We implemented a unique tree-climbing effort to examine nesting-habitat selection of Marbled Murrelets (Brachyramphus marmoratus) in managed forest stands of Washington and Oregon during 1996-1999. Researchers climbed over 3000 trees to search for old and active murrelet nests during the breeding season (May-Sept.) in a random sample of stands known to be occupied by murrelets. Within these stands, characteristics of murrelet nest sites and non-nest sites were measured at three fine spatial scales: nest limb or platform, nest tree, and nest-site or forest patch (0.5 ha). We report results of a Bayesian hierarchical logistic regression model using three covariates at each of the three fine spatial scales. All three branch/platform scale covariates positively predicted nest occupancy with higher probabilities of nesting occurring at branches/platforms with higher horizontal cover, larger platform diameters, and higher moss cover. Tree scale characteristics associated with higher probabilities of nesting included higher platform counts and higher moss depth. Effect of tree diameter on probability of nesting was unclear. At the patch scale, lower probability of nesting occurred for stands with higher densities of trees with platforms. This unexpected relationship may be due in part to decreasing likelihood of observing a nest on a given platform when there are more platforms in a patch. Variation in tree size and percent canopy cover at the patch scale showed no clear association with nest selection at the patch scale. The prevalence of nests in Dwarf Mistletoe-infected hemlock trees may have partially obfuscated the effect of tree diameter on probability of encountering a nest in portions of our study area. Fine scale conservation efforts for Marbled Murrelets may include recruiting or retaining trees with larger numbers of platforms, large branches with high percentages of moss cover and horizontal cover, and younger trees with platforms created by Dwarf Mistletoe deformities.

ABSTRACT Collisions with tall anthropogenic structures (power lines, wind turbines, communication towers, and buildings) are a regular cause of mortality for nocturnal avian migrants. To better understand relationships between weather and migrant collision risk, we compared nocturnal hourly mean barometric pressure, temperature, relative humidity, wind direction, and wind speed to avian passage rates (targets/km/h) and flight heights during 1 year of spring and fall migrations near a recently reconstructed transmission line crossing Kittatinny Ridge, New Jersey, using 2 marine radars. We found lower spring flight heights associated with decreasing barometric pressures, temperatures, and relative humidity across all wind directions. Spring flight heights showed the strongest decreases with increasing wind speeds for headwinds and crosswinds while flight heights slightly increased with stronger tailwinds. Spring passage rates increased with lower relative humidity and higher temperatures. With increasing wind speeds, spring passage rates declined faster with headwinds and crosswinds, and only slightly with tailwinds. We found lower fall flight heights with decreasing temperatures and relative humidity, but the relationships varied by wind direction. The lowest flight heights occurred under tailwind and crosswind conditions. Increasing fall passage rates were associated with increasing barometric pressures and when wind speeds were lowest. Fall passages rates declined with higher wind speeds but were more gradual under tailwinds and crosswinds when compared to headwinds. Overall, 2–4% of birds migrated under conditions that would have placed them at risk of collision with the transmission lines. Similar studies conducted along migratory pathways could be used to predict nights where birds exhibit low flight heights around other obstacles along their migration path. These predictions could improve detection rates for carcass searches documenting relatively rare collision events. For sites with topographic features likely to concentrate nocturnal migrants, radar studies could be conducted before siting towers so that impacts to migratory birds could be avoided at these sites.

Artificial lights can disorient birds and lead to injury or death. In Atlantic Canada, lights attract birds at sites along the coastline and offshore, but the relative impacts of lights on birds in this region are largely unknown. We summarized data on stranded bird encounters submitted annually to the Canadian Wildlife Service, Environment and Climate Change Canada, and quantified light radiance values at a selection of industrial sites in the region. Stranded birds were reported from offshore oil and gas production platforms, support vessels, and seismic ships, and from onshore oil and gas refineries and construction facilities. Leach's Storm-Petrel (Hydrobates leucorhoa) was the most abundant bird species to be stranded: most were found alive offshore Newfoundland and Labrador, and were subsequently released. Landbirds dominated the stranded bird reports from Nova Scotia. Offshore platforms in Newfoundland and Labrador were brighter than onshore sites, and were brighter than platforms located in Nova Scotia, particularly during the Leach's Storm-Petrel breeding season, in part due to flaring activity. Stranding events were more likely during nights with little or no moonlight, but systematic searches for stranded birds, with documentation of search effort by trained personnel, are needed to better understand how light characteristics, weather, and the location of sites influence strandings, and to monitor the effectiveness of light mitigation. Minimizing the threat of light attraction for declining populations of Leach's Storm-Petrels in the Atlantic is of particular importance given the species' current conservation status.

