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Full-Text Articles in Life Sciences

Plasticity Of Foraging Behaviors In Response To Diverse Environmental Conditions, Morgan E. Gilmour, José A. Castillo‐Guerrero, Abram B. Fleishman, Salvador Hernández‐Vázquez, Hillary S. Young, Scott A. Shaffer Jun 2018

Plasticity Of Foraging Behaviors In Response To Diverse Environmental Conditions, Morgan E. Gilmour, José A. Castillo‐Guerrero, Abram B. Fleishman, Salvador Hernández‐Vázquez, Hillary S. Young, Scott A. Shaffer

Scott A. Shaffer

Due to rapidly changing global environmental conditions, many animals are now experiencing concurrent changes in both resource availability and the foraging cues associated with finding those resources. By employing flexible, plastic foraging strategies that use different types of environmental foraging cues, animals could adapt to these novel future environments. To evaluate the extent to which such flexibility and plasticity exist, we analyzed a large dataset of a clade (Sulidae; the boobies) of widespread aerial tropical predators that feed in highly variable marine habitats. These surface foragers are typical of many ocean predators that face dynamic and patchy foraging environments and ...


Persistent Annual Migration Patterns Of A Specialist Seabird, Rachael A. Orben, Nobuo Kokubun, Abram B. Fleishman, Alexis P. Will, Takashi Yamamoto, Scott A. Shaffer, Rosana Paredes, Akinori Takahashi, Alexander S. Kitaysky Apr 2018

Persistent Annual Migration Patterns Of A Specialist Seabird, Rachael A. Orben, Nobuo Kokubun, Abram B. Fleishman, Alexis P. Will, Takashi Yamamoto, Scott A. Shaffer, Rosana Paredes, Akinori Takahashi, Alexander S. Kitaysky

Scott A. Shaffer

Specialization can make animals vulnerable to rapid environmental changes. For long-lived seabirds, foraging specialization may make individuals especially sensitive, as climatic changes are currently occurring over the course of one lifetime. The Bering Sea is a dynamic subarctic and arctic ecosystem where windblown sea ice mediates annual productivity and subsequent pathways to upper trophic levels. Red-legged kittiwakes Rissa brevirostris are endemic surface foraging seabirds specializing on myctophid fishes during reproduction. Their degree of specialization outside the breeding season is less understood. We examined their non-breeding ecology (migration, distribution, isotopic niche) during 4 winters with varying sea ice extent. Although we ...


Fisheries Exploitation By Albatross Quantified With Lipid Analysis, Melinda G. Conners, Chandra Goetsch, Suzanne M. Budge, William A. Walker, Yoko Mitani, Daniel P. Costa, Scott A. Shaffer Apr 2018

Fisheries Exploitation By Albatross Quantified With Lipid Analysis, Melinda G. Conners, Chandra Goetsch, Suzanne M. Budge, William A. Walker, Yoko Mitani, Daniel P. Costa, Scott A. Shaffer

Scott A. Shaffer

Mortality from incidental bycatch in longline fishery operations is a global threat to seabird populations, and especially so for the albatross family (Diomedeidae) in which fifteen out of twenty-two species are threatened by extinction. Despite the risks, fisheries remain attractive to many species of seabird by providing access to high-energy foods in the form of discarded fish and offal, target fish, and baited hooks. Current policy regarding fisheries management is increasingly aimed at discard reform, exemplified by a discard ban initiated in the European Union Common Fisheries Policy in 2014. While there is global agreement in the importance of minimizing ...


Variable Utilization Of Shelf Break-Associated Habitats By Chick-Brooding Rhinoceros Auklets In The California Current System, Bradley P. Wilkinson, Jaime Jahncke, Pete Warzybok, Russell Bradley, Scott A. Shaffer Mar 2018

Variable Utilization Of Shelf Break-Associated Habitats By Chick-Brooding Rhinoceros Auklets In The California Current System, Bradley P. Wilkinson, Jaime Jahncke, Pete Warzybok, Russell Bradley, Scott A. Shaffer

Scott A. Shaffer

Identifying frequently complex and dynamic spatial distributions of marine predators via the modeling of at-sea observations can be inherently challenging, especially when attempting to predict habitats of specific populations. Remotely-sensed tracking devices provide a viable alternative way to gather this information. We collected fine-scale spatiotemporal movement data for a small seabird, the rhinoceros auklet Cerorhinca monocerata, in the California Current System. Chick-brooding adults nesting on Southeast Farallon Island were outfitted with GPS loggers during the 2015 and 2016 breeding seasons (n = 15). Along with basic movement parameters, kernel density and residence time analyses were conducted to characterize at-sea distribution and ...


