Dawn singing reflects past territorial challenges in the winter wren

Territory defence can be seen as a dynamic long-term process that involves some learning. For example, a resident may adjust its territory proclamation behaviour depending on its prior experience with territorial intruders. We investigated whether short territorial challenges could have long-lasting effects on the singing behaviour of male birds. We used song playbacks to simulate intrusions into autumn territories of male winter wrens, Troglodytes troglodytes, shortly after dawn and compared male singing behaviour immediately before and I day after the simulated intrusion. As in many other bird species, unchallenged male wrens tended to sing more songs before than after sunrise. One day after a simulated intrusion, however, this pattern was much more pronounced. Males significantly increased their song output before sunrise, but maintained or even reduced song output after sunrise. This result suggests that dawn singing before sunrise is particularly important for territory defence. On the day after the intrusion, the start of dawn singing varied less between males, although the average starting time remained the same. Our findings suggest that a territorial challenge can influence singing behaviour almost 24 h after the intrusion. The amount and timing of birdsong, as a preventive territorial proclamation, can thus be adjusted to past territorial challenges.