UVic Seabird & Murrelet Research Group

Marbled Murrelet Research at UVic

The Marbled Murrelet (Brachyramphus marmoratus) is a small diving seabird within the family Alcidae (auks or alcids). It spends most of its life in the shallow nearshore oceans where it forages for small schooling fish, like juvenile herring and sand lance. Unlike most seabirds which nest in colonies on islands or cliffs, the Marbled Murrelet is unique in nesting primarily in the high mossy branches of very old coniferous trees in the coastal old-growth forests of the Pacific Northwest. The species ranges from the Aleutian Islands in Alaska through to central California. The bulk of the population is found in southeast Alaska and British Columbia.

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.

Audio-visual surveys

Using a standard protocol, still widely used, observers record all detections of murrelets seen or heard during a 2-hour dawn survey. Most detections are of flying birds going to and from nest sites or circling over and through the forest canopy. These detections are mainly used to determine occupancy of forest stands, but they also give a crude estimate of the amount of activity which might be associated with nesting in these stands.

Habitat associations based on audio-visual surveys

By linking audiovisual detections with the habitat features found at the survey sites, we have been able to identify habitat features which are important to nesting murrelets. These include large old trees, gaps in canopy, presence of large mossy limbs, elevation, proximity to streams and other more subtle features.

Sample publications:

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]

Tree climbing


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.

Marbled Murrelet nest showing the white ring of feces produced by the chick during its 30-40 day nestling period. Photo: Kevin Jordan.

The tree-climbing work we did in the 1990s has provided valuable data on nest tree re-use.

Re-use of nest trees

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]

Radar studies of the Marbled Murrelet

High-frequency marine radar (the type used on ocean-going vessels) has proved to be a valuable tool in studying Marbled Murrelets. Radar can detect the birds as they fly from the sea into the forested watersheds in the semi-darkness, and we have used this to count the birds, show the importance of various watersheds as nesting areas, compare numbers of murrelets with landscape-level habitat parameters, and derive densities of murrelets for areas of suitable nesting habitat. Go to our Murrelet Radar Page for more details.

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]

Predators of Marbled Murrelets

Nest predation is the greatest cause of breeding failure for Marbled Murrelets and adults are also vulnerable to predation in the forest nesting habitat. Corvids (jays, ravens and crows) are the most common nest predators, but squirrels are also suspected of taking chicks, and ravens, hawks, owls and eagles are known to kill adult murrelets. The risks of predation from corvids is likely higher at the edges of forests and where human activities attract these omnivorous birds.

Predators and the effects of forest fragmentation

Fragmentation of old-growth forest and the creation of hard edges between the forest patches and clearcuts or roads is a concern for Marbled Murrelets. There is evidence that murrelet nesting close to such forest edges have lower success than those nesting in the interior forest, although this does not seem to apply to forest patches bordered by natural edges. Research by Michelle Masselink for her MSc with Dr Burger, showed that Steller's Jays (a common nest predator of Marbled Murrelets) were strongly associated with forest edges. Michelle used radio-telemetry to track individual jays for two seasons, and also used point-counts to estimate relative densities of jays and other potential predators at forest edges, in interior forest and in clearcuts.

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.

Sample publications:

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]

Behaviour and vocalizations of Marbled Murrelets

Very little is known about the social behaviour of Marbled Murrelets either at sea or when they are inland at forest nesting habitat. Unlike most other seabirds, murrelets seem to remain in pairs for most of the year. Perhaps this is because they frequently change their nest sites and don't meet their mate back at the nest site at the start of each season, as most seabirds do. Murrelets are generally silent, but can be very vocal at times, calling to each other in a distinctive high "keer-keer" call with lots of variations. Pairs call to each other when separated on the water, and there is a lot of vocalization when murrelets are circling over the forest at dawn. UVic MSc graduate Sharon Dechesne showed that the calls of murrelets were extremely varied and graded, but there were features that could be used to identify individuals. This discovery might be applied in future to estimate the number of individual murrelets using a forest stand, and also determine whether individuals returned to the same stands each year.

Sample publication:
Dechesne, S.B.C. 1998. Vocalizations of the Marbled Murrelet (Brachyramphus marmoratus): vocal repertoire and individuality. MSc thesis, University of Victoria, Victoria, BC.

Helicopter Surveys

In collaboration with Louise Waterhouse (Ministry of Forests), Stewart Guy (Ministry of Water, Land and Air Protection) and many others, we have refined methods for using helicopters to do low-level aerial surveys of forest canopies. The helicopters allow a "murrelet's eye" view of the canopy and are used to check the presence and relative abundance of the micro-habitat features important for nesting murrelets. In particular the surveys indicate the presence and abundance of potential nest platforms (limbs or deformities 15 cm or more in diameter) and epiphyte cover (moss, lichens, ferns etc.). Aerial surveys also assess important stand features, such as height class, age class and canopy complexity. Details of the protocol are given in Burger (2004).

The aerial surveys have been used for many purposes, including assessing:

Sample publications:

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]

Cober, A., F.L. Waterhouse, A.E. Burger, A. Donaldson, B. Smart, and P.K. Ott. 2012. Using Low-level Aerial Surveys to Verify Air Photo Interpretation of Marbled Murrelet Nesting Habitat in Haida Gwaii. British Columbia Government Forestry Technical Report 070, Victoria, BC. URL: http://www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr070.htm

Clayoquot Sound Marbled Murrelet Research

From 1995-2000 we collaborated with Trudy Chatwin of the BC Ministry of Water, Land and Air Protection in comprehensive studies of Marbled Murrelets, involving at-sea surveys, radar surveys, inland audio-visual surveys, tree-climbing, GIS analysis of forest habitat, habitat modeling, and management. This research culminated in the following book.

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