A resampling-based method for effort correction in abundance trend analyses from opportunistic biological records

作者：Zbinden Niklaus; Kery Marc^*; Haefliger Guido; Schmid Hans; Keller Verena

来源：Bird Study, 2014, 61(4): 506-517.

DOI：10.1080/00063657.2014.969679

Capsule Resampling data from biological records databases yielded abundance trend estimates better corrected for increasing observation effort.
Aims To correct population trend estimates for the effects of annually changing observation effort in analyses of opportunistic data.
Methods We developed a resampling-based abundance index for analysis of population trends based on opportunistic citizen-science observations. To correct for the huge recent increase in observation effort every year, we resampled (with replacement) a species-specific constant number of records from the data and computed our index. To validate our standardized index, we used counts from the national waterbird census as a benchmark.
Results Over 22 winters (1991-2012), trend estimates based on resampled indices were substantially more similar to waterbird census-based trend estimates than were raw index-based trends. Raw index trends were off by 648% (se 72%) and typically overestimated trends, while trends computed from standardized indices were off by only 125-131% (se 12-13%) and over - and underestimated trends about equally frequently. Hence, our method of effort correction reduced the bias in trend estimates by a factor 5.
Conclusion Our resampling method may be useful for improving trend analyses from collections of opportunistic biological records, as they become increasingly available, especially via the internet.

• 出版日期2014-10-2