Coloured patches influence pairing rate in King Penguins
Publication Type: |
Journal Article |
Year of Publication: |
2007 |
Authors: |
P. Jouventin, P.M. Nolan, F.S. Dobson, M. Nicolaus |
Publication/Journal: |
Ibis |
Keywords: |
aptenodytes patagonicus, king penguin, mate choice, ornaments, plumage color, plumage colour, sexual selection |
Abstract:
Ever since Darwin’s (1871) original description of sexual selection, evolutionary biologists have been intrigued by colourful attributes of animals that appear to be ornamental, without offering direct visible benefits to animals. Nevertheless, the potential biological utility of ornaments was only recently tested, perhaps because traits like the Peacock’s Pavo cristatus tail offer no direct, visible reward such as an increase in food supply or escape from predators (Petrie et al . 1991). However, sexual selection based on seemingly ornamental traits makes sense if the traits bear a cost such as increased agonistic encounters with other males, resource investment in their production (Zahavi 1975), or because they correlate with the individual’s condition (Hamilton & Zuk 1982). The individuals able to bear such costs should be those of the highest quality, so by displaying an elaborate ornament an individual may be signalling its abundant health or ready access to resources.
The potential influence of sexual selection on individual time to pairing has long been recognized (Darwin 1871, Fisher 1935), and plumage ornaments are increasingly recognized as important signals in mate choice (Andersson 1994, Hill 2002). Feather length and size of coloured plumage patches are found to be often crucial cues in the process of sexual selection (Andersson 1994). For example, Møller (1994) showed female preference for the longest tail feathers in Barn Swallows Hirundo rustica and Hill (2002) showed that House Finch Carpodacus mexicanus females prefer males with larger patches of coloured plumage on the breast. Similarly, House Sparrow Passer domesticus males with the largest black patch on their throat and breast are dominant over smaller-patched males in the winter (Møller 1987). However, while passerines have been the subject of great attention, fewer studies have focused on seabirds where mutual mate choice occurs (O’Donald 1983, Velando et al. 2001, Daunt et al. 2003, Massaro et al. 2003, Jones et al. 2004), despite the colourful breeding plumages and age-related changes in plumage displayed by many species and particularly by the large Aptenodytes penguins (Harrison 1983).
Two pioneering experiments conducted on penguins inspired our current project. Stonehouse (1960) manipulated ornamental cues of two King Penguins Aptenodytes patagonicus by covering in black their entire ocular patch. The manipulated birds were unable to acquire mates until the paint wore off. Jouventin (1982) removed the coloured plumage found on the head in three species of penguins, cutting the crest or removing the yellow/orange top part of auricular feathers of a significant sample (n = 200 pairs) of Rockhopper Penguins Eudyptes chrysocome , Macaroni Penguins E. chrysolophus and King Penguins. This experiment showed a significant reduction in the penguins’ ability to pair. However, the removal of colour might have simply indicated the loss of adult status (i.e. feathers are reduced or lacking in immatures), thus confounding maturity with attractiveness of breeding birds in mate choice. In the present study, our goal was to investigate the influence of the size of the auricular feather patches on the ability of male King Penguins to acquire a mate. Specifically, we field-tested the prediction that a reduction in auricular patch size would increase the time necessary for a male to become paired.