Sanctuary Integrated Monitoring Network
Monitoring Project

Common Murre Restoration Project

Principal Investigator(s)

  • Gerry McChesney
    US Fish and Wildlife Service
  • Richard Golightly
    Humboldt State University
Start Date: January 12, 1996

In January 1996, social attraction equipment (Common Murre decoys, mirror boxes, and two sound systems) was deployed on Devil’s Slide Rock for the first time. Similar redeployment and gradual modification and reduction of equipment occurred each year until 2005. Breeding by six pairs of Common Murres was recorded in 1996 and the number of breeding pairs has increased steadily since then. Because of continued growth of the Devil’s Slide colony since 1996, and especially since 1999, the amount of social attraction equipment was reduced in later years to promote higher density nesting, provide additional breeding space within decoy areas, and prepare for eventual phase-out of equipment.

In 2005, after the colony had grown to well over 100 breeding pairs, decoys and one sound system were redeployed only on the eastern half of the rock to examine the potential effects of large-scale decoy removal. No negative effects were detected, and breeding murres occupied space formerly occupied by decoys. No decoys were deployed in 2006, and the remaining social attraction equipment (e.g., sound system, decoy mounting rods) was removed following the 2006 breeding season.

In 2005-2007, the Common Murre Restoration Project efforts to restore seabird colonies in central California were augmented by the Command Trustee Council. Under the Command Oil Spill Restoration Plan, the reduction of human disturbance to breeding colonies was identified as the main technique to restore seabird populations damaged from the spill. These additional efforts included disturbance surveillance and monitoring at previously studied colonies as well as Point Resistance, Millers Point Rocks, and Double Point Rocks.

Summary to Date

The Common Murre (Uria aalge) is the most abundant seabird found nesting along the central California coast. There are several mainland and nearshore murre colonies in this region, as well as the large offshore colonies found on the North and South Farallon Islands.

Murres spend much of their lives resting on the water or diving in search of food. These life history characteristics make them particularly susceptible to entanglement in fishing gear and to becoming fouled during oil spills. During the mid-1980s, the central California Common Murre population experienced a dramatic decline. This was the result of birds becoming entangled in gill nets that were set as part of the Halibut, Starry Flounder, and White Croaker fisheries. Common Murres also died in several oil spills that occurred along the central coast, and in particular during the 1986 Apex Houston spill. This spill, which killed about 9,900 Common Murres and other seabirds, resulted in the extirpation of a small colony of 3,000 murres that nested on a sea stack in northern San Mateo County, called Devil’s Slide Rock. In an effort to stop and reverse this decline, restrictions to the gill net fishery were enacted and the parties responsible for the Apex Houston oil spill agreed to a settlement that included funding the restoration of the Devil’s Slide Rock and other murre colonies in the region. Subsequently, the 1998 T/V Command oil spill killed about 1,490 murres and other seabirds. A damage assessment from that spill is also contributing funds toward the restoration of Common Murre colonies in central California.

Between 1996 and 2005, project biologists used social attraction methods including decoys, sound systems, and mirrors to encourage murres to re-colonize Devil’s Slide Rock. Project biologists use a combination of traditional methods and new technologies to monitor the murres and other seabirds. In traditional land-based monitoring, biologists use high powered spotting scopes and binoculars to determine daily and seasonal attendance patterns, record productivity, and census a variety of seabirds in addition to murres, including Brandt’s (Phalacrocorax penicillatus) and Pelagic (P. pelagicus) Cormorants, Western Gulls (Larus occidentalis), Black Oystercatchers (Haematopus bachmani), and Pigeon Guillemots (Cepphus columba). At Devil’s Slide Rock, remote-controlled video cameras were mounted within the colony in 2005-07 to assist with monitoring and conduct additional studies.

The central California Common murre population is recovering from the large declines of the 1980s, with almost all breeding colonies growing each year since the year 2000. Attendance at all colonies continues to be high despite two to three years of low productivity in 2005-2007. The restoration work at Devil’s Slide Rock has been very successful. Breeding occurred the first season that social attraction equipment was installed and the number of breeding pairs has increased with each year. The population of Common Murres at Point Reyes (Figure 1) has steadily increased for twenty years, after the low in 1986. The population exceeded the 1979 counts in 2006 when it reached almost 37,000 birds. In 2006, the social attraction work was discontinued because of the high colony growth and to provide more nesting habitat. In 2007, almost 400 murre pairs bred on Devil’s Slide Rock, the highest number recorded since the inception of the project in 1996.

Monitoring Trends

  • Common Murre attendance and breeding sites continued to increase at Devil’s Slide even though use of social attraction equipment ceased after 2005.
  • Brandt’s Cormorants nesting at southernmost colony (Castle/Hurricane) lay eggs earliest, and those at northernmost colony (Point Reyes) lay latest (Jones et al. 2008).
  • Increasing trend in aircraft and boat disturbance at Devil’s Slide Rock and Mainland colony is associated with increasing traffic.

Study Parameters

  • Reproduction
  • Behavior
  • Disturbance
  • Predation
  • Abundance
  • Distribution

Study Methods

Study Sites

The Common Murre Restoration Project conducted monitoring at four colony complexes Devil’s Slide Colony Complex (DSCC; San Mateo County); Castle/Hurricane Colony Complex (CHCC; Monterey County); Point Reyes (PRH; Marin County); and Point Resistance/Double Point Colony Complex (or, Drakes Bay; DBCC). DSCC included the Devil’s Slide Rock and Mainland (DSRM) and San Pedro Rock (SPR) colonies. CHCC included the Bench Mark-227X (BM227X), Castle Rocks and Mainland (CRM), and Hurricane Point Rocks (HPR) colonies. DBCC included the Point Resistance (PRS), Millers Point Rocks (MPR), and Double Point Rocks (DPR) colonies.

