thumbnail: Page 
741
    741