Available Burrows for Burrowing Owls in Imperial Valley, California, as provided by Imperial Irrigation District (IID) in shapefile format ("Available_Buow_Burrows_2007.shp" and "Available_Buow_Burrows_2008.shp").

According to "Burrowing Owl Population Size in the Imperial Valley, California: Survey and Sampling Methodologies for Estimation" by Jeffrey A. Manning, dated April 15, 2009: "A complete count of burrows that were 'potentially suitable' as nest burrows for BUOW was conducted along the IID's rights-of-way. A burrow/hole was considered to be potentially suitable if it entered into an earthen surface, space within a debris pile, or pipe with an entrance between 3.5-15 inches in diameter that was flush with the ground. All burrows/holes that met this criteria were counted, even if occupied by a small mammal, and burrows/holes <20 m apart were considered as a single count because these data were intended to predict the number of male BUOW territories, and a single BUOW can occupy such a complex."