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To better understand recent population growth of the Double-crested Cormorant Phalacrocorax auritus along the Pacific coast of North America, we assessed long-term breeding population trends in the Humboldt Bay area, California, using aerial photographic survey data collected since 1989 as well as available prior data. The earliest documentations of breeding (but without nest counts) are from 1924, 1943, and 1947 on the outer coast near Trinidad, and from 1959 in Humboldt Bay at Old Arcata Wharf. The breeding population increased from 188 nests (376 breeding birds) at one colony in 1961 to ~ 350 nests (700 breeding birds) at four colonies by 1980, and then to peaks of nearly 1 700 nests (3 400 breeding birds) in 1997 and 2004 at eight colonies. Breeding was documented at 13 coastal colonies through 2017. The population increased 100% (9% per annum) from 1989 to 1997, decreased during the strong 1998 El Niño, and rebounded by 2004. After the 2004 peak, three years of available data indicated slight population decline. For the entire 1989-2017 period, the population increased by 91% (2% per annum). Artificial habitats in Humboldt Bay allowed most of the population growth, especially Teal Island, which was colonized in 1993 and became the largest colony in all but one year thereafter. Nest totals on the outer coast decreased, likely because of movements to the Humboldt Bay colonies, which are closer to main foraging areas, and because of competition for nesting space with Common Murres Uria aalge at one colony (False Cape Rocks). Future growth of the population in the Humboldt Bay area appears limited by the availability of disturbance-free breeding habitat. Declines may occur if artificial habitats are lost. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined Brandt's Cormorant colonies between 1997 and 2001 to understand their breeding performance in the central California nearshore environment. In the 1998 El Niño event, breeding effort was reduced at Point Reyes (PR), Devil's Slide Rock (DS) and Castle-Hurricane Colony Complex (CH). Results showed that productivity at CH was lower than at PR. In addition, late-nesting birds laid fewer eggs and hatched fewer chicks. Variation in timing of breeding and reproductive success shows a value in maintaining study locations.

Eighteen years of field observations and five summer field experiments in a coastal California river suggest that hydrologic regimes influence algal blooms and the impacts of fish on algae, cyanobacteria, invertebrates, and small vertebrates. In this Mediterranean climate, rainy winters precede the biologically active summer low-flow season. Cladophora glomerata, the filamentous green alga that dominates primary producer biomass during summer, reaches peak biomass during late spring or early summer. Cladophora blooms are larger if floods during the preceding winter attained or exceeded "bankfull discharge" (sufficient to mobilize much of the river bed, estimated at 120 m3/s). In 9 out of 12 summers preceded by large bed-scouring floods, the average peak height of attached Cladophora turfs equaled or exceeded 50 cm. In five out of six years when flows remained below bankfull, Cladophora biomass peaked at lower levels. Flood effects on algae were partially mediated through impacts on consumers in food webs. In three experiments that followed scouring winter floods, juvenile steelhead (Oncorhynchus mykiss) and roach (Lavinia (Hesperoleucas) symmetricus) suppressed certain insects and young-of-the-year fish fry, affecting persistence or accrual of algae positively or negatively, depending on the predator-specific vulnerabilities of primary consumers capable of suppressing algae during a given year. During two post-flood years, these grazers were more vulnerable to small predators (odonates and fish fry, which stocked steelhead always suppressed) than to experimentally manipulated, larger fish, which had adverse effects on algae in those years. During one post-flood year, all enclosed grazers capable of suppressing algae were consumed by steelhead, which therefore had positive effects on algae. During drought years, when no bed-scouring winter flows occurred, large armored caddisflies (Dicosmoecus gilvipes) were more abundant during the subsequent summer. In drought-year experiments, stocked fish had little or no influence on algal standing crops, which increased only when Dicosmoecus were removed from enclosures. Flood scour, by suppressing invulnerable grazers, set the stage for fish mediated effects on algae in this river food web. Whether these effects were positive or negative depended on the predator-specific vulnerabilities of primary consumers that dominated during a given summer. [ABSTRACT FROM AUTHOR]

Presents a study which described the occurrence of Eastern equine encephalomyelitis virus (EEEV) infection in a yearling horse raised in southern California. Pathology; Hypotheses investigated to explain the occurrence of EEEV outside its usual range; Surveillance for EEEV in southern California; Molecular comparison of horse and vaccine strains.