Point Reyes National Seashore Research Articles

Population Dynamics of Tule Elk at Point Reyes National Seashore, California

The presence of locally abundant wildlife raises questions about natural regulation and ecological consequences of overpopulation. We sought to establish precise information about population size, structure, and productivity to examine the role of natural regulation in a closed tule elk (Cervus elaphus nannodes) population at Point Reyes National Seashore, California, USA. We estimated an instantaneous exponential growth rate of 0.19 with an adjusted R 2 = 0.98 during 1998, 20 years after the elk were introduced. We estimated annual survival for adult cows of nearly 0.95. Calf survival from birth through the rut ending during October-November was 0.85. Male calves exhibited higher mortality than female calves. Cow mortality was associated with the calving season. We measured a 42% increase in cow:calf density from 0.733 ha -1 to 1.043 ha -1 during 1996-1998. We observed a density-correlated reduction in the rate of increase and in the cow:calf ratios prior to high precipitation El Nino Southern Oscillation years, 1993, 1996, and 1997, precipitation >1.23 m year -1 . Given the high population growth rate and model evaluation of management scenarios, park managers will need to use a suite of approaches, such as contraception and removal, to maintain the elk population at levels at or near the closed-range carrying capacity for years between El Nino events.

DEMOGRAPHY OF A DECLINING POPULATION OF WARBLING VIREOS IN COASTAL CALIFORNIA

Abstract We investigated population trends, adult survival, and productivity indices of a breeding population of Warbling Vireos (Vireo gilvus) in north coastal California using capture-recapture data from 19 years of standardized mist-netting conducted at Point Reyes National Seashore. We found significant long-term declines in abundance of both breeding and migratory Warbling Vireos. In addition, we found a significant long-term decline of hatching-year birds captured during the breeding season. The number of new adults in a given year, defined as those birds not previously banded and assumed to be an index of adult recruitment, was significantly correlated with the capture rate of hatching-year birds in the previous year, suggesting a link between reproductive success and adult abundance and recruitment. Our analysis of capture-recapture data provided an estimate of 50.4% for adult annual survival, similar to estimates for other species in stable populations. We could detect no temporal trend in surviv...

The Use of Mist-Net Capture Rates to Monitor Annual Variation in Abundance: A Validation Study

Constant-effort mist-netting has become an increasingly popular tool in long-term monitoring of bird populations. Monitoring programs often assume that variation in the capture rates of adults reflects variation in breeding densities of the sampled population. We test this assumption by comparing annual variation in mist-net capture rates to known variation in breeding densities of four species breeding in coastal scrub habitat at Point Reyes National Seashore, California. For the period 1980 to 1992, breeding densities for each species were assessed using spot-mapping observations of color-banded individuals. These were compared to capture rates calculated from constant-effort mist-netting. Capture rates of adults correlated significantly with breeding density for Spotted Towhees (Pipilo maculatus), Song Sparrows (Melospiza melodia), and Wrentits (Chamaea fasciata), but not for White-crowned Sparrows (Zonotrichia leucophrys). Analysis of covariance confirmed that the relationship of mist-net capture rates to breeding density differed among species. Independent of the effects of breeding density on capture rates, adult capture rates of the four species were higher in years with high rainfall. Among Wrentits and Song Sparrows, approximately 50% or more of adults caught were not occupying territories at the study site; the same bias may exist among other species as well. We conclude that relative changes in breeding density over time can be inferred from variation in mist-net capture rates for some, but not all, species. Additional studies are needed to validate the use of mist nets to assess spatial differences in abundance and to monitor temporal changes in abundance in habitats other than coastal scrub.

