understory of bluebunch wheatgrass (Pseudoroegenria spiciata) and Sandberg’s bluegrass (Poa sandbergii).
Disturbance and Status
Due to loss of habitat the Washington Department of Fish and Wildlife has identified the Sage Sparrow as a candidate for “threatened, endangered or sensitive status” (Allen 2001). Over the past century conversion of shrubsteppe habitat in Washington to agricultural uses, urbanization, and fire has resulted in a fragmented landscape. Dobler et al (1996) estimated that 60% of the historical shrub-steppe habitat in Washington state has been lost. Fire plays a role in altering habitats by allowing invasive species such as cheatgrass (Bromus tectorum) to compete favorably with native flora. In fact, research has indicated there is an increase in fire frequency or intensity where cheatgrass occurs, resulting in a vicious cycle (Knick 1999).
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| Sage Sparrow |
The devastating June 2000, 160,000-acre fire on the Hanford Site, Arid Lands Ecological Reserve is the most recent dramatic example of a serious threat to the shrub-steppe habitat. A multi-agency effort is underway to seed burned areas with native flora before cheatgrass can establish itself (Teel 2001). Research suggests that once cheatgrass is established within shrub-steppe habitat there is little change back toward more native species (Fitzner 2000).
Migration and Nesting The majority of birds in Yakima County arrive in early-March, and the last birds
have typically left by mid-September (Stepniewski 1999). In Klickitat County late birds have also been seen in mid- September (Bacchus 2001). In Benton County the first birds recorded have been in early February, with the majority coming in by mid-March (Fitzner 2000). The sage sparrow is known as a “triple nester,” and can raise as many as three broods in a season, although two broods are typical (LaFramboise 2001,
Fitzner 2000). Nesting can begin in early-March and last until late-July. At Hanford Fitzner found that prior to mid- April nests were placed exclusively on the ground, but as the breeding season progressed greater numbers were elevated in the canopy. By mid-June 89% of the 75 nests observed were located above ground, preferentially in big sagebrush. She concluded the increase in elevation may be an attempt at behavioral thermoregulation. In other words, as the ambient temperatures rose, so did the height of the nests.
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| Sage Sparrow |
Habitat Relationship In Yakima county, Stepniewski (1999) notes the sage sparrow is a locally fairly
common summer resident in the shrubsteppe zone, but, “inexplicably absent .from many areas of sagebrush.” He speculates that the presence of dense cheatgrass in otherwise suitable habitat is not a suitable ground cover. He further suggests that bare ground between shrubs seems important in creating sage sparrow habitat.
Recent studies have provided new data to help quantify the relationship between the sage sparrow and habitat. Fitzner (2000) looked at how the presence of cheatgrass relates to the territory size, mating status and reproductive success of sage sparrows. She found that on the Hanford Site sage sparrow males tended to defend smaller territories when the amount of native grasses, bare ground and sagebrush cover were relatively high. Overall, her data indicated the more cheatgrass, the larger the sage sparrow territory. A statistically significant relationship between cheatgrass and pairing and nesting success was not observed. However, Fitzner did conclude, “there was a trend toward greater reproductive success in territories that contained less cheatgrasss.” The possibility this relationship was due to randomness could not be ruled out.
