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Postfledging habitat use and movements of Brewer’s Sparrows (Spizella breweri breweri) in the South Okanagan region Yu, Janet Ho Yan

Abstract

The postfledging period is one of the least understood portions of the avian life cycle, yet it may have critical ecological and conservation importance. In many species, independent fledglings are known to disperse from natal sites to form juvenile groups. However, relatively little is known about their movement patterns and the habitats they use, which may be vital pieces of information for habitat conservation. Brewer's Sparrow {Spizella b. brewer!), a sagebrush obligate, is red-listed in BC due to its limited range. I investigated the movement patterns and habitat use of Brewer's Sparrows during the postfledging period. This study was conducted at four sites in the South Okanagan Valley. In total, 272 nestlings were color-banded. Systematic surveys were conducted at each site from mid-June to mid-July to determine patterns of habitat use and movements of resighted birds. Non-nesting habitats such as young aspen gullies and areas with tall shrub were preferred by juveniles and adults during the postfledging period at two sites. At the other two sites, these habitats were poorly represented. By mid-July, few individuals remained in sites where sagebrush was the dominant vegetation, while activity remained high at sites where deciduous vegetation was present. Radio telemetry was conducted at one site in August. Fifteen radio-tagged birds (12 juveniles and 3 adults) also spent most of their time along aspen gullies. The extensive use of non-nesting habitats by postfledging juveniles and postbreeding adults suggests that protection of homogeneous sagebrush nesting habitats alone may not be adequate to protect Brewer's Sparrows in the summer breeding grounds.

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