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Segurança cibernética com hardware reconfigurável em subestações de energia elétrica utilizando o padrão IEC 61850 / Cyber security with reconfigurable hardware in power substations using the IEC 61850 standardJuliano Coêlho Miranda 20 September 2016 (has links)
Com a tecnologia digital, as redes de comunicação têm sido de fundamental importância para o bom funcionamento das subestações de energia elétrica. Criado em 2002, o padrão IEC 61850 busca harmonizar a diversidade de equipamentos e fabricantes, e possibilitar a integração de dados para que o máximo de benefícios possa ser extraído. Nesse contexto, o protocolo GOOSE (Generic Object Oriented Substation Event), pertinente ao padrão IEC 61850, é um datagrama multicast concebido para funcionar na rede local ou de longa distância que interliga as subestações de energia elétrica. Nos ambientes de longa distância, o tráfego de dentro para fora, e vice-versa, deveria passar por um firewall. Porém, a tecnologia de firewall atual não é capaz de inspecionar as mensagens GOOSE reais ou originadas a partir de um ataque, e afeta o tempo de transferência das mesmas, que, no enlace de comunicação, não deve exceder 5ms. Dessa forma, o objetivo deste trabalho é desenvolver um firewall em hardware reconfigurável, por meio da plataforma NetFPGA, de modo que o incremento no tempo de propagação de uma mensagem GOOSE, Tipo 1A (Trip), ao transpor o dispositivo de segurança, não ultrapasse 20% do tempo total destinado ao enlace de comunicação. Por ter a capacidade de ser um acelerador, construído por meio de hardware reconfigurável FPGA (Field Programmable Gate Array), a NetFPGA conduz enlaces Gigabit, e torna possível examinar e estabelecer regras iniciais de autorização ou negação para o tráfego de mensagens GOOSE, manipulando os campos do quadro ISO/IEC 8802-3. O incremento no tempo máximo de propagação de uma mensagem com 1518 bytes foi de 77,39 μs, com 77,38 μs de tempo médio. Um algoritmo de criptografia e outro de autenticação também foram testados e mensagens falsas não conseguiram transpor o firewall. No momento atual da pesquisa, concluiu-se que o firewall em NetFPGA, pertinente ao conjunto de recursos de hardware e software destinados a garantir a segurança de uma rede, é capaz de rejeitar mensagens GOOSE falsas e fornecer segurança aos dispositivos ativos de uma subestação, sem atrasos adicionais superiores a 1ms. / With the digital technology, the communication networks have been of fundamental importance for the good performance of power substations. Created in 2002, the IEC 61850 standard seeks for harmonization of the different equipment and manufacturers, enabling the integration of data for maximum performance. In this context, the GOOSE (Generic Object Oriented Substation Event) message, concerning the IEC 61850 standard, is a multicast datagram, designed to operate in LAN or WAN that connects power substations. In the long-distance environment, the propagation time in the communication link must not exceed 5ms. The current firewall technology is not able to differ true GOOSE messages from the ones originated from an attack, and it affects the transfer time of messages. The objective of this research is to develop a reconfigurable firewall hardware, using the NetFPGA platform, so that the increase in propagation time of a GOOSE message, Type 1A (Trip), does not exceed 20% of the total time allocated to the link communication. Due to the ability of NetFPGA of being an accelerator, and having been built by using reconfigurable FPGA (Field Programmable Gate Array) leading to Gigabit links, it was possible to examine and establish initial rules of authorization or denial of GOOSE messages by manipulating some of the fields from the table ISO/IEC 8802-3. The increase in the maximum propagation time of a message of 1518 bytes was 77.39 μs, with the average of 77.38 μs. Fake messages failed to cross the firewall. Results from a process of authentication and encryption were also presented. At the present study, it has been concluded that the firewall using NetFPGA, concerning the hardware and software in order to ensure the security of a network, is able to reject false GOOSE messages and provide security to devices of a power substation without time increments greater than 1ms.
