Dana L. Moseley

Research

 

             1. Does vocal performance indicate the level of threat to receivers?

    Mating behavior in many species involves communication displays that are vigorous or difficult to perform. Individuals that maximize such features might be of higher quality and thus favored as prospective mates. In songbirds, males produce song both for mate attraction and territory defense. Aspects of vocal performance might allow other males to assess the fighting prowess of signalers in territorial disputes, with males who are better able to sing at higher performance levels perhaps posing a greater threat. Here we tested, in swamp sparrows (Melospiza georgiana), how territorial males respond to playback of songs of various levels of performance.

    Our main findings are twofold. First, low-performance stimuli elicited significantly lower aggressive responses. Second, male response to normal and high performance songs showed significant individual variation. Closer examination revealed that male response varied with both the subject's own vocal performance, and the degree to which the performance level of the playback stimuli was elevated. Males approached less closely and spent less time near the speaker the more the high-performance playback had been increased.  However, subject males with higher-performance song approached more closely than did males with lower performance song types. These findings provide insight into if and how vocal performance may indicate threat levels posed by a signaler.

2. What factors affect the development of female preferences -

                learning, mate-choice copying, a bias for high performance?

    Female mating preferences are a crucial component of sexual selection, yet we have poor knowledge of how female preferences develop. Specifically the extent to which experience during development informs mate choice is largely unstudied. Multiple factors may shape mate choice including experiential learning, social copying, and a sexually selected bias for certain male traits such as the performance level of displays. For bird species in which males learn their songs, it is likely that early exposure to song may also influence females' preferences later in life. I address this question in the swamp sparrow (Melospiza georgiana), using a new method to elicit preferences from lab-raised birds. Adult, wild-caught females of this species are known to prefer songs of relatively high-performance, i.e. songs that are physically difficult to produce.  In 2009, I hand-raised females with tutor songs of normal-performance levels.  As further training in their first spring, I presented females with these songs again, but this time coupled with a video of an adult female responding with a copulation solicitation display (CSD, shown below). I then used the CSD assay to test female preferences for songs they had experienced during ontogeny against these same songs altered to higher and lower performance levels.

guide female preference development.

collaboration with David C. Lahti and Jeffrey Podos


     Females gave significantly fewer CSDs to low-performance songs than to the trained (normal-performance) songs. Females responded with the most CSDs to trained songs overall, but this value was not significantly different in a pairwise comparison to the high-performance songs, which was intermediate. A greater response to trained songs supports the hypothesis of a strong influence of early experience, but a preference for high-performance songs by some females cannot be ruled out. It appears that both experiential learning and a bias for high-performance