Summary: Differential effects of moving versus stationary territorial
intruders on territory defence in a songbird
Valentin Amrhein* and Sabine Lerch
Research Station Petite Camargue Alsacienne, Rue de la Pisciculture, 68300 Saint-Louis, France, and University of Basel,
Zoological Institute, Vesalgasse 1, 4051 Basel, Switzerland
1. In territorial contests, not only acoustic or other signals, but also the movements of a territorial
intruder are likely to influence the response of a resident.
2. We tested this movement hypothesis by simulating moving vs. stationary intruders into the ter-
ritories of winter wrens Troglodytes troglodytes, using the same non-interactive song playbacks in
3. Male winter wrens showed a different long-term singing reaction in response to a moving than
to a stationary intruder.
4. One day after experiencing an intruder that was switching between three locations, residents
started to sing earlier before sunrise, and they sang more and longer songs at dawn than before the
5. Residents receiving the same playback from one location only reacted by starting to sing later
relative to sunrise, and by singing fewer and shorter songs than before the intrusion.
6. We could not discriminate between the treatments when examining the short-term singing reac-
tions during and immediately after the playbacks. However, our results clearly demonstrate an