M Zachariah Peery

Publications (17)52.84 Total impact

• Article: Inferring recent historic abundance from current genetic diversity.

  Per J Palsbøll, M Zachariah Peery, Morten T Olsen, Steven R Beissinger, Martine Bérubé
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  ABSTRACT: Recent historic abundance is an elusive parameter of great importance for conserving endangered species and understanding the pre-anthropogenic state of the biosphere. The number of studies that have used population genetic theory to estimate recent historic abundance from contemporary levels of genetic diversity has grown rapidly over the last two decades. Such assessments often yield unexpectedly large estimates of historic abundance. We review the underlying theory and common practices of estimating recent historic abundance from contemporary genetic diversity, and critically evaluate the potential issues at various estimation steps. A general issue of mismatched spatio-temporal scales between the estimation itself and the objective of the estimation emerged from our assessment; genetic diversity-based estimates of recent historic abundance represent long-term averages, whereas the objective typically is an estimate of recent abundance for a specific population. Currently, the most promising approach to estimate the difference between recent historic and contemporary abundance requires that genetic data be collected from samples of similar spatial and temporal duration. Novel genome-enabled inference methods may be able to utilize additional information of dense genome-wide distributions of markers, such as of identity-by-descent tracts, to infer recent historic abundance from contemporary samples only.
  Molecular Ecology 11/2012; · 5.52 Impact Factor
• Article: Estimating population impacts via dynamic occupancy analysis of Before-After Control-Impact studies.

  Viorel D Popescu, Perry de Valpine, Douglas Tempel, M Zachariah Peery
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  ABSTRACT: Estimating environmental impacts on populations is one of the main goals of wildlife monitoring programs, which are often conducted in conjunction with management actions or following natural disturbances. In this study we investigate the statistical power of dynamic occupancy models to detect changes in local survival and colonization from detection-nondetection data, while accounting for imperfect detection probability, in a Before-After Control-Impact (BACI) framework. We simulated impacts on local survival and/or detection probabilities, and asked questions related to: (1) costs and benefits of different analysis models, (2) confounding changes in detection with changes in local survival, (3) sampling design trade-offs, and (4) species with low vs. high rates of turnover. Estimating seasonal effects on local survival and colonization, as opposed to estimating Before-After effects, had little effect on the power to detect changes in local survival. Estimating a parameter that accounted for pretreatment differences in local survival between Control and Impact sites decreased power by 50%, but it was critical to include when such differences existed. When the experimental treatment had a negative impact on species detectability but analysis assumed constant detection, the Type I error rates were dramatically inflated (0.20 0.33). In general, there was low power (< 0.5) to detect a 50% decrease in local survival for all combinations of sites (N = 50 vs. 100), seasons sampled (8 vs. 12), and visits per site per season (4 vs. 6). Unbalanced designs performed worse than balanced designs, with the exception of the case of treatments being implemented in different seasons at different sites. Adding more control sites improved the ability to detect changes in local survival. Surveying more seasons after impact resulted in modest power gains, but at least three seasons before impact were required to successfully implement BACI occupancy studies. Turnover rates had a low impact on power. Occupancy studies conducted in a BACI design offer the opportunity to detect environmental impacts on wildlife populations without the costs of intensive studies. However, given the low power to detect small changes (20%) in local survival, these studies should be used when researchers are confident that major treatment impacts will occur or very large sample sizes are obtainable.
  Ecological Applications 06/2012; 22(4):1389-404. · 5.10 Impact Factor
• Source

  Available from: wisc.edu

  Article: Detecting populations in the 'ambiguous' zone: kinship-based estimation of population structure at low genetic divergence.

