Brachyramphus Marmoratus Research Articles

Variation in MHC class II B genes in marbled murrelets: implications for delineating conservation units

AbstractConserving genetic variation is critical for maintaining the evolutionary potential and viability of a species. Genetic studies seeking to delineate conservation units, however, typically focus on characterizing neutral genetic variation and may not identify populations harboring local adaptations. Here, variation at two major histocompatibility complex (MHC) class II B genes was characterized in four populations of marbled murrelets Brachyramphus marmoratus, a threatened species in which little neutral genetic population structure has been detected. High diversity, as well as evidence of balancing selection, was detected in exon 2 of these genes. Genetic population structure based on MHC markers was uncorrelated to genetic structure estimated with neutral markers, suggesting that selection played a more important role in shaping population structure at these markers than genetic drift. A high proportion of alleles and inferred peptides were unique to a single population, with the Aleutian Islands and southeast Alaska having the highest richness of both. Murrelets sampled in Oregon had low MHC exon 2 allele and inferred peptide richness, and were significantly differentiated from individuals sampled in the Aleutian Islands based on the frequency of exon 2 alleles. In addition, murrelets sampled in Oregon were differentiated from murrelets in both the Aleutian Islands and southeast Alaska based on inferred peptide frequencies, suggesting that the Oregon population could be prioritized for conservation measures. More broadly, combining information from neutral and adaptive genetic markers can improve the delineation of conservation units in threatened species.

Integrating population and genetic monitoring to understand changes in the abundance of a threatened seabird

Population monitoring programs for threatened species are rarely designed to disentangle the effects of movements from changes in birth and death rates on estimated trends in abundance. Here, we illustrate how population and genetic monitoring can be integrated to understand the cause of large changes in the abundance of a threatened species of seabird, the Marbled Murrelet (Brachyramphus marmoratus). Specifically, we used genetic data to test whether a large apparent population decline and subsequent recovery in central California was due to a population collapse followed by dispersal from larger populations to the north (the “rescue hypothesis”), or whether it was due to local changes in distribution where resident individuals dispersed from and then returned to surveyed areas (the “distribution hypothesis”). An alternative explanation, that rapid population recovery was the result of positive local population growth, was not supported by demographic data. The post-recovery population was more similar genetically to the pre-decline population than it was to northern populations. In addition, both pre-decline and post-recovery populations had a similar proportion and number of individuals of migrant ancestry, as determined with genetic assignment tests. Thus, pre-decline and post-recovery samples appear to come from the same population and our results support the distribution hypothesis. By conducting concurrent genetic and population monitoring, we were able to understand observed changes in the abundance in a threatened species, which would not have been possible by only monitoring abundance.

Space use by Common Ravens in Marbled Murrelet nesting habitat in Northern California

Little is known about space use by Common Ravens (Corvus corax) in coastal old-growth redwood (Sequoia sempervirens) forests in northern California despite their identification as nest predators of federally threatened Marbled Murrelets (Brachyramphus marmoratus). We used radio-telemetry to examine home range sizes and space use of breeding Common Ravens in Redwood National and State Parks (RNSP), California, in 2009 (N = 3) and 2010 (N = 8). Mean home range size was 182.5 ha and no home ranges were >2 km from roads or human-use areas. Ravens exhibited high site fidelity between years, and we found little overlap in the home ranges of adjacent ravens. Areas where ranges did overlap were centered on anthropogenic food sources near territory boundaries. Areas most frequently used by ravens were near roads, old-growth edge, bare ground, and in mixed hardwood and prairie habitats; areas near human-use areas and in old-growth habitat were used less by ravens. Mean perch height of ravens (52 m, N = 38) in redwood trees was similar to the mean height of Marbled Murrelet nests in RNSP (48 m). In RNSP, Marbled Murrelet nests that have been located were in old-growth forest within 2 km of roads. The attraction to anthropogenic resources with frequent use of roads and old-growth edges and their tendency to perch high in the canopy may increase the likelihood of ravens locating and predating nests of murrelets in RNSP. RESUMEN Uso del espacio por Corvus corax en habitat de anidacion de Brachyramphus marmoratus en el norte de California Poco se conoce sobre el uso del espacio por Corvus corax en los bosques maduros costeros de Sequoia sempervirens en el norte de California a pesar de que han sido identificados como depredadores de nidos del federalmente amenazado Brachyramphus marmoratus. Usamos radio telemetria para examinar el tamano de los rangos de hogar y el uso del espacio de C. corax en reproduccion en Redwood Parque Nacional y Estatal (RPNS), California, en el 2009 (N = 3) y 2010 (N = 8). El promedio del tamano del rango de hogar fue de 182.5 ha y ningun rango de hogar fue >2 km desde las carreteras o areas usadas por humanos. C. corax mostro una alta fidelidad a lugares entre anos y encontramos poca superposicion en los rangos de hogar de C. corax adyacentes. Areas en donde los rangos se traslaparon se concentraron en fuentes de alimento antropogenico cercanas a los limites del territorio. Las areas usadas con mayor frecuencia por C. corax estuvieron cerca de las carreteras, bordes de los bosques maduros, suelo expuesto y en la mezcla de habitat de pradera y bosque; areas cerca de areas usadas por humanos y habitat de bosque maduro fueron usadas poco por C. corax. La altura promedio de las perchas de C. corax (52 m, N = 38) en arboles de S. sempervirens fueron similares a la altura promedio de los nidos de B. marmoratus en RPNS (48 m). En RPNS, los nidos de B. marmoratus que se han localizado en bosque maduro dentro de un rango de 2 km desde la carretera. La atraccion a recursos antropogenicos con frecuentes usos de carreteras y bordes de bosques maduros, y la tendencia a percharse alto en le dosel puede incrementar la probabilidad de que C. corax localice y deprede nidos de B. marmoratus en RPNS.

