Research
Additional
information
about
Marbled Murrelets
PNW
Funded Projects
2001
2000
1999
1998
1997
1996
1995
PNW Project Overview 1998
Are Forest Buffers Sufficient and Necessary for Reducing Predation on Marbled Murrelet Nests?
Principal
Investigator:
Dr.
John
Marzluff, University of Washington, College of Forest Resources
Awarded: $20,000
Project
Description:
The
U.S. Fish and Wildlife Service has identified three possible threats to
the continued survival of the Marbled Murrelet: habitat loss, gill-net
mortality, and increased predation following fragmentation due to
forestry. The main management solution directed at reducing nest predation
has been the creation of forest buffers around areas used by murrelets.
However, no data currently exist to test the effectiveness of such buffers
as predation deterrents. Creation of buffers requires substantial amounts
of timber to remain unharvested, creating an economic loss to landowners.
This project builds upon data collected during the 1995-1997 to assess the
effectiveness and necessity of buffers around murrelet nesting habitat to
determine the conditions under which conservation is and is not enhanced
by creation of buffers. The approach is to identify the mechanisms
responsible for correlations between buffer width and the viability of a
rare species. This enables managers to understand how their actions
influence wildlife and increases the likelihood that effective management
strategies can be developed. If buffers are found to be effective in some
settings but ineffective in others, managers can adjust their timber
harvest strategies to satisfy the nesting requirements of murrelets in
some areas while maximizing timber production in other areas. This is a
cooperative project involving private, state, and federal land managers to
assure research is relevant to their management needs and facilitate
implementation of results.
Objectives: Assess the effectiveness and necessity of buffers around murrelet nesting habitat to determine the conditions under which conservation is and is not enhanced by creation of buffers.
Project Status:
Project continued with
1999 funds.
Progress report:
Results
to date show that in fragmented habitats near humans, buffers of up to 200
meters may be ineffective at lowering predation because predators are
abundant and predation is intense. However,
in habitats greater than 5 kilometers from humans, buffers as small as 50
meters may be sufficient. Furthermore,
buffers of actual murrelet habitat (complex structured, mature stands)
thought to reduce predation, may actually increase predation rates. Most nest predators in Washington and Oregon are most
abundant and the rate of nest predation on murrelet nests is most intense
in stands with structure suitable for murrelet nesting.
This suggests that buffers could actually attract predators to the
stand instead of repelling them. This
complex relationship suggests that where buffers are beneficial, they may
be most effective at reducing predation if comprised of forest with simple
structure typical of a 60- to 90-year-old stand managed for timber
harvest. Therefore, specific
management recommendations aimed at reducing nest predation may need to be
qualified by a consideration of the surrounding landscape.
This research determined that nests close to the stand edge were preyed upon significantly faster than those farther from the stand edge if forage-producing shrubs surrounded stands. However, no such edge effect was evident when stands were surrounded by young regeneration without forest shrubs. These preliminary results are consistent with an increase in risk of nest predation in stands surrounded by vegetation that offers forage to nest predators.