  Per J Palsbøll, M Zachariah Peery, Martine Bérubé
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  ABSTRACT: Identifying population structure is one of the most common and important objectives of spatial analyses using population genetic data. Population structure is detected either by rejecting the null hypothesis of a homogenous distribution of genetic variation, or by estimating low migration rates. Issues arise with most current population genetic inference methods when the genetic divergence is low among putative populations. Low levels of genetic divergence may be as a result of either high ongoing migration or historic high migration but no current, ongoing migration. We direct attention to recent developments in the use of the tempo-spatial distribution of closely related individuals to detect population structure or estimate current migration rates. These 'kinship-based' approaches complement more traditional population-based genetic inference methods by providing a means to detect population structure and estimate current migration rates when genetic divergence is low. However, for kinship-based methods to become widely adopted, formal estimation procedures applicable to a range of species life histories are needed.
  Molecular Ecology Resources 09/2010; 10(5):797-805. · 3.06 Impact Factor
• Article: Genetic analyses of historic and modern marbled murrelets suggest decoupling of migration and gene flow after habitat fragmentation.

  M Zachariah Peery, Laurie A Hall, Anna Sellas, Steven R Beissinger, Craig Moritz, Martine Bérubé, Martin G Raphael, S Kim Nelson, Richard T Golightly, Laura McFarlane-Tranquilla, Scott Newman, Per J Palsbøll
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  ABSTRACT: The dispersal of individuals among fragmented populations is generally thought to prevent genetic and demographic isolation, and ultimately reduce extinction risk. In this study, we show that a century of reduction in coastal old-growth forests, as well as a number of other environmental factors, has probably resulted in the genetic divergence of marbled murrelets (Brachyramphus marmoratus) in central California, despite the fact that 7 per cent of modern-sampled murrelets in this population were classified as migrants using genetic assignment tests. Genetic differentiation appears to persist because individuals dispersing from northern populations contributed relatively few young to the central California population, as indicated by the fact that migrants were much less likely to be members of parent-offspring pairs than residents (10.5% versus 45.4%). Moreover, a recent 1.4 per cent annual increase in the proportion of migrants in central California, without appreciable reproduction, may have masked an underlying decline in the resident population without resulting in demographic rescue. Our results emphasize the need to understand the behaviour of migrants and the extent to which they contribute offspring in order to determine whether dispersal results in gene flow and prevents declines in resident populations.
  Proceedings of the Royal Society B: Biological Sciences 11/2009; 277(1682):697-706. · 5.41 Impact Factor
• Article: Characterizing dispersal patterns in a threatened seabird with limited genetic structure.

  Laurie A Hall, Per J Palsbøll, Steven R Beissinger, James T Harvey, Martine Bérubé, Martin G Raphael, S Kim Nelson, Richard T Golightly, Laura McFarlane-Tranquilla, Scott H Newman, M Zachariah Peery
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  ABSTRACT: Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (F(ST) approximately 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post-breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent-offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants.
  Molecular Ecology 11/2009; 18(24):5074-85. · 5.52 Impact Factor
• Article: Local Survival of Marbled Murrelets in Central California: Roles of Oceanographic Processes, Sex, and Radiotagging

  M. ZACHARIAH PEERY, STEVEN R. BEISSINGER, ESTHER BURKETT, SCOTT H. NEWMAN
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  ABSTRACT: We estimated annual local survival rates for after-hatch-year (≥1-yr old) marbled murrelets (Brachyramphus marmoratus) in central California using Cormack-Jolly-Seber mark–recapture models and radiotelemetry, and we modeled the effect of oceanographic conditions, sex, and radiotagging. We captured 331 after-hatch-year murrelets from 1997 to 2003, of which 117 were radiotagged. Recapture rates were best modeled using a term that reflected differences in capture effort among sampling occasions (peffort) and ranged from 0.068 to 0.166. The most highly ranked model (ΦPDO+radio, peffort) indicated that survival rates were positively related to the strength of the Pacific Decadal Oscillation (PDO) and were negatively affected by radiotransmitters in the year following tagging. Mortality was relatively low in warm-water years, perhaps because murrelets flew inland to breed less frequently and were less exposed to avian predators. Two competing models indicated that survival in the year following tagging was affected by (1) only radiotagging (model Φradio, peffort), and (2) radiotagging and sex (model Φsex+radio, peffort). Model-averaged survival estimates were 0.868 (SE = 0.074) and 0.896 (SE = 0.067) for males and females, respectively, that were not radiotagged and 0.531 (SE = 0.175) and 0.572 (SE = 0.181) for males and females, respectively, that were radiotagged. Mortality of radiomarked individuals was greatest during a domoic acid (a neurotoxin in the marine environment) bloom in 1998 (Φ = 0.160–0.400) and radiomarking impacts were much less pronounced during typical years (Φ = 0.724–0.810). Additional causes of mortality included predation by peregrine falcons (Falco peregrinus) and oil spills. Survival for nonmarked individuals was similar or higher than what was estimated for murrelets in British Columbia and what was predicted for murrelets based on comparative analyses of other Alcid species, suggesting that mortality of after-hatch-year murrelets is not an immediate threat to population viability in the region.
  Journal of Wildlife Management 09/2009; · 1.52 Impact Factor
• Article: Nesting Habitat Characteristics of the Marbled Murrelet in Central California Redwood Forests

