Constraint and Function in the Predefinitive Plumages of Manakins (Aves: Pipridae)

Abstract

Birds with delayed plumage maturation exhibit a drab predefinitive plumage, often despite gonad maturation, before developing the definitive plumage associated with increased reproductive success. Manakins are a diverse clade of neotropical lekking birds with extreme sexual dichromatism, radical sexual displays, and a unique diversity in the predefinitive plumages of males across species. Here, we provide the first full review of the natural history of manakin predefinitive plumages as the basis for qualitatively addressing the six major hypotheses about the production and function of predefinitive plumages. We find little evidence to support the possibilities that manakin predefinitive plumages are directly constrained by inflexible molt schedules, resource limitations to definitive coloration, or hormonal ties to reproductive behaviors. There is little evidence that could support a crypsis function, although direct experimentation is needed, and mimicry is refuted except for one unusual species in which predefinitive males sire young. Instead, evidence from a handful of well-studied species suggests that predefinitive plumages help young males explicitly signal their social status, and thereby gain entry to the social hierarchies which dictate future reproductive success. Our conclusions are especially influenced by the unique fact that males of at least 11 species throughout the family exhibit multiple predefinitive plumage stages with distinctively male patches. For each hypothesis, we highlight ways in which a better knowledge of female and young male birds offers critical opportunities for the use of manakins as a model clade.

Sneaky copulations by subordinate males suggest direct fitness benefits from male–male associations in spotted bowerbirds (Ptilonorhynchus maculatus)

“…Thus, much like in the majority of NRP birds, sneaky copulations by subordinate males appear to be very rare in bowerbirds. In manakins, there are also few reports of subordinate males with pre‐definitive (Araripe manakin Antilophia bokermanni , Gaiotti et al, 2020 ) or definitive plumage (long‐tailed manakin Chiroxiphia linearis , McDonald, 1989 ; white‐ruffed manakin Corapipo altera , Boyle & Shogren, 2019 ) gaining copulations and siring offspring (Rivers & DuVal, 2020 ; Schaedler et al, 2021 ). For instance, in white‐ruffed manakins ( Corapipo altera ), a single case of “cheating” by a beta male was reported in a recent paper (Boyle & Shogren, 2019 ).…”

“…In a number of species, it is not known whether subordinate males are indeed sexually mature. Most NRP birds retain immature secondary sexual characteristics for several years after hatching (Foster, 1987 ; Hawkins et al, 2012 ; Schaedler et al, 2021 ). For instance, long‐tail manakins attain definitive plumage in their fifth year—the longest delay yet documented in a manakin species (Doucet et al, 2007 ).…”

“…In a number of species, it is not known whether subordinate males are indeed sexually mature. Most NRP birds retain immature secondary sexual characteristics for several years after hatching (Foster, 1987;Hawkins et al, 2012;Schaedler et al, 2021).…”

Draft genome assemblies of four manakins

“…Manakins are characterized by a variety of plumage colors 57 – 59 . To explore the possible genetic mechanism of the color diversity, we investigated the signatures of selection on 37 orthologous genes related to plumage color reported in previous studies 60 – 69 .…”

Molt strategy and delayed plumage maturation in the Lined Seedeater

“…Such phenotypic variation is often age-related, with males acquiring the definitive plumage only after the first potential breeding season, a process known as delayed plumage maturation (Rohwer et al 1980, Hawkins et al 2012. Delayed plumage maturation is common strategy among many sexually dichromatic and monogamous songbirds (Rohwer et al 1980, Thompson 1991, Greene et al 2000, such as manakins (Schaedler et al 2021), tanagers (Palmerio and Massoni 2009), and seedeaters. For example, males of the Tawny-bellied Seedeater (Sporophila hypoxantha; Facchinetti et al 2011) and the Tropeiro Seedeater (S. beltoni) look like females in their first breeding season, with Tropeiro Seedeaters taking four years to attain the definitive plumage (Repenning 2012).…”