The crest of the peafowl: a sexually dimorphic plumage ornament signals condition in both males and females

Abstract

Both male and female peafowl grow crests on top of their head – iridescent blue in males, dull iridescent green and brown in females – but the potential signal function of this plumage ornament is unknown. In this study, peafowl crests were measured in three feral populations, and morphological variation in this ornament was studied in relation to body condition (body mass in relation to tarsus length) and health (white blood cell concentration and ectoparasite load). Prior to the start of the breeding season, male crests are wider with greater pennaceous area, and are more likely to have all feathers grown out compared with female crests. Only crest length changed with measurement date, increasing over time; in males, crest measurements were not related to the extent of train feather development. Crest morphology is a potential signal of individual health and condition in both sexes, but in different ways. In females, the amount of crest plumage grown out to its full extent was related to body condition at the start of the breeding season, whereas in males, the size and pennaceous area of the ornament were related to ectoparasite load. Observations of within‐sex agonistic behaviour suggest a possible role for the crest ornament in status signaling in males, because males that engage in more aggressive interactions tend to have wider crests. There was no evidence for a relation between crest morphology and agonistic behaviour in females.

Multi‐functional crest display in hoopoes Upupa epops

“…Crests are common ornaments among birds, and have been shown to convey information on individual quality and/or status both by their size (Jones and Hunter , Daunt et al , Dakin ) and colour (McGraw et al , Remy et al ), serving as intra‐ or intersexual signals to conspecifics. However, their potential to suddenly reveal conspicuous colour patterns when unfolded makes them suitable deimatic signals towards predators as those used by moths, mantis or amphibians (Umbers et al ).…”

Blood parasite infection differentially relates to carotenoid‐based plumage and bill color in the American goldfinch

“…; Griggio et al. ; Siefferman and Hill ; Dakin ). Moreover, some studies indicate that the physiological basis of condition dependence may be sex dependent when ornaments are expressed similarly in both sexes, such that, for example, the same ornament relates differently to measures of immunocompetence in the two sexes (e.g., Potti and Merino ; Roulin et al.…”

Assortative Pairings in Diamond Firetails (Stagonopleura guttata) are not the Result of Mutual Mate Choice for an Ornament

“…; Siefferman & Hill ; Hanssen et al. ; Dakin ; Zanollo et al. ) and/or fighting ability and dominance (Murphy et al.…”

“…The hypothesis was that in species in which males and females display similar ornamentation, the ornamented traits were thought to be functional only in males, while females displayed the ornaments because they carried the genes for those traits (Muma & Weatherhead 1989;Cuervo et al 1996Roulin et al 2001a). This hypothesis is increasingly being questioned, and there is growing evidence for active male choice of ornamented females (Amundsen et al 1994;Griggio et al 2005;Kraaijeveld et al 2007;Pryke & Griffith 2007;Clutton-Brock 2009), as well as for ornamental traits associated with condition (Roulin et al 2001b;Siefferman & Hill 2005;Hanssen et al 2006;Dakin 2011;Zanollo et al 2012) and/or fighting ability and dominance (Murphy et al 2009;Midamegbe et al 2011;Crowhurst et al 2012).…”