  LAUREN M. BAKER, M. ZACHARIAH PEERY, ESTHER E. BURKETT, STEVEN W. SINGER, DAVID L. SUDDJIAN, STEVEN R. BEISSINGER
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  ABSTRACT: The marbled murrelet (Brachyramphus marmoratus) is a threatened seabird that nests in old-growth forests in the Pacific Northwest. Despite concern for this species, little has been published on murrelet nesting habitat in the coast redwood (Sequoia sempervirens) region. Here we present the first comprehensive study of marbled murrelet nesting characteristics in redwood forests based on confirmed nest sites. In this study, we 1) described habitat characteristics at 17 murrelet nest sites in the Santa Cruz Mountains, California, USA, located using radiotelemetry and visual searches, and 2) compared nest sites with random sites located in nearby stands and centered on trees ≥120 cm diameter at breast height (dbh [potential nest trees or PNTs]). All 17 nests were located in stands of old-growth redwood forest and the mean dbh of nest trees was 210 cm (SD = 91 cm). Eighty-two percent of nests (90% of telemetry-found nests) were in unharvested stands and 18%, all on private property, had been lightly harvested but did not contain significantly fewer trees ≥120 cm dbh than unharvested nest sites. Twelve of 15 (80%) nests for which we were able to locate the nesting platform were on limbs and the remaining 3 (20%), all in redwood trees, were located on broken tops. Nest trees were significantly larger than PNTs and tended to be Douglas-fir (Pseudotsuga menziesii) despite the fact that nest stands were dominated by redwoods, perhaps because of greater nest platform availability in Douglas-fir trees. Nest sites were located closer to streams, had a greater basal area of trees ≥120 cm dbh, and were located lower on slopes than random sites based on analysis of variance models. We classified 71% of nest sites correctly with a simple logistic regression model that included only nest tree dbh and distance to stream—a model that could be used by managers in the region to identify potentially suitable nesting habitat. Our findings indicated that murrelets in central California, USA, primarily use old-growth redwood stands for nesting but will use partially harvested stands if a significant residual component remains; stands that have experienced some harvest but retain old-growth characteristics should be considered potential murrelet habitat in redwood forests.
  Journal of Wildlife Management 09/2009; · 1.52 Impact Factor
• Source

  Available from: Curt D Storlazzi

  Article: Meeting Reproductive Demands in a Dynamic Upwelling System: Foraging Strategies of a Pursuit-Diving Seabird, the Marbled Murrelet

