Movement behaviour and distribution of forest songbirds in an expanding urban landscape.

  • Author / Creator
    Tremblay, Marie Anne
  • Urbanization is viewed as a major threat to global biodiversity because of its role in the loss and fragmentation of low-lying, productive habitats associated with coastal plains and river valleys. My study examines the effects of urbanization on the movements and distribution of songbirds in Calgary, Alberta, Canada. I conducted playback and translocation experiments to assess the permeability of small-scale (e.g. transportation corridors, rivers) and large-scale (e.g. multi-lane expressways, areas of urban development) features of the urban landscape, respectively. I then used these empirical data to parameterize spatially explicit models and determine functional landscape connectivity across the study area. Finally, using point surveys conducted at 183 sites across the urban matrix, I examined the role of land cover type, local vegetation characteristics, landscape-level forest cover, and isolation from natural features on the distribution of songbirds. In 563 playback trials involving the responses of 2241 birds, I found that the size of the gap in vegetation was the most important determinant of movement across linear features; the likelihood of movement sharply decreasing as the gap in vegetation exceeded 30 m. The results of 176 translocation trials provided further evidence of the barrier effect of gaps. Multiple gaps, in particular, constrained the movements of both yellow warblers (Dendroica petechia) and black-capped chickadees (Poecile atricapillus). The bird surveys revealed that natural forest stands played a critical role in sustaining regional avian diversity in the study area. Moreover, functional distance to the nearest forested natural area or water body often explained more variation in the probability of occurrence of focal species than straight-line distance, suggesting that barriers identified from the permeability experiments may have affected not only the movements of songbirds but their settlement patterns as well. Taken together, my results suggest that preserving a functionally connected network of natural areas is vital to conserving avian biodiversity in cities. My research describes novel methodologies for characterizing the composition and configuration of highly heterogeneous and fragmented landscapes. It also provides a unique examination of the link between the movement behaviour of individual birds and population-level distribution patterns within this context.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosphy
  • 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.