Organizational and Financial Considerations of Wildlife Operations During Two Orphan Spills Off California1

ABSTRACT In November 1997 and again in January 1998, U.S. Coast Guard Marine Safety Office San Francisco Bay, California Department of Fish and Game Office of Spill Prevention and Response (OSPR), the National Park Service, and the Gulf of the Farallones National Marine Sanctuary responded to “mystery” oil spill incidents in the Point Reyes National Seashore, California area. These spill responses were unique because they were primarily wildlife recovery and rehabilitation operations; very little oil was sighted despite wildlife impacts that rank the event as the fourth worst in California history. A large-scale investigation including the use of multiple laboratories to identify the source of the oil has established a connection between the two spills, but no responsible party has been identified to defray the response costs. As a result of the spills, a significant effort is underway in Northern California to better define the role of wildlife operations within the incident command system and to rethink its organization and protocols. Other lessons to apply to future responses involve the funding issues revolving around the difference between response efforts and natural resource damage assessment when the Oil Spill Liability Trust Fund (OSLTF) is the primary source of funding.

Attendance and Effects of Disturbance on Coastal Common Murre Colonies at Point Reyes, California

-We surveyed six Common Murre (Uria aalge) colonies in the vicinity of Elephant Seal Cove Beach (ESCB), Point Reyes National Seashore, Marin County, California from 1995 through 1997 to investigate the effects of disturbance on local murre populations in the wake of a small shipwreck and to establish seasonal and diurnal attendance patterns of coastal murre populations. Following the shipwreck in 1995, one colony (Cliff Rock West) was abandoned, and three others (Flattop Rock, Mid Rock, and East Rock) experienced reduced productivity due to disturbance and predation by Brown Pelicans (Pelecanus occidentalis), Western Gulls (Larus occidentalis), and Common Ravens (Corvus corax). A fifth colony, Face Rock, farthest from the grounding site, was apparently not affected. Murres attended Cliff Rock West only early in 1996, and not at all in 1997. A new colony formed on another seastack (Northwest Rock) after murres left the Cliff Rock West colony in 1996. However, no eggs were observed at Northwest Rock in 1996 and this colony was abandoned early in 1997. Seasonal attendance among colonies on Flattop Rock, Mid Rock, and East Rock followed a similar trend in both 1996 and 1997. Murre attendance fluctuated widely until the onset of egg-laying in early May, but then stabilized and increased somewhat untilJuly, when numbers began to drop at the end of the fledging period. Both air temperature and the upwelling index (UI) were significantly correlated with murre attendance in May and June during the incubation and nestling periods. Mean attendance increased 18-30% at these colonies between 1996 and 1997. Diurnal attendance in 1996 and 1997 varied both within and between colonies and days, yet there was a significant downward trend in numbers throughout the day, as well as an effect of colony disruption by other marine species. Given that seasonal and diurnal attendance patterns of Flattop, East, and Mid Rocks in 1996 and 1997 appear similar, both between years and to other studies, we assume that these colonies recovered quickly following the 1995 shipwreck. However, interspecific interactions and predation continue to affect diurnal attendance patterns and productivity of these colonies. Received 5 April 1998, accepted 11 October 1998, final acceptance 27 March 1999. Waterbirds 22(1): 130-139, 1999 Seasonal and diurnal attendance has been examined for a number of Common Murre populations (Lloyd 1975; Birkhead 1978a; Slater 1980; Harris et al. 1983; Hatch and Hatch 1989; Takekawa et al. 1990). During the incubation and nestling periods, the number of birds on a colony may be influenced by ambient weather; numbers may be lower during periods of high winds (Birkhead 1978a; Gaston and Nettleship 1981) or warm temperatures (Murphy and Schauer 1994). Few studies have investigated attendance patterns in relation to disturbance. Aside from human disturbance, disruption to murre colonies may be caused by predators and competitors; such effects have been recorded in studies of murre behavior, survivorship, productivity, and the costs and benefits of coloniality (Birkhead 1977; Spear 1993; Sydeman 1993; Parrish 1995; Gaston and Elliot 1996; Schauer and Murphy 1996). On 10June 1995, the vessel Wayfarer, a 42' Grand Banks pleasure-craft, ran aground ne r Elephant Seal Cove Beach, Point Reyes Headlands, Marin County, California (Fig. 1). As a result of the wreck, engine oil, debris, and approximately 200 gallons of diesel fuel were released into coastal waters (Point Reyes National Seashore Case/Incident Record #950136). During the event, a U.S. Coast Guard helicopter was dispatched to the scene to rescue the one-man crew.

