Meeting Abstract
Male reproductive success commonly depends on the ability to attract a mate. While a wide variety of courtship techniques are used by males of different species, a common trade-off exists: Males that court more are more likely to attract a mate, but also more likely to attract a competing male. Males are known to disrupt one another’s courting attempts, which often results in loss of a potential mate, a risk that may be more severe in conditions of high competition. To examine this tradeoff, we used simulated territorial intrusions (STIs) to manipulate perceived competition level of 42 male Dark-eyed Juncos (Junco hyemalis). We exposed some males to frequent playback of conspecific male song for a day and treated others as controls. On the next day we simulated an opportunity for extrapair mating by presenting a live lure female on each male’s territory. We recorded male vocalizations to determine whether the perceived competition level altered male courtship as indicated by number and complexity of songs. Courtship did not differ significantly between the high competition and control groups. However, the data suggest an interaction between body size and male song as a function of competition level. Under low competition (controls) males courted similarly, but under high competition, smaller males tended to sing more frequently and to sing more complex songs than larger males. This indicates that only some males react to changes in competition level, and furthermore that this response may be dependent on body size.
