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Standardized surveys for abundance and distribution of marbled murrelets (Brachyramphus marmoratus) at sea from 1992 to 1999 were analyzed using 100-m-wide strip transects for a 106-km portion of the central Oregon coast from the Siletz River to the Sillslaw River. Densities showed a significant decline beginning in 1996, with no increase thereafter. Densities decreased in both near-shore and offshore strata

Density estimates for marbled murrelets (Brachyramphus marmoratus) are obtained from at-sea surveys, but survey methods vary among regions. We compared the performance of a single observer with that of an observer operating in a paired-observer team in detecting marbled murrelets during marine surveys in the San Juan Islands, Washington, USA. Performance was measured against an independent observer (IO) who selected a sample of birds; we used this sample to determine the proportion detected by the observer(s). To represent probability of success, we used a function that was the product of a half-normal detection function modified to incorporate scale covariates and a logistic function to represent detection probability on the line, g(0). We used Akaike's Information Criterion (AIC) to select the set of covariates (murrelet group size and behavior, observer, wave height, cloud cover, and the number of primary observers) that best explained variability in g(0) and scale (effect of distance on detection probability). Single observers detected 80% of 274 targets, and paired observers detected 84% of 343 targets selected by the IO. Detection probability was affected by observer, murrelet behavior, and group size; wave height influenced the effect of distance on detection probability. Estimates of detection probability on the line [g(0)] ranged from 0.78 to 0.95 with a single observer; average estimates from paired observers were similarly biased (0.84 to 0.93), but less variable. Options for surveying include retaining single- or paired-observer surveys and accepting bias and variability from g(0) < 1, attempting to reduce bias by using 2 or more observers in a different configuration with a different search pattern, or using an independent observer to remove bias.

Marbled Murrelets (Brachyramphus marmoratus) are threatened seabirds that nest in coastal oldgrowth coniferous forests throughout much of their breeding range. Currently, observer-based audio-visual surveys are conducted at inland forest sites during the breeding season primarily to determine nesting distribution and breeding status and are being used to estimate temporal or spatial trends in murrelet detections. Our goal was to assess the feasibility of using audio-visual survey data for such monitoring. We used an intensive field-based survey effort to record daily murrelet detections at seven survey stations in the Oregon Coast Range. We then used computer-aided resampling techniques to assess the effectiveness of twelve survey strategies with varying scheduling and a sampling intensity of 4-14 surveys per breeding season to estimate known means and SDs of murrelet detections. Most survey strategies we tested failed to provide estimates of detection means and SDs that were within ?20% of actual means and SDs. Estimates of daily detections were, however, frequently estimated to within ?50% of field data with sampling efforts of 14 days/breeding season. Additional resampling analyses with statistically generated detection data indicated that the temporal variability in detection data had a great effect on the reliability of the mean and SD estimates calculated from the twelve survey strategies, while the value of the mean had little effect. Effectiveness at estimating multi-year trends in detection data was similarly poor, indicating that audio-visual surveys might be reliably used to estimate annual declines in murrelet detections of the order of 50% per year. Received 1 7January 2001, accepted 29June 2001.

I used high-frequency marine radar to count marbled murrelets (Brachyramphus marmoratus) entering 20 watersheds in Clayoquot Sound, Vancouver Island, British Columbia, Canada, in 1996-1998. My goal was to develop standard protocols for radar inventory and to explain landscape-level habitat associations of this threatened species. Dawn counts were consistently higher and less variable than dusk counts, but both sampling periods produced similar rankings of watersheds and proportionate numbers of murrelets. Most dawn surveys showed a unimodal pre-sunrise pulse of incoming murrelets, but a few dawn surveys showed post-sunrise pulses, likely caused by repeat visits by some birds. These post-sunrise pulses, although rare, inflated estimates of incoming murrelets and were avoided by restricting analyses to pre-sunrise counts. Dawn and dusk counts were higher on cloudy days (≥80% cloud cover) than on clear days, but among cloudy days there was no additional effect on counts caused by precipitation (thick fog or drizzle). Numbers of murrelets entering watersheds varied seasonally, reflecting the breeding chronology, but counts restricted to the core period covering incubation and chick-rearing (mid-May through mid-Jul) showed no significant seasonal effects. Counts varied among years at some stations, but when all stations were considered together, no significant inter-annual variation occurred. Murrelets sometimes flew over low ridges (200-600 m), taking shortcuts into watersheds or crossing from 1 watershed into another. I therefore adjusted the boundaries of some inland catchment areas (based on topography and likely flight paths) to match correctly counts made at the watershed mouths with the appropriate inland catchment area. Radar counts at 18 watersheds were significantly correlated with total watershed area, areas of mature (>140 year old) forest, and-most strongly-with areas of mature forest below 600 m. Logging produced negative impacts. Three of the 5 watersheds with extensive logging of low-elevation forest had fewer murrelets per area than unlogged watersheds or those that were

Although the Marbled Murrelet (Brachyramphus marmoratus) usually nests in mature coniferous trees throughout most of its range, in south-central Alaska Marbled Murrelet nests have been found on the ground in unforested areas as frequently as they have been found in older-aged forests. Because ground nests are typically found serendipitously, the relative occurrence of ground nesting is unknown. Further, the importance of unforested habitat to nesting murrelets is unknown. Comparing murrelet dawn activity (related to breeding activity) in forested and unforested habitats in the Kenai Fjords National Park, Alaska inJuly, 1993, we found that the number of inland murrelet "detections" was appreciably and significantly higher in forested than in unforested habitat (forested stations: x = 48.1 detections per station, SE + 7.7; unforested stations: x = 17.4, SE ? 4.0). Visual observations of murrelets flying close to the ground or trees are indicators of nesting, and were much more frequently observed in forested areas. Within unforested areas, murrelet land-use may be related to the amount of low vegetation and shrubs, as stations with more vegetation had higher dawn activity. These data suggest that, although Marbled Murrelets nest on unforested ground in south-central Alaska, forested habitat is much more heavily occupied than unforested habitat. We propose that habitat devoid of older-aged coniferous forest is suboptimal due to the shortage of nest sites that are as protected from predators and weather as those provided by the 3-dimensional structure of mature trees and older-aged forests. Received 4 May 2000, accepted 30July 2000.

