Influence of forestry and conspecific attraction on habitat use and reproductive activity of the Canada warbler (Cardellina canadensis) in the western boreal forest: Implications for critical habitat identification

  • Author / Creator
    Hunt, Anjolene R
  • Recovery strategies for species at risk are legally mandated in Canada and the Government of Canada must identify which habitat is important for a species and which activities result in its destruction. The Canada Warbler (Cardellina canadensis) has been designated as a threatened species in Canada due to large population declines (~3% annually over the last 50 years). Forestry has been identified as a threat, but some studies suggest it can create productive breeding habitat. I quantified multiple orders of habitat use to study the response of the Canada Warbler to forestry, accounted for the effect of conspecific attraction which may affect habitat use patterns, and assessed how use patterns influenced reproductive activity. Specifically, my first objective was to quantify the relative importance of forestry-related stand metrics versus conspecific proximity on multiple levels of habitat use of Canada Warblers. I used point count surveys and tracked individuals to determine density, 2nd and 3rd order habitat use, and probability of pairing and fledging young for male Canada Warblers in Alberta, Canada. I found fewer territorial males in survey blocks with more harvesting, effects which were not mitigated by retention of unharvested fragments, stand regeneration ≤30 years post-harvest, or abundance of old-growth stands in the surrounding matrix. Male home ranges (2nd order use) in post-harvest were typically near edges of adjacent unharvested stands and near conspecifics. Males also had higher intensity of use in areas within their home ranges (3rd order use) that were further from edges and nearer to conspecifics. This suggests that forest harvesting poses a threat to Canada Warblers in Alberta, and that post-harvest stand use reported in other studies may be influenced more by conspecific attraction than by attributes of post-harvest stands themselves. Hence, large tracts of unharvested stands should be protected in Alberta, with higher prioritization in areas where territories are already established to support the Canada Warbler’s clustered distribution, and only post-harvest stands near conspecifics and near unharvested stands should be considered usable. My second objective was to test whether males using post-harvest stands suffered consequences to pairing success and/or probability of fledging young and whether density reflected these metrics of reproductive success. I found that use of post-harvest stands did not affect probability of pairing or fledging young, but that pairing success was lower when male densities were high. My final objective was to discuss potential reasons for discrepancies between conclusions about the effects of forestry on Canada Warblers across their breeding range, and provide specific recommendations to aid designation of critical habitat for this species. These include using information from breeding-range-wide point counts to determine important parts of the range to protect (i.e. areas with large breeding populations) and population recovery targets, in conjunction with studies specific to each Bird Conservation Region within the breeding range that address habitat quality, land-use effects, and clustered habitat use. At a minimum, incorporating proximity to undisturbed habitat and to conspecifics in regional models could provide valuable information when prioritizing areas for conservation.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Biological Sciences
  • Specialization
    • Ecology
  • Supervisor / co-supervisor and their department(s)
    • Dr. Erin Bayne (Biological Sciences)
  • Examining committee members and their departments
    • Dr. Lisa Mahon (Environment Canada)
    • Dr. Andrew Derocher (Biological Sciences)
    • Dr. Samuel Hache (Environment Canada)
    • Dr. Scott Nielsen