Egg Turning Behavior And Incubation Temperature In Forster’S Terns In Relation To Mercury Contamination, Gregory T. Taylor, Joshua T. Ackerman, Scott A. Shaffer Feb 2018

Egg Turning Behavior And Incubation Temperature In Forster’S Terns In Relation To Mercury Contamination, Gregory T. Taylor, Joshua T. Ackerman, Scott A. Shaffer

Scott A. Shaffer

Egg turning behavior is an important determinant of egg hatchability, but it remains relatively understudied. Here, we examined egg turning rates and egg temperatures in Forster’s terns (Sterna forsteri). We used artificial eggs containing a data logger with a 3-D accelerometer, a magnetometer, and a temperature thermistor to monitor parental incubation behavior of 131 tern nests. Overall, adults turned their eggs an average (±SD) of 3.8 ± 0.8 turns h-1, which is nearly two times higher than that of other seabirds. Egg turning rates increased with nest initiation date. We also examined egg turning rates and egg temperatures ...


The Political Biogeography Of Migratory Marine Predators, Autumn-Lynn Harrison, Daniel P. Costa, Arliss J. Winship, Scott R. Benson, Steven J. Bograd, Michelle Antolos, Aaron B. Carlisle, Heidi Dewar, Peter H. Dutton, Salvador J. Jorgensen, Suzanne Kohin, Bruce R. Mate, Patrick W. Robinson, Kurt M. Schaefer, Scott A. Shaffer, George L. Shillinger, Samantha E. Simmons, Kevin C. Weng, Kristina M. Gjerde, Barbara A. Block Dec 2017

The Political Biogeography Of Migratory Marine Predators, Autumn-Lynn Harrison, Daniel P. Costa, Arliss J. Winship, Scott R. Benson, Steven J. Bograd, Michelle Antolos, Aaron B. Carlisle, Heidi Dewar, Peter H. Dutton, Salvador J. Jorgensen, Suzanne Kohin, Bruce R. Mate, Patrick W. Robinson, Kurt M. Schaefer, Scott A. Shaffer, George L. Shillinger, Samantha E. Simmons, Kevin C. Weng, Kristina M. Gjerde, Barbara A. Block

Scott A. Shaffer

During their migrations, marine predators experience varying levels of protection and face many threats as they travel through multiple countries’ jurisdictions and across ocean basins. Some populations are declining rapidly. Contributing to such declines is a failure of some international agreements to ensure effective cooperation by the stakeholders responsible for managing species throughout their ranges, including in the high seas, a global commons. Here we use biologging data from marine predators to provide quantitative measures with great potential to inform local, national and international management efforts in the Pacific Ocean. We synthesized a large tracking data set to show how ...


Population-Level Plasticity In Foraging Behavior Of Western Gulls (Larus Occidentalis), Scott A. Shaffer, Sue Cockerham, Pete Warzybok, Russell W. Bradley, Jaime Jahncke, Corey A. Clatterbuck, Magali Lucia, Jennifer A. Jelincic, Anne L. Cassell, Emma C. Kelsey, Josh Adams Dec 2017

Population-Level Plasticity In Foraging Behavior Of Western Gulls (Larus Occidentalis), Scott A. Shaffer, Sue Cockerham, Pete Warzybok, Russell W. Bradley, Jaime Jahncke, Corey A. Clatterbuck, Magali Lucia, Jennifer A. Jelincic, Anne L. Cassell, Emma C. Kelsey, Josh Adams

Scott A. Shaffer

Background
Plasticity in foraging behavior among individuals, or across populations may reduce competition. As a generalist carnivore, western gulls (Larus occidentalis) consume a wide range of marine and terrestrial foods. However, the foraging patterns and habitat selection (ocean or land) of western gulls is not well understood, despite their ubiquity in coastal California. Here, we used GPS loggers to compare the foraging behavior and habitat use of western gulls breeding at two island colonies in central California.
Results
Gulls from offshore Southeast Farallon Island (SFI; n = 41 gulls) conducted more oceanic trips (n = 90) of shorter duration (3.8 ± 3 ...


