The murrelet is listed as Threatened in Canada and in three U.S. States (California, Oregon and Washington). Loss of nesting habitat in old-growth forests is recognized as the greatest threat throughout its range, because much of this habitat has been greatly depleted by clearcut logging over the past 150 years. The murrelet is extremely secretive when nesting, going to and from its high canopy nest in the twilight - usually in the hour before sunrise and sometimes in the evening. On the nest the murrelet is well-camouflaged and sits quietly to avoid attracting predators. As a result, it is extremely difficult to find nests. The first nest in Canada was not found until 1990, by Irene Manley who was then an undergraduate at UVic. Many nests have since been described, mainly by capturing murrelets at sea, fitting them with tiny radio-transmitters and then tracking them back to nest sites. Much of this work was done by researchers at Simon Fraser University.
Because of the difficulties in finding nests, many other methods have been developed to identify important habitat needed by nesting Marbled Murrelets and hence develop management plans to protect some of their nesting habitat. Our research at UVic has used and refined several methods.
Burger, A. E. & V. Bahn. 2004. Inland habitat associations of Marbled Murrelets on southwest Vancouver Island, British Columbia. Journal of Field Ornithology 75:53-66. [pdf version]
Burger, A. E., V. Bahn and A. R. M. Tillmanns. 2000. Comparison of coastal fringe and interior forests as reserves for Marbled Murrelets on Vancouver Island. Condor 102:915-920. [pdf version]
Professional tree-climber Kevin Jordan of Arbonaut Access was hired to climb the huge old-growth conifers to look for murrelet nests. Some nests were found at sites where we had seen murrelets entering the forest canopy. We also randomly selected trees in the Carmanah and Walbran valleys to determine the proportion of trees which contained nests and thus the density of trees per hectare of forest. This is the only way to determine nest density.
The tree-climbing work we did in the 1990s has provided valuable data on nest tree re-use.
With collated data from several sources (our UVic work, Simon Fraser University, B.C. Ministry of Environment, U.S. Forest Service) we recently summarised the sparse information on the re-use of nest trees by Marbled Murrelets in British Columbia. We used 3 types of data: a) evidence of return of adults to the same nest site; b) evidence of multiple nests within the same tree; and c) re-checking known nest trees in subsequent seasons for evidence of re-use. All 3 methods showed evidence of re-use of nest trees in different years, but there were marked regional differences in the degree of re-use. Re-use of nest trees was most frequent in regions with extensive loss of nesting habitat due to logging (Southern Mainland Coast and East Vancouver Island) and rare in a less disturbed region (West Vancouver Island). Overall, 26 (18%) of 143 nest trees climbed showed evidence of multiple nesting in separate seasons. Management of nesting habitat should incorporate these results by providing greater protection of habitat in regions where habitat is sparse and by minimizing predation risk where murrelets more frequently re-use nest sites. Since re-use of nest sites is infrequent, managers should aim to provide murrelets with multiple choices for nest sites, i.e., maintain large tracts of old-growth forest with many large trees containing potential nest platforms. This research has important implications for the application of the Canadian Species at Risk Act (SARA) in protecting murrelet habitat.
For more details see our publication:
Burger A. E., I. A. Manley, M. Silvergieter, D. B. Lank, K. M. Jordan, T. D. Bloxton and M. G. Raphael. 2009. Re-use of nest sites by Marbled Murrelets (Brachyramphus marmoratus) in British Columbia. Northwestern Naturalist 90:217-226. [pdf version]
Samples of our radar studies:
Burger, A. E. 1997. Behavior and numbers of Marbled Murrelets measured with radar. Journal of Field Ornithology 68:208-223. [pdf version]
Burger, A. E. 2001. Using radar to estimate populations and assess habitat associations of Marbled Murrelets. Journal of Wildlife Management 65:696-715. [ pdf version]
Burger, A. E. 2004. Radar a useful tool for managing Marbled Murrelets. Link (FORREX newsletter. Forest Research Extension Partnership, Kamloops, BC.) 6(2) p. 7. [pdf version]
Burger, A. E., T. A. Chatwin, S. A. Cullen, N. P. Holmes, I. A. Manley, M. H. Mather, B. K. Schroeder, J. D. Steventon, J. E. Duncan, P. Arcese, and E. Selak. 2004. Application of radar surveys in the management of nesting habitat of Marbled Murrelets Brachyramphus marmoratus. Marine Ornithology 32:1-11. [pdf version]
Ronconi, R.A., C.C. St. Clair, P. D. O'Hara, and A.E. Burger. 2004. Waterbird deterrence at oil spills and other hazardous sites: potential applications of a radar-activated on-demand deterrence system. Marine Ornithology 32: 25-33. [pdf version]
Additional research by our group showed that the relative densities of murrelet predators were significantly higher in the highly fragmented Klanawa valley on Vancouver Island than in the most pristine Carmanah and Walbran valleys nearby.