We report on nests of radio-marked marbled murrelets (Brachyramphus marmoratus) nesting in unusual habitats in southwestern British Columbia. We found 1 confirmed and 2 probable marbled murrelet nest sites on cliffs. These represent the 1st substantiated accounts of ground nesting in this species south of Alaska. In addition, we found a marbled murrelet nesting in a 130 (?5)-yr-old red alder (Alnus rubra) deciduous tree. A survey of available nesting sites in both the nest tree patch and the mixed coniferous-deciduous stand adjacent to this deciduous nest tree indicated most potential nesting trees were deciduous and that deciduous trees had a higher density of potential nesting sites. These unusual sites represent a very small proportion (7% of confirmed sites, 3% of suspected sites) of nest sites found in British Columbia using radio telemetry. Both confirmed nest sites consisted of a platform with heavy epiphyte cover and an adjacent flyway, similar to nests found in mature coniferous forest.

Morphometrics (culmen length, bill height, bill width, wing chord length, and tarsus length) were taken on 664 marbled murrelets at Desolation Sound and Mussel Inlet, British Columbia, during 1994 to 1997, in order to assess morphological differences within and between populations and the accuracy of a discriminant function analysis to identify the sex of birds. An assessment of interand intra-observer variability in measurements was also made. Significant inter-observer effects and some intra-observer effects were found. Data from recaptured murrelets indicated they had decreased in size with age, which was attributed to interobserver effects. Wing chord length had the highest measurement error (66.8%) among observers and tarsus length had the lowest error (36.8%). Deviations of measurements from the mean were compared among years and sites. No inter-annual differences were detected in any morphometric at Desolation Sound. Significant differences in culmen length, wing chord length, and tarsus length were found between birds from Mussel Inlet and Desolation Sound, which might indicate discrete populations. The degree of sexual dimorphism in this species was small (measurements of females average 98% of corresponding measurements of males) and discriminant function analysis revealed only about a 70% success rate in allocating birds to sex; therefore, its widespread use in this species is not recommended. Future studies of marbled murrelets, or other avian species, which involve large numbers of personnel, should incorporate extensive training of all observers, with data continually cross-checked in order to minimize intraand inter-observer differences in measurements.

We examined effects of season, time of day, tide stage, tidal oscillation, and sea surface temperature on Marbled Murrelet (Brachyramphus marmoratus) abundance and distribution at sea. We also evaluated whether constraining surveys to specific time periods or tide stages would reduce temporal variability in counts. Murrelets were surveyed daily from small boats and from shore in Auke Bay and Fritz Cove, Alaska, from May through August in 1992 and 1993. Murrelet numbers were high before egg-laying, declined by more than half during egg-laying and incubation and were highly variable during chick-rearing and fledging. Murrelet numbers were highest in early and late morning and declined throughout the day, sometimes increasing slightly in the evening. Peak murrelet numbers occurred on high or falling morning tides, especially in shallow areas where Pacific sand lance (Ammodytes hexapterus) were abundant. Differences between years in murrelet abundance and breeding phenology probably resulted from interannual differences in the pattern of seasonal warming and subsequent effects on production at lower trophic levels. We recommend that surveys for trends in abundance in Southeast Alaska be conducted in early morning, in June, at high or falling tides. Power analyses indicated that surveys conducted in this manner would minimize the number of years required to detect a significant change in abundance. Received 6 April 2000, accepted 3June 2000.

I sought to determine which seabird species initiated small, ephemeral, multispecies feeding flocks in Prince William Sound, AK (PWS). I observed 47 feeding flocks at five sites duringJune 1996 and determined the initiating species at 34. All of the latter flocks were initiated by pursuit divers, of which 76.5% were Marbled Murrelets (Brachyramphus marmoratus), the most abundant seabird in PWS. Formation of feeding flocks followed either of two scenarios: 1) larids were attracted to a feeding location by the presence or activity of Marbled Murrelets (26.9%), or 2) both larids and murrelets were present and flock feeding began after the murrelets dove from the surface (50.0%). Other principal participants were Black-legged Kittiwakes (Rissa tridactyla) and Glaucous-winged Gulls (Larus glaucescens). Received 14 April 1999, accepted I June 1999.

We measured activity levels of marbled murrelets (Brachyramphus marmoratus mar- moratus) at 4 inland locations in southeastern Alaska from December 1992 through November 1996. Activity levels were measured by recording the number of times marbled murrelets were detected during dawn surveys (n = 281). Detection rates peaked during the last half of July, following or coinciding with fledgling periods reported elsewhere. Post-sunrise detections and length of activity periods also peaked in July, possibly because of increased activity by breeding birds. Marbled murrelets were absent during September through October, corresponding to the pre-basic molt. Detection rates were also low in April during the pre-alternate molt. Throughout the rest of the year marbled murrelets were present during 90% of the surveys. Variability in detection rate did not decrease in winter. Our results support monitoring during the breeding season. We examined survey efficiency and found that the survey period in southeastern Alaska could be shortened substantially (31%) with only a small loss of detections (3%). Because few detections are made during some portions of the standard intensive survey (Ralph and others 1994), we recommend that other researchers examine their data to determine whether changes in the survey protocol for southeastern Alaska should be made.