Foraging Behavior And Energetics Of Albatrosses In Contrasting Breeding Environments, Michelle Antolos, Scott A. Shaffer, Henri Weimerskirch, Yann Tremblay, Daniel P. Costa Dec 2017

Foraging Behavior And Energetics Of Albatrosses In Contrasting Breeding Environments, Michelle Antolos, Scott A. Shaffer, Henri Weimerskirch, Yann Tremblay, Daniel P. Costa

Scott A. Shaffer

Animals can maximize fitness by optimizing energy acquisition through the selection of favorable foraging habitats, but trade-offs exist between time spent in preferred feeding habitats, energetic costs of travel, and reproductive constraints. For pelagic seabirds, geographic distribution of suitable breeding islands can restrict access to marine prey resources and influence foraging strategies. Laysan (Phoebastria immutabilis) and black-footed albatrosses (P. nigripes) breeding in the Northwest Hawaiian Islands, and Indian yellow-nosed albatrosses (Thalassarche carteri) breeding in the Southern Indian Ocean, utilize productive subtropical-subpolar transition zones during their breeding and non-breeding periods, but this marine feature is at a comparatively greater distance for ...


Data Loggers In Artificial Eggs Reveal That Egg-Turning Behavior Varies On Multiple Ecological Scales In Seabirds, Corey A. Clatterbuck, Lindsay C. Young, Eric A. Vanderwerf, Alexander D. Naiman, Geoff C. Bower, Scott A. Shaffer Mar 2017

Data Loggers In Artificial Eggs Reveal That Egg-Turning Behavior Varies On Multiple Ecological Scales In Seabirds, Corey A. Clatterbuck, Lindsay C. Young, Eric A. Vanderwerf, Alexander D. Naiman, Geoff C. Bower, Scott A. Shaffer

Scott A. Shaffer

In most avian species, egg-turning behavior during incubation is vital for proper embryonic development and hatching success. However, changes in turning behaviors are rarely studied across different temporal scales (e.g., day–night or across incubation phases), though the timing of incubation behaviors affects reproductive success. We used data loggers encapsulated in artificial eggs to measure turning rates and angle changes of eggs in Western Gull (Larus occidentalis) and Laysan Albatross (Phoebastria immutabilis) nests. We examined diurnal and daily cycles in egg-turning behaviors across early, middle, and late incubation phases. Our results indicate that (1) egg-turning behaviors remain similar throughout ...


Applying Global Criteria To Tracking Data To Define Important Areas For Marine Conservation, Ben Lascelles, P. R. Taylor, M. Miller, M. P. Dias, S. Oppel, L. Torres, A. Hedd, M. Le Corre, R A. Phillips, Scott A. Shaffer, H. Weimerskirch, C. Small Mar 2016

Applying Global Criteria To Tracking Data To Define Important Areas For Marine Conservation, Ben Lascelles, P. R. Taylor, M. Miller, M. P. Dias, S. Oppel, L. Torres, A. Hedd, M. Le Corre, R A. Phillips, Scott A. Shaffer, H. Weimerskirch, C. Small

Scott A. Shaffer

Aim Enhanced management of areas important for marine biodiversity are now obligations under a range of international treaties. Tracking data provide unparalleled information on the distribution of marine taxa, but there are no agreed guidelines that ensure these data are used consistently to identify biodiversity hotspots and inform marine management decisions. Here, we develop methods to standardize the analysis of tracking data to identify sites of conservation importance at global and regional scales. Location We applied these methods to the largest available compilation of seabird tracking data, covering 60 species, collected from 55 deployment locations ranging from the poles to ...


