Personality predicts song complexity in superb fairy-wrens

Abstract

In birds, singing behaviours play a critical role in mating and territory defence. Although birdsong can signal individual quality and personality, very few studies have explored the relationship between individual personality and song characteristics, and none has investigated this in females. Here, we examined the relationships between song complexity and two ecologically relevant personality traits (exploration and aggressiveness) in wild superb fairy-wrens (Malurus cyaneus), a species in which both sexes learn to produce complex songs. First, we assessed personality in males and females (including juveniles) by quantifying their exploration behaviour (novel environment test) and aggressiveness (mirror stimulation test) during short-term captivity. After birds were released, we recorded their songs over several months to assess individual variation in song complexity (i.e. element types per song and syllables per song) in relation to personality. Regardless of their sex or life stage, individuals that were more exploratory had more element types per song. Additionally, more aggressive individuals produced songs with fewer syllables, and more aggressive fledglings, but not adults, had more element types per song. Our study supports the idea that both male and female birds can advertise their personality when singing, which may be important for mate choice.

Keywords: Maluridae; aggressiveness; exploration; learnt signals; sexual signalling.

Figure 1.

Examples of four different superb fairy-wren chatter songs from (a) an adult male, (b) an adult female, (c) a male fledgling and (d) a female fledgling. We considered an element as a single trace on the spectrogram and a syllable as a unit of elements separated by less than 1 s (examples of each indicated in figure 1a).

Figure 2.

Relationships between exploration (‘total sector visits’ in a novel environment test) and song characteristics in superb fairy-wrens (n = 102 individuals). Data are presented for (A) ‘element types per song’ (mean number of element types per song) and (B) ‘syllables per song’ (mean number of syllables per song).

Figure 3.

Relationships between aggressiveness (‘time close to mirror’ in a mirror stimulation test) and song characteristics in superb fairy-wrens, grouped by life stage (n = 102 individuals). Data are presented for (A) ‘element types per song’ (mean number of element types per song) and (B) ‘syllables per song’ (mean number of syllables per song). Data are presented separately for (i) adults and (ii) fledglings.