Treesearch

We assessed the occurrence patterns of Marbled Murrelets (Brachyramphus marmoratus) offshore of Waddell Creek, in central California. Data were derived primarily from cruises during the height of the murrelet breeding season, in June, between 1986 and 1994, as well as some cruises during the prebreeding period, February to early April. The large majority of sightings occurred within 10 km of Point Año Nuevo, directly offshore the species’ breeding area. Only three sightings occurred farther offshore (12-24 km). The physical factors that explained a small but significant portion of variabili...

We described habitat associations of Marbled Murrelet (Brachyramphus marmoratus) nesting (n = 10) and occupied (n = 184) sites in Oregon. We compared habitat characteristics of 177 occupied sites to a random sample of 9,625 sites (n = 531) of unknown murrelet status. In addition, we briefly described the characteristics of 22 nests and compared 10 of the nest sites to adjacent sites. In general, occupied sites were older, had larger midstory trees, and had larger and greater densities of dominant (or remnant) trees than random sites. In addition, dominant tree height and density, midstory...

Evidence of breeding and natal dispersal in alcids is typically provided by the resightings of banded birds, the establishment of new colonies, and/or evidence of immigration to established colonies. The difficulties in banding, observing, and censusing Marbled Murrelets at nesting areas preclude using any of these methods for this species. Based on the limited number of nests observed in consecutive breeding seasons, breeding site fidelity (birds breeding in the same nest as the previous year) may be lower than most other alcids. This is likely due to low breeding success associated with...

The majority of Marbled Murrelets (Brachyramphus marmoratus) nest in Alaska, where they sometimes nest on the ground, and their nesting habitat requirements are not well understood. The inland activity of murrelets was surveyed, and habitat features measured, between 1991 and 1993, in Prince William Sound, Kenai Fjords National Park and Afognak Island, Alaska (n = 262 sites). We used these data to develop statistical models that explain variation in murrelet activity levels and predict the occurrence of occupied behaviors (indicative of nesting), based on temporal, geographic, topographic,...

We summarize available information on Marbled Murrelet (Brachyramphus marmoratus) productivity and sources of mortality compiled from known tree nests in North America. We found that 72 percent (23 of 32) of nests were unsuccessful. Known causes of nest failure included predation of eggs and chicks (n = 10), nest abandonment by adults (n = 4), chicks falling from nests (n = 3), and nestlings dying (n = 1). The major cause of nest failure was predation (56 percent; 10 of 18). Predators of murrelet nests included Common Ravens (Corvus corax) and Steller’s Jays (Cyanocitta stelleri); predation...

Most Marbled Murrelets (Brachyramphus marmoratus) in British Columbia nest in the Coastal Western Hemlock biogeoclimatic zone. In this zone, detection frequencies were highest in the moister ecosections and in low elevation forests. Nests and moderately high levels of activity were also found in some forest patches in the subalpine Mountain Hemlock zone. There was no evidence of nesting in subalpine scrub forest, lowland bog forest, or alpine tundra. Studies on the Queen Charlotte Islands and Vancouver Island reported consistently higher detection frequencies in old-growth than second...

A variety of factors influence the results of surveys conducted for Marbled Murrelets (Brachyramphus marmoratus) in the forest. In this paper we examine observer variability and survey station placement as factors influencing murrelet survey data. A training and evaluation protocol (Ralph and others 1993) was developed to insure high field abilities and comparability of data among and between observers. Site characteristics which may limit the hearing and sighting of murrelets (e.g., wind, road, or stream noise, visual obstructions) can largely be controlled through the sensible placement...

We summarize the characteristics of 61 tree nests and nesting stands of the Marbled Murrelet ( Brachyramphus marmoratus ) located from 1974 to 1993 in Alaska, British Columbia, Washington, Oregon, and California. Evidence of breeding 30-60 km inland was common in California, Oregon, and Washington. Nesting greater distances from the coast may have evolved to avoid nest predation by corvids and gulls which are more abundant in coastal areas. In California, Oregon, Washington, and British Columbia, murrelets nested in low elevation old-growth and mature coniferous forests, with multi-layered...

Patterns in the daily activity of Marbled Murrelets (Brachyramphus marmoratus) at inland sites has been studied throughout their range from California to Alaska. Murrelets are most active at inland sites around dawn, and to a lesser degree, at dusk. Throughout their range, peak levels of activity (detections) occur in the hour around dawn, but detections begin progressively earlier as one moves from south to north, corresponding to changing daylight regimes (e.g., California: 45 minutes before to 75 minutes after sunrise; Alaska: 90 minutes before to 40 minutes after sunrise). Timing of...

I compared the mean level of detections of Marbled Murrelets by month over five years at three inland sites in northern California. These areas all have relatively high levels of detections. There were no significant differences in mean detection levels year to year at any site, and for any month with the exception of April at one site. This lack of evidence for significant interannual variation in the number of detections of birds suggests that data from any one of the years would have been sufficient to detect occupancy of these stands by Marbled Murrelets. Caution must be used in...