Environmental Temperatures, Artificial Nests, And Incubation Of Cassin's Auklet, Emma C. Kelsey, Russell W. Bradley, Pete Warzybok, Jamie Jahncke, Scott A. Shaffer Nov 2015

Environmental Temperatures, Artificial Nests, And Incubation Of Cassin's Auklet, Emma C. Kelsey, Russell W. Bradley, Pete Warzybok, Jamie Jahncke, Scott A. Shaffer

Scott A. Shaffer

Hatching success in birds is influenced by the temperature and turning rate of the egg, but our understanding of the environmental factors that effect incubation temperatures and egg turning rates in birds is limited. Especially little is known of these effects for species that nest in burrows or crevices, such as the Cassin's auklet (Ptychoramphus aleuticus). On Southeast Farallon Island, California, USA, a subset of the Cassin's auklet (hereafter auklet) population nest in artificial nest boxes. The nest boxes are above ground and made out of a single layer of plywood. Temperatures in unshaded nest boxes can increase ...


Individual-Level Variation And Higher-Level Interpretations Of Space Use In Wide-Ranging Species: An Albatross Case Study Of Sampling Effects, Sarah E. Gutowsky, Marty L. Leonard, Melinda G. Conners, Scott A. Shaffer, Ian D. Jonsen Nov 2015

Individual-Level Variation And Higher-Level Interpretations Of Space Use In Wide-Ranging Species: An Albatross Case Study Of Sampling Effects, Sarah E. Gutowsky, Marty L. Leonard, Melinda G. Conners, Scott A. Shaffer, Ian D. Jonsen

Scott A. Shaffer

Marine ecologists and managers need to know the spatial extent of at-sea areas most frequented by the groups of wildlife they study or manage. Defining group-specific ranges and distributions (i.e., space use at the level of species, population, age-class, etc.) can help to identify the source or severity of common or distinct threats among different at-risk groups. In biologging studies, this is accomplished by estimating the space use of a group based on a sample of tracked individuals. A major assumption of these studies is consistency in individual movements among members of a group. The implications of scaling up ...


Body Size Affects Individual Winter Foraging Strategies Of Thick-Billed Murres In The Bering Sea, Rachael A. Orben, Rosana Paredes, Daniel D. Roby, David B. Irons, Scott A. Shaffer Oct 2015

Body Size Affects Individual Winter Foraging Strategies Of Thick-Billed Murres In The Bering Sea, Rachael A. Orben, Rosana Paredes, Daniel D. Roby, David B. Irons, Scott A. Shaffer

Scott A. Shaffer

  1. Foraging and migration often require different energetic and movement strategies. Though not readily apparent, constraints during one phase might influence the foraging strategies observed in another. For marine birds that fly and dive, body size constraints likely present a trade-off between foraging ability and migration as smaller bodies reduce flight costs, whereas larger bodies are advantageous for diving deeper.
  2. This study examines individual wintering strategies of deep diving thick-billed murres (Uria lomvia) breeding at three colonies in the south-eastern Bering Sea: St Paul, St George and Bogoslof. These colonies, arranged north to south, are located such that breeding birds forage ...


Wintering North Pacific Black-Legged Kittiwakes Balance Spatial Flexibility And Consistency, Rachael A. Orben, Rosana Paredes, Daniel D. Roby, David B. Irons, Scott A. Shaffer Oct 2015

Wintering North Pacific Black-Legged Kittiwakes Balance Spatial Flexibility And Consistency, Rachael A. Orben, Rosana Paredes, Daniel D. Roby, David B. Irons, Scott A. Shaffer

Scott A. Shaffer

Background: Marine environments are inherently dynamic, yet marine predators are often long-lived and employ strategies where consistency, individual specialization, routine migrations, and spatial memory are key components to their foraging and life-history strategies. Intrinsic determinates of animal movements are linked to physiological and life-history traits (e.g. sex, colony, experience), while extrinsic influences occur as the result of an animal’s interactions with either other animals or the environment (e.g. prey availability, weather, competition). Knowledge of the factors affecting animal movements is critical to understand energetic bottlenecks and population dynamics. Here, we attempt to understand the interaction of some ...


