Sexual selection in Estrildid finches, with further review of the evolution of nesting material holding display in relation to cooperative parental nesting

Abstract

Estrildid finches (family: Estrildidae) are characterised by great intraspecific and intersexual variations in sexual traits, which include courtship song, dance and ornamental colourations of plumage. These features are expected to help us answer some questions about the evolution of sexual signals: (1) why multiple ornaments evolve in socially monogamous species; and (2) why, in certain species, males and females share identical sexual traits. To discuss these, first, I briefly review the past phylogenetic comparative studies of Estrildids and show that the three sexual traits evolved independently. Secondly, I focus on one behavioural component of the courtship dance, nesting material holding display, and test the idea that the display evolved as a signal of nest building ability using phylogenetic comparative approaches. The results showed that males exhibited nesting material holding displays in species where males tend to work harder to prepare nests, which indicates that parental cooperation plays a role in the evolution of sexual signals.

Sex and age differences in the preference for materials for the communal nests of sociable weavers Philetairus socius

“…Females could prefer males that build with longer straws because they lead to the most durable communal nests, and/or because these longer straws are harder to carry, revealing the males' quality (see review by Mainwaring and Hartley (2013) arguing that nest building is a costly activity). Holding nest material was found to be used as a display in male estrildid finches, a group that is phylogenetically close to the weaver bird family (De Silva et al., 2017) and this behaviour was considered to be a display that indicates nesting ability (Soma, 2018).…”

Star finches Neochmia ruficauda have a visual preference for white dot patterns: a possible case of trypophilia

“…This could be either because dot plumage pattern plays a role in social dominance in each sex (e.g. Crowhurst et al 2012 ), or because dots function in mutual mate choice, given that most Estrildid finches are characterised by behavioural and morphological sexual signals shared between the sexes and functioning for mutual courtship (Gahr and Güttinger 1986 ; Geberzahn and Gahr 2011 ; Ota et al 2015 ; Soma and Garamszegi 2015 ; Gomes et al 2017 ; Soma and Iwama 2017 ; Soma 2018 ; Soma and Garamszegi 2018 ). It should be also noted that plumage patterns in Estrildid finches can have dual roles as sexual and social signals (Swaddle and Cuthill 1994 ; Crowhurst et al 2012 ; Zanollo et al 2013 ; Marques et al 2016 ; Soma and Garamszegi 2018 ), making it hard to disentangle them.…”

Nesting strategy and the niche partitioning in two socially monogamous songbirds

“…Furthermore, understanding the nesting strategies of wild Estrildids may also give us a hint to elucidate the evolution of their courtship behavior, in which laboratory experiments have accumulated copious amounts of information. Some Estrildid finches including cordon-bleus are known to hold a piece of nest materials in the beak as a courtship component during song and dance (Ota et al 2015, Ota 2020, which is presumably derived from nest-building behavior (Soma 2018). It remains unclear how and why they choose the nest materials during courtship, especially from the viewpoint of ecological plausibility.…”