On 13 June 1993, a new Kittlitz's murrelet (Brachyramphus brevirostris) nest was discovered near Red Mountain on the Kenai Peninsula, Alaska. The nest was on a 22° slope at about 900 m elevation with a northeast aspect, and contained a 60.2 x 40.6 mm egg that weighed 49.0 g. Downy feathers and weathered fecal material found at the nest indicated re-use from a previous year, suggesting possible nest site fidelity. The nest was located in an area scoured by winds and free of snow during early spring, suggesting that this may be an important mesoscale factor influencing selection of nesting habitat. Proximity to suitable foraging habitat, particularly sheltered bays and glacial river outflows, may affect breeding habitat choice over larger spatial scales.

Analyses of marine bird surveys conducted in Prince William Sound, Alaska in July 1972 were compared to surveys in July 1989, 1990, 1991, and 1993 and indicated that populations of several taxa of marine birds that prey on fish have declined in Prince William Sound, but most taxa that feed on other prey species, such as benthic invertebrates, have not declined. Red-throated Loon (Gavia stellata), Pacific Loon (G. pacifica), cormorant (Phalacrocorax spp.), Surf Scoter (Melanitta perspicillata), Bonaparte's Gull (Larus philadelphia), terns (Sterna spp.), Pigeon Guillemot (Cepphus columba), Brachyramphus murrelets (Brachyramphus marmoratus and B. brevirostris), Parakeet Auklet (Cyclorrhynchus psittacula), Tufted Puffin (Fratercula cirrhata), and Horned Puffin (Fratercula corniculata) populations declined by >50%. Most of these are piscivores, feeding on schooling fish. Some non-piscivorous taxa, such as Harlequin Ducks (Histrionicus histrionicus), goldeneyes (Bucephala clangula and islandica), and Black Oystercatchers (Haematopus bachmani), have increased in Prince William Sound between 1972 and 1989-1993, although a portion of the population was killed by the T/VExxon Valdez oil spill. Declines in piscivorous bird populations also have been documented in the Gulf of Alaska, the Bering Sea, and along the California coast in the past two decades and have been coincidental to changes in forage fish species in the North Pacific Ocean. Many of the declines appear to be related to changes in forage fish abundance that occurred during a climatic regime shift in the north Pacific Ocean, although some taxa were also affected by the Exxon Valdez oil spill. Received 11 November 1998, accepted 6January 1999.

Because the reproductive success of marbled murrelets (Brachyramphus marmoratus) cannot be efficiently monitored directly, we investigated a productivity index for marbled murrelets in Alaska that uses at-sea counts of hatching-year (HY) birds and after-hatching-year (AHY) birds. Our objectives were to define seasonal patterns of abundance by age class and to develop a protocol for estimating productivity. In Prince William Sound (PWS), we conducted replicate boat surveys at 2 sites in 1994 and 6 sites in 1995 (45-60 km of shoreline per survey). At all sites, numbers of AHY birds peaked in late July and declined throughout August, whereas HY birds appeared after 18 July and peaked between 28 July and 28 August. Because AHY numbers decreased in August, the percentage of HY birds increased. Numbers of HY birds in July-August ranged among sites from 2-13% of total murrelets. Comparing HY densities among sites and years, rather than HY:AHY ratios, might avoid problems associated with postbreeding migration of adults. The HY densities in July-August were highly correlated with June AHY densities; thus, HY:AHY ratios derived from AHY densities during incubation phase may be more reliable than concurrent July-August HY:AHY ratios. We decreased variance in juvenile densities by selecting a core survey period of approximately 3 weeks, centered around peak juvenile abundance. One potential method of identifying the core period is the numbers of adults holding fish for delivery to inland nests. Power to detect a 50% change in juvenile abundance generally was >80% when 5 surveys occur each year for ≥10 years (when CV = 0.4 and α = 0.1). Power to detect a 50% change in abundance in 5 years is >80% when 8 surveys are conducted each year. The slope formed from the regression of June AHY versus July-August HY counts may also provide a regional index of marbled murrelet reproductive success. Our results suggest that marbled murrelet productivity in PWS is high compared to regions farther south.

The nest of a marbled murrelet (Brachyramphus marmoratus) was found at the in- land edge of the species' range late in the nesting season in 1994. The nest was located 47.9 m high in an 80.5-m high, 1.8-m diameter old-growth Douglas-fir, 49 km E of the Pacific Ocean in Douglas County, Oregon. A single chick apparently was fledged successfully after 17 August. Mean landing time of adults at the nest tree was 25 min after sunrise, and 77% of morning detections included both visual and audio observations. It is likely that all observations of mur- relets in this stand were of a single pair of nesting birds.

We captured 575 Xantus' Murrelets (Synthliboramphus hypoleucus) with spotlights and dip nets at 3 islands in the Southern California Channel Islands during April and May of 1995-1997. Working at night (2100-0500 h), 3-person teams in inflatable boats located murrelets with a spotlight and captured them in dip nets from the waters near known breeding colonies at Santa Barbara, Anacapa, and San Clemente Islands. Our average capture rate was 4.7 murrelets hr'1, but we captured up to 12.3 murrelets hr. We recaptured 34 murrelets or 6% of the capture total. We recommend this simple, inexpensive, safe and effective night-lighting capture technique for Xantus' Murrelets and other seabirds. Received 7 March 1997, accepted 26 May 1997, final version received 26 September 1997.

