Vocal performance – an animal's ability to produce physically challenging vocalizations – can reflect a signaller's overall condition and can be a reliable signal of quality. It has been suggested recently that songbirds improve vocal performance through recent practice during intense dawn singing. We tested whether recent practice improves vocal performance in swamp sparrows, Melospiza georgiana, a species for which the biomechanical constraints and biological implications of vocal performance are well established. We measured vocal deviation – a measure of performance – in 1527 songs recorded from 11 captive swamp sparrows, four of which were developmentally stressed as juveniles. Vocal performance improved across the morning as a function of both the cumulative number of songs previously performed and the time of day. Song types with introductory syllables showed greater improvement than more typical song types composed solely of trilled syllables, and across all song types, as song output increased, the average improvement in vocal performance also increased. However, males with high song output exhibited greater variability in vocal performance, suggesting that some individuals might experience fatigue in song production. Furthermore, birds that had been developmentally stressed as juveniles showed greater improvement over the morning than birds that were not stressed. If conspecifics attend to within-individual variation in vocal performance, then improvement in vocal performance over the course of a day may drive birds to sing early and often, although fatigue may limit the extent to which this advantage may be gained.

中文翻译：

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整个早晨在鸣禽中持续歌唱，歌曲表现得到改善

声音表现——动物发出身体上具有挑战性的发声的能力——可以反映信号员的整体状况，并且可以是质量的可靠信号。最近有人建议鸣禽通过最近在强烈的黎明歌唱期间的练习来提高声乐表现。我们测试了最近的练习是否改善了沼泽麻雀的声音表现，Melospiza georgiana，这种物种的声音表现的生物力学限制和生物学意义已经得到很好的确立。我们测量了从 11 只圈养沼泽麻雀录制的 1527 首歌曲中的声音偏差——一种表现的衡量标准，其中 4 只在幼年时期受到了发育压力。整个早上的声乐表现都随着先前演奏的歌曲累计数量和一天中的时间而有所改善。具有介绍音节的歌曲类型比仅由颤音音节组成的更典型的歌曲类型表现出更大的改进，并且在所有歌曲类型中，随着歌曲输出的增加，人声表现的平均改进也增加了。然而，歌曲输出量高的男性在声乐表现方面表现出更大的变异性，这表明某些人可能会在歌曲制作中感到疲劳。此外，与没有受到压力的鸟类相比，在幼年时期受到发育压力的鸟类在早上表现出更大的进步。如果同种动物注意个体内部声音表现的差异，那么一天中声音表现的改善可能会促使鸟类尽早并经常唱歌，尽管疲劳可能会限制获得这种优势的程度。