Moult speed constrains the expression of a carotenoid‐based sexual ornament

Abstract

We investigated the effect of moult speed on the expression of a sexually selected, carotenoid‐based feather ornament in the rock sparrow (Petronia petronia). We experimentally accelerated the moult speed of a group of birds by exposing them to a rapidly decreasing photoperiod and compared the area and the spectral characteristics of their ornaments with those of control birds. Birds with accelerated moulting rate showed a smaller yellow patch with lower yellow reflectance compared to their slow‐moulting counterparts. Considering that the time available for moulting is usually constrained between the end of the breeding season and migration or wintering, carotenoid feather ornaments, whose expression is mediated by moult speed, may convey long term information about an individual's condition, potentially encompassing the previous breeding season. Furthermore, the observed trade‐off between moult speed and ornament expression may represent a previously unrecognized selective advantage for early breeding birds.

Why are bird migration dates shifting? A review of weather and climate effects on avian migratory phenology

“…The quality of feathers affects the manoeuvrability and flying performance of individuals (Swaddle et al 1996, Gorney & Yom-Tov 2001, as well as the resistance to abrasion, thermoregulatory capacity and coloration (Serra et al 2007). In aerial feeders, like the barn swallow, this could have serious repercussions on its foraging ability and thus on body condition ( Fig.…”

“…moulting period). The longer the moulting period, the better, potentially, the feather quality (Dawson et al 2000, Hall & Fransson 2000 and, consequently, the better the sexual character phenotype (Serra et al 2007). Therefore, it is interesting to note the potential existence of a trade-off between moulting and departure time, which merits further attention (Saino et al 2004a, Serra et al 2007).…”

The possible effect of dirtiness on structurally based ultraviolet plumage

“…Many studies have demonstrated that coloured plumage signals correlate with some aspect of individual quality at the time of the moult, such as parasite resistance, immunocompetence, diet and moult duration (e.g. Hill & Montgomerie 1994;Olson & Owens 1998;McGraw & Hill 2000;Serra et al 2007;Griggio et al 2009). Feather colours, however, can change after moult, and dirt accumulation has been suggested to contribute to variation in colouration (e.g.…”

Ultraviolet reflectance influences female preference for colourful males in the European serin

“…The expression of carotenoid colouration can be considered an honest signal of individual quality used by females for mate choice (Hill 1999), since it is generally costly to produce and condition dependent (reviewed in Olson and Owens 1998). This type of colouration can be influenced by different factors, such as dietary access to pigments (McGraw 2006), moult speed (Serra et al 2007) or parasite infections (Lozano 1994). Thus, it can be a reliable indicator of breeding performance (Serra et al 2007), foraging ability (García-Navas et al 2012), capacity to absorb and metabolise carotenoids (Hill 2000;McGraw et al 2005), immunocompetence (Brawner et al 2000;Saks et al 2003b) or nutritional condition at the time of moult (Hill and Montgomerie 1994).…”