Risk-based alarm calling in a nonpasserine bird

摘要: Recent studies have demonstrated the presence of risk-based variation in alarm calling many vertebrate species. Most on birds, however, focused passerine systems perhaps due to traditional view that vocalizations are more complex. We investigated a system nonpasserine, herring gull, Larus argentatus, by recording birds presented with varying degrees threat, and experimentally exposing quantifying responses manipulated calls. found gulls communicate threat urgency their calls using both frequency time parameters. Sound recordings indicated change centre modulation patterns calls, generate discontinuities notes increase rate increases perceived level. Playback experiments showed conspecifics pay attention parameters respond most urgently playbacks high-threat at high call rate. A less urgent response low low-threat suggests information is reinforced type gull system. This study one first demonstrations nonpasserine.