Ehrlichia spp. in cervids from California.

Blood samples from six mule deer (Odocoileus hemionus hemionus), 15 black-tailed deer (O. hemionus columbianus), and 29 elk (Cervus elaphus nannodes) were assayed for human monocytic and human granulocytic ehrlichiosis (HGE) by polymerase chain reaction (PCR), DNA sequencing, and serology to determine whether or not cervids are involved in the maintenance of these potential human pathogens in California (USA). The deer were sampled in August to October 1992-95. The 29 tule elk from Point Reyes National Seashore were sampled in August 1997. All deer were seronegative for antibodies to HGE/Ehrlichia equi, while the E. equi seroprevalence among elk was 17%. The 16S rDNA PCR prevalence in deer was 38% (in mule deer and black-tailed deer) for Ehrlichia-like sp. of white-tailed deer, 5% (one black-tailed deer only) for E. equi, and 0% for E. chaffeensis. The PCR prevalence in elk was 0% for Ehrlichia-like sp. of white-tailed deer, 31% for E. equi, and 0% for E. chaffeensis. The E. equi from two positive elk samples was successfully propagated in HL-60 cell cultures. DNA sequencing confirmed that the Ehrlichia-like sp. sequences from deer in California were closely related to sequences reported from white-tailed deer from Oklahoma and Georgia. The E. equi strain from deer and elk resembled other E. equi strains from California. These results suggest that cervids may be important in the natural maintenance of E. equi in California.

Radiometric culture of Mycobacterium avium paratuberculosis from the feces of tule elk.

To determine if Mycobacterium avium paratuberculosis has persisted in tule elk (Cervus elaphus nannodes) at Point Reyes National Seashore (California, USA), 100 fresh fecal samples were collected. Feces were cultured on a modified BACTEC 12B radiometric medium for detection of M. avium paratuberculosis. Four samples, coming from two separate groups of elk tested positive for M. avium paratuberculosis. Thus, a noninvasive technique was used to document the continued presence of M. avium paratuberculosis in elk at Point Reyes National Seashore. These findings document persistence of this organism for a period of at least 13 yr in a free ranging herd of elk, with a 6 yr absence of observed clinical signs.

Aggression and Song Development in White-Crowned Sparrows

14008, BNS-85-21812) to M. C. Baker. We gratefully acknowledge the National Park Service for permission to conduct field studies at Point Reyes National Seashore. We thank Dr. Lewis Petrinovich and an anonymous reviewer for their valuable suggestions for improving the manuscript. Also, we acknowledge the special contributions of Drs. Richard Tracy, Philip Lehner, Thomas Boardman, and Simon Tavare.

Herbivory and Species Replacement in the West Coast Searockets (Cakile, Brassicaceae)

Two species of searockets (Cakile maritima and C. edentula ssp. edentula var. edentula) have been sequentially established on the West Coast of North America since the 1880s. In California, C. maritima has replaced C. edentula in the southern 1000 km of their former sympatric distributions. This research tested the hypothesis that differential herbivory contributed to the ascendance of C. maritima. Choice experiments were conducted with three herbivores (two insects and a rodent) which consume Cakile at Point Reyes National Seashore, California, where only C. maritima now occurs. Larvae of the moth Platyprepia virginalis (Arctiidae) displayed a significant preference for foliage of C. maritima in a laboratory test. No evidence of any foliage preference was found for the short-horned grasshopper Microtes occidentalis (Acrididae) in laboratory and field experiments. Field experiments with deer mice (Peromyscu's maniculatu,s) demonstrated a significant preference for C. edentula seedlings and fruits. Degree of preference by mice for seedlings was affected by the distance from the experimental location to patches of introduced beachgrass (Ammophila arenaria), which mice use for nesting sites and cover, but this distance-dependence did not occur for fruit predation. Herbivory by the two insect species was not a factor in this case of species replacement. Peromyscus preference for seedlings and fruits of C. edentula would have affected the rapidity of local species replacement at Point Reyes, but this preference does not explain the current distribution of Cakile on the Pacific Coast. I concluded that differential predation by mice was not the ultimate cause of Cakile species replacement in California.

