Ydenberg Ronald C, Barrett Jennifer, Lank David B, Xu Cailin, Faber Michiel
Centre for Wildlife Ecology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
Biology Department, University of the Fraser Valley, 33844 King Road, Abbotsford, V2S 7M8, BC, Canada.
Oecologia. 2017 Apr;183(4):1101-1110. doi: 10.1007/s00442-017-3835-2. Epub 2017 Feb 18.
Large-scale changes in predator populations are occurring worldwide due to (re-)introductions, over-exploitation, or recovery after decimation by pesticides and persecution. These widespread changes may affect the distribution of their prey. We studied the continental-scale distributions of non-breeding Calidris alpina pacifica and C. a. hudsonia (Pacific and Atlantic dunlins, respectively), as numbers of their major predators-peregrines (Falco peregrinus) and merlins (F. columbarius; together 'falcons')-increased after DDT was banned in 1973. For the period 1975-2010 we compiled the number of dunlins and falcons in each of 244 Christmas Bird Count circles, which cover most of the dunlins' non-breeding ranges. Over the study period, falcons increased by 6.5- (Pacific) and 3.1- (Atlantic) fold, spread to more count circles, and the number of dunlins per falcon fell. The annual total count of the two dunlin sub-species fluctuated strongly and independently. We measured annual aggregation as the expected proportion of a subspecies total found on the same count circle as a randomly selected dunlin. The average aggregation of Pacific dunlins (0.117) was about double that of Atlantic dunlins (0.059), with annual variation largely attributable to changes in a few large count circles. The slope of the aggregative response to year-on-year changes in dunlin numbers was identical on the two coasts. The response to the ongoing falcon increase was positive and significant on the Pacific and slightly negative on the Atlantic. We interpret these results using a version of the ideal free distribution that includes predation danger.
由于（重新）引入、过度捕猎，或在遭受杀虫剂迫害及数量锐减后恢复，全球范围内食肉动物种群正在发生大规模变化。这些广泛的变化可能会影响它们猎物的分布。我们研究了非繁殖期的太平洋滨鹬和哈德逊滨鹬（分别为太平洋斑尾塍鹬和大西洋斑尾塍鹬）在大陆尺度上的分布情况，因为它们的主要捕食者——矛隼和灰背隼（统称为“隼”）的数量在1973年滴滴涕被禁用后有所增加。在1975年至2010年期间，我们统计了244个圣诞鸟类计数圈中斑尾塍鹬和隼的数量，这些计数圈覆盖了斑尾塍鹬大部分的非繁殖区域。在研究期间，隼的数量增长了6.5倍（太平洋地区）和3.1倍（大西洋地区），分布到了更多的计数圈，并且每只隼对应的斑尾塍鹬数量减少。这两个斑尾塍鹬亚种的年度总数波动剧烈且相互独立。我们将年度聚集度衡量为一个亚种总数中与随机选择的一只斑尾塍鹬在同一个计数圈中被发现的预期比例。太平洋斑尾塍鹬的平均聚集度（0.117）约为大西洋斑尾塍鹬（0.059）的两倍，年度变化主要归因于少数几个大计数圈的变化。在两个海岸，对斑尾塍鹬数量逐年变化的聚集反应斜率是相同的。对隼数量持续增加的反应在太平洋地区是正向且显著的，在大西洋地区则略显负向。我们使用一个包含捕食危险的理想自由分布版本来解释这些结果。