Foraging Behavior Links Climate Variability And Reproduction In North Pacific Albatrosses, Lesley H. Thorne, Elliott L. Hazen, Steven J. Bograd, David G. Foley, Melinda G. Conners, Michelle A. Kappes, Hyemi M. Kim, Daniel P. Costa, Yann Tremblay, Scott A. Shaffer Sep 2015

Foraging Behavior Links Climate Variability And Reproduction In North Pacific Albatrosses, Lesley H. Thorne, Elliott L. Hazen, Steven J. Bograd, David G. Foley, Melinda G. Conners, Michelle A. Kappes, Hyemi M. Kim, Daniel P. Costa, Yann Tremblay, Scott A. Shaffer

Scott A. Shaffer

Background: Climate-driven environmental change in the North Pacific has been well documented, with marked effects on the habitat and foraging behavior of marine predators. However, the mechanistic linkages connecting climate-driven changes in behavior to predator populations are not well understood. We evaluated the effects of climate-driven environmental variability on the reproductive success and foraging behavior of Laysan and Black-footed albatrosses breeding in the Northwest Hawaiian Islands during both brooding and incubating periods. We assessed foraging trip metrics and reproductive success using data collected from 2002–2012 and 1981–2012, respectively, relative to variability in the location of the Transition Zone ...


Reproductive Constraints Influence Habitat Accessibility, Segregation, And Preference Of Sympatric Albatross Species, Michelle A. Kappes, Scott A. Shaffer, Yann Tremblay, David G. Foley, Daniel M. Palacios, Steven J. Bograd, Daniel P. Costa Sep 2015

Reproductive Constraints Influence Habitat Accessibility, Segregation, And Preference Of Sympatric Albatross Species, Michelle A. Kappes, Scott A. Shaffer, Yann Tremblay, David G. Foley, Daniel M. Palacios, Steven J. Bograd, Daniel P. Costa

Scott A. Shaffer

Background
The spatiotemporal distribution of animals is dependent on a suite of factors, including the distribution of resources, interactions within and between species, physiological limitations, and requirements for reproduction, dispersal, or migration. During breeding, reproductive constraints play a major role in the distribution and behavior of central place foragers, such as pelagic seabirds. We examined the foraging behavior and marine habitat selection of Laysan (Phoebastria immutabilis) and black-footed (P. nigripes) albatrosses throughout their eight month breeding cycle at Tern Island, Northwest Hawaiian Islands to evaluate how variable constraints of breeding influenced habitat availability and foraging decisions. We used satellite tracking ...


Shadowed By Scale: Subtle Behavioral Niche Partitioning In Two Sympatric, Tropical Breeding Albatross Species, Melinda G. Conners, Elliott L. Hazen, Daniel P. Costa, Scott A. Shaffer Sep 2015

Shadowed By Scale: Subtle Behavioral Niche Partitioning In Two Sympatric, Tropical Breeding Albatross Species, Melinda G. Conners, Elliott L. Hazen, Daniel P. Costa, Scott A. Shaffer

Scott A. Shaffer

Background: To meet the minimum energetic requirements needed to support parents and their provisioned offspring, the timing of breeding in birds typically coincides with periods of high food abundance. Seasonality and synchrony of the reproductive cycle is especially important for marine species that breed in high latitudes with seasonal booms in ocean productivity. Laysan and black-footed albatrosses breeding in the northwestern Hawaiian Islands have a dual reliance on both seasonally productive waters of high latitudes and on nutrient-poor waters of low latitudes, because their foraging ranges contract during the short but critical brood-guard stage. Therefore, these species face an additional ...


North Or South? Niche Separation Of Endemic Red-Legged Kittiwakes And Sympatric Black-Legged Kittiwakes During Their Non-Breeding Migrations, Rachael A. Orben, David B. Irons, Rosana Paredes, Daniel D. Roby, Richard A. Phillips, Scott A. Shaffer Jan 2015

North Or South? Niche Separation Of Endemic Red-Legged Kittiwakes And Sympatric Black-Legged Kittiwakes During Their Non-Breeding Migrations, Rachael A. Orben, David B. Irons, Rosana Paredes, Daniel D. Roby, Richard A. Phillips, Scott A. Shaffer

Scott A. Shaffer

Aim
Species that breed sympatrically often occupy different foraging niches to mitigate competition for prey. When resource availability declines at the end of the breeding season, some animals migrate to regions with more favourable environmental conditions. When these life-history traits combine, foraging habitat preferences may continue to influence migration patterns and habitat utilization. The Bering Sea is home to the red-legged kittiwake (RLKI), Rissa brevirostris, which is endemic, and the black-legged kittiwake (BLKI), Rissa tridactyla, which has a circumpolar breeding distribution. Since the 1970s, numbers of RLKIs at the largest colony have declined and then recovered, whilst the BLKI population ...


