Ferruginous hawks (Buteo regalis) are the largest hawk in North America and are found in the grasslands of southern Canada and the mid-west of the United States of America (Ng et al. 2017). As one of just a few grassland avian predators, ferruginous hawks help maintain ground squirrel populations within their territory, with a breeding pair and their young consuming roughly 500 ground squirrels in a single breeding season (Migaj et al. 2011). This can be important to ranchers and farmers, as large numbers of these rodents can lead to decreased crop yields and the potential for injury to livestock due to burrows (AARD 2012). Richardson’s ground squirrels are also found in many human-altered landscapes, and their burrows can cause injury when on sports fields, or even cause avian predator deaths if they are being hunted near airports (AARD 2012). As grasslands change, it is important to protect specialized predators, as changes in their population size can greatly impact the balance of organisms in lower trophic levels and, in turn, change the frequency and types of human-wildlife interactions
Figure 1. Light-morph Ferruginous Hawk perched near its nest. Photo Credit: Ronena Wolach
Ferruginous hawk populations have substantially declined and are currently found in just 48% of their historic Canadian range (Hoffman and Smith 2003, COSEWIC 2008). These hawks are currently classified as threatened in Canada and endangered in Alberta (COSEWIC 2008). Declines in Ferruginous Hawk populations since 1977 have been attributed to sensitivity to human disturbance, the conversion of native grassland to cultivated land across western North America, and the loss of nesting structures such as poplar trees, which have either been cleared by landowners or larger trees becoming brittle with age and losing limbs (Schmutz 1987, COSEWIC 2008, Alberta Ferruginous Hawk Recovery Team 2009). Conservation initiatives for ferruginous hawks in Alberta began following their classification as endangered in 2006 (Alberta Ferruginous Hawk Recovery Team 2009). Some of these strategies include encouraging positive land stewardship with landowners and industry, developing industry guidelines for working in proximity to ferruginous hawk nests, and the construction of artificial nesting platforms (ANPs) to increase available nesting structures on the landscape (AEP 2018).
As natural nesting substrates become harder to find in agricultural regions, energy companies and private landowners have been encouraged by conservation groups to construct artificial nesting platforms (ANPs) as an attractant for nesting ferruginous hawks (Migaj et al. 2011). ANPs can be built on distribution poles or transmission towers and are often a stand-alone pole with an attached nest box to encourage nesting away from electric lines (APLIC 2006, Migaj et al. 2011). Previous work has also shown that ANPs can increase productivity of raptor nests, and may be preferred over natural nest substrates like trees (Gilmer and Stewart 1983, Steenhof et al. 1993).
Figure 2. Artificial Nesting Platform (ANP) with a nesting Ferruginous Hawk. Photo Credit: Ronena Wolach
My objective is to investigate whether ferruginous hawks select for certain types of landscape attributes within their home range in order to update current conservation strategies and support increasing the ferruginous hawk population in Canada. Specifically, I intend to use these results to help government and industry effectively choose where to increase ANP construction in southern Alberta.
GPS data gathered over eight years from 12 male ferruginous hawks that breed in southern Alberta will be compared with land use and human settlement data to determine the amount of landscape types and their use within each hawk’s home range. I expect to see high use of grassland area and low use of human development in ferruginous hawk home ranges, due to their historic use of grassland habitat and their documented sensitivity to human disturbance. Because of the large amount of cropland present in southern Alberta, I could also find that ferruginous hawks have been forced to adapt to the cultivation of grasslands and will have high proportions of cropland within their home range. If I find there to be equal or higher use of these croplands compared to grassland in ferruginous hawk home ranges, this may provide evidence for increasing construction of ANPs in cultivated fields, rather than concentrating these efforts to the relatively few grassland habitats left in southern Alberta
Figure 3. Expected results of a habitat selection analysis of male Ferruginous Hawks nesting in southern Alberta. I expect that Ferruginous Hawks will both select home ranges with mostly grassland, at least some cropland, and minimal human development, and use these habitats with similar proportions.