Three marbled murrelet tree nests were discovered in the Carmanah-Walbran region on the west coast of Vancouver Island, British Columbia in 1992. A11 nests were located by climbing trees in an area where murrelets were active and were unoccupied when found. The nests were in Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) trees on large (> 35 cm dbh), moss-covered limbs that appeared accessible by the birds only from below. The nest trees were the largest trees within a 25-m radius and all sites were located in valleybottom old-growth (> 200 yr) forest. A11 previously known murrelet nests in British Columbia had been found in Sitka spruce trees. Marbled murrelets (Brachyramphus marmoratus) are associated with the old-growth forest habitat along the Pacific coast of North America, where they nest on branch platforms in large conifers (Quinlan and Hughes 1990, Singer et al. 1991, 1995, Hamer and Nelson 1995a, Kerns and Miller 1995, Manley and Kelson 1995, Naslund et al. 1995). Marbled murrelets have also been found nesting on the ground and in cavities in southcentral and western Alaska (Simons 1980; Johnston and Carter 1985; Mendenhall 1992). In areas where murrelets nest in trees, their nesting habitat is threatened by logging and development. In the United States, the marbled murrelet is listed as a threatened species (U. S. Fish and Wildlife Service 1992) and although it is on the provincial blue-list of endangered species in Canada, only a small portion of murrelet nesting habitat is protected (Rodway 1990). In 1990 and 1991, forest surveys for marbled murrelets were initiated (Rodway et al. 1991, Manley et al. 1992) and the first 2 tree nests were located (Manley and Kelson 1995). These records were all associated with old-growth forest habitat. Limited information on marbled murrelet nest-site characteristics in Canada has seriously restricted the facilitation of meaningful management decisions for the conservation of this species (Rodway et al. Present address: Box 27062, Victoria, British Columbia, Canada V9B 5S4. 1992). This paper describes the characteristics of 3 additional murrelet nest sites found in the Carmanah and Walbran valleys of British Columbia in 1992.

We discovered 3 active marbled murrelet (Brachyramphus marmoratus) nests in the same coast redwood (Sequoia sempervirens) tree between 1991 and 1994. The nest tree was in an old-growth redwood-Douglas fir (Pseudotsuga menziesii) forest in Big Basin Redwoods State Park, Santa Cruz County, California. Two of the nests, situated on different branches, were monitored intermittently through fledging in 1991 and 1992. The 1994 nest was in the 1991 nest cup. Eggshell fragments with indications of predation were found under the nest tree in 1993, suggesting that the tree may have been used for at least 4 consecutive years. One fragment encompassed almost two-thirds of a complete egg and is described here. Below-canopy flights were common within the nesting stand, but were concentrated along repeatedly used flight routes. Adults accessed nest sites by flying for at least 100 m through the canopy along these routes. Fledging occurred on 3 July 1991 and on 7 June 1992, 19 and 18 min after sunset, respectively. At fledging, murrelets neither vocalized nor behaved conspicuously. Fledging occurred on the first day in which the nestling had lost all or nearly all of its concealing down. On both occasions, the nestling fledged alone and flew a route not used by the adults. The small (24 cm long) marbled murrelet (Brachyramphus marmoratus) is the only member of the alcid family that nests in trees. It nests on high, large-diameter branches of old-growth trees found in coastal coniferous forests (Hamer and Nelson 1995a). In California, logging of such forests has eliminated most murrelet habitat and reduced population levels such that, in 1992, the species was listed as endangered by the state of California, and as threatened throughout California, Oregon and Washington by the U.S. Fish and Wildlife Service (California Fish and Game Commission 1992, U.S. Fish and Wildlife Service 1992, Nelson and Singer 1994). Through 1994, 65 murrelet tree nests have been found in North America, of which only 22 were active (Nelson and Hamer 1995a). Six of these active nests were from Big Basin Redwoods State Park, Santa Cruz County, California (Binford et al. 1975; Singer et al. 1991, 1992; this study). We conducted field observations of marbled murrelets in Big Basin Redwoods State Park during the breeding seasons of 1991 through 1994. Our primary goal was to observe the fledging of a marbled murrelet from a tree nest, a previously unobserved phenomenon. A secondary goal was to describe behavioral and forest-stand characteristics associated with a successful nest. We report here on the first murrelet nest to be found in a coast redwood (Sequoia sempervirens), the first direct observations of fledging from a tree nest, the first reported re-use of a known successful nest, and the first probable instance of murrelets nesting in the same tree for 4 consecutive years.

