Ferruginous Hawk (Buteo regalis) Home Range and Resource Use on Northern Grasslands in Canada

• Author / Creator

  Watson, Jesse L

• Human alteration of the landscape can have implications for wildlife at the individual and population levels. The grassland ecosystem has been highly altered and is at risk of further alteration due to increasing demand for human food, pastureland, and energy development. The Ferruginous Hawk (Buteo regalis), a grassland obligate, has experienced declines across its range due to loss of habitat leading to its listing as a Threatened species in Canada. Understanding how breeding Ferruginous Hawks have been affected by anthropogenic change in the grassland region of southern Alberta and Saskatchewan is important to inform species recovery and management. My goal was to investigate how anthropogenic development has affected Ferruginous Hawk range use and perch choice at the level of 3rd-order selection. I tracked 48 breeding, male Ferruginous Hawks during the 2012-2017 breeding seasons, and used high-resolution satellite telemetry to address this goal.
  
  In Chapter 2, I measured the size of hawk core areas (50% contour; x̄ = 3.54 km2 ± 8.52 SD) and home ranges (95% contour; x̄ = 36.33 km2 ± 94.74 SD) (n = 92), the first range-size estimates for satellite-tracked Ferruginous Hawks in Canada. I used linear mixed models to test the relationship of perch density and land-cover type on range size as an indicator of range quality. I found the density of fencelines and proportion of cropland were significant influences on range quality, with higher densities of fenceline and lower proportions of cropland resulting in smaller core areas. However, at the home-range scale, there was a significant interaction between fenceline density and the proportion of cropland, with increasing densities of fenceline mediating the effect of proportion of cropland on home-range size. Additionally, increasing proportions of tame grass and tame hay resulted in smaller home ranges and thus higher range quality.
  
  In Chapter 3, I studied 24 hawks that were monitored intensively in 2013 and 2014 with GSM transmitters, which generated a high volume of location fixes. My objective was to evaluate perch use by Ferruginous Hawks at two scales. Firstly, I estimated Resource Utilization Functions at the home-range level to compare use intensity among elevated perch types (fencelines, power distribution lines, and power transmission towers), and also among common land-cover types (native grassland, cropland, tame grass, tame hay, and idle field). Resource Utilization Functions indicated that hawks showed the highest relative use at areas near transmission towers, but they were the least abundant elevated perch types on the landscape. Hawks also showed highest use in areas near distribution lines and areas far from fencelines. Among vegetated land-cover types and relative to areas with native grassland, hawks showed highest use in areas with low levels of cropland and high levels of tame grass and tame hay. Secondly, I visited 1,436 perches of known use, distributed among 20 hawk home ranges, and measured micro-site land-cover characteristics and relative prey abundance, indexed by mammal burrow counts, within the hypothetical viewscape (i.e., 50 m) of a perched hawk. I tested the influence of these predictors on intensity of perch use, with mixed effects logistic regression. Fence posts were the most common elevated perch type, comprising 52% of all perches. Transmission towers were the most heavily-used perch type but were the least abundant perch type on the landscape, resulting in less overall use. Hawks showed higher use at perches with higher proportions of bare ground, higher burrow counts, and less cropland within 50 m. I concluded that, although prey abundance is important for Ferruginous Hawks, prey accessibility and visibility, as influenced by the juxtaposition of perch height, amount of bare ground, and relative abundance of prey are the best indicators of perch use within home ranges.
  
  In Chapter 4, I summarize potential benefits and consequences related to human-made elevated perches on Ferruginous Hawks and recommend that future studies should investigate perch use of Ferruginous Hawks through direct observation and experimentation to determine how placement of new perches may affect breeding individuals.

• Subjects / Keywords

  • Buteo regalis
  • Satellite telemetry
  • Home-range use
  • Perch
  • Raptor research
  • Bird of prey
  • Ferruginous Hawk

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-snrd-yp91

• License

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