Birds harbor diverse microorganisms in their guts, which collectively fulfill important roles in providing their hosts with nutrition and protection from pathogens. Although numerous studies have investigated the presence of certain pathogenic bacteria in the feces of wild birds, only a few have attempted to investigate the microbiota of the gut. This study analyzed the avian bacteria present in the cloaca of avian scavengers captured on coastal beaches of Washington and Oregon between 2013 and 2015: 10 turkey vultures ( Cathartes aura ), 9 bald eagles ( Haliaeetus leucocephalus ), and 2 common ravens ( Corvus corax ). We used illumina sequencing based on the V4 region of the 16s gene was to characterize the bacterial diversity. Our investigation revealed phylum-level differences in the microbiome of turkey vultures, compared with bald eagles and common ravens. Substantial microbiome differences were found between bald eagles and ravens below the phylum level. Although little is known about the possible relations among these microorganisms, our analyses provides the first integrated look at the composition of the avian microbiota and serves as a foundation for future studies in this area.

Received 17 September 2010, accepted 31 January 2011 SUMMARY STUMPF, J .P ., DENIS, N ., HAMER, T .E ., JOHNSON, G . & VERSCHUyL, J . 2011 . Flight height distribution and collision risk of the Marbled Murrelet Brachyramphus marmoratus: methodology and preliminary results . Marine Ornithology 39: 123–128 . Modified X-band marine radar was used to quantify flight heights, passage rates and flight behavior of Marbled Murrelets Brachyramphus marmoratus on the Olympic Peninsula, Washington, and to assess the collision risk associated with future coastal wind developments . Over three mornings, 287 height observations were collected for targets matching murrelet speed, flight height and density on radar . Mean height above ground level was 246 (SE 4 .7) m . The lowest murrelet-type target detected was at 62 m, while the highest was recorded at 663 m . Fifty percent of murrelet-type targets were detected between 196 m and 286 m . A maximum-likelihood model of flight heights estimated that 4 .6% of murrelets were flying at or below the average wind turbine rotor-swept height of 130 .5 m as the birds transited to and from nest sites . From the same model, it was estimated that 0 .5% and 0 .01% of birds, respectively, were flying at or below the heights of typical communication towers and transmission lines . These data comprise three days of sampling at a single location, and thus may not be representative of height distributions found in other sites or regions . Flight heights likely vary with topography, distance from the ocean, weather, and other factors, and thus the proportion of birds flying below turbine height likely varies both spatially and temporally . Additional data on murrelet flight heights are now being collected to determine how the relative risk of collision changes with topography and weather conditions . This information should help predict the risk of collision with artificial structures, including wind energy developments that may pose a risk to murrelets .

A site specific model of avian-turbine collision risk is an important component of assessing environmental impacts from wind power projects. Existing models assume, however, that avian flight paths are either parallel or perpendicular to the turbine orientation and that other orientations do not significantly affect the predicted collision probability. We describe a mathematical model which estimates the probability of a collision between a bird passing through a wind turbine and one of the turbine components. Our model improves significantly upon the reference “Tucker Model”, and Band model, by accounting for different angles of avian approach other than perpendicular or parallel to the turbine rotor plane. We demonstrate, using a case study of fall raptor migration data, that the angle of approach between the flight path and the turbine orientation has a significant effect on the collision probability and resulting mortality estimates. We conclude that the angle of approach should be considered when estimating avian-turbine collision risk.

