Exploratory analysis of avian point pattern data: approximating methods of intensity on airfield habitat of interior Alaska

Abstract

The Animal and Plant Health Inspection Service agency of the United States Department of Agriculture began their work on United States Army Garrison Fort Wainwright of Alaska in 2018. In conjunction with airfield personnel, the main objective of this agency is to protect aircraft on Ladd Army Airfield (LAAF) from wildlife hazards and mitigate human-wildlife interactions on Post. The main wildlife hazard for aircraft is of the avian variety. The patterns of avian use on LAAF were examined for the first time using various non-parametric and parametric spatial methods. The main non-parametric technique applied was kernel density estimation of points in two-dimensional contour plots and three-dimensional surfaces. As for parametric means, Poisson point process modeling was used to estimate intensity (points per unit area) of the spatial region in question. Each year displayed a unique pattern of use among density plots that were consistent with an inhomogeneous process upon tests of complete spatial randomness. The baseline estimated intensity (homogeneous process) for years 2018, 2019, and 2020 were 1.609, 0.986, and 1.450 observations per hectare, respectively. Spatial locations as covariates revealed that intensity varies in North-South or East-West directions depending on the year. In addition to fleshing the dataset at hand, I outline theory and steps taken to numerically approximate the likelihood of the inhomogeneous Poisson point process. Logistic regression of observations on a continuous covariate (minimum distance to water) was used to demonstrate that fine pixel approximation yields adequate estimates of intensity.