Dietary Overlap among Axis, Fallow, and Black-Tailed Deer and Cattle

Seasonal diets of native Columbian black-tailed deer (Odkoileus hemionus cohunbbznus) and exotic axis deer (Axis axis axis), fallow deer (Dama dama dama), and cattle (Bos taurus) on Point Reyes National Seashore were determined by microhistological technique to assess their dietary overlap. Throughout the year black-tailed deer ate mostly forbs, axis deer and fallow deer ate mostly grasses and forbs, and cattle ate mostly grasses. Only a few plant species comprised most of their diets. Percent composition of food species was not related to their preference indexes. Diets of axis and fallow deer overlapped more with each other and cattle than with black-tailed deer except during the summer when the dietary overlap among all species was similar at a lower level. Comparison of seasonal diets of deer with this and other studies indicated that food consumption of deer was not limited to particular food classes. Authors are former graduate student, Department of Agronomy and Range Science, University of California, Davis and now consulting biologist, 1012 Sand Bar Circle, Carmichael, Calif. 95608; and associate professor, Department of Forestry and Resource Management, University of California, Berkeley. The project was funded by the National Park Service-Western Region. Carole F. Truman and Jennie Dushek determined composition of food species. Drs. William M. Longhurst and John W. Menke were advisors to this project. Manuscript accepted January 28, 1985. 546 Exotic ungulates introduced into favorable habitats may erupt in numbers, deplete their food resources, and then crash (Scheffer 1951, Klein 1968, Caughley 1970). At Point Reyes National Seashore, as a result of an introduction of 2 species of exotic deer during the 1940’s and early 1950’s (Wehausen and Elliott 1982) and the continuation of commercial beef and dairy operations, 4 ungulates now coexist in the Seashore’s pastoral zone: cattle (Bos tauno); Indian axis deer (Axis axis axis), European fallow deer (Dama dama dama); and native Columbian black-tailed deer (Odocoileus hemionus columbianus). Previous studies at Point Reyes National Seashore (Elliott 1973, Wehausen 1973) suggested that these deer and cattle have similar diets, and that unlimited growth of the exotic deer population could have significant negative effects on the nutrition of all resident ungulates, particularly in the fall when the amount of the forage and its nutritional value are low. Since the National Park Service was shooting the exotic deer within the pastoral zone to maintain their density at 1973 levels and knowledge of the ecological relationships between these species and their habitat was limited, this project was undertaken to provide information on which to base management decisions. JOURNAL OF RANGE MANAGEMENT 36(6), November 1965 Many studies have indicated that competitive effects between sympatric ungulate species involved the use of food (Anthony and Smith 1977, Sinclair 1977, Mackie 1978, McCullough 1980, Kasworm et al. 1984). Therefore, to investigate the likelihood of competition among deer and between deer and cattle at their current densities on Point Reyes Peninsula, the botanical composition of their diets, their preference for these food species, and their dietary overlaps were assessed.

Nutrient and productivity relations of the dune grasses Ammophila arenaria and Elymus mollis : I. Blade photosynthesis and nitrogen use efficiency in the laboratory and field.

