Delayed plumage maturation and delayed reproductive investment in birds

Abstract

Delayed plumage maturation is the delayed acquisition of a definitive colour and pattern of plumage until after the first potential breeding period in birds. Here we provide a comprehensive overview of the numerous studies of delayed plumage maturation and a revised theoretical framework for understanding the function of delayed plumage maturation in all birds. We first distinguish between hypotheses that delayed plumage maturation is attributable to a moult constraint with no adaptive function and hypotheses that propose that delayed plumage maturation is a component of an adaptive life-history strategy associated with delayed reproductive investment. We then recognize three potential benefits of delayed plumage maturation: crypsis, mimicry and status signaling. Evidence suggests that delayed plumage maturation is not a consequence of developmental constraints and instead represents a strategy to maximize reproductive success in circumstances where young adults cannot effectively compete with older adults for limited resources, particularly breeding opportunities. A multi-factorial explanation that takes into account lifespan and the degree of competition for limited breeding resources and that combines the benefits of an inconspicuous appearance with the benefits of honest signaling of reduced competitiveness provides a general explanation for the function of delayed plumage maturation in most bird species. Delayed plumage maturation should be viewed as a component of alternative reproductive strategies that can include delay in both plumage and sexual development. Such strategies are frequently facultative, with individuals breeding prior to the acquisition of definitive plumages when conditions are favourable. Presumably, the benefits of delayed plumage maturation ultimately enhance lifetime reproductive success, and studying delayed plumage maturation within the context of lifetime reproductive success should be a goal of future studies.

Sex- and age-dependent patterns of survival and breeding success in a long-lived endangered avian scavenger

“…These species show delayed maturity such that individuals typically do not recruit into the breeding populations until they have at least acquired adult plumage patterns after several years of life23 (but see ref. 24).…”

Thamnophilidae (antbird) molt strategies in a central Amazonian rainforest

“…A number of hypotheses have been proposed to explain delayed plumage maturation in other birds, particularly for independent subadults of temperate migratory species (reviewed in Thompson 1991) and lekking species (Foster 1987, McDonald 1993, Anciães and Del Lama 2002, Ryder and Durães 2005. These hypotheses are founded on explanations related to the social environment (Hawkins et al 2012), such as the juvenile mimicry hypothesis (Lawton andLawton 1986, Foster 1987) and summer female mimicry hypothesis (Rohwer et al 1980), but slight modifications to these hypotheses may be necessary when considering non-lekking resident tropical species. Our antbird study species maintain year-round territories held by an often sexually monogamous male-female pair, thus breeding is expected to be reserved for territory-holding individuals (Stutchbury andMorton 2001, Zimmer andIsler 2003).…”

“…Delaying plumage maturation until after the formative plumage is a strategy employed by a wide variety, albeit a minority, of temperate and tropical passerines, perhaps most famously among manakins (Pipridae) but also among a variety of other migratory suboscines and oscines (e.g., Thompson 1991, McDonald 1993, Hill 1996, Saetre and Slagsvold 1996. Delayed plumage maturation is often considered an adaptation to a social consequence in which not advertising maturity is adventitious (reviewed in Hawkins et al 2012). Unfortunately, the frequency and role of delayed plumage maturation within the diverse antbird family has not been systematically examined.…”

Evolution of male life histories and age-dependent sexual signals under female choice

“…When traits are age-dependent they can develop their most exaggerated forms at older ages when selection is less intense. Age-dependent traits or mating success occur in a wide variety of taxa, including mammals (Poissant et al, 2008; Pemberton et al, 2004; Clinton & Le Boeuf, 1993), birds (Hawkins, Hill & Mercadante, 2012; Evans, Gustafsson & Sheldon, 2011; Taff et al, 2011; Ballentine, 2009; Garamszegi et al, 2007; Evans, 1997), fish (Johnson & Hixon, 2011; Jacob et al, 2007; Miller & Brooks, 2005; Candolin, 2000a; Candolin, 2000b) and insects (Verburgt, Ferreira & Ferguson, 2011; Judge, 2011; Kivleniece et al, 2010; Jones & Elgar, 2004; Jones, Balmford & Quinnell, 2000). Despite the demographic problems of age-dependence, widespread occurrence of age-dependent traits suggests that life-histories promoting age-dependence are common.…”