The marbled murrelet (Brachyramphus marmoratus) is a small Pacific seabird with a breeding range that extends from the Aleutian Islands to central California. Throughout most of its breeding range, it uses mature and old-growth coniferous forests as nesting habitat. Although most murrelets seem to nest within 60 km of the coast, occupied nesting habitat has been identified as far as 84 km from the ocean in Washington state. Due to the extensive inland distances within which birds are known to breed, the area requiring surveys to identify breeding sites can be enormous. Therefore, the standard 2-year survey protocol can be expensive and time-consuming for forest management agencies and companies to administer. We developed a logistic regression model to determine whether a suite of forest structural characteristics could be used to reliably predict occupancy of a forest patch by marbled murrelets. We tested the performance of the final model using cross-validation procedures and a sample of independent sites. We used 50 sites surveyed for marbled murrelets to estimate the model, and 48 independent sites were available to test model performance. All 50 sites were on private forestland owned by Rayonier located in the western lowlands of Olympic Peninsula within the Sitka spruce and western hemlock transition zones. We sampled forest habitat at each site, and we collected information on 15 explanatory variables. The best-fitting logistic regression model contained variables that measured number of canopy layers (P < 0.001, approx. F test) and mistletoe (Arceuthobium sp.) abundance (P = 0.031, approx. F test). The model misclassified 2 of 33 (94% correct) unoccupied sites as occupied using a classification cut-off (c) of c = 0.25. In the other direction, under cross-validation the final model misclassified 2 of 17 (88% correct) occupied sites as unoccupied. On a test of the model against an independent sample, using a classification cut-off value of c = 0.25, the final model correctly classified 36 of 48 sites (75% correct). The final model misclassified 3 of 31 occupied sites as unoccupied (90% correct). Use of predictive models could greatly reduce the amount of forest that requires surveys by screening out those sites with little probability of use and by focusing remaining effort on higher probability sites, resulting in a higher likelihood of identifying occupied sites and thereby more efficiently conserving marbled murrelet nesting habitat.

We compared home range areas and habitat selection of radio-marked Spotted Owls (Strix occidentalis) and Barred Owls (Strix varia) in an area of sympatry in the northern Cascade Range of Washington in 1986–1989. On average, home ranges of Spotted Owls were 3–4 times larger than ranges of Barred Owls, and there was little overlap of home ranges during the breeding season. Ranges of both species tended to expand during winter. Home range size of both species was negatively correlated with the amount of old forest, but the negative slope of the regression was much steeper for Spotted Owls than for Barred Owls. For both species, home ranges of individual owls typically had high overlap among seasons and years, indicating high site fidelity. Barred Owls generally occupied home ranges at lower elevations than Spotted Owls (mean = 386 ± 27 m vs. 750 ± 68 m). Both species tended to use old forests more than expected, but Spotted Owls tended to use other cover types less than expected, whereas Barred Owls used most other cover types in proportion to their availability. We suggest that Spotted Owls may use larger ranges than Barred Owls because they prey selectively on a few species of nocturnal mammals, whereas Barred Owls forage more evenly across a broad range of prey types, including diurnal and aquatic species. The low overlap of Barred Owl and Spotted Owl home ranges suggests that territorial Barred Owls exclude Spotted Owls from their territories, at least during the breeding season, thus reducing the amount of habitat available to Spotted Owls.

Xantus’s Murrelets Synthliboramphus hypoleucus nest in loose colonies on the Channel Islands off southern California, USA, and islands off northwestern Baja California, Mexico (Hunt et al. 1980, Murray et al. 1983, Carter et al. 1992, Drost & Lewis 1995). The colonies are vulnerable to extirpation from breeding islands through predation by introduced mammalian predators (Jehl & Bond 1975, McChesney & Tershy 1998). Nest sites of Xantus’s Murrelets occur mainly in rock crevices and to a much lesser extent under plants and artificial structures. At many colonies, a large proportion of nests occur in cliffs and steep slopes that are not easily accessible by humans without extensive climbing skill and equipment. Nest sites are visited only at night during the long incubation period (averaging 34 days), parents take long incubation shifts (one to six days), and eggs are periodically neglected (for one to four days). Chicks are precocial upon hatching and at two days old they depart from nest sites, accompanied by adults, for further rearing at sea (Murray et al. 1983). The birds’ use of largely inaccessible island habitats and of nocturnal and non-daily nest visitations and their foraging far from shore makes it difficult to find colonies, estimate population size and monitor population changes.

