Humboldt County Research Articles

Humboldt County General Plan Update Health Impact Assessment: A Case Study

As a tool for deliberately planning for and optimizing the ways in which we design our environments, Health Impact Assessment (HIA) holds promise for achieving environmental justice and health equity. This case study describes the application of HIA to updating a rural county's General Plan. Humboldt County, California is currently considering three development plans to accommodate future population growth, and the described HIA process successfully identified and analyzed potential health outcomes associated with each. Although the General Plan Update process is not yet complete as of this writing, the HIA has already accomplished one of its initial goals, which was to build awareness of health impacts related to planning decisions among county agencies, project decision-makers, participating community members, and the general public. Another noteworthy outcome of this process, which is intended to aid in planning future equitable and just communities, was the development of the “Rural Healthy Development Measurement Tool,” a tool for considering health in rural development decisions.

Distinct Ecologically Relevant Strains ofAnaplasma phagocytophilum

Distinct Ecologically Relevant Strains of<i>Anaplasma phagocytophilum</i>

ECOLOGY OF ANAPLASMA PHAGOCYTOPHILUM INFECTION IN GRAY FOXES (UROCYON CINEREOARGENTEUS) IN NORTHWESTERN CALIFORNIA

Although granulocytic anaplasmosis, caused by infection of Anaplasma phagocytophilum, is an emerging human and domestic animal disease, the ecology and natural history of the parasite is not well understood. Gray foxes (Urocyon cinereoargenteus) are relatively common, occasionally peri-urban mesocarnivores whose geographic distribution overlaps the reported distribution of granulocytic anaplasmosis in humans and domestic animals in North America. We evaluated the potential of foxes as hosts and reservoirs of A. phagocytophilum in both urban and backcountry habitats of the Hoopa Valley Indian Reservation, Humboldt County, California, USA. We trapped 54 individual foxes and had 16 recaptures for a total of 70 fox samples between June 2003 and October 2004 in delineated urban and backcountry zones. We collected 296 adult and 145 nymphal ticks from the 70 captured foxes including 193 Ixodes pacificus, 149 Ixodes texanus, 98 Dermacentor variabilis, and one Dermacentor occidentalis. There were seasonal differences in tick intensities, with most I. pacificus adults occurring in winter and spring (P < 0.001), most I. texanus nymphs in spring (P = 0.03), and most D. variabilis adults in spring and summer (P = 0.01). Thirty-six (51%) of the 70 fox sera had antibodies against A. phagocytophilum, with a higher (P = 0.24) prevalence in backcountry foxes (16 of 23) than in urban-zone foxes (12 of 31). Six (9%) of 70 fox samples were polymerase chain reaction-positive for A. phagocytophilum. Twenty-eight (31%) of 90 domestic dogs sampled from vaccine clinics within the study area were seropositive for A. phagocytophilum. There was a significant difference in prevalence between dogs and backcountry foxes (70%), but no differences were found between dogs and urban foxes (39%). We propose that gray foxes are a good sentinel species for A. phagocytophilum infections in northwestern California.

Développement de rejets épicormiques sur des séquoias californiens : intensité de l’élagage, génotype, caractéristiques des rejets

• Young coast redwood (Sequoia sempervirens (D. Don.) Endl.) trees were pruned to various heights to examine the effect of pruning severity on epicormic sprouting. Seven separate stands were used with as many as six treatments per stand in coastal Humboldt County, California, USA. • Epicormic sprout development was affected by pruning severity but primarily at the most severe pruning treatments that removed all but the branches in the top 15% of tree height. Less severe treatments produced sprouts but the number and size of these sprouts were comparable to unpruned trees. • Natural clonal patterns were also used to explore patterns of sprouting between genotypes. Linear mixed-effects models were developed to predict sprouting frequency as a function of pruning severity while accounting for the nested data structure (i.e., stem sections sampled nested within genotypes within treatments within sites). • Comparing variances attributed to each of these random effects indicated that at any level of pruning severity, differences in epicormic sprouting between genotypes and sites expressed soon after pruning had disappeared after six growing seasons. Epicormic branches were more common two years after pruning than six years indicating many branches were dying. Branches were more common in the middle of the pruned bole, possibly because of competition from basal sprouts and the expanding tree crown.