Between 1990 and 1992, 9 active marbled murrelet (Brachyramphus marmoratus) tree nests were found in western Oregon. Incubation was shared equally between adult birds with each bout lasting approximately 24 hr. Incubation exchanges took place during a relatively narrow time period, 30 to 8 min prior to official sunrise, and on average lasted 16 sec. Feedings occurred primarily at dawn, but adults also returned to feed nestlings at dusk and occasionally during mid-day. In contrast to incubation exchanges, the time adults arrived at nests to feed nestlings varied, both within and among nests, and occurred within 104 min and 90 min of official sunrise and sunset, respectively. The duration of feeding visits was also highly variable and ranged from 18 sec to 46 min in length (x = 16.7 min, SE = 1.3). Weather influenced arrival times of adults during incubation and nestling stages; on average birds arrived earlier on clear (' 75% cloud cover) than cloudy (> 75%) mornings. Murrelets at each nest used consistent flight paths when entering and exiting nest trees. Soft vocalizations from adults ("groan" and "whistle" calls) and chicks ("begging") were heard at all nests during incubation and feeding visits. In contrast, loud calls ("keer" and "groan"), which were frequently uttered by adults in flight, were uncommon and detected at only 3 nests. The behaviors observed at murrelet nests were secretive and probably designed to minimize detection by predators. While these behaviors pose challenges for locating nests in forests, knowledge of marbled murrelet activity patterns and behaviors associated with nesting will aid in monitoring efforts and in identifying areas that are used for nesting. The behavior of marbled murrelets (Brachyramphus marmoratus) at nest sites is poorly known. The first marbled murrelet ground and trees nests were not found until 1959 and 1974, respectively (Day et al. 1983, Binford et al. 1975). Locating nests for study has proved difficult because murrelets nest solitarily or in loose aggregations, and are active primarily in low light levels (Sealy and Carter 1984, Eisenhawer and Reimchen 1990, Rodway et al. 1993, Naslund et al. 1995, Nelson and Hamer 1995a). In addition, tree nesting murrelets nest on naturally occurring branch platforms high in the canopies of large, mature conifers (Singer et al. 1991, 1995, Nelson and Hamer 1992, Hamer and Nelson 1995a, Jordan and Hughes 1995, Kerns and Miller 1995, Manley and Kelson 1995, Naslund et al. 1995). The marbled murrelet was recently listed as a threatened species in Washington, Oregon, and California (U. S. 1 Present address: Department of Forest Science, Oregon State University, 020 Forest Sciences Lab, Corvallis, OR 97331-7501, USA. Fish and Wildlife Service 1992) and information on its activity patterns and behaviors at nests is needed to develop monitoring protocols and define future research directions. Prior to 1992, the characteristics of marbled murrelet nests and nesting sites had been documented and described at 10 ground nests in Alaska and 6 tree nests from southcentral Alaska to central California (Binford et al. 1975, Simons 1980, Hirsch et al. 1981, Day et al. 1983, Johnston and Carter 1985, Carter and Sealy 1987b, Quinlan and Hughes 1990, Singer et al. 1991). However, information on the behavior and activity patterns of murrelets at nests was summarized at only 4 of these sites. At 2 ground nests in Alaska, Simons (1980) and Hirsch et al. (1981) described the timing and frequency of feeding visits and measured growth of nestlings. More recent observations of 2 tree nests in central California (Singer et al. 1991, Naslund 1993) provided details on the timing and frequency of nest visits, and descriptions of adults and chicks during feeding bouts at the nest. Additional information on

We summarized data from 2,479 intensive 2-hr morning surveys and 950 general surveys (< 2 hr duration) between 1988 and 1994 to determine the distribution of marbled murrelets (Brachyramphus marmoratus) in mature and old-growth forest stands on the Siskiyou National Forest of southwestern Oregon. Marbled murrelets were detected on 449 of these surveys. Murrelets were found in Douglas-fir (Pseudotsuga menziesii) or coast redwood (Sequoia sempervirens) stands within the western hemlock (Tsuga heterophylla) vegetation zone on the western part of the Forest. Murrelets were not detected in the mixed conifer/mixed evergreen zone on the eastern part of the Forest. This zone, which extends from 20-60 km inland, is drier and has smaller trees than the western hemlock vegetation zone. The distribution of murrelets on the Siskiyou National Forest may be limited by the availability of trees with suitable nesting limbs. Marbled murrelets (Brachyramphus marmoratus) are closely associated with older-aged coniferous forests (Marshall 1988, Hamer 1995, Hamer and Nelson 1995a, Miller and Ralph 1995). Unlike most species of the family Alcidae, marbled murrelets most often nest in trees. Sixty-five tree nests have been found in North America (Hamer and Nelson 1995a). Stands used for nesting by murrelets usually have large-diameter trees, relatively low canopy closure, and high numbers of potential nesting platforms (Grenier and Nelson 1995, Hamer and Nelson 1995a). The marbled murrelet was listed as a threatened species in Washington, Oregon and California (U.S. Fish and Wildlife Service 1992) primarily because of habitat loss from logging and development. Currently, surveys for marbled murrelets are mandatory for all proposed activities (primarily timber harvest) on federal lands within 80 km of the ocean that may affect their potential (old-growth and mature) habitat. Murrelets primarily travel up to 84 km inland in search of suitable nest sites (Carter and Sealy 1986, Paton and Ralph 1990, Nelson et al. 1992, Hamer 1995, Hamer and Nelson 1995a), although sightings are known from as far as 108 km inland in Oregon, and 101 km in British Columbia (Rodway et al. 1992; S. K. Nelson, pers. comm.). S. K. Nelson (unpubl. data) and P. W. C. Paton (unpubl. data) conducted limited surveysfor murrelets on the Siskiyou National Forest between 1988 and 1990. They found murrelets as far as 42 km inland. Additional information was needed on murrelet distribution in the coastal forests of the Siskiyou Mountains to aid in habitat management. Therefore, between 1991 and 1994 we conducted additional surveys for murrelets. The purpose of this study was to summarize marbled murrelet distribution from existing information and our surveys, and relate its presence to general habitat features. Because marbled murrelets nest primarily in large trees with large moss-covered limbs and they appear more abundant close to the coast (Hamer and Nelson 1995a), we hypothesized that factors such as habitat suitability, vegetation type, topography, climate (including temperature and relative humidity), and distance from the ocean would limit murrelet distribution.