Common Murre Seasonal Attendance Patterns

At each colony, seasonal attendance patterns of Common Murres were monitored from standardized mainland vantage points using 65-130X or 15-60X spotting scopes. Attending murres were counted at each colony, subcolony, or index plot. For each survey, three consecutive counts were performed and a mean was determined. Seasonal attendance data were collected at all active subcolonies during the “pre-breeding season” (before 15 April) at DSRM and CHCC and at all colonies throughout the “breeding season” (15 April until all chicks fledged and adult attendance ceased). Non-breeding season counts were conducted between 0730-1100 h when murres were more likely to be present. Breeding season counts were conducted between 1000-1400 h when murre numbers are less variable.

Common Murre Productivity

As in prior years, productivity of Common Murres was monitored at DSRM, CRM and PRH every two to three days at minimum (weather permitting) from standardized mainland vantage points using either 65-130x or 15-60x spotting scopes. A “breeding site” was defined where an egg was laid. A “territorial site” was defined as a location with attendance greater than or equal to 15% of monitored days but an egg was not recorded. Some territorial sites likely were breeding sites where eggs were lost at or shortly after lay without our detection. A “sporadic site” was defined as a location attended on at least two days but on less than 15% of days. Many possible sporadic sites were not identified because of frequent movement by visiting birds. Chicks were considered to have fledged if they survived to at least 15 days of age and were not known to perish afterwards.

Common Murre Co-attendance and Chick Provisioning

Co-attendance and chick provisioning observations were conducted at DSR during chick-rearing period. Observations were conducted from sunrise to sunset on 10-15 breeding sites with hatched chicks. High powered spotting scopes (65-130X) were used to conduct observations. Adult arrivals, departures, and food deliveries to chicks (including prey type, size, and fate) at each monitored site were recorded to the nearest minute. In addition, the number of birds at each site was recorded every 15 minutes throughout the entire watch.

Nest Surveys

To assess breeding population sizes, nest and bird counts of all seabird species (except murres) were conducted weekly during the breeding season. For Brandt’s Cormorant, nest and territorial sites were counted. Nests were classified into five groups that roughly described nesting stages: poorly built nest; fairly built nest; well-built nest; and brooded chicks. In addition, large cormorant chicks (ca. >30 days old; often outside of nests) were counted. To provide more complete colony coverage, mainland nest surveys were augmented with boat surveys.

Brandt’s Cormorant Productivity

Breeding phenology and productivity of Brandt’s Cormorants were monitored at DSRM, CHCC, and PRH. Monitored nests were checked every 2-7 days from mainland vantage points using binoculars and spotting scopes. Chicks were considered to have fledged if they survived to at least 30 days of age. After that age, chicks begin to wander from their nests and become impossible to associate with specific nests without marking. Breeding success per nest was defined as the number of nests that fledged at least one chick divided by the total number of nests that laid eggs. Non confident data were excluded from analysis.

Pelagic Cormorant, Black Oystercatcher, and Western Gull Productivity

Productivity of Pelagic Cormorants, Black Oystercatchers, and Western Gulls was determined at select nests that were easily visible from mainland vantage points. Nests were checked at least once per week at DSRM, CHCC, PRH, DPR, and MPR.

Pigeon Guillemot Surveys

Because Pigeon Guillemots are crevice nesters, we counted the number of birds rafting on the water and roosting on land (intertidal and nesting areas) to assess relative population size and seasonal attendance patterns at DSCC, CHCC, and PRH. Surveys were conducted approximately once per week from standardized observation points between one-half hour after sunrise and 0830 h, from mid-April to late July. At PRH, in addition to standardized weekly counts of the lighthouse area, a single survey of the entire Point Reyes colony was conducted. Pigeon Guillemots were also counted during boat surveys of colonies.


All observed anthropogenic disturbance events affecting murres and other seabirds at study colonies were recorded. Significant non-anthropogenic (e.g., avian) disturbances also were recorded. A disturbance event was defined an event where adult birds were alarmed or agitated (e.g, head-bobbing in murres, raised head or wing flapping in cormorants), flushed (i.e., birds flew from rock) or otherwise displaced (i.e., birds moved from nest site or roosting site). The numbers of birds affected and the numbers of eggs or chicks exposed, displaced, or depredated were recorded. For anthropogenic disturbances, numbers of disturbance events and numbers of disturbance events per observation hour were reported for comparisons between sites and years. Monitoring effort was calculated for each colony and colony complex. For non-anthropogenic disturbances, we report the species causing disturbances and summarize major events.

In addition to events causing disturbance, all aircraft flying at or below about 1,000 feet (305 m) above sea level (ASL) and boats within about 1,500 feet (460 m) of the nearest seabird nesting or roosting area were recorded to examine use patterns of potential sources of anthropogenic disturbance. Information recorded included: aircraft or boat type, identification number or name, direction of travel, activity, and distance from the nearest seabird nesting or roosting area.

Figures and Images

Figure from:
National Park Service
U.S. Department of the Interior
Pacific Coast Science and Learning Center
Research Project Summary June 2008

Figure 4. Aerial photograph of Devil’s Slide Rock, 29 May 2007, showing the distribution of the Common Murre and Brandt’s Cormorant breeding colony.