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Assessment of impacts of Canada geese on wheat productionLouhaichi, Mounir 22 January 1999 (has links)
Numbers of wild Canada geese (Branta canadensis) have increased dramatically during the past 30 years in the lower Columbia and Willamette Valley systems. The damage they cause by grazing and trampling plants can be substantial.
The objectives of this research were to:
1) Develop methods that provide reliable estimates of goose impact on wheat yield and quality, and 2) Develop methods to separate goose damage from other factors that lower
yield such as poor soil or waterlogging.
To document grazing impacts, color aerial photography was combined with Global Positioning System (GPS) and precision farming technology. Field-scale color aerial photographs (1:14,000 scale) were acquired four times during each growing season: in January, March, April, and just prior to harvest in July. Each flight was coupled with ground truth data collection to verify exact cause of spectral signature variation or variations in wheat cover. Such data included wheat height, number of goose droppings, and a relative rating of goose grazing intensity. At each sampling point a platform photograph and a GPS location were taken.
Wheat yield impact varied considerably as field size, shape and proximity to road varied. Yield maps revealed that, goose grazing had reduced grain yield by 25% or more in heavily grazed areas. At harvest time during the first year, wheat grain in the heavily grazed areas had higher moisture content due to delayed maturity. Therefore those areas were harvested two weeks later. Heavily grazed areas also had more weeds than ungrazed portions of the field. Late-season (April) grazing was more damaging to wheat yield than was earlier season grazing, but early season grazing did have an impact on yield. Intensely hazed fields had lower levels of damage than did fields or portions of fields that were not as vigorously guarded.
Our results illustrate very practical ways to combine image analysis capability, spectral observations, global positioning systems, precision farming and ground truth data collection to map and quantify field condition or crop damage from depredation, standing water, or other adversities. Image analysis of geopositioned color platform photographs can be used to stratify winter wheat fields into impact units according to grazing intensity. Ground-truth data, when collected in conjunction with a GPS, provided the information needed to locate and establish the spectral properties of impacted areas. Once the spectral properties of a representative area were identified, information could be extrapolated to other areas with the same characteristics. In addition, this method could be used in conjunction with aerial photography to verify areas of grazing. The combination of two or more of these tools would provide farm managers and agricultural consultants with a cost-effective method to identify problem areas associated with vegetation stress due to heavy grazing by geese or other factors. / Graduation date: 1999
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The domestication history of the European goose:a genomic perspectiveHeikkinen, M. (Marja) 09 June 2017 (has links)
Abstract
Animal domestication is a complex evolutionary process. Multiple forces influence the genetic variation of the species under domestication and leave their mark on the genome of the species. The European domestic goose is an economically and culturally important species, but knowledge about the domestication history of the species has been lacking. My doctoral thesis has focused on elucidating the genetic background of goose domestication using mitochondrial control region sequences and nuclear single nucleotide polymorphisms (SNPs). By comparing the patterns of genetic diversity observed in the greylag goose (Anser anser) and its descendant European domestic geese, I was able to conclude that genetic diversity has decreased in domestic geese following the domestication albeit being still relatively high. In