The behavioural ecology of the whooper swan (Cygnus cygnus cygnus)

• Main Author: Brazil, Mark Andrew
• Other Authors: Henty, Cliff J., School of Natural Sciences, Psychology
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 1981
• Subjects: Cygnus cygnus; whooper swan; Swans; Animal behaviour; Iceland; Whooper Swan
• Online Access: http://hdl.handle.net/1893/2395; http://dspace.stir.ac.uk/bitstream/1893/2395/1/brazil-mark-thesis.pdf

The behaviour and ecology of Whooper Swans (Cygnus cygnus) were studied on the wintering grounds in Scotland and the summering grounds in Iceland, with a view to extending our general knowledge of the biology of this little studied species. Comparisons are drawn between feeding behaviour shown in terrestrial, freshwater and marine habitats. In Central Scotland Whooper Swans were found to feed mainly on agricultural land and to actively select stubble fields, where they fed on waste grain, from their arrival in autumn until mid-winter. They then changed to feeding on grass from mid-winter until their departure in the spring. They were found to have adopted an activity pattern similar to that of geese, i. e. they were diurnal and flew each morning and evening between a roost-site and a feeding site. The daily activity cycle of feeding varies between habitats, but the differences are not fully explained by functional requirements. The factors affecting the timing of morning and evening flights are discussed. The length of the feeding day increased with daylength and the level of feeding per hour increased so that more time was spent feeding in the spring than at any time during the winter. Although Whooper Swans were found to compensate to some extent for the shortness of winter days by departing to the roost later relative to sunset, it is suggested that it is in the spring when their energetic requirements are highest; they need to store enough energy for migration and breeding and/or moult. The percentage of birds head-up was found to decline curvi-linearly with increasing flock size while the percentage feeding increased. Since there was no apparent relationship between peck rate and flock size, birds in larger flocks gain from increased food intake. A seasonal change in flock size was noted in Central Scotland with larger flocks occurring more frequently between autumn arrival and mid-winter than from mid-winter to spring departure. Although other factors may be involved as well, it is suggested that the ...