Plastic ingestion in marine-associated bird species from the eastern North Pacific

In addition to monitoring trends in plastic pollution, multi-species surveys are needed to fully understand the pervasiveness of plastic ingestion. We examined the stomach contents of 20 bird species collected from the coastal waters of the eastern North Pacific, a region known to have high levels of plastic pollution. We observed no evidence of plastic ingestion in Rhinoceros Auklet, Marbled Murrelet, Ancient Murrelet or Pigeon Guillemot, and low levels in Common Murre (2.7% incidence rate). Small sample sizes limit our ability to draw conclusions about population level trends for the remaining fifteen species, though evidence of plastic ingestion was found in Glaucous-Winged Gull and Sooty Shearwater. Documenting levels of plastic ingestion in a wide array of species is necessary to gain a comprehensive understanding about the impacts of plastic pollution. We propose that those working with bird carcasses follow standard protocols to assess the levels of plastic ingestion whenever possible.

Recent Population Decline of the Marbled Murrelet in the Pacific Northwest

Abstract. We document here a decline of nearly 30% in the Marbled Murrelet (Brachyramphus marmoratus) population of Washington, Oregon, and northern California between 2000 and 2010. The Northwest Forest Plan is an ecosystem-management plan for federal forest lands in the Pacific Northwest of the United States that incorporates monitoring to determine if species' conservation objectives are met. To evaluate the plan's effectiveness in conserving populations of the murrelet, a species associated with older, late-successional forests, we estimated the murrelet's density in near-shore marine waters of Washington, Oregon, and northern California south to San Francisco Bay. We sampled annually, using line transects and distance estimation. We divided the study area of about 8800 km2 into five geographic subareas corresponding to existing murrelet-conservation zones. Annual population estimates for the plan ranged from an estimated 23 700 (95% CI: 18 300 to 29 000) birds in 2002 to a low of 16 700 (95% CI: 13 1...

Assessing the effects of sound on a forest-nesting seabird, the threatened marbled murrelet (Brachyramphus marmoratus)

The marbled murrelet is a forest-nesting seabird that is federally listed under the Endangered Species Act. This species is unusual in that it flies up to 70 miles inland to nest in mature trees rather than on shorelines near its foraging habitat. The first nest was not discovered until 1974, and much remains to be learned about this difficult-to-study species, including its basic hearing sensitivities and response to auditory stimuli. In evaluating the effects of federal actions on this species, we must assess the potential effects of anthropogenic sound from a variety of sources, both at-sea and in the forested environment. Over the past ten years, we have developed an approach for analyzing the effect of anthropogenic sound by conducting literature reviews, convening expert panels, and drawing from information on other species. We address both impulsive and continuous sounds from sources including impact pile driving, blasting, heavy equipment noise, and sonar. Interim thresholds for expecting injurious effects from some of these sources are in use, and refinements to our analysis of forest-management activities were recently applied to landscape-scale consultations. The bioacoustic research needs of this unique species continue to emerge as we apply these approaches in both the aquatic and terrestrial environments where murrelets occur.