addition, admixture of populations increased the genetic diversity in both greylag geese and domestic geese. The results also confirmed that greylag geese and domestic geese hybridise in certain locations. What is more, many breeds of European domestic geese shared a substantial amount of ancestry with Chinese domestic geese, domesticated from the swan goose (Anser cygnoid). While the timing and location of goose domestication remains unresolved, the results do not disagree with the suggested origin of domestication in the Eastern Mediterranean. More sampling in this region would be needed to further investigate the matter. Lastly, multiple regions in the goose genome have been targeted by selection which is likely to have contributed to phenotypic divergence of greylag and domestic geese, but the functional basis of these differences needs further investigation. / Tiivistelmä
Eläinlajin kesyttäminen on monimutkainen evolutiivinen prosessi. Useat geneettiset tekijät vaikuttavat kesytettävän lajin perinnöllisen monimuotoisuuden määrään ja jättävät lajin perimään jälkensä. Eurooppalainen kesyhanhi on kulttuurillisesti ja taloudellisesti merkittävä laji, mutta tieto sen kesytyshistoriasta on puutteellista. Väitöskirjassani olen keskittynyt tutkimaan hanhen kesytyksen perinnöllistä taustaa käyttäen apuna mitokondrio-DNA:n kontrollialueen sekvenssejä ja yhden emäksen polymorfismeja. Kun vertailin perinnöllisen monimuotoisuuden jakautumista merihanhissa (Anser anser) ja eurooppalaisissa kesyhanhissa, pystyin toteamaan, että perinnöllinen monimuotoisuus on kesytyksen seurauksena vähentynyt kesyhanhissa, mutta se on edelleen suhteellisen korkeaa. Lisäksi risteytyminen muiden populaatioiden kanssa lisäsi perinnöllistä monimuotoisuutta sekä meri- että kesyhanhissa. Tulokset myös vahvistivat, että meri- ja kesyhanhet risteytyvät paikoitellen keskenään. Tämän lisäksi moniin eurooppalaisiin kesyhanhirotuihin on kohdistunut geenivirtaa kiinalaisesta kesyhanhesta, joka on kesytetty joutsenhanhesta (Anser cygnoid). Saadut tulokset vastaavat aiempia näkemyksiä, joiden mukaan hanhi kesytettiin Välimeren idänpuoleisilla alueilla, kanssa, mutta kesytyksen ajankohdan ja paikan tarkempi selvittäminen vaatii vielä lisätutkimuksia ja lisää näytteitä tältä alueelta. Lopuksi voidaan todeta, että useat alueet hanhen perimässä osoittivat merkkejä valinnasta, joka on todennäköisesti vaikuttanut meri- ja kesyhanhien välisiin fenotyyppisiin eroihin, mutta erojen funktionaalinen tausta vaatii lisätutkimuksia.
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Influence de l’alimentation sur les performances des oies et la durabilité du système de production du foie gras : effets de la substitution du maïs par du sorgho et de la forme de présentation de l’aliment / Substitution on corn by sorghun in the diet of gease : technical interests and consequences on the sustainability of systemArroyo, Julien 18 December 2012 (has links)
Ce travail de thèse présente une synthèse de 5 expérimentations qui ont été réalisées afin d’évaluer les possibilités techniques (essais 1 et 4), l’intérêt zootechnique (essais 2, 3 et 5) et les conséquences sur la durabilité d’une substitution du maïs par du sorgho dans la ration alimentaire des oies en phase de croissance-finition et pendant le gavage. Le mode d’alimentation (entièrement granulée ou sous la forme d’un mélange de graines de céréales entières et de granulés riches en protéines) a également été étudié. Nous avons mesuré les performances des animaux (gain de poids, IC, consommation, développement corporel comportement alimentaire) ainsi que la qualité des produits (magret et foie gras) obtenus après gavage. Nous avons évalué in fine les conséquences de ces innovations sur la durabilité du système de production du foie gras à l’échelle de l’atelier de production (méthode S+Durable?) et sur le cycle de production d’un kilo de foie gras (méthode des ACV). Nos résultats montrent que la nature de la céréale (maïs vs. sorgho) utilisée pendant la phase de croissance-finition (6 à 14 semaines) n’a aucune influence sur les performances des animaux. Cependant, nous