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Résumé :
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We studied the breeding biology of Loggerhead Shrikes (Lanius ludavicianus) in northeastern Oregon from 1995 to 1997 and 2000 to 2001. A wildfire in 1998 burned approximately half the big sagebrush (Artemisia tridentata) at this site, permitting comparison Of Population parameters before and after this event. Shrike density after the fire was half that before the fire, a reduction likely due to loss of suitable nesting habitat. Mayfield estimates of nest survivorship were 39% (range: 30-46%) in the years before and 19% (range: 12-26%) after the fire, among the lowest ever recorded for this species. In 2000, young fledged from only 21% of the territories. Due to persistent renesting, young Hedged from 67% of the territories in 2001, a percentage similar to that before the fire. After the fire, shrikes nested more frequently in Substrates other than big sagebrush, especially juniper trees (Juniperus occidentalis). Clutch size, fledglings per Successful nest, and fledgling Survival were similar in both periods of the study Poor nesting Success across all years Suggests that productivity may play a role in regional declines of shrike populations, and that the loss and fragmentation of nesting habitat due to fire may further reduce productivity. Given the threats facing remaining sagebrush habitat, as well as Loggerhead Shrike population declines, we recommend aggressive fire control measures and further protection for remaining tall sagebrush communities.
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