The Return of the Intruder: Immediate and Later Effects of Different Approach Distances in a Territorial Songbird

Abstract

Male songbirds often maintain territories throughout the breeding season, and one of the main functions of song is to deter invaders. Therefore, the distance of an unknown singing rival should play a crucial role within territorial singing interactions of males. This distance is expected to be assessed as more threatening the closer the rival approaches. Here, we tested this assumption by conducting nocturnal playbacks from two different distances in territorial Common nightingales (Luscinia megarhynchos). Immediate vocal responses of birds were examined by analysing changes in song structure as well as temporal response features. The next morning, follow‐up playbacks from an intermediate distance allowed us to investigate longer‐lasting effects of nocturnal playbacks. We found that the distance of a simulated rival had an effect on both immediate and later vocal responses of territorial male nightingales with different song parameters being affected during nocturnal and diurnal singing. This indicates that birds perceive intruder distances and adjust their response behaviour both immediately and in later interactions.

The use of network analysis to study complex animal communication systems: a study on nightingale song

“…As part of a long-term project on song and breeding behaviour, males of the population were individually marked by coloured leg rings (for details, see e.g. [31]). The age class (yearling or older) was determined by subtle, though characteristic feather features [30,32,33].…”

“…[30,31]). To test whether the birds in our study responded differently to the two playback treatments, we analysed the target birds' reactions to the playbacks by comparing the following response measure between the two playback treatments: for each song type a bird sang during a playback trial, we assigned the respective out degree/in degree value calculated based on the song of 19 birds (see above).…”

Female calling? Song responses to conspecific call playbacks in nightingales, Luscinia megarhynchos

“…Naguib & Kipper, 2006;. The occurrence and latency of initial whistles were also determined (Bartsch et al, 2012;Sprau et al, 2010). In nightingale vocalizations, these initial whistles have rather call-like characteristics since they can precede any given song type, but are never performed within a song.…”

“…Bartsch et al, 2012), these four features were determined not only during the playback, but also for 1 min after the playback ended. To control for individual variation in song, changes in response parameters both during and after the playback were compared to the undisturbed singing 2 min prior to the playback (with one exception: the latency to produce initial whistles was calculated after playback onset).…”

“…When playbacks are conducted during the day, males usually respond with both changes in song and/or other vocal output, as well as approaches to the sound source (e.g. Bartsch, Weiss, & Kipper, 2012;Sprau, Roth, Schmidt, Amrhein, & Naguib, 2010). At night, however, males avoid moving, and thus nocturnal playbacks allow the exclusive study of song in response to a conspecific.…”