avons observé que la consommation d’aliments (+ 5% ; P < 0,05), le poids vif (+ 4% ; P < 0,05) et le développement des intestins (+ 9% ; P < 0,05) en phase de croissance-finition étaient plus élevés lorsque le régime alimentaire contenait des graines entières. L’incorporation de sorgho pendant la phase de gavage, entraine une augmentation du poids des foies gras (+ 11% ; P < 0,05) et une diminution de l’intensité de la couleur jaune du foie gras (- 25% ; P < 0,05). Une substitution totale du maïs par du sorgho pendant les phases d’élevage et de gavage réduit les impacts environnementaux de la fabrication d’1 kg de foie gras et améliore les performances de durabilité économique et sociale de l’atelier de production. L’ensemble des résultats suggère que l’utilisation de sorgho dans l’alimentation des oies est techniquement possible pendant les phases de croissance-finition et de gavage, prometteuse zootechniquement et intéressante pour améliorer la durabilité du système de production. / This thesis presents a summary of five experiments which were conducted to evaluate the technical feasibility (studies 1 and 4), zootechnical inetrest (studies 2, 3 and 5) and consequences on sustainability performance of the substitution of corn by sorghum in the diet of geese in growing-finishing period and during overfeeding. The form of diet presentation (totally pelleted or in form of a mixture of cereal whole seeds and protein rich pellets) was also studied. We measured animal performance (weight gain, FCR, feed intake, body characteristics, feeding behavior) and product quality (magret and foie gras) obtained after overfeeding period. We evaluated ultimately the consequences of these innovations on the sustainability of the foie gras production system at the level of rearing unit (S + Durable? method) and over the production cycle of 1 kg of foie gras (LCA method). Our results showed that the type of cereal (corn vs. sorghum) used during the growingfinishing period (6-14 weeks) has no effect on animal performance. However, we observed that feed intake (+ 5%; P < 0.05), body weight (+ 4%; P < 0.05) and the gut development (+9%; P < 0.05) during the growing-finishing period were higher when the diet contained whole grains. The use of sorghum during the overfeeding resulted in an increased weight of fatty liver (+11%; P < 0.05) and a decreased in the intensity of its yellow color (-25%; P < 0.05). A total substitution of corn by sorghum during both growing and overfeeding periods reduced the environmental impacts of 1 kg of foie gras production and increased the economic and social performance of the rearing unit. These results suggest that the use of sorghum in the diet of geese is feasible both during the growing-finishing and overfeeding period, promising from a zootechnical point of view and interesting to improve the sustainability of production system
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A PERFORMANCE GUIDE: AN ANALYSIS OF RICHARD FAITH’S SETTINGS OF MOTHER GOOSEBaker, David B. 01 January 2018 (has links)
This study provides a performance guide to the nine song settings of Mother Goose Lyrics and Mother Goose Lyrics II by American composer Richard Faith (b. 1926). Included is a biography of the composer. The primary purpose is to provide analysis that shows that these nine songs are accessible to undergraduate singers and that these are arguably Faith’s most approachable songs for the young singer. As is pertinent to each individual song the discussion may include information on the poetry, musical form, textual support, pedagogical issues, harmonic progressions, melodic ideas, rhythmic devices, character analysis, as well as information on text setting devices. This is accomplished through the author’s own analysis and study of Faith’s songs, interviews with the composer, and references to the three other dissertations covering Faith’s song compositions. This performance guide will provide an introduction to Richard Faith and his musical style, as well as provide a tool for teachers and singers seeking performance practice guidance.