  M. Zachariah Peery, Scott H. Newman, Curt D. Storlazzi, Steven R. Beissinger
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  ABSTRACT: Las aves marinas mantienen una plasticidad en sus comportamientos de forrajeo para poder con las demandas energéticas y las restricciones de forrajeo que varían durante el ciclo reproductivo. Sin embargo, los estudios sobre comportamiento que comparan individuos reproductivos y no reproductivos son raros. Aquí caracterizamos cómo los individuos de la especie Brachyramphus marmoratus ajustan sus esfuerzos de forrajeo en respuesta a sus demandas reproductivas en un sistema de surgencias marinas en el centro de California. Marcamos 32 individuos, de quienes conocíamos su estado reproductivo, usando radiotransmisores (9 en reproducción, 12 reproductores potenciales y 11 no reproductivos) y estimamos tanto las áreas de forrajeo como las tasas de buceo durante la época reproductiva. Los individuos de B. marmoratus permanecieron más tiempo buceando durante los periodos de surgencia que durante los periodos de relajación oceanográfca, aumentaron su área de forrajeo con el aumento del tiempo del periodo de relajación y redujeron sus áreas de forrajeo después de la transición al periodo de surgencias. Cuando los individuos no se encontraban incubando, se movieron siguiendo un patrón circadiano, permaneciendo durantes las horas de descanso nocturnas cerca de las rutas de vuelo que utilizan para alcanzar el hábitat de anidación y forrajeo durante el día, las que en promedio se encontraron a 5.7 km (DE 6.7 km) de las localidades de reposo nocturno. Las aves en fase reproductiva forrajearon más cerca de las áreas de anidación una vez que iniciaron la anidación y cuando la atención a los polluelos fue máxima, y luego volvieron a viajar distancias mayores una vez terminado el periodo de anidación. Las aves en fase no reproductiva presentaron distribuciones diurnas y nocturnas similares y tendieron a localizarse más lejos de las rutas de vuelo tierra adentro. Las aves en fase reproductiva aumentaron en un 71–73% el tiempo que permanecieron buceando cuando estas tenían un nido activo, aumentando el número de zambullidos sin aumentar la frecuencia de anaerobiosis. Así, para alcanzar las demandas reproductivas durante la anidación, los individuos de B. marmoratus adoptaron una estrategia mixta en que redujeron el gasto de engría de los vuelos hacia los sitios de forrajeo y aumentaron las tasas de zambullidos aeróbicos.
  The Condor 02/2009; · 1.12 Impact Factor
• Source

  Available from: Benjamin Becker

  Article: AGE RATIOS AS ESTIMATORS OF PRODUCTIVITY: TESTING ASSUMPTIONS ON A THREATENED SEABIRD, THE MARBLED MURRELET (BRACHYRAMPHUS MARMORATUS)

  M. Zachariah Peery, Benjamin H. Becker, Steven R. Beissinger
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  ABSTRACT: Le rapport entre les jeunes de l’année (HY) et les jeunes de plus d’un an (AHY) (HY:AHY) peut être une mesure très utile pour estimer la productivité aviaire car il ne nécessite pas le suivi de sites de reproduction individuels et peut souvent être estimé sur de grandes échelles géographiques et temporelles. Toutefois, l’estimation rigoureuse du rapport des âges nécessite que les classes d’âge des jeunes et des adultes soient échantillonnées d’une manière non biaisée, une hypothèse qui est rarement testée. Nous avons estimé le rapport HY:AHY pour l’Alque marbrée (Brachyramphus marmoratus), un oiseau de mer menacé, dans le centre de la Californie en utilisant des inventaires et des captures en mer afin d’évaluer si les différences de comportement et de répartition spécifiques à l’âge résultent en des estimés de productivité biaisés. Les Alques marbrées AHY et HY étaient similairement répartis en mer et les individus HY ne se rassemblaient pas sur des aires de crèches. De plus, la dispersion des Alques marbrées AHY marquées d’un émetteur à l’extérieur de notre aire d’inventaire s’est produite à un faible taux et les densités des AHY étaient constantes pendant la période d’inventaire, ce qui suggère que l’immigration et l’émigration des AHY n’a pas biaisé significativement les estimés de productivité. La densité des HY a augmenté linéairement durant la période d’inventaire tel qu’attendu si peu de dispersion se produisait, ce qui suggère que les estimés de productivité n’étaient pas significativement biaisés par la dispersion des HY. Finalement, des modèles de simulation ont indiqué que la variation annuelle associée à la synchronisation de la reproduction n’a entraîné que de faibles biais des rapports HY:AHY. Les rapports HY:AHY ont été corrigés en tenant compte de la proportion d’Alques marbrées AHY en train d’incuber et de la proportion d’individus HY n’ayant pas atteint l’envol au moment de l’échantillonnage. Les rapports HY:AHY corrigés moyens étaient faibles pour les inventaires réalisés entre 1996 et 2003 (0.032; SE = 0.011) et les captures effectuées de 1999 à 2003 (0.037; SE = 0.028), ce qui suggère que la productivité était faible dans le centre de la Californie. L’estimation des rapports d’âge peut être un moyen efficace pour suivre les changements du succès de reproduction et identifier les facteurs environnementaux qui affectent les populations d’Alque marbrée, même si des tests d’hypothèses sont nécessaires dans d’autres régions.
  The Auk 01/2009; · 2.16 Impact Factor
• Article: TRENDS IN RADAR-BASED COUNTS OF MARBLED MURRELETS ON THE OLYMPIC PENINSULA, WASHINGTON, 1996–2004

