The function of long tails in female barn swallows (Hirundo rustica): an experimental study

Racketed tail of the male and female turquoise-browed motmot: male but not female tail length correlates with pairing success, performance, and reproductive success

“…A handful of studies on the adaptive significance of elaborate monomorphic traits have supported the sexual selection hypothesis for only males and have found no benefits associated with elaborate female traits (Hill 1993;Cuervo et al 1996;Muma and Weatherhead 1989;Wolf et al 2004). These studies have concluded that the genetic correlation hypothesis, which was the null, was likely to account for the expression of what the authors interpreted as nonfunctional female traits (but see Hill 2002 for updated results).…”

“…This hypothesis serves as the null hypothesis in investigations into the function of elaborate female traits (for review, see Amundsen 2000a) and has received support from studies that have found no evidence of sexual selection maintaining elaborate female traits (Hill 1993;Cuervo et al 1996;Muma and Weatherhead 1989;Wolf et al 2004). …”

How do birds' tails work? Delta–wing theory fails to predict tail shape during flight

“…A theory that provided a model of the aerodynamics of birds' tails allowed new areas of investigation to be instigated. Thomas and co-workers initially used this theory to examine the effects of sexually selected tail shapes on bird flight (Balmford et al 1993(Balmford et al , 1994, and this has subsequently been taken up by others (Møller 1994;Cuervo et al 1996;Fitzpatrick & Price 1997). Delta-wing theory has also been applied in aerodynamic considerations of flight (Norberg 1995;Tucker 1995;Pennycuick 1997;Warrick et al 1998;Tobalske et al 1999), fluctuating asymmetry (Evans et al 1994), and the evolution of early birds (Gatesy & Dial 1996).…”

Same trait, different receiver response: unlike females, male American goldfinches do not signal status with bill colour

“…This hypothesis has generally been put forward in systems in which only the male ornament has been found to have a signal function (e.g. Cuervo et al, 1996;Muma & Weatherhead, 1991;Wolf et al, 2004). The genetic correlation hypothesis requires that selection operates more strongly on one sex, so there is no reason to expect that the sex under stronger sexual or social selection has to be the male.…”

“…for antipredation : Heinsohn, Legge, & Endler, 2005;Montgomerie, Lyon, & Holder, 2001;Murphy, 2006Murphy, , 2007Packer, 1983) . In addition, studies have found that elaborate traits may be functional in males, yet be expressed in females as nonadaptive by-products of genetic correlation (Cuervo, de Lope, & Møller, 1996;Lande, 1980;Muma & Weatherhead, 1991;Murphy & Pham, 2012;Wolf, Casto, Nolan, & Ketterson, 2004). As such, knowledge of the ornamental function in one sex does not necessarily describe the function of a similarly expressed trait in the other sex.…”