Department of Biological Sciences, The University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
Conserv Biol. 2013 Feb;27(1):210-8. doi: 10.1111/j.1523-1739.2012.01917.x. Epub 2012 Sep 14.
Although the genetic and ecological effects of population declines in endangered species have been well studied, little is known of the social consequences. Changes in signaling behavior may result in disrupted communication and affect both reproductive and conflict-resolution activities. The North Island Kōkako (Callaeas wilsoni) is an endangered, duetting (i.e., alternating, coordinated singing by mated pairs) songbird endemic to New Zealand temperate rain forests. Scattered populations (approximately 1500 individuals in 13 surviving and 11 translocated populations) in isolated conservation areas of different sizes have been rescued from extirpation and are currently recovering. We examined key song attributes of the Kōkako to assess whether population size or growth rate are related to song complexity, the reduction of which may compromise effective communication. We analyzed song repertoire size and phrase-type sharing (i.e., Jaccard index of similarity), vocal performance (singing rates, song switching rates, and diversity of phrase types), and song syntactical characteristics (i.e., unpredictability in sequences of phrase types) in surviving and translocated populations (populations of approximately 19-250 territorial individuals). Population size was positively correlated with a population's song repertoire, song diversity, and switching of song phrase types and negatively correlated with shared phrase types and variation in syntactical structure of songs. Population growth rate correlated positively with pair repertoire size, population repertoire size, and singing rates during song bouts. As for solo-singing species in fragmented landscapes, songs in the fragmented populations of Kōkako appear to be undergoing microevolution as occurs in island colonization events. Our results suggest that vocal changes in small populations could affect population establishment and growth, particularly in multiple-source translocations. We believe measurement of vocal behavior could be used as a supplement to periodic population censuses to allow more frequent monitoring of population size.
尽管人们对濒危物种种群减少的遗传和生态影响进行了深入研究，但对其社会后果却知之甚少。信号行为的变化可能导致沟通中断，并影响繁殖和解决冲突活动。北岛凤头鹦鹉（Callaeas wilsoni）是一种濒危的、对偶的（即由配对的个体交替、协调地歌唱）鸣禽，原产于新西兰温带雨林。在不同大小的孤立保护区中，有分散的（大约 1500 只，分布在 13 个现存和 11 个迁移种群中），这些种群从灭绝中被拯救出来，目前正在恢复。我们检查了凤头鹦鹉的关键歌曲属性，以评估种群大小或增长率是否与歌曲复杂性有关，因为歌曲复杂性的降低可能会影响有效的沟通。我们分析了歌曲曲目大小和短语类型共享（即相似性的杰卡德指数）、声乐表现（歌唱率、歌曲转换率和短语类型的多样性）以及歌曲句法特征（即短语类型序列的不可预测性）在现存和迁移种群（大约有 19-250 个有领地个体的种群）中。种群大小与种群的歌曲曲目、歌曲多样性和歌曲短语类型的转换呈正相关，与共享短语类型和歌曲句法结构的变异性呈负相关。种群增长率与对的曲目大小、种群曲目大小和歌曲回合中的歌唱率呈正相关。对于在破碎景观中生存的独居物种来说，凤头鹦鹉的破碎种群的歌声似乎正在经历微观进化，就像在岛屿殖民事件中发生的那样。我们的研究结果表明，小种群中发声的变化可能会影响种群的建立和增长，特别是在多源迁移中。我们认为，测量发声行为可以作为定期人口普查的补充，以便更频繁地监测种群规模。
