Male Purple-crowned Fairy-wrens use their purple crowns to show off about their social status and strength, according to a new study by Monash biologists published in the Journal of Animal Ecology.
Some male birds seasonally produce a brightly coloured nuptial plumage to attract females at the start of the breeding season.
Researchers studying the male Purple-crowned Fairy-wrens say that despite being faithful to their partners, these birds take the trouble every year to change their head colour from dull brown to a stunning combination of purple and black plumage.
The question is why.
“These showy males actually use their purple crowns to signal social status and competitive strength to other males,” said study author Associate Professor Anne Peters, from the Monash School of Biological Sciences.
The study’s lead author, PhD student Marie Fan, supervised by Associate Professor Peters, studied the role of the nuptial plumage in competitive interactions among male Purple-crowned Fairy-wrens.
“They strongly resemble other fairy-wrens, that all develop seasonal attractive plumages,” said Marie.
“However, other fairy-wrens show extreme levels of sexual infidelity and use their seasonal plumages to attract extra-pair mates.”
“Because Purple-crowned Fairy-wrens practice monogamy, they represent a useful study species for understanding how different evolutionary processes may lead to apparently similar seasonal plumages.”
Purple-crowned Fairy-wrens form family-like groups living in well-defined territories, each owned by a dominant breeding pair accompanied by subordinate helpers. Acquiring and defending a dominant breeder position is therefore critical for male reproductive success.