Stable isotopes reveal strategic allocation of resources during juvenile development in a cryptic and threatened seabird, the Marbled Murrelet (Brachyramphus marmoratus)

Identifying factors that influence growth throughout development is important for understanding the consequences of variation in resource quality on recruitment. Marbled Murrelets ( Brachyramphus marmoratus (J.F. Gmelin, 1789)) are threatened seabirds that are extremely cryptic in their nesting behaviour, which makes it challenging to understand how juveniles allocate resources during development. From a single capture at sea, we analyzed stable carbon isotopes in feathers and blood of juvenile murrelets to infer diet composition during both the pre- and the post-fledging periods. Consistent with the challenges juveniles face during their first year of life, we found that wing and bill growth were prioritized in the nest, whereas development of energy stores was delayed until after nest departure. We also found that diet quality after nest departure influenced bill size and body condition, two body components that continue to grow after independence. Our results provide evidence that murrelets strategically allocate resources according to their stage of development and that the availability of high-quality prey is likely to be important to juvenile development. These results identify a potential mechanism through which feeding conditions may influence reproduction of murrelets and demonstrate the utility of stable isotopes to examine the influence of diet quality on growth over multiple stages of development.

Relating Microclimate to Epiphyte Availability: Edge Effects on Nesting Habitat Availability for the Marbled Murrelet

Industrial timber harvesting typically creates forest edges with altered microclimate regimes, causing reduced growth and survival of some canopy epiphytes. This process has implications for the marbled murrelet (Brachyramphus marmoratus), a threatened seabird that nests on moss platforms in old-growth forests of the coastal Pacific Northwest in North America. We investigated microclimate and epiphyte availability in old-growth forests of southwestern British Columbia, Canada. We contrasted mean and maximum temperature, mean humidity, mean vapor pressure deficit (VPD) and mean epiphyte cover and platform tree density between forest edge and interior plots at hard edges (recent clearcuts), soft edges (regenerating forest) and natural edges (rivers and avalanche chutes). Differences measured in VPD and epiphyte availability varied due to edge proximity and edge-type. Hard edges had fewer trees with suitable marbled murrelet nest platforms relative to adjacent interiors, and hard-edged patches had the lowest epiphyte cover overall. This suggests that microclimate edge effects and substrate availability can negatively impact epiphyte growth and survival, and may reduce the availability of marbled murrelet nest sites. These negative effects may decrease with time as forests regenerate, as edge effects were lower in magnitude at soft-edged patches. In contrast, natural-edged patches had the greatest levels of epiphyte cover and platform tree density, suggesting that these areas provide an abundant source of potential nest sites. Minimizing the ratio of anthropogenic edge to suitable interior habitat, and maintaining natural edges will limit negative edge effects on moss availability and provide nesting habitat for marbled murrelets.

Extra-Pair Visitations to a Marbled Murrelet Nest in Northern California

Although nest prospecting, natal philopatry, and nest-site fidelity have been observed in many alcids, few data demonstrate these behaviors in Marbled Murrelets (Brachyramphus marmoratus). Prior to the 2003 breeding season, we installed a permanent video camera adjacent to a Marbled Murrelet nest site that had been used in 2001 and 2002. Video recordings in 2003 detected the simultaneous presence of 3 murrelets in alternate plumage on the nest branch, once during the incubation period, and once during the chick period. We did not observe aggression, suggesting familiarity between the extra-pair birds and site holders, and possibly avoidance of detection by predators. Without banded individuals we hypothesize extra-pair visitations at an active nest reflect nest-site prospecting, natal philopatry, or nest-site fidelity.

Foraging space as a limited resource: inter- and intra-specific competition among sympatric pursuit-diving seabirds

Competition is thought to play a fundamental role in structuring avian communities, yet this has been difficult to quantify and demonstrate in marine ecosystems. We tested for fine-scale competition over foraging space between sympatric pursuit-diving seabirds, Marbled Murrelet ( Brachyramphus marmoratus (J.F. Gmelin, 1789)) and Common Murre ( Uria aalge (Pontoppidan, 1763)). We simultaneous assessed the effects of inter- and intra-specific competition among these predators, predicting that the larger Common Murres would out-compete the smaller Marbled Murrelets for foraging space. A theodolite was used to map the fine-scale (±2 m) distributions of birds on the water; distance from shore measurements and nearest-neighbour spatial statistics quantified the spatial overlap and segregation between species. Species distributions differed with respect to distance from shore, but overlapped extensively within 1200 m of the shoreline. Nearest-neighbour statistics, assessed with randomization tests, showed Marbled Murrelets foraging farther from Common Murres (mean distances 294 m) than from other Marbled Murrelets (95 m), but groups of Common Murres foraged with similar spacing among conspecifics (266 m) and competitors (186 m). These results suggest avoidance of Common Murres by Marbled Murrelets (interspecific competition) but intraspecifc competition among Common Murres. Avoidance behaviour may minimize the impacts of aggression or competition, but by avoiding Common Murres, the Marbled Murrelets may also be reducing their foraging opportunities.

