Spatial Analysis
Analyzing the data.
For the distance calculations that dealt with the foraging locations, there were only 14 nests that had foraging locations tied to their nest. As such, only those nests are included in the analysis. Furthermore, the structure and organization of the spreadsheets made it difficult to calculate the individual average distances for each nest. To solve this, each nest was made into its own shapefile and all of the foraging locations associated with it were also made into their own shapefile. This allowed ArcMap to specifically calculate the average distance of a nest with its foraging locations with the Near Tool. The average distance numbers for the valid nests were then added to the nest shapefile as a new attribute.
The range maps and average area used was calculated by first creating a polygon that encompassed a nest and its foraging locations. This polygon was then calculated for its area and added to the nest shapefile as a new attribute.
The distance to water and urban areas also used the Near Tool, which analyzes the distance from the nest location to the closest water and urban polygon. This distance uses the edge of those land use polygons, not the center. Both water and urban distances were created as new attributes of the nest shapefile.
The competitor and starling ratios were calculated using the field calculator within the nest shapefile. New attributes were created for the following: competitor numbers, starling numbers, overall competitor ratio, and starling ratio. These were shown as decimal numbers, with a value of 0 meaning no competitors and 1 meaning an equal number of competitors to cavity availability. These were then reclassified to show no, low, medium, and high competition ratios. The same was applied to the Starling ratios. To indicate nests where no cavity data was obtained, those nests were given a ratio of -1 and classified as gray (two of them in total).