The Long-billed Murrelet (Brachyramphus perdix), a small alcid of the northwestern Pacific, and its former conspecific, the Marbled Murrelet (Brachyramphus marmoratus; American Ornithologists’ Union 1997), have long been recognized as “enigma(s) of the Pacific” (Guiguet 1956) because details about their breeding biology remained a mystery for more than a century. While extensive research has been conducted on the biology of B. marmoratus during the last 10 years (see Ralph et al. 1995, Nelson 1997), only limited opportunistic information is available on the distribution, abundance and habitat associations of B. perdix. Because of a variety of potential threats to the Long-billed Murrelet in Japan, including habitat loss and oil spills (e.g., Helm et al. 1997), determining its breeding status and habitat use will be important for future management and conservation of this species. Herein we describe our recent efforts to learn more about the inland habitat use of this elusive species in northern Japan. At present, the general breeding distribution of the Long-billed Murrelet is described as extending from the Kamchatka Peninsula and Komandorski Islands (Russia) in the north, southward through the Kuril Islands, along the north and west coasts of the Sea of Okhotsk (Magadan to Sakhalin Island, Russia), south to Hokkaido Island, Japan, and south and east along the coast of the Primorye Region (Primorski Krai) and the Sea of Japan to Vladivostok, Russia (Konyukhov and Kitaysky 1995, Nelson 1997). Available information suggests that its breeding range is primarily determined by the distribution of taiga forest in coastal areas of the region (Kistchinski 1968). In Russia, five nests are known in coniferous and mixed forest within 30 km of the coast. One ground nest was found on an open scree slope in mixed coniferous/broad-leaved forest at 700 m in elevation and 30 km inland in the mountains above Shelikhova Bay, near Magadan (A. Kistchinski unpublished data). Four tree nests were found in Larix gmelini (Dahurian larch) trees in taiga forests up to 12 km inland near the cities of Magadan and Okhotsk, on Sakhalin Island, and at Olga Bay on the Primorye coast, 274 km north of Vladivostok

163 Abstract: Little research has been done to quantify and describe the structural characteristics of forest stands that are associated with Marbled Murrelet ( Brachyramphus marmoratus ) nesting in the Pacific Northwest. Vegetation measurements and murrelet surveys to determine occupancy were conducted in stands located throughout western Washington. I used logistic regression to contrast stand attributes between occupied ( n = 64) and unoccupied ( n = 87) stands. The probability of occupancy of an old-growth stand increased with increasing total number of potential nest platforms, percent moss coverage on the limbs of dominant trees ( ≥81 cm d.b.h.), percent slope, the stem density of dominant trees, and the mean d.b.h. of western hemlock. The probability of occupancy of a stand decreased as lichen coverage on the limbs of dominant trees, stand elevation, and canopy closure increased. Mean detection rates and the percent of stands surveyed and verified as occupied declined sharply with an increase in elevation over 1,067 m, and for stands >63 km from salt water. The relationship of the number of potential nest platforms and elevation to the probability of occupancy was best explained by comparing the structural characteristics of old-growth trees for the five conifer species available for nesting. Land management activities that reduce or affect the number of potential nest platforms/ha, composition of low elevation conifers, moss cover on tree limbs, stem density of dominant trees ( ≥81 cm d.b.h.), or canopy closure, would reduce the quality of a site as nesting habitat for murrelets. Reproductive success should be used as a measure of habitat suitability in future studies by intensively studying occupied stands that have high detection rates of Marbled Murrelets and locating a sample of active nests to observe.

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.

