Between 2013 and 2017, 12 adult male Ferruginous Hawks in southern Alberta (Figure 4) were trapped and tagged by members of the Raptor Ecology and Conservation Team (REACT) from the University of Alberta. Only male hawks were used in this study, as we did not want to inadvertently increase stress on females during nesting, and there is limited evidence to how the backpack-attachment method for transmitters may impact brooding or nest productivity and success.Hawks were captured using Dho Gaza traps and live great-horned owls following established trapping methods at their nest sites (Figure 5; Bloom et al. 1992). Owls are used in this capture method to elicit a territorial or predator response in the ferruginous hawk, leading to it attempting to attack the perceived threat or prey item (the owl). Much effort is put into ensuring the owl is safe and won't be harmed by the hawk, and this trapping method is widely used. All methods used for this study have been approved by the University of Alberta Animal Care and Use Committee (ACUC) and meet Canadian Council on Animal Care (CCAC) animal use guidelines.
Two types of Global Positioning System (GPS) transmitters were used; either a Global System for Mobile Communication (GSM) 20-70 solar or 30 g platform transmitter terminal (PTT)-100 Argos satellite transmitter. Both transmitters were manufactured by Microwave Telemetry Inc. (Columbia, Maryland), were 30 g each, and were attached with an “X-attachment” backpack using 7-mm wide Teflon® ribbon (Figures 6 & 7; Bally Ribbon Mills, Bally, Pennsylvania). The GPS point accuracy was ± 18 m. The fix rate, or frequency at which GPS points were taken, for the GSM transmitters varied depending on battery voltage, where fix acquisition increased with higher voltage and vice versa. Daylight hours had fix rates between 1 – 60 minutes dependent on the battery voltage. The fix rate for the PTT transmitters was consistent at one-hour intervals.
Telemetry data was used to calculate the 95% Minimum Convex Polygon (MCP) for individuals using the Home Range Tool 2.0 (Rodger et al. 2015) in ArcGIS (ESRI 2019). I used the 95% MCP calculated by the floating mean as home range in my analysis. Only GPS positions between April 15 and June 30 inclusive were used, as nests are established by April 15th, females are able to leave the nest to hunt more by June 30th, and males may fly further and spend more time away from the nest and the associated home range (REACT unpublished data). I also removed data from breeding seasons that did not have a complete April-June dataset.
Following the creating of 95% MCPs (Figure 8), I calculated the proportion of human settlements, cropland, and grassland in each home range. I then calculated the proportion of GPS points found in each habitat type within the home range for each hawk (Figure 9). By analyzing the proportion of GPS points in each habitat type, I was able to determine the individual hawk’s use of the landscape and differing habitat types rather than determining the amount of each habitat type available for use by the hawk.
An ANOVA test was used to determine whether there was a statistically significant difference between the mean proportion of GPS points in each of the three reported habitat types. ANOVA assumes the data is normally distributed, and that Bonferroni adjustment was used to correct for the multiple habitat types, which required three pairwise-wise comparisons to determine the statistical differences between each habitat. From the Bonferroni adjustment, a calculated experiment-wise alpha-level of 0.0167 was used to determine statistical significance from this analysis. Using these statistical methods allowed me to determine whether ferruginous hawks spend more time in certain habitat types, which will provide evidence for where to effectively build ANPs specifically for ferruginous hawks.
Figure 8. Map of all 12 analyzed hawk 95% home ranges. Each home range colour corresponds to an individual hawk and their nest in the same colour as home range. Nest locations are for the last known nesting site for each individual. Names of towns (human developments) have not been added to protect the locations of study nests and minimize the chance of increased human activity near these endangered hawks. Water bodies were not included in analysis.
Figure 9. Map of Bird 805's 95% home range. 95% of all breeding season telemetry (GPS) fix points can be found within this home range boundary. The size of this hawk's home range is 20.9 kmĀ².