To identify potential marbled murrelet (Brachyramphus marmoratus) nesting habitat we surveyed western Prince William Sound, Alaska, for murrelet activity between 12 June and 3 August 1992. We evaluated methods specific to boat-based surveys (vessel and shoreline) by comparing the number of murrelet detections and subcanopy flights during dawn watches adjacent to inland stations. We conducted boat-based surveys from a l9-m vessel (N = 44) and from shoreline stations (N = 23), and concurrently from adjacent inland stations (N = 17). Murrelet activity level and seasonal variation of activity were not significantly different when conducted from the vessel or from shoreline and were similar to surveys at adjacent inland stations. Survey stations near bay heads had higher activity levels than those near exposed coastlines, with the exception of bays that were glaciated or recently deglaciated. We used a timber-type database on a geographic information system to analyze relationships between murrelet activity and habitat within a l-km radius of each survey station. Forested habitat, particularly forests with trees > 28 cm diameter, showed the strongest correlation to murrelet activity. Boat-based surveys are useful for a preliminary identification of potential murrelet nesting areas in remote and otherwise inaccessible, coastal habitat. In North America, most marbled murrelets (Brachyramphus marmoratus) breed in Alaska (Mendenhall 1992), and within this state, Prince William Sound (PWS) is 1 of 3 major population centers (Piatt and Ford 1993). The PWS population of murrelets was affected in the 1989 Exxon Valdez oil spill by direct mortality and possibly by disruption of breeding (Piatt et al. 1990; Ecological Consulting, Inc. 1991; Kuletz, in press). Part of the restoration effort included the identification of marbled murrelet nesting habitat throughout the affected area. During the breeding season most of the murrelet population is found offshore of old-growth forests (Piatt and Ford 1993), and many studies have shown that mature and old-growth forest constitute the primary habitat for nesting marbled murrelets south of Alaska (Paton and Ralph 1990, Rodway et al. 1993, Hamer and Nelson 1995a, Ralph et al. 1995a). In southcentral Alaska, murrelet nesting habitat includes both forested and nonforested areas (Simons 1980, Day et al. 1983, Kuletz et al. 1995). Search techniques based on observing murrelet behavior or signs of nesting (Singer et al. 1991, Nelson and Hamer 1992, Naslund 1993, Naslund et al. 1995, Nelson and Peck 1995) and radiotelemetry (Quinlan and Hughes 1992) have been used to locate small numbers of murrelet nests. Unlike many seabirds, marbled murrelets are thought to nest at relatively low densities (Carter and Sealy 1986, Naslund et al. 1995). This, combined with their concealing plumage and secretive behavior, make nests difficult to locate. Because of the difficulty in finding nests, many efforts to define habitat use have focused on surveying marbled murrelets when they fly to inland nesting areas around dawn (e.g., Paton et al. 1990). Large-scale surveys of murrelet activity at inland sites outside of Alaska are facilitated by road and trail systems that provide access to potential nesting habitat. In contrast, much of Alaska is difficult to traverse, and most coastal areas are remote and accessible only by boat or aircraft. Searches from the ground for murrelet nests are too labor-intensive to use over large areas. Before this study, methods for surveying and mapping murrelet nesting habitat over a large and remote geographic area had not been developed for Alaska. We tested new boatbased methods to survey sunrise activity of

A modified vehicle-mounted, X-band marine radar system was used to study the movements of marbled murrelets (Brachyramphus marmoratus) at inland and coastal sites in northern California during July. The ability of the radar to discriminate murrelets from other targets, and to estimate abundance was assessed. Murrelets were detected by radar at distances up to 1.3 km. Radar recorded the distance, ground speed, flight direction, and flight behavior (such as circling). The average ground speed of murrelets was 77 km/hr (range = 56-105 km/hr). Ground-based observers recorded an average of 67% of the murrelets within 700 m at inland sites that were recorded by radar. Using ground speed as a identification criterion, radar correctly distinguished murrelets from other bird species 87.8% of the time at coastal sites and 97.8% at inland sites. The only species contributing to identification error at inland sites was the band-tailed pigeon (Columba fasclata). Radar has advantages over round-based observers as it does not rely on murrelets to vocalize for detection and can detect murrelets over a large area, regardless of variability in light conditions, observers' auditory and visual abilities, fog, and background noise. The benefits of using radar to understand the inland flight behavior of murrelets include better interpretations of ground-based observer survey data, better estimates of the number of birds using an area, collection of data that are not biased by murrelet vocalization rates, increased understanding of landscape level flight behaviors and use of flight corridors, 24-hr sampling ability, and a more detailed analysis of seasonal and daily changes in abundance inland sites.

We surveyed marbled murrelets (Brachyramphus marmoratus) at Long Inlet and Shields Bay in the Queen Charlotte Islands, British Columbia, from May through July during the 1990 breeding season. Abundance varied daily and through the season. Maximum counts at sea were recorded prior to the egg-laying period in early May, and numbers were lowest in mid-June, during incubation, at both Long Inlet and Shields Bay. Mean numbers peaked in July during the latter part of the nestling period at Long Inlet but remained low at Shields Bay. The distribution of birds in Long Inlet changed over the season with a greater proportion of birds gathering at the head of the inlet as the season progressed. More birds were observed on morn- ing surveys, 2-5 hr after sunrise, than on afternoon and evening surveys in Long Inlet. In Shields Bay, birds were more abundant in the evening. Numbers of detections in the forest peaked in late July at both sites and were positively correlated with abundance of murrelets in Long Inlet but not in Shields Bay. Contrasting patterns of abundance in Long Inlet and Shields Bay pose complications for survey design, and indicate that at-sea distribution does not dependably re- flect breeding distribution.

