Imperial Irrigation District Surveys of Burrowing Owls in Imperial Valley, California (2006, 2007, 2008, 2011, 2012). In 2006, a pilot population survey was performed on select IID rights-of-way in Imperial Valley. In 2007 and 2008, valley-wide population surveys were performed on IID rights-of-way. In 2011 and 2012, population surveys were performed on IID rights-of-way within preselected grid cells, with the goal of identifying population trends rather than total population. See the layer "Areas Surveyed in IID Surveys", which describes what regions were surveyed in 2007-2008 and 2011-2012.

Shapefiles provided by IID. Data and methodologies described in the reports below. Data adapted for use in this map by Audubon California. 

"Burrowing Owl Population Size in the Imperial Valley, California: Survey and Sampling Methodologies for Estimation" by Jeffrey A. Manning, dated April 15, 2009. 
"Burrowing Owl Monitoring Results: Imperial Irrigation Distriction Rights-of-Way: Imperial County, California" by AECOM, dated November 20, 2012. 


Data Dictionary: 


Field: Year 
Observation year.


Field: Season
Observation season. Estimated based on observation month. 


Field: Month 
Observation month. 


Field: Date 
Observation date. 


Field: Time 
Observation time. 


Field: Owl or Burrow 
Indicates type of observation (Burrowing Owl or Burrow). Estimated from data provided by IID. 


Field: Number of Owls 
Indicates number of owls observed. Calculated from data provided by IID. 


Field: Owl Activity 
Indicates activities noted by observers. 


Field: Drain Type 
Type of water conveyance structure bank (earthen, concrete, or unknown). 


Field: Drain Vegetation 
Drain vegetation noted by observers. 


Field: Percent Vegetative Cover 
Percent vegetative cover noted by observers, within an approximated 8-degree radius circle centered on the detected owl from observer’s view. This was based on a 6-m radius circle surrounding an owl at 21 m from the observer because many vantage points for detecting owls were approximately 21 m from where owls often perched (across the water conveyance structure). 


Field: Crop 1 
Habitat / crop type noted by observers. 


Field: Crop 2 
Habitat / crop type noted by observers. 


Field: Crop 3 
Habitat / crop type noted by observers. 


Field: Crop 4 
Habitat / crop type noted by observers. 


Field: Bank Aspect 
Bank aspect. 


Field: Bank Texture 
Bank texture, within an approximated 8-degree radius circle centered on the detected owl from observer’s view. This was based on a 6-m radius circle surrounding an owl at 21 m from the observer because many vantage points for detecting owls were approximately 21 m from where owls often perched (across the water conveyance structure). 
 
Field: Precipitation 
Precipitation during observation period. 



Field: Temperature 
Temperature (degrees Fahrenheit) during observation period. 


Field: Wind 
Wind speed (average, mph) during observation period. 


Field: Comments 
Comments recorded by observers. 


Field: Source 
Source of observation record.