Stable Isotope Values Delineate The Non-Breeding Distributions Of Sooty Shearwaters Puffinus Griseus In The North Pacific Ocean, David R. Thompson, Leigh G. Torres, Graeme A. Taylor, Matt J. Rayner, Paul M. Sagar, Scott A. Shaffer, Richard A. Phillips, Sarah J. Bury Dec 2014

Stable Isotope Values Delineate The Non-Breeding Distributions Of Sooty Shearwaters Puffinus Griseus In The North Pacific Ocean, David R. Thompson, Leigh G. Torres, Graeme A. Taylor, Matt J. Rayner, Paul M. Sagar, Scott A. Shaffer, Richard A. Phillips, Sarah J. Bury

Scott A. Shaffer

Following breeding, sooty shearwaters Puffinus griseus leave New Zealand waters and migrate to 1 of 3 distinct areas in the North Pacific Ocean, effectively exploiting environmental resources across a large proportion of this northern ocean basin. In this study, we combined electronic tracking technology with stable isotope analyses (δ15N and δ13C) of feathers grown during the non-breeding period in order to evaluate whether isotope signatures can be used to identify specific non-breeding areas used by sooty shearwaters. A region to the east of Japan was utilised by the majority of tracked birds, whereas others used areas ...


Daily Activity Budgets Reveal A Quasi-Flightless Stage During Non-Breeding In Hawaiian Albatrosses, Sarah E. Gutowsky, Lee Fg Gutowsky, Ian D. Jonsen, Marty L. Leonard, Maura B. Naughton, Marc Romano, Scott A. Shaffer Nov 2014

Daily Activity Budgets Reveal A Quasi-Flightless Stage During Non-Breeding In Hawaiian Albatrosses, Sarah E. Gutowsky, Lee Fg Gutowsky, Ian D. Jonsen, Marty L. Leonard, Maura B. Naughton, Marc Romano, Scott A. Shaffer

Scott A. Shaffer

Background
Animals adjust activity budgets as competing demands for limited time and energy shift across life history phases. For far-ranging migrants and especially pelagic seabirds, activity during breeding and migration are generally well studied but the “overwinter” phase of non-breeding has received less attention. Yet this is a critical time for recovery from breeding, plumage replacement and gaining energy stores for return migration and the next breeding attempt. We aimed to identify patterns in daily activity budgets (i.e. time in flight, floating on the water’s surface and active foraging) and associated spatial distributions during overwinter for the laysan ...


As The Egg Turns: Monitoring Egg Attendance Behavior In Wild Birds Using Novel Data Logging Technology, Scott A. Shaffer, Corey A. Clatterbuck, Emma C. Kelsey, Alex D. Naiman, Lindsay C. Young, Eric A. Vanderwerf, Pete Warzybok, Russell Bradley, Jaime Jahncke, Geoff C. Bower Dec 2013

As The Egg Turns: Monitoring Egg Attendance Behavior In Wild Birds Using Novel Data Logging Technology, Scott A. Shaffer, Corey A. Clatterbuck, Emma C. Kelsey, Alex D. Naiman, Lindsay C. Young, Eric A. Vanderwerf, Pete Warzybok, Russell Bradley, Jaime Jahncke, Geoff C. Bower

Scott A. Shaffer

Egg turning is unique to birds and critical for embryonic development in most avian species. Technology that can measure changes in egg orientation and temperature at fine temporal scales (1 Hz) was neither readily available nor small enough to fit into artificial eggs until recently. Here we show the utility of novel miniature data loggers equipped with 3-axis (i.e., triaxial) accelerometers, magnetometers, and a temperature thermistor to study egg turning behavior in free-ranging birds. Artificial eggs containing egg loggers were deployed in the nests of three seabird species for 1–7 days of continuous monitoring. These species (1) turned ...