We discovered 2 marbled murrelet (Brachyramphus marmoratus) tree nests in West Walbran Valley on the west coast of Vancouver Island, British Columbia, by observing murrelet behavior during dawn surveys and climbing potential nest trees. Both nests were in old-growth Sitka spruce (Picea sitchensis) trees. They were unoccupied when found but each had distinct fecal rings and contained eggshell fragments, indicating that they had been used recently. These were the first marbled murrelet nests found in British Columbia and the first nests located in Sitka spruce trees within the murrelet's range in North America. Marbled murrelets (Brachyramphus marmoratus) are widely distributed in the nearshore waters of British Columbia (Campbell et al. 1990), with 45,000-50,000 breeding birds in the population (Rodway 1990, Rodway et al. 1992). Research before 1990 focused primarily on birds at sea (Sealy 1974, Carter 1984, Sealy and Carter 1984), few forest surveys had been conducted, and no marbled murrelet nests had been documented in the Province. Nesting evidence, derived from records of young discovered at inland locations and probable nests found during logging operations (Carter and Sealy 1987b, Campbell et al. 1990), indicated that murrelets likely nested in coastal old-growth forests in British Columbia. These forests are threatened by logging and development, especially on Vancouver Island. Because of these and other threats, the marbled murrelet was listed as threatened in British Columbia in 1990

In 1991 and 1992, we located 14 tree nests of the marbled murrelet (Brachyramphus marmoratus) on Naked, Kodiak, and Afognak islands, Alaska. All nests were in old-growth forests on moss-covered platforms of western hemlock (Tsuga heterophylla; N = 2), mountain hemlock (T. mertensiana; N = 7), and Sitka spruce (Picea sitchensis; N-5). Most nest trees were located in large tree-size class and volume-class forests (the highest in the region). In addition, 21 trees were recorded where murrelets landed but where nests were not known to occur. The diameters at breast height (dbh) of nest and "landing" trees were 30-104 cm and 35-118 cm, respectively. Naked Island nest and landing trees were similar to each other. They were larger in diameter, had more potential nest platforms, and had greater epiphyte cover than did the 9 closest upper-canopy trees adjacent to each. Nest trees were similar to those at more southern latitudes in that they were old-growth conifers that contained large moss-covered platforms with foliage shielding the nest from above. Sitka spruce possessed qualities that seem to be important to nesting murrelets more frequently than the other 2 conifer species. All 7 nests where reproductive success was known failed due to nest abandonment, predation or unknown causes. Reuse of landing trees, and nesting in a landing tree from the previous year, indicate some degree of site fidelity. The proximity of nest sites on each island suggested clumped or semi-colonial nesting. Marbled murrelets (Brachyramphus marmortus) are unusual for their family because they nest almost exclusively on large branches of old-growth or mature coniferous trees (Quinlan and Hughes 1990; Singer et al. 1991; Hamer and Nelson 1995a). They are also remarkable because they nest solitarily or in small groups, perhaps as far as 100 km inland (Carter and Morrison 1992; T. E. Hamer, pers. comm.). Characteristics of murrelet nests and nesting habitat have been difficult to document. In Alaska, most murrelets are distributed offshore of old-growth coniferous forests during the breeding season, and a small percentage are found offshore of treeless areas (Piatt and Ford 1993; Piatt and Naslund, in press). Only 1 tree nest and 5 ground nests were documented in Alaska prior to 1991 (Day et al. 1983, Johnston and Carter 1985, Quinlan and Hughes 1990), although many tree nests have been 1 Present address: US. Fish and Wildlife Service, Marine Mammals Management, 1011 E. Tudor Road, Anchorage, AK 99503, USA. found in the southern portion of the murrelet's range (Binford et al. 1975, Singer et al. 1991, 1994, Hamer and Nelson 1995a, Jordan and Hughes 1995, Kerns and Miller 1995, Manley

