HawkWatch International was awarded the prestigious Neotropical Migratory Bird Conservation Act grant from the U.S. Fish and Wildlife Service (USFWS) in 2012 to support our Western Ridge Modeling project.
We have been involved in western raptor migration counts for over 30 years to track long-term population trends and identify species of concern, such as the American Kestrel and Golden Eagle. Although we've conducted annual counts at dozens of locations throughout the West, and conducted shorter "exploratory" counts at many more sites, there remain many blank spots on the map. These blank spots represent a challenge when attempting to frame the trends we detect at our sites in the proper context. Additionally, in recent years wind energy developers have begun to seek out western ridge tops for their great wind potential, putting migrating raptors that may seek out such areas for similar reasons at risk of collision. For these reasons and more, we recently recognized an opportunity to use our existing data and insights to identify areas of potential high raptor migration volume across the West.
How are we using data from existing migration count sites to identify other likely places for migration on the landscape? Modeling! Modeling is an attempt to represent complex systems in a simplified manner. In this situation we are using a few measures, such as ridge elevation, orientation, and "connectivity" to represent the highly complex combinations of topography, weather, and vegetation encountered by migrating raptors traversing the West. For example, migrating raptors are thought to favor north-south oriented ridgelines, partly because such areas intercept the predominant western winds and create updrafts that allow low-energy travel. After we simplify our western landscape into representative variables such as ridge orientation using spatial analysis software ("GIS"), we can use modeling techniques to identify other ridges on the landscape that "look similar" to our known migration sites. A sample of our first model output can be seen below.
If you would like to learn more about this project or are interested in ground truthing projects in your area, please contact us:
- Dr. Steve Slater, Conservation Science Director, HawkWatch International