  Brian A. Cooper, Martin G. Raphael, M. Zachariah Peery
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  ABSTRACT: Tendencias en los Conteos por Radar deBrachyramphusMarmoratus en Olympic Peninsula,Washington, Entre 1996 Y 2004 Brachyramphusmarmoratus es un ave marinadestacada que se encuentra amenazada a nivelfederal. A pesar de esto, no existen estimacionesconfiables sobre las tendencias poblacionales deesta especie en las áreas reproductivascontinentales. Realizamos estudios deB.marmoratus con radares ubicadosen el continente en 3 a 7 sitios de OlympicPeninsula, Washington, entre 1996 y 2002, y en2004, para estimar los cambios poblacionales y paraexaminar las relaciones entre nuestros conteos ylas condiciones oceanográficas, laproductividad de B.marmoratus y los conteos marinosregionales de esta especie. Los conteos por radarmatutinos variaron significativamente entre ydentro de los sitios, pero no disminuyeron entre1996 y 2004, sugiriendo que las poblaciónreproductiva continental de B.marmoratus permanece estable enesta área. Un análisis retrospectivode poder indicó que tuvimos una probabilidaddel 25% y del 56% de detectardisminuciones anuales del 2% y 4%,respectivamente. De este modo, si se presentarondisminuciones anuales relativamente menores durantenuestro periodo de estudio, existe una altaprobabilidad de que no fueran detectadas, inclusoaunque su efecto se hubiera acumulado hasta tenerconsecuencias biológicas importantes. Sinembargo, es poco probable que B.marmoratus haya disminuidoanualmente en un 6% o más en OlympicPeninsula, debido a que los análisisretrospectivos indicaron que el poder para detectarestas disminuciones fue mayor al 88%. Nohubo una relación significativa de losconteos por radar con los conteos en el mar o conla productividad de B.marmoratus en las vecinas Islasde San Juan durante el periodo de estudio. Tampocodetectamos una relación entre los conteospor radar con la temperatura media superficial delmar, ni con el Índice de Oscilacióndel Norte, sugiriendo que la variación enlas condiciones oceanográficas (e.g.,el fuerte evento de El Niño de 1998) noestuvo asociada con la variación en losconteos. Un análisis retrospectivo de poderindicó que pequeñas disminucionesanuales (2%–4%)podrían ser detectadas con un poderrazonablemente alto (≥80%) conel diseño actual de muestreo por radar,mediante la extensión del estudio por 11 a15 años más.
  The Condor 01/2009; · 1.12 Impact Factor
• Source

  Available from: berkeley.edu

  Article: Characterizing source-sink dynamics with genetic parentage assignments.