Patch Scale Nest-Site Selection by Marbled Murrelets (Brachyramphus marmoratus)

Patch Scale Nest-Site Selection by Marbled Murrelets (Brachyramphus marmoratus)

Marbled Murrelets Select Distinctive Nest Trees within Old-Growth Forest Patches

Silvergieter, M. P., and D. B. Lank. 2011. Marbled murrelets select distinctive nest trees within old-growth forest patches. Avian Conservation and Ecology 6(2): 3.http://dx.doi.org/10.5751/ACE-00462-060203

Diel Shifts in the Marine Distribution of Marbled Murrelets Near Port Snettisham, Southeast Alaska

Abstract. Little is known about seabird distributions at night. Densities of Marbled Murrelets (Brachyramphus marmoratus, hereafter “murrelets”) and potential prey were determined along fixed-width transects in spring and summer of 2007 and 2008, and compared during night and day in two regions of Port Snettisham, near Juneau, Southeast Alaska. Murrelets moved from a shallower, more sheltered inner region, used during the day for foraging and staging for inland flights (2007 night densities = 15 ± 13 murrelets·km-2; 2007 day densities = 172 ± 67 murrelets·km-2), to a deeper, more exposed outer region, further from shore, during dark hours (2007 night densities = 113 ± 61 murrelets·km-2; 2007 day densities = 41 ± 23 murrelets·km-2). Prey school density and relative prey density were significantly higher at night in the inner region compared with the outer region (2.2 times higher prey school density and 3.8 times higher relative prey density), suggesting that murrelets were not redistributing themselves to...

The Preformative Molt of Marbled Murrelets

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Recovering marbled murrelets via corvid management: A population viability analysis approach

The expansion of human activities into rural areas and natural landscapes has resulted in widespread increases in the abundance of synanthropic species that threaten rarer native species. Quantitative assessments of how much impacts need to be reduced to reach acceptable levels of risk to the affected species are rarely conducted prior to the implementation of control measures, and it is perhaps not surprising that many efforts have not yielded the desired outcome. Here, we used matrix-based population viability analysis models to show that reducing predation by rapidly growing corvid populations on marbled murrelet ( Brachyramphus marmoratus) nests likely constitutes an effective means for recovering a declining murrelet population in central California. For example, a modest 40% reduction in predation reduced extinction risk dramatically from 95.8% to 4.6% over 100 years and a 60% reduction resulted in a stable population ( λ = 1) when the proportion of breeders, renesting rates, and corvid predation rates were assumed to be 0.77, 0.13, and 0.69, respectively. However, nest predation would only need to be reduced by 40% to produce a stable population if corvid management was coupled with a modest increase in after-hatch-year survival from 0.896 to 0.910. Corvid control resulted in greater gains in murrelet population size when the maximum number of breeders was allowed to increase over the projection period, as might be expected if the amount of old-growth nesting habitat increased over time, but extinction risk was insensitive to the presence of a carrying capacity. Approximately half of known murrelet nests in central California are within 1 km of heavily used campgrounds in a single state park, indicating that significant gains in viability could be achieved by targeting efforts in small areas providing corvid food subsidies. Risk assessments such as ours can provide quantitative prioritization rationale for efforts intended to mitigate the impacts of synanthropic species on threatened species.

Factors affecting the availability of thick epiphyte mats and other potential nest platforms for Marbled Murrelets in British Columbia

Nest platforms (mossy pads, limbs, and deformities >15 cm in diameter) are key requirements in the forest nesting habitat of the threatened Marbled Murrelet ( Brachyramphus marmoratus (J.F. Gmelin, 1789)). Little is known about factors that affect the availability of platforms or the growth of canopy epiphytes that provide platforms. We examined variables affecting these parameters in coastal trees in British Columbia using data from 29 763 trees at 1412 sites in 170 watersheds. Tree diameter (diameter at breast height (DBH)) was the most important predictor of platform availability in the pooled data and within each of six regions. In most regions, platforms become available at DBH > 60 cm, but on East Vancouver Island, DBH needs to be >96 cm and possibly on the Central Coast >82 cm. Other regional predictors of platforms included tree height, tree species, and to a lesser extent elevation, slope, and latitude. Most (72%) trees providing platforms had epiphytes (mainly moss) covering one third or more of branch surfaces and 81% had intermediate or thick epiphyte mats. Mistletoe deformities provided <7% of platforms. Our model predictions help to define and manage suitable habitat for nesting Marbled Murrelets and also contribute to understanding forest canopy ecosystems.

