Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Environmental Factors Associated with Avian Distributional Boundaries

Terry Root
Journal of Biogeography
Vol. 15, No. 3 (May, 1988), pp. 489-505
Published by: Wiley
DOI: 10.2307/2845278
Stable URL: http://www.jstor.org/stable/2845278
Page Count: 17
  • Download ($42.00)
  • Subscribe ($19.50)
  • Cite this Item
Environmental Factors Associated with Avian Distributional Boundaries
Preview not available

Abstract

This study investigates, on a continent-wide scale, which environmental factors associate with the distributional boundaries of wintering North American avifauna. Distribution and abundance maps of 148 land birds wintering in the contiguous United States and southern Canada are compared with maps of six environmental factors: average minimum January temperature, mean length of frost-free period, potential vegetation, mean annual precipitation, average general humidity, and elevation. The species maps were generated from 10 years of National Audubon Society's Christmas Bird Count data. The comparisons reveal that average minimum January temperature, mean length of frost-free period, and potential vegetation frequently associate with the northern range limits of wintering species (60.2%, 50.4%, 63.7%, respectively). Only two factors, potential vegetation and mean annual precipitation, are coincident with a large proportion of species' eastern range boundaries (62.8% and 39.7%, respectively). The frequency of association between the environmental factors and the western boundaries of the species' ranges is lower than in the other two directions, and more factors exhibit a correspondence. These include potential vegetation (46.0%), mean annual precipitation (36.0%) and elevation (38.0%). Associations with species' southern boundaries are ignored, because 89.2% of the species have range limits abutting the edge of the study area. Only 0.6% of the possible associations between the species' ranges and environmental factors are expected to occur by chance. To enhance the understanding of the correspondence between species' range limits and environmental factors, four mutually exclusive feeding guilds are examined. These include Raptors and Shrikes, Bark Gleaners, Foliage Gleaners, and Seed Eaters. Predictably, both temperature factors, minimum January temperature and mean length of frost-free period, associate with northern range limits of many species in all four guilds (Raptors and Shrikes, 54.5% and 36.4%; Bark Gleaners, 46.1 and 46.1%; Foliage Gleaners, 86.4% and 68.2%; and Seed Eaters, 60.0% and 56.0%, respectively). Isopleths of mean lenght of frost-free period also coincide with the western boundaries of Foilage Gleaners (55.6%). Potential vegetation corresponds with the northern distributional boundaries of a large proportion of species in all four guilds (Raptors and Shrikes, 54.5%; Bark Gleaners, 76.9%; Foliage Gleaners, 68.2%; Seed Eaters, 68.0%), while along the eastern and western boundaries, vegetation is coincident with members of the two guilds most strongly linked with vegetation: Bark Gleaners (East 88.9% and West 66.7%) and Seed Eaters (East 62.5% and West 42.9%). The western range edges of the Bark and Foliage Gleaners associate with elevation (44.4% and 44.4%).

Page Thumbnails

  • Thumbnail: Page 
489
    489
  • Thumbnail: Page 
490
    490
  • Thumbnail: Page 
491
    491
  • Thumbnail: Page 
492
    492
  • Thumbnail: Page 
493
    493
  • Thumbnail: Page 
494
    494
  • Thumbnail: Page 
495
    495
  • Thumbnail: Page 
496
    496
  • Thumbnail: Page 
497
    497
  • Thumbnail: Page 
498
    498
  • Thumbnail: Page 
499
    499
  • Thumbnail: Page 
500
    500
  • Thumbnail: Page 
501
    501
  • Thumbnail: Page 
502
    502
  • Thumbnail: Page 
503
    503
  • Thumbnail: Page 
504
    504
  • Thumbnail: Page 
505
    505