High Predation On Small Populations: Avian Predation On Imperiled Salmonids, Ann-Marie K. Osterback, Danielle M. Frechette, Andrew O. Shelton, Sean A. Hayes, Morgan Bond, Scott A. Shaffer, Jonathan W. Moore Sep 2013

High Predation On Small Populations: Avian Predation On Imperiled Salmonids, Ann-Marie K. Osterback, Danielle M. Frechette, Andrew O. Shelton, Sean A. Hayes, Morgan Bond, Scott A. Shaffer, Jonathan W. Moore

Scott A. Shaffer

Generalist predators can contribute to extinction risk of imperiled prey populations even through incidental predation. Quantifying predation on small populations is important to manage their recovery, however predation is often challenging to observe directly. Recovery of prey tags at predator colonies can indirectly provide minimum estimates of predation, however overall predation rates often remain unquantifiable because an unknown proportion of tags are deposited off‐colony. Here, we estimated overall predation rates on threatened wild juvenile steelhead (Oncorhynchus mykiss) by generalist adult Western Gulls (Larus occidentalis) in six central California (USA) watersheds. We estimated predation rates by gulls from the recapture ...


Contemporary And Historical Separation Of Transequatorial Migration Between Genetically Distinct Seabird Populations, M J. Rayner, M E. Hauber, T E. Steeves, H A. Lawrence, D R. Thompson, P M. Sagar, S J. Bury, R A. Phillips, T J. Landers, L Ranjard, Scott A. Shaffer Dec 2010

Contemporary And Historical Separation Of Transequatorial Migration Between Genetically Distinct Seabird Populations, M J. Rayner, M E. Hauber, T E. Steeves, H A. Lawrence, D R. Thompson, P M. Sagar, S J. Bury, R A. Phillips, T J. Landers, L Ranjard, Scott A. Shaffer

Scott A. Shaffer

Pelagic seabirds are highly mobile, reducing the likelihood of allopatric speciation where disruption of gene flow between populations is caused by physically insurmountable, extrinsic barriers. Spatial segregation during the non-breeding season appears to provide an intrinsic barrier to gene flow among seabird populations that otherwise occupy nearby or overlapping regions during breeding, but how this is achieved remains unclear. Here we show that the two genetically distinct populations of Cook's petrel (Pterodroma cookii) exhibit transequatorial separation of non-breeding ranges at contemporary (ca. 2–3 yrs) and historical (ca. 100 yrs) time scales. Segregation during the non-breeding season per se ...


Shearwater Foraging In The Southern Ocean: The Roles Of Prey Availability And Winds, B Raymond, Scott A. Shaffer, S Sokolov, E Woehler, D P. Costa, L Einoder, M Hindell, G Hosie, M Pinkerton, P M. Sagar, D Scott, A Smith, D R. Thompson, C Vertigan, H Weimerskirch Dec 2009

Shearwater Foraging In The Southern Ocean: The Roles Of Prey Availability And Winds, B Raymond, Scott A. Shaffer, S Sokolov, E Woehler, D P. Costa, L Einoder, M Hindell, G Hosie, M Pinkerton, P M. Sagar, D Scott, A Smith, D R. Thompson, C Vertigan, H Weimerskirch

Scott A. Shaffer

Background Sooty (Puffinus griseus) and short-tailed (P. tenuirostris) shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. Methodology/Principal Findings Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140°E ...


Niche Partitioning Among And Within Sympatric Tropical Seabirds Revealed By Stable Isotope Analysis, H S. Young, D J. Mccauley, R Dirzo, R D. Dunbar, Scott A. Shaffer Dec 2009

Niche Partitioning Among And Within Sympatric Tropical Seabirds Revealed By Stable Isotope Analysis, H S. Young, D J. Mccauley, R Dirzo, R D. Dunbar, Scott A. Shaffer

Scott A. Shaffer

The low productivity and unpredictable nature of resources in tropical waters would appear to make resource partitioning among predators difficult. Yet, stable isotope data from the present study suggest that substantial resource partitioning occurs among tropical seabird communities, both between and within species. In the present study, we compared δ13C and δ15N levels among 8 sympatric tropical seabird species. For a subset of these species, we also examined isotopic levels across years, breeding periods, and sexes. When breeding and non-breeding periods were both considered, we found that all species occupied distinct isotopic niches across at least one time period. Resource ...