Masselink, M.N.M. 2001. Responses by Steller's jays to forest fragmentation on southwest Vancouver Island and potential impacts on marbled murrelets. Department of Biology. Victoria, BC, University of Victoria, 138 pp.
Burger, A.E., M.M. Masselink, A.R. Tillmanns, A.R. Szabo, M. Farnholtz, and M.J. Krkosek. 2004. Effects of habitat fragmentation and forest edges on predators of Marbled Murrelets and other forest birds on southwest Vancouver Island. Pp. 1-19, In T.D. Hooper, editor. Proceedings of the Species at Risk 2004 Conference. March 2-6, 2004, Victoria, BC. [pdf version]
Dechesne, S.B.C. 1998. Vocalizations of the Marbled Murrelet (Brachyramphus marmoratus): vocal repertoire and individuality. MSc thesis, University of Victoria, Victoria, BC.
The aerial surveys have been used for many purposes, including assessing:
Burger, A.E., F.L. Waterhouse, A. Donaldson, C. Whittaker, and D.B. Lank. 2009. New methods for assessing Marbled Murrelet nesting habitat: Air photo interpretation and low-level aerial surveys. BC Journal of Ecosystems and Management 10(1):4–14. URL: www.forrex.org/publications/jem/ISS50/vol10_no1_art2.pdf
Waterhouse, F.L., A.E. Burger, D.B. Lank, P.K. Ott, E.A. Krebs, and N. Parker. 2009. Using the low-level aerial survey method to identify Marbled Murrelet nesting habitat. BC Journal of Ecosystems and Management 10(1):80–96. URL: www.forrex.org/publications/jem/ISS50/vol10_no1_art8.pdf
Waterhouse, F.L., A.E. Burger, A. Cober, A. Donaldson, and P.K. Ott. 2007. Assessing habitat quality of Marbled Murrelet nest sites on the Queen Charlotte Islands/Haida Gwaii, by algorithm, airphoto interpretation, and aerial survey methods. Research Section, Coast Forest Region, BC Ministry of Forests and Range. Nanaimo, BC. Technical Report TR-035. URL: http://www.for.gov.bc.ca/rco/research/wildpub.htm
Burger, A. E. (ed.) 2004. Standard methods for identifying and ranking nesting habitat of Marbled Murrelets (Brachyramphus marmoratus) in British Columbia using air photo interpretation and low-level aerial surveys. Ministry of Water, Land and Air Protection, Victoria, BC and Ministry of Forests, Nanaimo, BC. Available at: http://www.env.gov.bc.ca/wld/documents/fia_docs/mamu_standard.pdf
Burger, A. E., J. Hobbs, and A. Hetherington. 2005. Testing models of habitat suitability for nesting Marbled Murrelets, using low-level aerial surveys on the North Coast, British Columbia. Report to Ministry of Water, Land and Air Protection, Smithers, BC. [pdf version]
Burger, A. E. and T. A. Chatwin (eds.). 2002. Multi-scale studies of populations, distribution and habitat associations of Marbled Murrelets in Clayoquot Sound, British Columbia. Ministry of Water, Land and Air Protection, Victoria, BC. (ISBN 0-7726-4739-9). Available at: http://env.gov.bc.ca/wld/documents/techpub/mamuwebs.pdf