NEST-SITE CHARACTERISTICS AND NEST PREDATION IN HARRIS SPARROWS AND WHITE-CROWNED SPARROWS IN THE NORTHWEST-TERRITORIES, CANADA

Authors
Citation
Cj. Norment, NEST-SITE CHARACTERISTICS AND NEST PREDATION IN HARRIS SPARROWS AND WHITE-CROWNED SPARROWS IN THE NORTHWEST-TERRITORIES, CANADA, The Auk, 110(4), 1993, pp. 769-777
Citations number
47
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Ornithology
Journal title
ISSN journal
0004-8038
Volume
110
Issue
4
Year of publication
1993
Pages
769 - 777
Database
ISI
SICI code
0004-8038(1993)110:4<769:NCANPI>2.0.ZU;2-N
Abstract
I examined the relationship of nest-site and nest-patch characteristic s to nest success in ground-nesting Harris' Sparrows (Zonotrichia quer ula) and Gambel's White-crowned Sparrows (Z. leucophrys gambelii) in t he forest-tundra ecotone of the Northwest Territories, Canada. I found 34% of all Harris' Sparrow nests depredated, primarily by arctic grou nd squirrels (Spermophilus parryii), while no White-crowned Sparrow ne sts were disturbed by predators. White-crowned Sparrow nests appeared to be less susceptible to predation than Harris' Sparrow nests because the former were placed in areas with more shrubs and ground cover, an d denser vegetation, than were Harris' Sparrow nests. Comparison of su ccessful and depredated Harris' Sparrow nests supported the idea that interspecific differences in rates of nest predation were due to diffe rences in concealment rather than to density-dependent nest predation. Successful Harris' Sparrow nests were placed in areas with more shrub cover and more dense vegetation within 5 m of the nest than were depr edated nests. Orientation of the nest entrance did not differ between Harris' and White-crowned sparrow nests, nor between successful and de predated Harris' Sparrow nests. However, nest entrances of both specie s were nonrandomly oriented, with mean orientation vectors 135-degrees to 170-degrees from prevailing storms. Reasons for the tendency of Ha rris' Sparrows to select sites where chances of predation are relative ly high are unclear, but could be related to a lack of suitable nest s ites in the study area.