Notes On Early Collections and the Distribution Of the Red Alga Cumathamnion sympodophyllum

Abstract Specimens (in FH and PC) of Cumathamnion sympodophyllum M.J. Wynne and K. Daniels (Delesseriaceae, Rhodophyta) made by C. G. Pringle at Cape Mendocino, northern California in 1882 are the first known collections of this rare monospecific genus. A collection (US) made by E.Y. Dawson from Trinidad Head, Humboldt County, and reported in 1965 as a “very compact, short-bladed” form of Delesseria decipiens J. Agardh is re-determined to be C. sympodophyllum. Records of C. sympodophyllum from Oregon, Washington, and British Columbia (Canada) are based on one collection from British Columbia, which cannot be verified. This taxon is most likely restricted to very exposed lower littoral rocky outcrops of Sonoma, Mendocino, and Humboldt counties in California.

The 1906 Earthquake on California's North Coast

Humboldt County on California’s north coast was the furthest region from the 1906 epicenter to suffer significant damage in the 1906 earthquake. This study reassesses the impacts described in the state earthquake investigation commission report (Lawson, 1908) and subsequent intensity studies by examining reports from local newspapers, weather service logs, and the large collection of photographs, journals, and letters collected by local historical societies and museums. The highest intensity (modified Mercalli [MMI] IX) occurred in the Petrolia and upper Mattole Valley. The entire coastal region from Shelter Cove to the Eel River Valley experienced intensities of at least VIII. The most detailed damage descriptions come from Ferndale, where newspaper reports detail the damage to over 40 structures in the downtown area. Fewer than 2% of chimneys survived, both brick buildings were severely damaged, and about 25% of the commercial wood buildings were twisted by the ground shaking. Liquefaction was observed in the Mattole Valley throughout the Eel River Valley and as far north as Fields Landing on Humboldt Bay, which exceeded the aerial extent and scale of any other historic event, including the 1992 Cape Mendocino earthquake ( M w 7.2). In contrast to the isoseismal map published in the Lawson Report, damage in Eureka and the Humboldt Bay region was less than in Ferndale. Based on the severity of damage and scale of liquefaction, the 1906 earthquake was Humboldt County’s strongest historic event. Peak intensities likely exceeded the Cape Mendocino earthquake, the intensity VII or larger isoseismal was about twice as large, and peak ground velocity values likely exceeded 50 cm/sec in much of southern Humboldt County. The strong shaking in Humboldt County supports models showing significant slip along the northern segment of the 1906 rupture zone.

First Report of the European Lineage of Phytophthora ramorum on Viburnum and Osmanthus spp. in a California Nursery.

