Plumage color and reproduction in the red-backed fairy-wren: Why be a dull breeder?

Experimental evidence that extra-pair mating drives asymmetrical introgression of a sexual trait

“…Other populations of red-backed fairy-wrens are known to exhibit low variance in within-pair paternity and high rates of extra-pair paternity [17,18], and this study revealed a similarly high rate in the experimental population. Because of this, extra-pair paternity is thought to be the main component contributing to sexual selection in this species (see also [30]), and the evolutionary force driving asymmetrical introgression of this sexual signal.…”

“…We further predicted that the mating advantage of both naturally redder and experimentally reddened males would be due in large part to siring more extra-pair young and being cuckolded (losing paternity) less than orange males. Because red-backed fairy-wrens exhibit high rates of extra-pair paternity and high variance in extrapair mating [17,18], this component of their reproductive success is thought to be the main factor contributing to the opportunity for sexual selection [29] in this species, as it is for other fairy-wren species [30].…”

Testosterone activates sexual dimorphism including male-typical carotenoid but not melanin plumage pigmentation in a female bird

“…80 µl) from the jugular vein, and took a series of morphological measurements. These included measurement of the size of the swelling posterior to the vent or CP (converted to volume using the formula π×depth/2×width×length; see Karubian, 2002;Mulder and Cockburn, 1993), an objective measure of bill color using a color reference chart ranging from 1 (cream colored) to 40 (complete black; Lindsay et al, 2011), the extent of molt based on the number of feathers encased in feather shafts (scored 0-3 across six body regions -head, back, tail, wing, belly and breast -and summed to generate a maximum score of 18; Lindsay et al, 2011), and the percentage of the body showing red/black nuptial coloration [a score of 0-10 given to each of five body regions -head, back, tail, belly and breast -for a cumulative score of 50, converted to percent (×2) following Webster et al, 2008]. We separated plasma from red blood cells via centrifugation and stored samples in liquid nitrogen until transport to Washington State University, where they were kept at −20°C awaiting further analysis.…”

“…Male red-backed fairy-wrens express discrete sexually selected (Karubian, 2002;Webster et al, 2008) and T-dependent variation in plumage and bill coloration (Karubian et al, 2011;Lindsay et al, 2011Lindsay et al, , 2009); males with low T titres during the prenuptial molt produce female-typical brown plumage and pale bills, whereas those with high T produce ornamented red/black plumage and black bills (Lindsay et al, 2009). Females can naturally produce some elements of the elaborate male phenotype (red feathers and darkened bill; see Results), though trait elaboration is rare and never reaches levels expressed by males despite elevated and variable T during the breeding season (Schwabl et al, 2014).…”

Vocal imitation of mother's calls by begging Red-backed Fairywren nestlings increases parental provisioning

“…Similar to members of the genus (Mulder et al 1994, Webster et al 2004), extra-pair paternity rates are high, with approximately half or more of the young being sired by extra-pair males (Webster et al 2008). At our study sites, breeding starts at the beginning of the rainy season (around SeptemberOctober) and continues until February (Karubian et al 2009.…”