Bird vocalizations are critical cues in social interactions as they convey temporary information varying with the social context, for example, the signaler motivation when facing a rival or a potential mate. To date, literature mainly focused on learning birds. Burrowing petrels (Procellariidae) are nonlearning birds with a limited vocal repertoire. Bachelor males communicate with conspecifics with a single call emitted in three situations: in the absence of a certain auditory (spontaneous calls), toward females (female-directed calls), and toward males (male-directed calls). We first hypothesized that, although the call structure is preserved, temporal and spectral parameters vary between the three call types of bachelor males, translating different motivations (Motivation Hypothesis). To go further, we hypothesized that acoustic variations in male-directed calls indicate the signaler’s aggressive motivation and, therefore, the variations are similar whether calls are produced by breeder or bachelor males (Breeding Status Hypothesis). We tested the two hypotheses performing field playback experiments on two petrel species: the blue petrel (Halobaena caerulea) and the Antarctic prion (Pachyptila desolata). Despite the obvious call stereotypy, we observed temporal variations and frequency shifts when males react to a female or a male, which may translate the sexual or aggressive motivation of the signaler. Furthermore, the similarity of variations in male-directed calls of both breeder and bachelor males suggests the aggressive motivation. So far, vocal plasticity in nonlearning birds has been greatly underestimated. Here, we highlighted the expression of different motivations through vocal variations and the ability to produce frequency variations in species with genetically coded vocalizations.

中文翻译：

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两种非生物鸟叫声的语境变化：蓝海燕 Halobaena caerulea 和南极朊病毒 Pachyptila desolata

鸟类的发声是社交互动中的关键线索，因为它们传达的临时信息会随社交环境而变化，例如，面对竞争对手或潜在伴侣时发出信号的动机。迄今为止，文献主要集中在学习鸟类上。穴居海燕（Procellariidae）是非学习型鸟类，发声能力有限。单身汉通过在三种情况下发出的单一呼叫与同类进行交流：在没有特定听觉的情况下（自发呼叫），对女性（女性定向呼叫）和男性（男性定向呼叫）。我们首先假设，虽然呼叫结构被保留，但时间和频谱参数在单身男性的三种呼叫类型之间有所不同，从而转化为不同的动机（动机假设）。为了更进一步，我们假设雄性呼叫中的声学变化表明信号者的攻击性动机，因此，无论呼叫是由饲养员还是单身男性产生的变化都是相似的（育种状态假设）。我们测试了对两种海燕物种进行现场回放实验的两个假设：蓝海燕 (Halobaena caerulea) 和南极朊病毒 (Pachyptila desolata)。尽管存在明显的通话刻板印象，但我们观察到男性对女性或男性做出反应时的时间变化和频率变化，这可能会转化信号者的性或攻击性动机。此外，育种者和单身男性的雄性呼叫变化的相似性表明了攻击性动机。到目前为止，非学习鸟类的声音可塑性被大大低估了。这里，