Flower Petals for Romance (We Think)

Last week I talked about the highly monogamous albatross, who will form long term pairs even when mates of the opposite sex aren’t available. This week I decided I’d address a species who are socially very monogamous, yet cheat on one another relentlessly.

Fairy Wrens are a group of birds that are quite common in Australia, and are well known for the iridescently bright plumage on the males. All species of the group are socially monogamous, pairing together for years on end with a very low divorce rate, and raising offspring together. However, not all those offspring are biologically the father’s. Sexually the Fairy Wrens are quite promiscuous, and from this a rather odd behavior has arisen.

Males of several species of fairy wren, notably the Red-Backed Fairy Wren, have been observed carrying colored petals of either pink or red in their beaks when pursuing females. The petals either help enhance their nuptial colors, or as the case of the Splendid Fairy Wren who is a bright blue act as contrast to their coloration.

Splendid Fairy Wren with a light pink petal for display.

There was a question at one point as to whether the petal displays were for courtship, or for as a territorial display towards other males in their territories. This was tested by Karubian and Alvarado (2003), but they were unable to come to any true conclusion on the matter.

Their results showed that while the males with petals only presented them to other males about 10% of the time, the amount of time females spent with males was not any different with the petal or without. This is interesting because it seems to be an arbitrary behavior the males have evolved which do not provide any direct advantage in increasing their mating chances with their mate or for extra-pair copulations, nor in keeping other males away from their territories.

There is always a chance that this behavior is a relic of a past mating strategy that required more displays and potentially gifts. It could also be a remnant of a time when these birds were more sexually monogamous, and using petals to show off their own fitness was a way to ward off competitors. Or, fairy wrens just like petals! This is one of those interesting cases when a notable behavior is seemingly unexplainable, though quite obviously tied to romance. As all flower petals should be, really.

References

Karubian, J & Alvarado, A 2003, ‘Testing the function of petal-carrying in the Red-backed Fairy-wren (Malurus melanocephalus)’, Emu, vol. 103, no. 1, pp. 87–92.

Picture: http://dailyorganism.blogspot.com.au/2011/08/splendid-fairy-wren.html