  M Zachariah Peery, Steven R Beissinger, Roger F House, Martine Bérubé, Laurie A Hall, Anna Sellas, Per J Palsbøll
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  ABSTRACT: Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly with demographic methods, and indirect genetic methods are subject to a variety of assumptions that are difficult to meet or to apply to evolutionary timescales. Furthermore, such methods cannot be rigorously applied to high-gene-flow species. Here, we employ genetic parentage assignments in conjunction with demographic simulations to infer the level of immigration into a putative sink population. We use individual-based demographic models to estimate expected distributions of parent-offspring dyads under competing sink and closed-population models. By comparing the actual number of parent-offspring dyads (identified from multilocus genetic profiles) in a random sample of individuals taken from a population to expectations under these two contrasting demographic models, it is possible to estimate the rate of immigration and test hypotheses related to the role of immigration on population processes on an ecological timescale. The difference in the expected number of parent-offspring dyads between the two population models was greatest when immigration into the sink population was high, indicating that unlike traditional population genetic inference models, the highest degree of statistical power is achieved for the approach presented here when migration rates are high. We used the proposed genetic parentage approach to demonstrate that a threatened population of Marbled Murrelets (Braclhyrarmphus marmotus) appears to be supplemented by a low level of immigration (approximately 2-6% annually) from other populations.
  Ecology 11/2008; 89(10):2746-59. · 4.85 Impact Factor
• Source

  Available from: Benjamin Becker

  Article: Effects of Rapid Flight-Feather Molt on Postbreeding Dispersal in a Pursuit-Diving Seabird

  M Zachariah Peery, Laird A Henkel, Scott H Newman, Benjamin H Becker, James T Harvey, Christopher W Thompson, Steven R Beissinger
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  ABSTRACT: Breeding seabirds have been well studied but seabird ecology during the nonbreeding season is poorly understood because many species disperse far from breeding colonies to molt at sea. We characterized the timing of prebasic molt and postbreeding dispersal, described postbreeding dispersal movements, and estimated changes in body mass during molt for Marbled Murrelets (Brachyramphus marmoratus; Alcidae) in central California, 1999–2004. According to mark–recapture and at-sea surveys, 248–315 of 496–637 individuals (43–50%) used Año Nuevo Bay, located immediately adjacent to nesting areas, for their prebasic molt in August– October. Long-distance dispersal (≥100 km) from Año Nuevo Bay by radiomarked Marbled Murrelets was low during breeding (9–13%, n = 46), but was greater for individuals radiomarked at the end of the breeding season (69–90%, n = 20). The mean dispersal dates were 18 May and 21 October for the breeding and postbreeding samples, respectively, and postbreeding dispersal occurred an average of two weeks after molt completion. Mean dispersal distances were 184 km and 256 km in the breeding and postbreeding periods, respectively. Of 12 long-distance dispersers, all moved south except one. Marbled Murrelets gained mass during molt (n = 184), except during a moderate El Niño event in 2002 when mass remained constant. However, birds did not take longer to molt in 2002, which suggests that individuals allocated more energy reserves to molt processes in that year. Apparently, sufficient prey resources were available in Año Nuevo Bay for both basic metabolic requirements and the demands of molt, even when water was moderately warm.
  The Auk 01/2008; 125:113-123. · 2.16 Impact Factor
• Source

  Available from: esa.org

  Article: Reconstructing the historic demography of an endangered seabird.

  Steven R Beissinger, M Zachariah Peery
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  ABSTRACT: Reducing extinction risk for threatened species requires determining which demographic parameters are depressed and causing population declines. Museum collections may constitute a unique, underutilized resource for measuring demographic changes over long time periods using age-ratio analysis. We reconstruct the historic demography of a U.S. federally endangered seabird, the Marbled Murrelet (Brachyramphus marmoratus), from specimens collected approximately 100 years ago for comparison with predictions from comparative analyses and with results from contemporary field studies using both age-ratio analysis and conventional demographic estimators. Reproduction in the late 1800s and early 1900s matched predictions from comparative analysis, but was 8-9 times greater than contemporary estimates, whereas adult survival was unchanged. Historic reproductive rates would support stable populations, but contemporary levels should result in population declines. Contemporary demographic estimates derived from age-ratio analysis were similar to estimates from conventional estimators. Using museum specimens to reconstruct historic demography provides a unique approach to identify causes of decline and to set demographic benchmarks for recovery of endangered species that meet most assumptions of age-ratio analysis.
  Ecology 03/2007; 88(2):296-305. · 4.85 Impact Factor
• Source

  Available from: Benjamin Becker

  Article: Ocean climate and prey availability affect the trophic level and reproductive success of the marbled murrelet, an endangered seabird

