Aggressiveness, reliable signaling and survival in a wild songbird

22 The evolution and maintenance of honest or reliable signaling has been a major question 23 in evolutionary biology. The question is especially puzzling for a particular class of signals used 24 in aggressive interactions: threat signals. Here we report a study on song sparrows (Melospiza 25 melodia) in which we assayed males with playbacks in their territories to quantify their 26 aggressiveness and aggressive signaling levels and asked whether these affect their survival on 27 territory. We found that the effect on survival of residual signaling (signaling above or below the 28 level predicted by their aggressiveness) depended on aggression levels such that among males 29 with low aggression, those with higher residual signaling scores had higher survival. The 30 residual signaling did not have a strong effect among high aggression males. Aggressiveness by 31 itself did not have an effect on survival. These results present a first step in understanding the 32 fitness consequences of honest signaling in aggressive contexts. 33