A comparative study of blade photosynthesis and nitrogen use efficiency was made on the dune grasses Ammophila arenaria and Elymus mollis. In the laboratory, an open system gas analysis apparatus was used to examine the gas exchange characteristics of blades as influenced by nitrogen supply. Plants were grown under near-ambient coastal conditions in a greenhouse near Bodega Bay, California, and given either high or low supplies of nitrogen in an otherwise complete nutrient solution. In the field, 14CO2 uptake techniques were employed to measure the seasonal patterns of blade photosynthesis of plants growing in situ at Point Reyes National Seashore. Blades used in the lab and field studies were analyzed for total nitrogen content, thus allowing for calculations of photosynthetic nitrogen use efficiency (CO2 fixed/unit of blade N.).Under laboratory conditions, the introduced Ammophila developed higher rates of light-saturated photosynthesis than the native Elymus, especially under the nitrogenlimited growth regime. Higher rates of photosynthesis and lower concentrations of blade N resulted in a significantly greater nitrogen use efficiency for Ammophila regardless of nutrient treatment. Low N availability induced qualitatively similar physiological responses in both species, including reductions in maximum net photosynthesis, mesophyll conductance, leaf conductance, dark respiration, and blade nitrogen content, and an increase in the CO2 compensation point.Although the photosynthetic rates of Ammophila blades were higher in the lab, those of Elymus blades were consistently higher in the field. This could have resulted from differential effects of drought on the two species (i.e. Ammophila may have been more sensitive) or a higher photosynthetic capacity in Elymus that reflected the greater (1.2-1.5 X) nitrogen content of its blades. However, the nitrogen use efficiency of Ammophila blades was greater than that of Elymus throughout most of the sampling year, despite lower average rates of field photosynthesis.The results indicated that rates of photosynthesis perunit of blade area do not account for the greater aboveground productivity of Ammophila stands along the Pacific coast of North America. Instead, efficient nitrogen use in photosynthesis maycomplement other structural and physiological traits and thereby enhance long-term carbon gain in Ammophila relative to Elymus.

Population biology of White-crowned Sparrows: Residence time and local movements of juveniles

A field study of the ranging behavior of post-fledging White-crowned Sparrows (Zonotrichia leucophrys nuttalli) was carried out in undisturbed natural habitat in the Point Reyes National Seashore, Marin Co., California, USA. Forty-three first-brood juveniles, with tail feathers still growing, were banded at an estimated average age of 27 days and re-trapped an average of an additional 24 days for a total minimum time in residence in the immediate natal area of 51 days (Table 1).

Dune Scrub Communities and Their Correlation with Environmental Factors at Point Reyes National Seashore, California

Dune scrub vegetation characterized by three soft-leaved shrubs, Haplopappus ericoides, Lupinus arboreus and Lupinus chamissonis, was sampled at Point Reyes National Seashore (PRNS), Marin County, California, using the Braun-Blanquet releve method. Eighty-one releves were made over a 1 year period and soil samples at 10 and 40 cm were analysed for particle diameter, per cent organic matter, per cent nitrogen, field capacity, and pH. Releves and species were organized into an association table using a computer program. Four plant community types were recognized from the association table: a type dominated by Lupinus arboreus, a type co-dominated by the latter with Haplo- pappus ericoides and Baccharis pilularis, a type dominated by L. chamissonis, and a type characterized by Eriophyllum staechadifolium with Lupinus arboreus. The releves were ordinated along three axes. Their grouping along two axes showed good agreement with the community types derived from the association table. One of the axes was correlated with organic matter, nitrogen, and particle diameter (per cent < 0.25 mm) which were all highly correlated with each other. Distance inland, which field measurements indicate affects the amount of salt spray deposition, is ordered along the second axis.