  Benjamin H. Becker, M. Zachariah Peery, Steven R. Beissinger
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  ABSTRACT: We investigated relationships between oceanographic processes, prey availability, diet and the reproductive success of the marbled murrelet Brachyramphus marmoratus (Alcidae), a federally threatened seabird. We predicted that cooler ocean conditions (which increase primary productivity in this eastern boundary upwelling system) should result in heightened prey availability and hence higher reproductive success for the murrelet. We also expected that murrelet diets should reflect those potential prey species that are most abundant during any given season or year. Oceanographic conditions were considered at 2 spatial scales: synoptic (Northern Oscillation Index, NOI; Pacific Decadal Oscillation Index, PDO; the North Pacific Index, NPI), and local (upwelling index, UI; sea surface temperature, SST; strength of the spring turnover). To infer seasonal and annual variation in murrelet diets in central California, we used stable isotope analyses of δ15N and δ13C in murrelet feathers and prey tissues during the pre- and postbreeding seasons of 1998 to 2002. Isotopic signatures of 10 species of potential prey clustered into 3 distinct groups (low, mid and high trophic level seabird prey). During 1999 to 2001, when more krill (low trophic level prey) were available, murrelet δ15N and trophic level were lower prior to breeding than after breeding, whereas pre- and postbreeding diets were similar during 1998 and 2002 when fewer krill were available. δ13C was always lower in prebreeding than postbreeding diets, which tracked availability of 13C enriched juvenile rockfish and market squid. Diet did not differ by sex for either isotope. Murrelet productivity (juvenile:adult ratios) was positively correlated with both rockfish and krill abundance. PDO, NOI, UI, spring turnover strength and NPI indices were unrelated to murrelet productivity and to prey abundances. Murrelet productivity was also positively related to the proportion of mid trophic level prey in postbreeding diets, and thus negatively related to the proportion of low and high trophic level prey consumed. Furthermore, productivity was markedly higher following the apparent 1998 to 1999 PDO regime shift to cooler conditions. These data suggest that cooler local temperatures support increased availability of krill and juvenile rockfish to murrelets, and that this improves murrelet reproductive success.
  Marine Ecology Progress Series 02/2007; 329:267-279. · 2.71 Impact Factor
• Source

  Available from: Benjamin Becker

  Article: Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird.

  M Zachariah Peery, Benjamin H Becker, Steven R Beissinger
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  ABSTRACT: Identifying source-sink dynamics is of fundamental importance for conservation but is often limited by an inability to determine how immigration and emigration influence population processes. We demonstrate two ways to assess the role of immigration on population processes without directly observing individuals dispersing from one population to another and apply these methods to a population of Marbled Murrelets (Brachyramphus marmoratus) in California (USA). In the first method, the rate of immigration (i) is estimated by subtracting local recruitment (recruitment from within the population due to reproduction) estimated with demographic data from total recruitment (f; recruitment from within the population plus recruitment from other populations) estimated using temporal symmetry mark-recapture models developed by R. Pradel. The second method compares population growth rates estimated with temporal symmetry models (lambdaTS) and/or population growth rates estimated from counts of individuals over multiple sampling periods (lambdaC) with growth estimates from a stage-structured projection matrix model (lambdaM). Both lambdaTS and lambdaC incorporate all demographic processes affecting population change (birth, death, immigration, and emigration), whereas matrix models are usually constructed without incorporating immigration. Thus, if lambdaTS and lambdaC are > or = 1 and lambdaM < 1, the population is sustained by immigration and is considered to be a sink. Using the first method, recruitment estimated with temporal symmetry models was high (f= 0.182, SE = 0.058), the mean adult birth rate, as estimated using the ratio of juveniles to > or = 1 year old individuals (observed during ship-based surveys) was low (bA = 0.039, SE = 0.014), and immigration was 0.160 (SE = 0.057). Using the second method, murrelet numbers in central California were stable (lambdaC = 1.058, SE = 0.047; lambdaTS = 1.064, SE = 0.033), but were projected to decline 9.5% annually in the absence of immigration (lambdaM = 0.905, SE = 0.053). Our results suggest that Marbled Murrelets in central California represent a sink population that is stable but would decline in the absence of immigration from larger populations to the north. However, the extent to which modeled immigration is due to permanent recruitment or temporarily dispersing individuals that simply mask population declines is uncertain.
  Ecological Applications 09/2006; 16(4):1516-28. · 5.10 Impact Factor
• Source