Phytophthora ramorum S. Werres & A.W.A.M. de Cock is the causal agent of sudden oak death in California and Oregon forests and ramorum blight on a broad range of host species in wildlands and nurseries. It is thought to be an introduced pathogen and only three clonal lineages are known (3). The North American lineage (lineage NA1, mating type A2) is responsible for infections in California and Oregon forests. The European lineage (lineage EU1, predominantly A1) is responsible for infections in Europe, but has also been found in nurseries in Oregon and Washington. A third lineage (NA2) has only been isolated in a few instances from nurseries in Washington and California. In June 2006, P. ramorum was isolated from diseased Viburnum tinus, Osmanthus heterophyllus, and O. fragrans cultivars from a Humboldt County retail nursery in northern California. We genotyped isolates and placed them into clonal lineages using microsatellite markers developed for P. ramorum (3,4). Genomic DNA was extracted from mycelia with the FastDNA SPIN kit (Q-Biogene, Morgan, Irvine, CA). Primers used were PrMS6, Pr9C3, PrMS39, PrMS43a, PrMS43b, and PrMS45 (3) and 18, 64, and 82 (4). We sized fluorescently labeled amplicons using capillary electrophoresis (3100 Avant Genetic Analyzer, Applied Biosystems, Foster City, CA). Isolate genotypes were compared with control isolates of known clonal lineage, including BBA9/95 (EU1), Pr102 (NA1), and WSDA3765 (NA2). Three of four isolates belonged to genotype EU1. The fourth isolate, obtained from O. fragrans, belonged to genotype NA1. We repeated genotyping on independent genomic DNA extractions and obtained identical results. Two EU1 isolates and the single NA1 isolate were tested for mating type (1) and found to be of A1, A1, and A2 mating type, respectively. The coexistence of A1 and A2 mating types in the same retail nursery suggests the potential for sexual reproduction, as is the case in P. infestans where clonal and sexual populations exist (2), although to date, sexual reproduction in nature has not been documented in P. ramorum. The California retail nursery infestation highlights the risks associated with the unintentional transport of host nursery stock infested with P. ramorum.

The Distribution of Modified Mercalli Intensity in the 18 April 1906 San Francisco Earthquake

We analyze Boatwright and Bundock’s (2005) modified Mercalli intensity (MMI) map for the 18 April 1906 San Francisco earthquake, reviewing their interpretation of the MMI scale and testing their correlation of 1906 cemetery damage with MMI intensity. We consider in detail four areas of the intensity map where Boatwright and Bundock (2005) added significantly to the intensity descriptions compiled by Lawson (1908). We show that the distribution of off-fault damage in Sonoma County suggests that the rupture velocity approached the P -wave velocity along Tomales Bay. In contrast, the falloff of intensity with distance from the fault appears approximately constant throughout Mendocino County. The intensity in Humboldt County appears somewhat higher than the intensity in Mendocino County, suggesting that the rupture process at the northern end of the rupture was relatively energetic and that there was directivity consistent with a subsonic rupture velocity on the section of the fault south of Shelter Cove. Finally, we show that the intensity sites added in Santa Cruz County change the intensity distribution so that it decreases gradually along the southeastern section of rupture from Corralitos to San Juan Bautista and implies that the stress release on this section of rupture was relatively low.

Zinclipscombite, ZnFe 2 3+ (PO4)2(OH)2, a new mineral species

Zinclipscombite, a new mineral species, has been found together with apophyllite, quartz, barite, jarosite, plumbojarosite, turquoise, and calcite at the Silver Coin mine, Edna Mountains, Valmy, Humboldt County, Nevada, United States. The new mineral forms spheroidal, fibrous segregations; the thickness of the fibers, which extend along the c axis, reaches 20 μm, and the diameter of spherulites is up to 2.5 mm. The color is dark green to brown with a light green to beige streak and a vitreous luster. The mineral is translucent. The Mohs hardness is 5. Zinclipscombite is brittle; cleavage is not observed; fracture is uneven. The density is 3.65(4) g/cm3 measured by hydrostatic weighing and 3.727 g/cm3 calculated from X-ray powder data. The frequencies of absorption bands in the infrared spectrum of zinclipscombite are (cm−1; the frequencies of the strongest bands are underlined; sh, shoulder; w, weak band) 3535, 3330sh, 3260, 1625w, 1530w, 1068, 1047, 1022, 970sh, 768w, 684w, 609, 502, and 460. The Mossbauer spectrum of zinclipscombite contains only a doublet corresponding to Fe3+ with sixfold coordination and a quadrupole splitting of 0.562 mm/s; Fe2+ is absent. The mineral is optically uniaxial and positive, ω = 1.755(5), ɛ = 1.795(5). Zinclipscombite is pleochroic, from bright green to blue-green on X and light greenish brown on Z (X > Z). Chemical composition (electron microprobe, average of five point analyses, wt %): CaO 0.30, ZnO 15.90, Al2O3 4.77, Fe2O3 35.14, P2O5 33.86, As2O5 4.05, H2O (determined by the Penfield method) 4.94, total 98.96. The empirical formula calculated on the basis of (PO4,AsO4)2 is (Zn0.76Ca0.02)Σ0.78(Fe 1.72 3+ Al0.36)Σ2.08[(PO4)1.86(AsO4)0.14]Σ2.00(OH)1. 80 · 0.17H2O. The simplified formula is ZnFe 2 3+ (PO4)2(OH)2. Zinclipscombite is tetragonal, space group P43212 or P41212; a = 7.242(2) A, c = 13.125(5) A, V = 688.4(5) A3, Z = 4. The strongest reflections in the X-ray powder diffraction pattern (d, (I, %) ((hkl)) are 4.79(80)(111), 3.32(100)(113), 3.21(60)(210), 2.602(45)(213), 2.299(40)(214), 2.049(40)(106), 1.663(45)(226), 1.605(50)(421, 108). Zinclipscombite is an analogue of lipscombite, Fe2+Fe 2 3+ (PO4)2(OH)2 (tetragonal), with Zn instead of Fe2+. The mineral is named for its chemical composition, the Zn-dominant analogue of lipscombite. The type material of zinclipscombite is deposited in the Mineralogical Collection of the Technische Universitat Bergakademie Freiberg, Germany.

