Pyle Peter, Foster Kenneth R, Godwin Christine M, Kaschube Danielle R, Saracco James F
The Institute for Bird Populations, Petaluma, CA, USA.
Owl Moon Environmental Inc., Fort McMurray, AB, Canada.
PeerJ. 2020 Apr 24;8:e8898. doi: 10.7717/peerj.8898. eCollection 2020.
Landbird vital rates, such as productivity and adult survivorship, can be estimated by modeling mist-netting capture data. The proportion in which an adult breeding bird is 1 year of age (a "yearling"), however, has been studied only minimally in a few landbird species. Here we relate yearling proportion to habitat-structure covariates, including reclamation age, in a boreal forest landbird community. Data were collected at 35 constant-effort mist-netting stations over a 6-year period, and consisted of 12,714 captures of adults, of 29 landbird species, including 4,943 captures of yearlings. Accuracy of age determination (yearling or older) was assessed based on recapture data and error rates were estimated at a mean of 8.1% (range 0.0-19.4%) among the 29 species, with 20 species showing age-error rates <10%. The estimated mean yearling proportion was 0.407, ranging from 0.178 to 0.613 among species. Remote-sensed Enhanced Vegetation Index (EVI), a measure of habitat greenness, was positively correlated with age since reclamation up to 20 years, at which time it became comparable to that of natural stations. The probability of capturing a yearling for species associated with mature forest was lower at stations with higher EVI and the opposite was the case for species favoring successional habitats. These results suggest that yearling birds are being excluded from preferred breeding habitats by older birds through despotism and/or that yearlings are simply selecting poorer habitat due to lack of breeding experience or other factors. This dynamic appears to be operating in multiple species within this forest landbird community. Captured yearlings may also be "floaters", or non-breeding individuals not holding territories. However, presuming that yearlings show lower reproductive success whether floating or not, our results suggest that stations with high yearling proportions could be located within sink as opposed to source habitats. Overall, we infer that yearling proportion may become an important vital-rate measure of habitat quality and reclamation efforts, when combined with indices of population size, productivity, reproductive condition and survivorship.
通过对雾网捕获数据进行建模，可以估算陆地鸟类的关键率，如繁殖力和成年存活率。然而，在少数陆地鸟类物种中，对1岁成年繁殖鸟（“一岁鸟”）的比例研究甚少。在此，我们将一岁鸟比例与包括开垦年限在内的栖息地结构协变量联系起来，研究对象是北方森林陆地鸟类群落。在6年时间里，我们在35个固定工作量的雾网站点收集数据，共捕获了29种陆地鸟类的12714只成年鸟，其中包括4943只一岁鸟。根据重捕数据评估年龄判定（一岁鸟或成年鸟）的准确性，29个物种的错误率平均估计为8.1%（范围为0.0 - 19.4%），其中20个物种的年龄错误率<10%。估计的一岁鸟平均比例为0.407，物种间范围为0.178至0.613。遥感增强植被指数（EVI）是栖息地绿色度的一种度量，在开垦后20年内与年龄呈正相关，到那时它与自然站点的指数相当。对于与成熟森林相关的物种，在EVI较高的站点捕获一岁鸟的概率较低，而对于偏好演替栖息地的物种则相反。这些结果表明，一岁鸟正被成年鸟通过专制行为排除在首选繁殖栖息地之外，和/或一岁鸟由于缺乏繁殖经验或其他因素而只是选择了较差的栖息地。这种动态似乎在这个森林陆地鸟类群落的多个物种中都存在。捕获的一岁鸟也可能是“漂泊者”，即没有领地的非繁殖个体。然而，假设一岁鸟无论是否漂泊都表现出较低的繁殖成功率，我们的结果表明，一岁鸟比例高的站点可能位于汇生境而非源生境中。总体而言，我们推断，当与种群大小、繁殖力、繁殖状况和存活率等指标相结合时，一岁鸟比例可能成为栖息地质量和开垦成效的一项重要关键率指标。