In 1992 and 1993, we repeated at-sea surveys of marbled murrelets (Brachyramphus marmoratus) in Clayoquot Sound, British Columbia, that were conducted originally in 1982. Murrelet distribution was determined by counting birds in 341 contiguous l-km2 quadrats in fiord, channel, and inshore marine habitats. Counts for this area totaled 4500 birds in 1982, 2704 birds in 1992, and 2622 birds in 1993 which constituted a 40% decline in the population size from 1982-1993. Birds were clumped in all surveys, with the highest densities in inshore (28, 14.3, 7.85 birds/km2 in 1982, 1992, and 1993, respectively) and channel (11.8, 9.1, 14.2 birds/ km2 in 1982, 1992, and 1993, respectively) marine habitats. The average change in the number of birds in each quadrat between the 1982 and 1992-93 surveys was significant for all quadrats combined, and individually for inshore quadrats. We consider the loss of nesting habitat in oldgrowth forest to be the probable cause of most of the observed population decline. By 1992 approximately 15-24.5% of the originally forested area in Clayoquot Sound had been logged. Oil spills, gill-net fishing, and oceanographic conditions (E1 Nino) were also considered as possible factors contributing to the population decline. This study is the first in North America to document a decline in a marbled murrelet population using a single, standardized at-sea survey technique. Marbled murrelets (Brachyramphus marmoratus) nest on tree branches in the canopies of oldgrowth and mature forests from southern Alaska to California (see recent su maries in Singer et al. 1991, Carter and Morrison 1992, Ewins et al. 1993, Hamer and Nelson 1995a). Standardized methods have been developed to monitor the activity of birds at inland nesting locations (e.g., Paton et al. 1990), but nests are difficult to locate and population size must be determined and monitored using surveys at ocean foraging areas (Sealy and Carter 1984). Previous to 1982, few at-sea surveys had been conducted for this species, and population size and distribution still are incompletely known for most areas on the west coast of North America (Carter and Morrison 1992). Thus, it has been difficult to document population trends for this species related to the loss of old-growth forest nesting habitat and mortality from oil spills and gill-net fishing. These threats are cause for concern and have led to the recent federal listing of the marbled murrelet as threatened in British Columbia, Washington, Oregon and California (Rodway 1990, U.S. Fish and Wildlife Service 1992) and state listing as endangered in California (California Fish and Game Commission 1992). In British Columbia, portions of the coast have been surveyed for marbled murrelet populations (Carter 1984, Sealy and Carter 1984, Kaiser et al. 1991, Lawrence and Backhouse 1991, Savard and Lemon 1992). Provincial estimates of 45,000-50,000 breeding birds (Rodway et al. 1992) are poorly substantiated for the most part because many areas have not been surveyed and survey data have been difficult to convert into reliable population estimates (Rodway et al. 1992, 1995). In addition, marbled murrelet populations have been considered to have declined in some areas in the province, based on anecdotal evidence (Brooks 1926, Pearse 1946) and loss of nesting habitat, yet quantitative data have not been available to investigate the degree of possible declines. Estimates of population size for large geographic areas have been published only for Clayoquot and Barkley sounds on the west

A marbled murrelet (Brachyramphus marmoratus) chick and three small eggshell fragments (UWBM 43053) were found on the ground in the Helena Creek drainage 9.5 km south and 2.5 km east of Darrington in Snohomish County, Washington. The chick was found partially decomposed on 27 June 1989; the eggshell fragments were found on 14 July 1989, 1.5 m from where the chick was found. The site is 2.7 km up Helena Creek from its confluence with Clear Creek, or 6.3 km from its confluence with the Sauk River. The specimens were found 18 m north of a dry stream bed (about 4 m wide), and 240 m east of Helena Creek; elevation is 594 m. The mouth of the Snohomish River, 45-50 km to the southwest, is the closest salt water. The chick was identified by comparison with a color photograph and descriptions of chicks by Simons (1980) and Binford et al. (1975). The bird was maggoty when found; judging from the size of the larvae, it had been dead for perhaps 4 days. The chick nevertheless retained most of its plumage upon preparation. It was entirely downy, with a wing length (wrist to the end of the down) of less than 25 mm, suggesting that it was less than 3 days old (Simons 1980; Hirsch et al. 1981). Subtracting 30 days for the incubation period (Sealy 1974), we estimate a hatching date of 22-23 June and a laying date of 23-24 May. The three eggshell fragments, the largest of which is 6 mm across, were identified based on their similarity to Kiff's (1981) description of marbled murrelet egg specimens and a comparison with an egg (UWBM 43031) found on Long Island in Pacific County, Washington, in July 1989 (J. Atkinson, pers. comm.). Using Munsell color notation (Anon. 1976), the fragments had a ground color between 5GY 8/4 and 2.5GY 7/4; one had a 7.5Y 7/6 spot, and two were marked with blackish scrawls. These colors closely resemble those of UWBM 43031 and Kiff's descriptions. The chick and eggshell were found in unmanaged forest dominated by western hemlock (Tsuga heterophylla) and western red cedar (Thuja plicata) on a west-facing 30% slope. The overstory was western hemlock and western red cedar with some pacific silver fir (Abies amabilis). The hemlocks were primarily 40-45 cm dbh (diameter breast-height), with an understory of 10-20 cm dbh hemlocks. Canopy closure was 60-65%. The forest understory was comprised of sword fern (Polystichum munitum), devil's club (Oplopanax horridum), Oregon grape (Mahoma oregona), bunchberry (Cornus canadensis), deer fern (Blechnum spicant), huckleberry (Vaccinium sp.), western hemlock and vine maple (Acer circinatum). Tree size in the stand and the presence of scattered large remnant Douglasfirs support the assertion that the area was burned in the large "Sauk Prairie" fire which occurred around 1825 (Henderson and Peter 1984). The chick and eggshell fragments were found at the base of a western hemlock 23 m high and 41 cm dbh. There was no depression, scrape, droppings or other evidence of a ground nest; furthermore, ground vegetation would make access to a ground nest difficult. The hemlock was heavily infected with dwarf mistletoe (Arceuthobium tsugense), which results in multiple branches at infected sites along the tree limbs (known as witches' brooms). Witches' brooms collect organic material and are often covered with thick blankets of moss. The hemlocks in this part of the drainage were heavily infected with dwarf mistletoe, making witches' brooms common. The hemlock was 3 m from a large remnant Douglas-fir (Pseudotsuga menziesii) about 38 m high and 152 cm dbh. This tree had many large lateral branches covered with moss. The top of the Douglas-fir extended above most of the canopy and projected over the hemlock under which the chick was found. The proximity of the chick and eggshells to the trunk of the hemlock and to each other suggests that they fell from a nest in either the hemlock or the Douglas-fir. This habitat is consistent with that of other marbled murrelet tree nests (Marshall 1988), although the nest may possibly have been in a smaller tree than usual. The western hemlock with witches' brooms could have provided sheltered horizontal moss-covered nest sites like the large limbs on which other nests have been found.