DISCOVERY OF A LARGE POPULATION OF THE RARE WINTER STONEFLY ISOCAPNIA MOGILA RICKER IN THE MAD RIVER, CALIFORNIA (PLECOPTERA, CAPNIIDAE)

Isocapnia mogila, a rare winter stonefly, is found in good numbers in Humboldt County, California. In the 50 years since this species was described, very few specimens were recorded from only 4 sites in California and Oregon. Emergence seems to be higher in the fall and early winter than in the late winter and spring.

First Report of the Rust Phragmidium violaceum on Pennsylvania Blackberry in California.

In April 2005, a rust fungus on Pennsylvania blackberry, Rubus pensilvanicus Poiret (= R. abactus Bailey), was collected in Humboldt County, CA. Although native to eastern North America, this host is an escaped cultivar that occurs in disturbed areas throughout California. Morphological and molecular data suggest that this rust is Phragmidium violaceum (Schultz) G. Winter. To confirm the identification of the specimen from California, an ~1,000-bp section of ribosomal DNA from the 28S large subunit was amplified and sequenced with rust-specific primers (M. C. Aime, unpublished data) (Genbank Accession No. EF672358). This sequence was 100% homologous to sequences of this rust species from Oregon and France. Widespread in Europe and introduced into Australasia as a biological control agent, P. violaceum has recently been reported from Oregon on Himalayan and evergreen blackberries, R. armeniacus Focke and R. laciniatus Willd. (2). Finding this rust in California about the same time as in Oregon suggests that its distribution may be widespread, possibly existing in the United States for some time. To our knowledge, this the first report from California and of the rust species on this plant host (1). The specimen from California is infected with urediniospores but lacks teliospores; it has been deposited at the U.S. National Fungus Collections as BPI 877816.

