Nebraska Cooperative Fish & Wildlife Research Unit


Date of this Version



Ecological Modelling 316 (2015) 185–190


© 2015 Elsevier B.V. All rights reserved.


Sampling by spatially replicated counts (point-count) is an increasingly popular method of estimating population size of organisms. Challenges exist when sampling by point-count method, and it is often impractical to sample entire area of interest and impossible to detect every individual present. Ecologists encounter logistical limitations that force them to sample either few large-sample units or many small sample-units, introducing biases to sample counts. We generated a computer environment and simulated sampling scenarios to test the role of number of samples, sample unit area, number of organisms, and distribution of organisms in the estimation of population sizes using N-mixture models. Many sampleunits of small area provided estimates that were consistently closer to true abundance than samplescenarios with few sample units of large area. However, sample scenarios with few sample units oflarge area provided more precise abundance estimates than abundance estimates derived from samplescenarios with many sample units of small area. It is important to consider accuracy and precision of abundance estimates during the sample design process with study goals and objectives fully recognized, although and with consequence, consideration of accuracy and precision of abundance estimates is often an afterthought that occurs during the data analysis process.