Does interpretation of Marbled Murrelet nesting habitat change with different classification methods?

Accurate and reliable identification of potential nesting habitat is required to manage for the threatened Marbled Murrelet (Brachyramphus marmoratus). Three habitat classifications are typically used by wildlife planners: a bivariate suitability algorithm following recommendations of the Canadian Marbled Murrelet Recovery Team (CMMRT) and based on geographical information systems (GIS), and two habitat classifications based on air photo interpretation mapping and low-level aerial survey mapping. The CMMRT model uses vegetation resource inventory data. The air photo interpretation and low-level aerial survey methods directly assess the forest for attributes likely to provide nesting platforms, cover, and access into the stand by the bird. The prime indicators of nesting habitat potential for murrelets are large (generally mossy) branches for use as nest platforms. These are only directly visible using low-level aerial surveys. Methods involving GIS cost the least to apply, and low-level aerial surveys cost the most. We compared and assessed the consistency of the three methods using 243 sites. The CMMRT model proved least reliable by underestimating habitat suitability of sites compared to both the air photo interpretation and aerial survey estimates. The air photo interpretation and aerial survey methods were generally aligned in the ordinal ranking of sites by habitat class, but only 44% had matching ranks. Sites that differed tended to be ranked lower by air photo interpretation and mostly occurred in the “Moderate” and “Low” air photo interpretation classes. Either classification may refine information from the CMMRT model, particularly for habitat classed as “Unsuitable.” Using air photo interpretation first and then applying the aerial surveys as a further refined assessment of moderate and low habitat classes may provide the most cost-effective approach for accurately classifying and mapping habitat potential for management planning.

Endangered Seabird Habitat Management as a Partially Observable Markov Decision Process

The marbled murrelet (Brachyramphus marmoratus) is an endangered seabird that nests in coastal forests from Alaska to California. The value of these forests for human use, coupled with the difficulty of determining whether a forest stand is occupied by nesting marbled murrelets, poses a dilemma for land managers. Should they implement a costly survey to gather information on whether a potential nest site is occupied, or should they allow human use, effectively assuming the site is unoccupied? This article demonstrates the application of the partially observable Markov decision process (POMDP) as a framework for addressing this question. The analysis yields a policy in which the optimal action is a function of the decision-maker’s subjective probability that a potential nest site is occupied by marbled murrelets. By incorporating stochastic state dynamics and the choice of whether to invest in learning, the POMDP provides a formal representation of adaptive management when active learning is possible.

Re-Evaluation of the First Three Marbled Murrelet Nests Reported in British Columbia

Abstract In northern British Columbia, nests of the Marbled Murrelet (Brachyramphus marmoratus) were first reported in burrows at Marble Island (1901), Cox Island (1920), and Banks Island or Porcher Island (1921), but none were subsequently accepted, and the 1901 and 1920 nests were considered to be Ancient Murrelet (Synthliboramphus antiquus) nests. We collated and reconsidered available information on these 3 nests (including obscure literature, recently uncovered correspondence, and museum records) to re-evaluate their authenticity and clarify past literature, concluding that the 1920 nest should be considered the first possible but unverified nest of the Marbled Murrelet, whereas 1901 and 1921 nests were more convincingly dismissed as belonging to Ancient Murrelet and probably Rhinoceros Auklet (Cerorhinca monocerata), respectively. The 1901 nest also represented the first documented breeding of the Ancient Murrelet in British Columbia, actually at the Limestone Islands.

The effects of including marine ecological values in terrestrial reserve planning for a forest-nesting seabird

Theoretical advances in systematic reserve design aim to promote the efficient use of limited conservation resources and to increase the likelihood that reserve networks enhance the persistence of valued species and ecosystems. However, these methods have rarely been applied to species that rely on spatially disjunct habitats. We used the marbled murrelet, a seabird that requires old-growth forest in which to nest and high quality marine habitats in which to forage, as a case study to explore methods of incorporating multiple ecological values into single species spatial reserve design. Specifically, we used the cost function in MARXAN to include the ecological value of marine habitats while identifying spatial solutions for terrestrial nesting habitat reserves. Including marine values influenced terrestrial reserve designs most when terrestrial habitat targets were low and little or none of the target was represented in pre-existing protected areas. Our results suggest that including marine values in the planning process will influence marbled murrelet terrestrial reserve designs most where substantial terrestrial nesting habitat still exists, where new reserves are relatively unconstrained by pre-existing reserves, or when conservation resources only allow the protection of a small fraction of available habitat. This paper presents a novel framework for incorporating multiple measures of ecological value in the spatial reserve design process and should be particularly useful for species that rely on multiple habitats during their life cycle.