Is Half a Humboldt Better Than None? Numbers and Wisdom in Natural History

Is Half a Humboldt Better Than None?Numbers and Wisdom in Natural History Thomas R. Dunlap (bio) Aaron Sachs. The Humboldt Current: Nineteenth-Century Exploration and the Roots of American Environmentalism. New York: Viking, 2006. xii + 496 pp. illustrations, maps, notes, and index. $25.95 (cloth); $16.00 (paper) In September 1869, to honor the centenary of the German scientist Alexander von Humboldt, New Yorkers placed his bust on Explorers' Gate at 77th Street and Central Park West—their contribution to what the New York Times described as "'Celebration Generally Throughout the Country.'" In those days Humboldt's name lay scattered on maps from the Humboldt Current in the Pacific to the Humboldt River (Nevada) and Humboldt County (California) and his ideas on the intellectual landscape from science to fine art. Only a decade before Frederic Church, the foremost landscape painter of the period, had exhibited to general acclaim and a stream of visitors his Heart of the Andes, a five and a half by ten feet canvas of a South American landscape that showed Humboldt's bio-geographical zones from tropic jungle to snow-capped peaks. Today, as Aaron Sachs mournfully notes and the blank in most readers' minds testifies, Humboldt's fame has dwindled to the names on the map. Visitors to Central Park pay more attention to the sledge dog Balto, immortalized in bronze at 67th Street and East Drive, than to Humboldt's bust, and his name rouses associations only among historians of early-nineteenth-century science. Sachs wants to revive that reputation, less for historical justice than contemporary interest, for he believes Humboldt's "radical approach to nature and humanity makes him an astonishingly relevant figure for the twenty-first century," for his theories and writings provide a "powerful alternative" to the "simple, preservationist environmentalism I grew up with" and the "ecological science I subsequently studied" (p. 2). The Humboldt current, which "formed an intellectual torrent that swept through the Western world—the United States in particular—for about a century before it evaporated in the desert heat of social Darwinism, which endorsed both human and environmental exploitation" ran so strongly because Humboldt, like Boss Plunkitt's honest grafter, seen his opportunities and he took 'em (p. 13). Born in Berlin in 1769, he came of age as Europeans [End Page 225] were using natural history to organize their knowledge of a world they were so energetically exploring and he took full advantage of that expansive science. It took in research on the earth, the air, the oceans, plants, animals, even non-European peoples (a mélange modern natural history museums preserve to this day) and— descended from natural theology as much as natural philosophy—valued not just information but Higher Truths. In the course of a long and productive life (he died at ninety), Humboldt probed almost every aspect of the scientific field, and his writings established his wide fame. Early in his career, his Personal Narrative of the five years (1799–1804) he spent in the Americas defined the romantic figure of the scientist-explorer and inspired two generations of naturalists (a list that includes Charles Darwin, Alfred Russell Wallace, and John Muir) to head for the tropics. At its end his unfinished Cosmos, a survey of knowledge about the physical universe, caused an intellectual sensation in Europe and the United States. Explorer, collector, savant, social critic, and defender of the republican ideal, Humboldt filled the intellectual space created by the field in his time. Sachs follows Humboldt's influence across half a century of American history through the lives and careers of a gloriously mixed cast of Humboldtian characters, ranging from an entrepreneur of exploration in Jacksonian America to a shipwrecked naval engineer in the 1880s. After an introductory chapter describing Humboldt's passion for finding connections—between the land and organisms, between organisms, between nature and culture—and his understanding of exploration as a process of self-discovery and change as well as discovery and conquest, Sachs develops these themes in four parts named for compass directions. "East" presents the two poles of Humboldt's thought, the "Radical Romanticism" that led him to climb volcanoes and explore the land...

A NEW MICROSPORIDIAN INFECTING THE MUSCULATURE OF THE ENDANGERED TIDEWATER GOBY (GOBIIDAE)

A previously unrecognized microsporidian (Kabatana newberryi n. sp.) is described from the musculature of Eucyclogobius newberryi (Gobiidae) in Big Lagoon, Humboldt County, California. Spores are ovoid, ranging in size from 2.8 +/- 0.3 microm in total length and 1.9 +/- 0.4 microm in width (measurements of 30 spores made by calculation from micrograph). The polar filament has 9-10 coils in 1-2 rows. Development occurs in direct contact with host muscle cell cytoplasm, without xenoma or sporophorous vesicle. Phylogenetic analysis of the new species and of 35 other microsporidians known to infect fish using 1115 base pairs of aligned 16S rRNA gene indicate the new species is most closely related to Kabatana takedai. However, the new species differs by 11% sequence divergence from K. takedai. Divergence in morphology and genetic data allow for diagnosis from all other fish-infecting microsporidia and supports recognition of a new species of microsporidian, Kabatana newberryi n. sp., presently known only from a suspected specific host, the endangered tidewater goby Eucyclogobius newberryi.