  Available from: Benjamin Becker

  Article: Individual and temporal variation in inland flight behavior of marbled murrelets: implications for population monitoring

  M Zachariah Peery, Steven R Beissinger, Scott H Newman, Benjamin H Becker, Esther Burkett, Tony D Williams
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  ABSTRACT: We studied the inland flight behavior of 46 radio-marked Marbled Murrelets (Brachyramphus marmoratus) in 2000 and 2001 in central California to determine how the frequency of inland flights varied among individuals and over time. All breeding murrelets regularly flew inland (mean 82% of daily surveys), but we observed considerable variation in the inland flight behavior of non-nesters. Non-nesters that were physiologically in breed-ing condition (potential breeders) regularly flew inland (90% of individuals; mean 41% of daily surveys), but non-nesters that were not in breeding condition (nonbreeders) rarely flew inland (20% of individuals; mean 1% of daily surveys). The mean percentage of surveys on which individual murrelets flew inland increased from 20% in 2000 to 61% in 2001, which was partly due to an increase in the percentage of breeders from 11% in 2000 to 50% in 2001. The frequency of inland flights was greatest during the incubation and chick-provisioning stages (100% in both stages), and lowest during the pre-and postbreeding stages (70% and 78%, respectively). Although the mean percentage of flights increased dramatically between years, the regional population estimate from at-sea surveys increased only 28% from 496 to 637 individuals during the same period, indicating that monitoring techniques such as radar that count inland flights are more likely to reflect annual variation in breeding effort than changes in regional population size. Moreover, the inland flight behavior of potential breeders indicates that radar surveys will overestimate breeding pop-ulation size, even though the lack of inland flights by nonbreeders indicates that radar surveys will underestimate regional population size.
  The Condor 01/2004; 344(106):344-353. · 1.12 Impact Factor
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  Available from: Martin Raphael

  Article: Trends in radar-based counts of marbled murrelets on the Olympic Peninsula, Washington, 1996-2004.

  Brian A. Cooper, Martin G Raphael, M Zachariah Peery
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  ABSTRACT: The Marbled Murrelet (Brachyramphusmarmoratus) is a highprofile, federally threatened seabird, but noreliable estimates of population trends at inlandbreeding areas exist for this species. We conductedland-based radar studies of Marbled Murrelets at 3-7 sites on the Olympic Peninsula,Washington, in 1996-2002 and 2004 to estimatepopulation changes and to examine relationshipsbetween our counts and oceanographic conditions, murrelet productivity, and regional at-sea countsof murrelets. Morning radar counts of murreletsvaried significantly among and within sites but didnot decline from 1996-2004, suggesting thatthe inland breeding population of murrelets isstable in this area. A retrospective power analysisindicated that we had a 25% and 56%chance of detecting 2% and 4% annualdeclines, respectively. Thus, if relatively smallannual declines did occur during our study period,there is a high probability that they would havegone undetected, even though they could add up to abiologically important decline over time. It isunlikely that murrelets on the Olympic Peninsuladeclined by >or= 6% annually, however,because retrospective analyses indicated that powerto detect such declines was >88%. Therewas no significant relationship between radarcounts and at-sea counts or productivity ofmurrelets in the nearby San Juan Islands during thestudy period. We also did not detect a relationshipbetween radar counts and mean sea-surfacetemperatures or the Northern Oscillation Index,suggesting that variation in oceanographicconditions (e.g., the strong 1998 ElNiño event) was not associated withvariation in morning radar counts of MarbledMurrelets. A prospective power analysis indicatedthat small (2%-4%)annual declines could be detected with reasonablyhigh power (>or= 80%) with thecurrent radar sampling design by extending thestudy to 11-15years.