Interspecific hybridization has been reported in at least 52 of 516 nonmarine bird species in North America (Johnsgard 1970, Mayr and Short 1970, Short 1965, 1972). It tends to occur infrequently, however, except where allopatric species are brought into contact by range expansions (Cade 1983). Groups in which interspecific hybridization is particularly common include warblers, grouse, and hummingbirds (Mayr and Short 1970, Oliphant 1991). Instances of interspecific hybridization in birds of prey are uncommon except in captivity (Newton 1979, Cade 1983, Oliphant 1991). In owls, interspecific hybridization appears to be rare. Johnsgard (1988) reported instances of hybridization between Eastern Screech-Owls (Otus asio) and Western Screech-Owls (0. kennicottii) in Texas, and Voous (1989) reported instances of hybridization between Whiskered Screech-Owls (0. trichopsis) and Western Screech-Owls in Arizona. Evidence of hybridization in the genus Strix has been limited to Ural Owls (S. uralensis) hybridizing with Tawny Owls (S. aluco) in captivity (Mikkola 1983). We present the first records of hybridization between the Northern Spotted Owl (S. occidentalis caurina) and Northern Barred Owl (S. varia varia), two species that are thought to be closely related and that have recently become sympatric (Grant 1966, Taylor and Forsman 1976, Hamer 1988). Since at least the early 1950s, the Barred Owl has been expanding its range into western North America. In the process, it has invaded much of the historical range of the Spotted Owl (Grant 1966, Taylor and Forsman 1976, Hamer 1988). Barred Owls are now common in forested areas in southwestern British Columbia and northern Washington (Hamer 1988, Dunbar et al. 1991), and they are rapidly increasing in Oregon and northern California. Increasing sympatry between Barred and Spotted owls has led to speculation that the Northern Spotted Owl, which is listed as a threatened species (U.S. Fish and Wildlife Service 1990), may be further threatened by competition with the Barred Owl, as well as by habitat loss (Taylor and Forsman 1976, Dunbar et al. 1991). The possibility that sympatry might also result in hybridization between the two species has not been previously considered. Records of hybrids.-Three adult Spotted Owl/Barred Owl hybrids, two in Washington and one in Oregon, were confirmed during 1989-1992, and one juvenile hybrid was produced by a female Barred Owl paired to a yearling male Spotted Owl in Oregon in 1992. All hybrids were identified by their unique plumage characteristics, vocalizations, and measurements. The first hybrid was an adult male seen on 23 March 1989 at Baker Lake in the Washington Cascades Range, 30 km south of the United States/Canadian border. This bird was fitted with a radio transmitter in 1989 and recorded in the same area in spring 1990, 1991, and 1992. Its nesting status was not determined, but it was always seen with a female Barred Owl. Both birds aggressively defended the territory in response to playback calls. The second hybrid, an adult male located in the Klamath Mountains 29 km northeast of Medford, Oregon, in 1990 was paired with a female Barred Owl. This pair produced two young in 1990 and three young in 1991. In 1992 the Medford hybrid was displaced by a male Barred Owl. It was relocated in June 1992, 1 km from its previous nesting site and did not appear to be paired (James Harper pers. comm.). Another suspected hybrid (or possibly the same individual) was seen and heard in this area in 1987 (James Harper pers. comm.). The third hybrid was an adult female observed several times in May 1991, 2 km south of Ozette Lake, Washington, near the northwestern tip of the Olympic Peninsula. When this bird was captured, we found that it had been banded as a juvenile in 1986, 277 km to the southeast in the Cascade Range of southern Washington. The original bander suspected that the bird may have been a hybrid, but was unsure because it was not fully feathered and because both parents were not observed (H. Allen pers. comm.). When located in 1991, the Ozette Lake female was paired with an adult male Spotted Owl. No young were observed, but the female had a brood patch that was regressing, which suggested that nesting may have been attempted. Both birds were observed together in 1992 when nesting was again attempted but failed for unknown reasons. In addition to the three adult hybrids described above, a fourth hybrid from a pairing between a Barred Owl and Spotted Owl was confirmed in 1992 in Douglas County, Oregon, 8 km southeast of Canyonville. This pair consisted of a yearling male Spotted Owl and an adult female Barred Owl. They produced one young, which was first observed on 1 June 1992. The F, hybrid juvenile was fitted with a tail-mounted radio

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 of a nest by a Great Horned Owl (Bubo virginianus) was also suspected. We believe that changes in the forested habitat, such as increased amounts of edge, are affecting murrelet productivity. Successful nests were significantly further from edges (x = 155.4 versus 27.4 m) and were better concealed (x = 87.2 versus 67.5 percent cover) than unsuccessful nests. The rate of predation on Marbled Murrelet nests in this study appear higher than for many seabirds and forest birds. If these predation rates are representative of rates throughout the murrelet's range, then the impacts on murrelet nesting success will be significant. We hypothesize that because this seabird has a low reproductive rate (one egg clutch), small increases in predation will have deleterious effects on population viability. Rigorous studies, including testing the effects of various habitat features on recruitment and demography, should be developed to investigate the effects of predation on Marbled Murrelet nesting success. Nesting success in seabirds is influenced by a variety of physical and biological factors, including food availability, habitat quality, energetics, predation, and climatic conditions (Croxall 1987, Nettleship and Birkhead 1985, Vermeer and others 1993). Because the effects of these factors can vary spatially and temporally, seabird nesting success can be highly variable among years (Birkhead and Harris 1985; Boekelheide and others 1990; De Santo and Nelson, this volume). For example, in some years, anomalous warm oceanographic conditions (El Niño) cause a decrease in prey availability, thus impacting nesting attempts and nest success (Ainley and Boekelheide 1990, Hodder and Greybill 1985, Vermeer and others 1979). In addition, disturbance to nesting habitat (e.g., habitat loss, modification) and associated cumulative impacts can affect the ability of seabirds to The influence of these biological and physical factors on the nesting success of Marbled Murrelets (Brachyramphus marmoratus) is not fully known. In order to completely address …