Treatments could slow spread of sudden oak death

UC Cooperative Extension (UCCE) researchers are now testing new treatments that may help keep sudden oak death from spreading. First detected in California in 1995, the pathogen (Phytophthora ramorum) that causes this disease now infests 14 coastal counties and has killed more than a million native oaks and tanoaks. While experts acknowledge that there is little chance of eradicating sudden oak death where it is well established, there is still hope for stopping new infestations. “We have to learn to live with this disease,” says project leader Yana Valachovic, UCCE forest advisor for Humboldt and Del Norte counties. “Our goals are strategic containment and developing long-term management options for landowners.” Her collaborators include the USDA Forest Service, California State Parks and the California Department of Forestry and Fire Protection. In early 2006, the team began testing treatments in four forested areas totalling 140 acres in Humboldt County, the state’s northern limit of sudden oak death. The treatments include:

Sinter-Vein Correlations at Buckskin Mountain, National District, Humboldt County, Nevada

Sinter-Vein Correlations at Buckskin Mountain, National District, Humboldt County, Nevada

Life History of the Southern Torrent Salamander (Rhyacotriton variegatus) in Coastal Northern California

Southern Torrent Salamanders (Rhyacotriton variegatus) range widely from north coastal Oregon to northern California but are a patchily distributed inhabitant of forested seeps and headwater springs. We collected bimonthly samples of this species from managed forest sites in the Mad River watershed, Humboldt County. Larvae were measured, marked, and released, but a limited number of transformed individuals were preserved for laboratory analyses. North coastal R. variegatus breeds annually and has an extended courtship and egg-laying period. Cloacal spermatophores were present in gravid females from February through June, and oviposition likely occurs spring through fall. A prolonged larval period (hatching to metamorphosis) lasts 2–2.5 yr; transformed females require another 1.5–2 yr until first breeding, and clutch size averages 7.5 eggs. Adult sizes, size at metamorphosis, and developmental times were comparable to north coastal Oregon R. variegatus, suggesting that a simple north-south, harsh-mild environmental cline does not influence developmental time for coastal populations. Unexpectedly, clutch size and size-fecundity relationships for the California population of R. variegatus were more similar to Rhyacotriton cascadae, an inland, northern species with longer larval periods and larger sizes at metamorphosis, than to R. variegatus in north coastal Oregon. Rhyacotriton variegatus has limited rates of population increase because of long generation times and low fecundities and could be highly sensitive to frequent disturbances that impact numbers.

Use of Real-Time Quantitative PCR Targeting themsp2Protein Gene to Identify CrypticAnaplasma phagocytophilumInfections in Wildlife and Domestic Animals

Anaplasma phagocytophilum is an emerging pathogen throughout much of the Holarctic, where Ixodes spp. tick vectors occur. This organism was expected to be present at study sites in Humboldt County, north-western California, based on the presence of appropriate tick vectors, seropositivity in sentinel hosts, and previously reported human infections. However, despite high seroprevalence suggesting circulating A. phagocytophilum, active infections in dogs and wildlife (including suspected reservoir species) were rare using published polymerase chain reaction (PCR) protocols. This finding was possible if the published PCR protocol lacked sensitivity for strains in the study areas. We report a new TaqMan-PCR (TM-PCR) assay targeting the msp2 gene that has greater sensitivity and specificity for diverse A. phagocytophilum strains from this region. The new assay detected as few as one plasmid copy and a range of genetically diverse strains of A. phagocytophilum. Specificity was confirmed by failure to amplify targets of closely related bacteria. Application of the TM-PCR to samples from northern California confirmed PCR-positivity in 94 woodrats (71%; n=134), three (4%; n=80) bears, and seven (7%; n=97) domestic dogs. The msp2 TM-PCR protocol appears to be more sensitive for use in assays of samples from parts of western North America and possibly in other regions where populations are genetically diverse or divergent from eastern United States strains of A. phagocytophilum.

