Forest Investment Account (FIA) - Forest Science Program
FIA Project Y073342

    Experiments on edge effects in Marbled Murrelets: incorporating reproductive performance into habitat quality
Project lead: Lank, David
Author: Lank, David B.
Imprint: [Vancouver, BC] : Simon Fraser University, 2007
Subject: Forest Investment Account (FIA), Marbled Murrelet, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
This continuing project fits within the Sustainability Program, most closely under theme 1.0: Ecosystem structure and function, and processes, and biodiversity relative to forest management, topic 3: coarse filter approaches to maintaining biodiversity at the landscape scale. This may seem an odd focal topic choice for a study of a single species at risk (e.g. Theme 4 topic 1- recovery research), but in fact the issue we ultimately wish to address is one of animal community structure as a function of landscape configuration, involving both Marbled Murrelets and their predator communities. Both these topics are identified as 2005/6 funding priorities. Marbled Murrelets, seabirds that use large branches of old trees (>140 yr) for nesting platforms in coastal forests, are listed as a threatened species federally (Committee on the Status of Endangered Wildlife in Canada) because of the perceived rate of population reductions from loss of nesting habitat with a lengthy (e.g. 150 yr.) regeneration time. They are managed under the provincial Forest and Range Practices Act (Identified Wildlife Management Strategy Account, IWMS 2004) and Federal Species at Risk Act. A Recovery Plan to guide future management is being produced by Canadian Marbled Murrelet Recovery Team (CMMRT)). Habitat management for murrelets currently focuses on maintenance of acceptable quantities and quality of nesting habitat and follows habitat definitions and habitat assessment methods proposed by the CMMRT (2003). The CMMRT (2003) habitat quality rankings and IWMS 2004 guidelines are based heavily on (1) the availability of large tree branches suitable as nesting platforms (more large branches better habitat), and (2) structural stand characteristics related to the birds ease of access to platforms (more complex stands easier access). Both documents leave open contentious questions about the relative value of murrelet nesting platforms in patches of different sizes and of landscape configurations in general. Opinion varies from strong opposition to recognizing the potential value of smaller patches to considering the possibility that variable retention treatments could be incorporated into the mixture of management approaches (Burger 2002; CMMRT 2003; B.C. Ministry of Water Air & Land Protection 2004; McShane et al. 2004). In many landscapes, industry and provincial planners have had difficulty locating larger patches of highly suitable habitat. Artificially creating larger patches by amalgamating higher and lower quality habitat wastes some of the set-aside budget by including sub-optimal habitat. Planners, and perhaps murrelets also, could benefit from increased flexibility. The primary concern with utilizing small patches is the hypothesis that edge habitat is less productive, due to higher rates of egg predation. If so, planners should adjust the potential contributions of patches to murrelet productivity by the proportion of edge versus interior habitat and their relative values. Smaller (and narrower) patches contain a higher proportion of edge habitat than larger (and rounder) ones. Ironically, there is a consensus that murrelet nests occur disproportionately near edges, including streams, wetlands, forest gaps, large natural openings, or avalanche chutes, and anthropogenic edges such as clearcuts, roads, or regenerating forest (Nelson & Hamer 1995; McShane et al. 2004; Huettmann et al. submitted; Zharikov et al. submitted). This apparent preference may facilitate safer nest platform access for these heavily wing-loaded birds, or better first-flight chances for their fledging young. Despite this presumably adaptive preference, murrelet biologists have argued that industrial edges present a novel situation that may produce maladaptive site-choice behaviour (Burger 2002). In addition to concerns about higher nest predation rates, much of the murrelet management community is concerned that changes in microclimate associated with industrial edges will, in some areas, create poorer growth conditions for the epiphytes used by murrelet as nesting platforms. Our research will evaluate the relative value of 'edge' versus 'interior' habitat for nesting marbled murrelets with respect to edge type and larger landscape variables.
Related projects:  FSP_Y051342FSP_Y062342
Contact: Lank, David, (604) 291-3010,


Executive Summary (26Kb)

To view PDF documents you need Adobe Acrobat Reader, available free from the Adobe Web Site.

Updated August 16, 2010 

Search for other  FIA reports or other Ministry of Forests and Range publications.

Please direct questions or comments regarding publications to