Bringing Home The Trash: Do Differences In Foraging Lead To Increased Plastic Ingestion In Laysan Albatrosses?, L C. Young, C Vanderlip, D C. Duffy, V Afanasyev, Scott A. Shaffer Dec 2008

Bringing Home The Trash: Do Differences In Foraging Lead To Increased Plastic Ingestion In Laysan Albatrosses?, L C. Young, C Vanderlip, D C. Duffy, V Afanasyev, Scott A. Shaffer

Scott A. Shaffer

When searching for prey, animals should maximize energetic gain, while minimizing energy expenditure by altering their movements relative to prey availability. However, with increasing amounts of marine debris, what once may have been ‘optimal’ foraging strategies for top marine predators, are leading to sub-optimal diets comprised in large part of plastic. Indeed, the highly vagile Laysan albatross (Phoebastria immutabilis) which forages throughout the North Pacific, are well known for their tendency to ingest plastic. Here we examine whether Laysan albatrosses nesting on Kure Atoll and Oahu Island, 2,150 km apart, experience different levels of plastic ingestion. Twenty two geolocators ...


Wind, Waves, And Wing Loading: Their Relative Importance To The At-Sea Distribution And Movements Of North And Central Pacific Albatrosses, R M. Suryan, D J. Anderson, Scott A. Shaffer, D D. Roby, Y Tremblay, D P. Costa, F Sato, K Ozaki, G Balogh Dec 2007

Wind, Waves, And Wing Loading: Their Relative Importance To The At-Sea Distribution And Movements Of North And Central Pacific Albatrosses, R M. Suryan, D J. Anderson, Scott A. Shaffer, D D. Roby, Y Tremblay, D P. Costa, F Sato, K Ozaki, G Balogh

Scott A. Shaffer

Among the varied adaptations for avian flight, the morphological traits allowing large-bodied albatrosses to capitalize on wind and wave energy for efficient long-distance flight are unparalleled. Consequently, the biogeographic distribution of most albatrosses is limited to the windiest oceanic regions on earth; however, exceptions exist. Species breeding in the North and Central Pacific Ocean (Phoebastria spp.) inhabit regions of lower wind speed and wave height than southern hemisphere genera, and have large intrageneric variation in body size and aerodynamic performance. Here, we test the hypothesis that regional wind and wave regimes explain observed differences in Phoebastria albatross morphology and we ...


Perspectives In Ornithology: Application Of Tracking And Data-Logging Technology In Research And Conservation Of Seabirds, A E. Burger, Scott A. Shaffer Dec 2007

Perspectives In Ornithology: Application Of Tracking And Data-Logging Technology In Research And Conservation Of Seabirds, A E. Burger, Scott A. Shaffer

Scott A. Shaffer

No abstract provided.


Corticosterone And Foraging Behaviour In A Pelagic Seabird, F Angelier, Scott A. Shaffer, H Weimerskirch, C Trouvé, O Chastel Dec 2006

Corticosterone And Foraging Behaviour In A Pelagic Seabird, F Angelier, Scott A. Shaffer, H Weimerskirch, C Trouvé, O Chastel

Scott A. Shaffer

Because endocrine mechanisms are thought to mediate behavioral responses to changes in the environment, examining these mechanisms is essential for understanding how long-lived seabirds adjust their foraging decisions to contrasting environmental conditions in order to maximize their fitness. In this context, the hormone corticosterone (CORT) deserves specific attention because of its major connections with locomotor activities. We examined for the first time the relationships between individual CORT levels and measurements of foraging success and behavior using satellite tracking and blood sampling from wandering albatrosses (Diomedea exulans) before (pretrip CORT levels) and after (posttrip CORT levels) foraging trips during the incubation ...


Validation Of Water Flux And Body Composition In Glaucous Gulls (Larus Hyperboreus), Scott A. Shaffer, Gabrielsen, G.W., Verreault, J, Costa, D.P Dec 2005

Validation Of Water Flux And Body Composition In Glaucous Gulls (Larus Hyperboreus), Scott A. Shaffer, Gabrielsen, G.W., Verreault, J, Costa, D.P

Scott A. Shaffer

Water influx rates (WIR) measured with tritiated water dilution were compared with direct measures of water and energy intake in glaucous gulls (Larus hyperboreus). Total body water (TBW) measured isotopically was also compared with TBW determined by body composition analysis (BCA) of the same birds. Seventeen wild gulls were captured and studied in outdoor enclosures at Ny-Ålesund, Svalbard, in July 2002. Gulls were hand-fed known quantities of Arctic cod (Boreogadus saida) or given water on the basis of one of four experimental treatments: (A) fasting, (B) fish only, (C) water only, or (D) fish and water. Water and energy content ...