Ibis (2008), 150, 193–196 © 2007 The Authors Journal compilation © 2007 British Ornithologists’ Union Blackwell Publishing Ltd Oxford, UK IBI Ibis 0019-1019 © The Authors Journal compilation © 2007 British Ornithologists’ Union XXX Short communication Coloration influences pairing in penguins P. Jouventin et al. Short communication Coloured patches influence pairing rate in King Penguins PIERRE JOUVENTIN, 1 * PAUL M. NOLAN, 2 F. STEPHEN DOBSON 3 & MARION NICOLAUS 1 1 C.N.R.S. -C.E.F.E., Equipe Ecologie Comportementale, 1919 Route de Mende, 34293 Montpellier France 2 Department of Biology The Citadel, Charleston, SC 29409, USA 3 Department of Biological Sciences, 331 Funchess Hall, Auburn University, AL 36849, USA Keywords: Aptenodytes patagonicus, King Penguin, mate choice, ornaments, plumage colour, sexual selection. 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. Never- theless, 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 con- dition (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) manipu- lated 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. METHODS From November 2001 to January 2002 we worked in a large colony (~16 000 pairs) of King Penguins on Possession Island, Crozet Archipelago (46°25′ S, 51°45′ E). We captured 46 adult males in newly-moulted plumage, after observing each individual perform sex-specific courtship calls for several minutes (see Jouventin 1982). We attached temporary plastic flipper bands to birds to allow individual identification, and then randomly assigned each male to either the control or experimental group. Because we expected higher variance in time-to-pairing among the experimental birds, we decided a priori to make the experimental group approximately 50% larger than the control group. We accomplished this by assigning every third bird we captured to the control group. Both male and female King Penguins have coloured plumage patches on the auricular regions of both sides of the head. Each of these plumage patches can range in colour from yellow to dull orange to a rusty brown. We reduced auricular patch size of the experimental males by approx- imately 50%, by applying a black non-toxic permanent *Corresponding author. Email: pierre.jouventin@cefe.cnrs.fr