Survey design for broad-scale, territory-based occupancy monitoring of a raptor: Ferruginous hawk (Buteo regalis) as a case study.

Autor: Johnson TN; Department of Fish and Wildlife Sciences, University of Idaho, Moscow, Idaho, United States of America., Nasman K; Western Ecosystems Technology, Inc., Cheyenne, Wyoming, United States of America., Wallace ZP; Wyoming Natural Diversity Database, University of Wyoming, Laramie, Wyoming, United States of America., Olson LE; Rocky Mountain Research Station, U.S. Forest Service, Missoula, Montana, United States of America., Squires JR; Rocky Mountain Research Station, U.S. Forest Service, Missoula, Montana, United States of America., Nielson RM; Western Ecosystems Technology, Inc., Cheyenne, Wyoming, United States of America., Kennedy PL; Department of Fisheries and Wildlife and Eastern Oregon Agriculture Research Center, Oregon State University, Union, Oregon, United States of America.
Jazyk: angličtina
Zdroj: PloS one [PLoS One] 2019 Mar 22; Vol. 14 (3), pp. e0213654. Date of Electronic Publication: 2019 Mar 22 (Print Publication: 2019).
DOI: 10.1371/journal.pone.0213654
Abstrakt: Given the uncertain population status of low-density, widely-occurring raptors, monitoring changes in abundance and distribution is critical to conserving populations. Nest-based monitoring is a common, useful approach, but the difficulty and expense of monitoring raptor nests and importance of reliable trend data to conservation requires that limited resources are allocated efficiently. Power analyses offer a helpful tool to ensure that monitoring programs have the ability to detect trends and to optimize financial resources devoted to monitoring. We evaluated alternative monitoring designs for raptors to identify appropriate survey effort to detect population trends. We used data collected from a territory-occupancy study of ferruginous hawks throughout Wyoming to guide simulations and evaluate the ability to detect trends in occupancy rates. Results suggest that greater gains in precision of trend estimation may be achieved through the addition of more sites and not more visits; statistical power was ≥80% when monitoring lasted 20 years and population declines were 20%; and probability of detection affected statistical power less than rates of population decline. Monitoring at least 150 sites for 20 years would provide reasonable estimates of trend in occupancy given certain rates of detection and occupancy, but only for population declines of 20%. Removal sampling did not result in substantial changes of any metrics used to evaluate simulations, providing little justification for employing the standard design if territory occupancy is the variable of interest. Initial rates of territory occupancy may be biased high, a problem inherent to many studies that monitor territory occupancy. We explored the effects of lower rates of initial occupancy on the ability to detect trends. Although we present data from a study of ferruginous hawks, our simulations can be applied to other raptor species with similar life history and population dynamics to provide guidance for future trend estimation of territory occupancy.
Competing Interests: K. Nasman is employed by Western Ecosystems Technology, Inc., as were T.N. Johnson (now employed by University of Idaho) and R.M. Nielson (now employed by Eagle Environmental, Inc.) at the time of this study. This affiliation does not alter our adherence to PLOS ONE policies on sharing data and materials.
Databáze: MEDLINE
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