Pacific Coast Populations Research Articles

GERMINATION AND SEEDLING EMERGENCE IN SPERGULA ARVENSIS

Spergula arvensis L. (Caryophyllaceae) is a cosmopolitan weedy annual that exhibits a genetically based seed coat polymorphism in which two primary seed types, papillate (P) and nonpapillate (NP), are produced. This study examined germination response of the two morphs and seedling emergence in Pacific coast populations. Germination behavior was complex and variable among populations and between seed morphs. Seeds from some populations exhibited greater temperature sensitivity and/or differentiation between morphs. Freshly produced seeds from grassland and ruderal populations were strongly dormant at the time of dispersal, in contrast to seeds from cultivated or summer‐wet populations. In San Francisco Bay area populations, germination and seedling emergence was largely simultaneous, following the first substantial fall rains.

Tubercular Lesions in Pacific Coast Populations of Striped Bass

Abstract Tubercular lesions were found in striped bass Moroue saxatilis from four areas in northern California and Coos Bay, Oregon. The prevalence of infected striped bass ranged from 25% to 68% in California and was 46% in Oregon. This is the first report of tubercles caused by an acid-fast bacillus in wild populations of west coast striped bass. Received October 25, 1982 Accepted April 24, 1983

Pacific Coast Caspian Terns: Dynamics of an Expanding Population

Abstract Nesting distribution, age-related seasonal movements, survivorship, and mechanisms of population expansion in Pacific Coast Caspian Terns (Sterna caspia) were examined primarily through analysis of 412 recoveries of birds banded as juveniles between 1935 and 1980. Since the beginning of this century, the population has shifted from nesting in numerous small colonies associated with freshwater marshes in interior California and southern Oregon to nesting primarily in large colonies on human-created habitats along the coast. Colonies at Grays Harbor, Washington and San Francisco and San Diego bays, California account for 77% of the current Pacific Coast population (6,000 pairs), which has breeding and wintering areas separate from those of populations east of the continental divide. There also appears to be some segregation on the wintering grounds by birds from the three major colonies within the Pacific population. Age-related seasonal movements in the Pacific population are characterized by (1) a brief period of northward dispersal by newly fledged birds before migrating to the wintering grounds, (2) a residency on the wintering grounds through their second winter, (3) a return to the breeding grounds the third summer, when most birds are thought to prospect breeding sites and some may breed, and (4) attainment of adulthood the fourth summer, with subsequent annual movements between wintering and breeding grounds. The Pacific population has increased 70% since 1960, apparently all by intrinsic growth. Over half (57%) of the fledglings reach their fourth year, and they have a subsequent annual survival rate of 89% and a mean breeding life expectancy of 8.6 yr. An average annual fledging rate of 0.64 young per pair was calculated as necessary to have provided the observed growth of the population during its recent expansion. Growth of some of the individual colonies, however, particularly those in Washington, could only have resulted from extensive recruitment of birds from other Pacific Coast colonies. Philopatry is low in this population, and the growth of the northern colonies involved recruitment primarily of first-time breeders but also of some older adults. Factors promoting both first-time breeders and older adults to join new and often distant colonies are discussed.

Biochemical genetic evidence for a third species of Metridium (Coelenterata: Actiniaria)

Systematic relationships within the sea anemone genus Metridium have been problematical for many years. The genus has been considered to consist of a single, highly variable species, M. senile (L.), which has been divided into several somewhat arbitrary morphs. One, the “clonal” morph, is characteristically small, found in shallow water and reproduces both sexually and asexually. Another, the “solitary” morph, may grow very large, is found to great depths and has been thought to reproduce primarily, if not exclusively, sexually. The existence of a second species, M. exilis, described by Hand (1955), has been questioned (Riemann-Zuerneck, 1975). In the present study, the taxonomic status of the morphs and species of Metridium was examined by starch-gel electrophoresis to analyze genic variation at 16 enzyme loci in samples of the two morphs of M. senile and M. exilis collected at 3 locations on the Pacific coast of the USA (Bodega Bay, California; Monterey Bay, California; Puget Sound, Washington) and at 1 location on the Atlantic coast of the USA (Maine). Intrapopulation levels of gene enzyme variation were quite high (P0.95=47.9,, and H=15.1), and some genetic differentiation among geographically separated populations of a single morph was seen, particularly between Atlantic and Pacific coast populations of the clonal M. senile. However, genetic differentiation (D) among pooled populations of M. exilis, clonal M. senile and solitary M. senile was much greater (D=1.14). Thus, the genus Metridium contains not one highly variable species but three distinct species, each with a relatively narrower ecological range and a relatively less variable morphology.

STUDIES OF WATERFOWL IN BRITISH COLUMBIA GREEN-WINGED TEAL

The migrations of the Pacific Coast population of Anas carolinensis parallel in time and space those of Anas acuta. Both use the same migration routes along the coast and along the main north and south river systems of the interior. So also both nest more commonly in Alaska than elsewhere. The peak of the spring migration usually is reached in late March or early April; the peak of the autumn migration usually is in late October and early November. A relatively large number normally winter on the Coastal Plain. Very few winter in the interior. Study of banding data reveals that (1) autumn transients through the Coastal Plain follow the coast route south to the mouth of the Columbia River and beyond through Oregon and California, rarely passing east of the High Sierras, (2) few individuals among the population following interior routes reach the coast, the tendency being to swing eastward to the Great Basin. The two main flyways through British Columbia, one on the coast the other through the interior, differ in at least one important respect, viz., along the interior route are many more or less isolated areas of suitable nesting grounds whereas on the coast there are none. A small nesting population, fluctuating annually in numbers, is widely distributed through the interior, the center of abundance being the Cariboo Parklands—the term abundance being used in a relative sense. Actually the population is small and dispersed. In the year 1938 a total of only 17 broods was counted on a study area of 60 sq. mi. containing a high average of highly productive waterfowl territory. Smaller counts were made here in each of the years following 1938. Egg-laying begins in May; there is some loss of early clutches through crow predation compensated for by later, and usually more successful, nesting. It is not unusual for females to be incubating a second clutch of eggs in early July. Nest sites are in dry places nearly always adjacent to a small pond or marsh in the grasslands. The earliest and latest dates for records of downy young are June 20 and Aug. 10. The average number of young in 48 broods counted in July, and 17 broods counted in August, was the same viz. 6.2. This high survival rate may be attributed in part to the spirited defense of young commonly practised by the female parent. Adult males in small number may associate on a common loafing place during the egg-laying period, and for a week or so after incubation has started. Later they retreat to marsh habitat and begin the yearly molt. Full eclipse of the body plumage usually is attained prior to renewal of the flight feathers. The molt from eclipse to nuptial dress is not completed until late October. The first adult plumage of young males is not fully attained until January. The sex ratio appears to maintain a not unfavorable biological balance—a total of 4264 banded green-winged teal was composed of 2225 males and 2039 females. The food range of the species is not extensive. Seeds, chiefly those of aquatic plants, were present in the stomachs of all 69 adults examined, and in many constituted the bulk of food eaten. Insects are second, miscellaneous animals third, in importance. The green-winged teal is a valuable game species; none of its habits is detrimental to agricultural or other human interests.

Intermountain Agriculture and Pacific Coast Populations

Intermountain Agriculture and Pacific Coast Populations