The Microdistribution and Feeding Preferences of Peromyscus maniculatus in the Strand at Point Reyes National Seashore, California

A grid of 100 traps in a 1-ha study plot that included beach and dune was used for 1.5 years. The only rodent captured was Peromyscus maniculatus. Estimated density fluctuated between 15 and 40 ha-' but these estimates may be too high. Stomach analyses showed Peromyscus to be an omnivorous, generalized feeder, taking both immature and adult coleopterans, and seeds and herbage of various plants. Choice experiments showed herbage of Montia perfoliata, Stellaria media and Erysimum concinnum and seeds of Cakile maritima, Lupinus arboreus, Lathyrus littoralis and Amsinckia spectabilis to be preferred. In nature, however, peak animal activity coincided with regions densely covered by Ammophila arenaria or Juncus lesueurii. The microdistribution of Peromyscus was inversely correlated with light intensity. Shaded habitats provide nesting material, a more stable substrate, dampened temperature oscillations and protection from aerial predators. Ammophila depressed plant species richness, including food plants of Peromyscus. INTRODUCTION Recent synecological work on the beach and dune vegetation of California (Barbour et al., 1976; Barbour and Robichaux, 1976; Barbour and Johnson, 1977) has shown that general data on plant-animal interactions in the California strand are lacking. To correct this deficiency, we established a 1-ha permanent study plot along the central California coast in strand dominated by Ammophila. Our objective was to identify herbivores and pollinators and to correlate their distribution and activity patterns with plant distribution and microenvironmental gradients. The work with Peromyscus reported here is a part of that larger study (Pitts, 1976). MATERIAL AND METHODS Study site.--Point Reyes National Seashore is located in Marin, Calif., on Point Reyes Peninsula, approximately 37015'-38015' N lat. Our study site is halfway between Beach North and Abbotts Lagoon. It is situated on a small parcel of private land, owned by American Telephone and Telegraph, but it is surrounded by National Seashore property and its receives very little foot traffic. We located a 1-ha study site, (100 m on a side, in November 1974. It was oriented in such a way as: to include a wide range of habitats, from open beach to densely vegetated dunes. The plot was subdivided into 100 1OM2 tracts, each marked by a numbered stake. Rows 1 through 10 were aligned with an E-W trending orientation (roughly perpendicular to shore). Columns were aligned N-S (roughly parallel to shore) and numbered 1.0-10.1 for column 1, 1.1-10.1 for column 2, etc. (Fig. 1). This region is characterized by a marine-moderated Mediterranean climate. The lighthouse at the Point proper records a yearly mean temperature of 11.7 C, with relatively little seasonal fluctuation. Summer fogs no doubt contribute to the moderate temperatures. Point Reyes is one of the foggiest regions on the Pacific Coast. The lighthouse there had an average of 1500 hr of operation a year, about 1/6 of all possible hours. Fog coincides with the months of least rainfall, July-September, and fog drip may play a role in the biota here as it does in other coastal vegetation types of California. Average rainfall is 30 cm year-', with 75% falling November-March I Present address: Department of Biological Sciences, San Jose State University, San Jose, California 95192.

An Albinistic Marbled Godwit: A First Record

Albinism occurs infrequently in the family Scolopacidae as compared to other avian families (Sage 1963, Gross 1965). There are apparently no previous records of albinism for the Marbled Godwit (Limosa fedoa) (Ross 1963), although there is one record each for the Hudsonian Godwit (Limosa haemastica) (Deanne 1880), and the Bar-tailed Godwit (Limosa lapponica) (Sage 1962). At 15:30 on 9 February 1974 on the east shore of Drake Estero, Point Reyes National Seashore, Inverness, California, I spent approximately 15 min observing an albinistic Marbled Godwit foraging on mudflats among a relatively large flock of godwits. Observations were made from a distance of about 30 m with a 15-60x zoom telescope. There were no clouds or wind, and glare was minimal. A description follows: Bill-flesh colored with black tip, apparently normal; Irides-black, apparently normal; Legs-dark or black, apparently normal; Body and head-entirely or almost entirely diluted to white on all parts except axillae and wing linings, which were heavily tinged cinnamon. The back and the wing coverts retained a distinct pattern of dusky, transverse barring. A less distinct pattern of faint barring was present ventrally on the rectrices. The coloration of this individual seems to have resulted from extreme dilution of the rufous-brown, and cinnamon pigmentation in most of the plumage and should therefore be considered as a case of imperfect albinism (Pettingill 1956).