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Habitat for wide-ranging species should be addressed at multiple scales to fully understand factors that limit populations.
The marbled murrelet (Brachyramphus marmoratus), a threatened seabird, forages on the ocean and nests inland in large trees. We developed statistical relationships between
murrelet use (occupancy and abundance) and habitat variables quantified across many spatial scales (statewide to local) and
two time periods in California and southern Oregon, USA. We also addressed (1) if old-growth forest fragmentation was negatively
associated with murrelet use, and (2) if some nesting areas are more important than others due to their proximity to high
quality marine habitat. Most landscapes used for nesting were restricted to low elevation areas with frequent fog. Birds were
most abundant in unfragmented old-growth forests located within a matrix of mature second-growth forest. Murrelets were less
likely to occupy old-growth habitat if it was isolated (> 5 km) from other nesting murrelets. We found a time lag in response
to fragmentation, where at least a few years were required before birds abandoned fragmented forests. Compared to landscapes
with little tono murrelet use, landscapes with many murrelets were closer to the ocean's bays, river mouths, sandy shores,
submarine canyons, and marine waters with consistently high primary productivity. Within local landscapes (≤ 800ha), inland
factors limited bird abundance, but at the broadest landscape scale studied (3200 ha), proximity to marine habitat was most
limiting. Management should focus on protecting or creating large, contiguous old-growth forest stands, especially in low-elevation
areas near productive marine habitat.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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