A LOOK BACK AT 1906--PERSPECTIVES ON GREAT EARTHQUAKES AND POST-EARTHQUAKE INVESTIGATIONS

At 5:12 am on April 18, 1906, a fracture formed some 10 km below the Earth's surface offshore of the Golden Gate. It propagated upward and outward, reaching the surface and extending north and south. To the south it broke along the San Francisco peninsula, climbed through the Santa Cruz Mountains, and stopped abruptly at San Juan Bautista. To the north it hugged the coast in Marin, Sonoma, and Mendocino counties, passed into the Pacific Ocean north of Pt. Arena, and came to halt on land in Humboldt County. Approximately one and one-half minutes after it began, the rupture stopped. Fourhundred-seventy km of the Pacific–North American plate boundary had shifted an average of 4½ m along the San Andreas Fault, and the M 7.9 San Francisco earthquake had occurred. An on-land strike-slip earthquake the size of 1906 is not an everyday occurrence, and diverse messages are to be taken away from it.... For me, one of the most compelling messages is the incalculable importance of post-earthquake investigations—both for what they provide at the moment and the legacy they leave for the future. This year, 2006, is the centennial of the 1906 San Francisco earthquake. This anniversary has prompted a broad range of earthquake-centered scientific, historical, cultural, and political activities. Scientifically it has refocused attention on the ground motions and the regional distribution of shaking intensity that the 1906 earthquake generated, the potential effects of its repeat on the San Francisco Bay Area and northern California, and its place in the development of earthquake science. In July 2005, I was in northern Mongolia for an international field trip celebrating the 100th anniversary of another great earthquake, the 1905 rupture of the Bulnay Fault. I admit to a fascination for these great on-land surface-faulting earthquakes, having had the good fortune to work …

Private Strawberry Breeders in California

Private Strawberry Breeders in California

COMMON MURRES PROSPECTING WITHIN CORMORANT COLONIES IN DEL NORTE AND HUMBOLDT COUNTIES, CALIFORNIA, 1996 to 2004

Between the 1940s and 1960s, common murres (Uria aalge) colonized or recolonized several islands in Del Norte and Humboldt Counties, northern California, during an extended period of population growth following heavy prior impacts from early settlers and native peoples (Carter and others 2001). The exact timing of these colony formations and various factors influencing them were not well documented. Since the 1st complete northern California seabird colony survey in 1979–80 (Sowls and others 1980), almost annual June aerial photographic surveys have been conducted of breeding colonies of murres and cormorants (Brandt’s and double-crested, Phalacrocorax penicillatus and P. auritus) in northern California (Briggs and others 1983; Takekawa and others 1990; Carter and others 1992, 1995, 1996, 2001; Capitolo and others 2004a; US Fish and Wildlife Service [USFWS], unpubl. data). While several murre colony formations have been documented in Mendocino County primarily with aerial photographs since 1979–80, no colony formations have been documented in Del Norte and Humboldt Counties. In 1996–2004, we documented (1) the 1st known attendance by murres on 4 offshore rocks in Del Norte County (High Bluff South, White Rock, Prince Island, Unnamed Small Rocks); (2) continued sporadic attendance by murres without recent confirmed breeding on 2 other offshore rocks in Del Norte County (Rock R and Sister Rocks); and (3) the 1st recent attendance by murres on 1 offshore rock in Humboldt County (Sea Lion Rock). In this note, we describe these observations of prospecting murres, show relationships with nesting cormorants, and discuss their potential importance to understanding possible future colony formations. We use the term ‘‘prospecting’’ to describe murres attending potential breeding habitats on land where murre breeding has not been recently documented, though we usually did not know what activities occurred on land nor how long murres were present on land. Because murres do not attend such habitats without a breedingrelated purpose, we consider that prospecting for a breeding site or mate are the chief reasons for such attendance (see later discussion). However, without marked birds or access to colonies, source colonies for these prospecting murres cannot be specifically determined.