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The Goose at Goldie's Milk Bar: The Nature of Human Animal Relationships in Three Modern Literary Fairy Tales.Teasdale, Dion, d.teasdale@yarraranges.vic.gov.au January 2007 (has links)
The Goose at Goldie's Milk Bar is a modern literary fairy tale written in the form of a novel for adult readers. Set in the fictional Australian small country town of Baxters Creek, it tells the story of Goldie Sullivan, an elderly former milk bar proprietor who has an affair with a gigantic cognisant gander. Goldie lives out the back of the town's old milk bar, hiding from the surrounding narrow-minded community, until late one night she witnesses a bolt of lightning strike the bell tower on the nearby church. When she goes to investigate, Goldie finds the body of a large bird buried in the debris and, believing it is an omen, she carries the half-dead bird home on her back. As she rehabilitates the bird, Goldie discovers there is more to the feathered creature than she first thought. The bird, a giant gander blown off course and struck down in the middle of migration, reveals an advanced awareness of humanity and the profound ability to comprehend the sorrow in Goldie's life. Through a shared appreciation of jazz music, Goldie and the goose learn to communicate and a close friendship ensues. Goldie teaches the goose to dance, the pair share baths and the goose moves into Goldie's bedroom. Before too long, Goldie finds herself in the midst of a most indecent affair. Goldie's relationship with the gander unfolds against a backdrop of other unconventional relationships. Kevin Dwyer, the new reporter in town finds himself drawn to the shire maintenance worker, Travis Handley. Real estate agent Alexander Bourke has taken Lynne Fontaine, the chef at the local Chinese restaurant, as his oriental mistress, and recently windowed farmer, Mary Peddley, sets tongues wagging with the one-legged publican, Jack Diamond. The novel uses the human animal narrative to explore the premise that fate is driven by unseen, sometimes magical forces that manifest in inexplicable ways to reveal the hidden truths of people. The writing of the novel has been supported by research conducted for an exegesis titled, The Nature of Human Animal Relationships in Three Modern Literary Fairy Tales. The exegesis identifies and discusses the nature of the central human animal relationships in three novels: Yann Martel's Life of Pi, Peter Hoeg's Woman and the Ape and the writing project, The Goose at Goldie's Milk Bar. The exegesis identifies and discusses the roles and functions the human and animal characters perform in the three novels through a comparative analysis of the narrative theories of early Russian Structuralist, Vladimir Propp. The exegesis also identifies and discusses the types of transformation the human and animal characters undergo, and conducts a comparative analysis of the theories of English academic and fairy tale historian, Jack Zipes. Finally, the exegesis analyses and discusses the multi-dimensional nature of the bonds formed by the human and animal characters and demonstrates how writers of modern literary fairy tales seek to awaken the reader to the possibilities of relationships with animals beyond usual human understanding or experience.
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Population biology of Ross's geese at McConnell River, NunavutCaswell, Jason Hughes 25 March 2009
Understanding what influences movement patterns in animals is important to the understanding of colonization, range expansion, and sourcesink dynamics. Rosss geese (Chen rossii) have been expanding their nesting range eastward, and, as recently as 1994, have been nesting in large numbers in such newly colonized areas. I sampled nests at the McConnell River Migratory Bird Sanctuary (MCR), the largest known Rosss goose nesting colony outside the Queen Maud Gulf Migratory Bird Sanctuary (QMG) to estimate its nesting population size. To understand whether immigration by Rosss geese to a new colony located outside traditional nesting areas has an adaptive basis, I compared nutritional, nesting, and survival metrics between geese nesting at the MCR and those nesting at Karrak Lake (KAR) in QMG. I hypothesized that because of longer nesting season, Rosss geese at MCR would have more fat and protein reserves, larger clutch sizes, and greater nest success than those at KAR. Additionally, I hypothesized that population change at MCR was due largely to in situ recruitment. To better understand factors motivating dispersal, movement by Rosss geese between nesting attempts at MCR was measured between years. I hypothesized that dispersal distance of nesting females between years t, and t+1 was a function of both a females own reproductive success as well as that of her neighbours.<p>
In 1997 over 23,000 Rosss geese were counted at MCR. By 2007, population estimates (± SE) had increased to 81,408 (±12,367). Survival of both juvenile and adult geese marked at MCR was similar to those nesting at KAR; however, recovery rate estimates were greater than those for KAR. On average, Rosss geese arrived and initiated nests at MCR seven days earlier than at KAR. Abdominal fat was lower when nest initiation date was later in both areas, but was generally greater in geese nesting at MCR. Similarly, there was more indexed protein in geese at MCR than those at KAR in 2 of 3 years. Nesting indices such as clutch size and nest success did not show a consistent area effect, which interacted with a year effect.<p>
Rosss geese at MCR did not appear to use individual or conspecific reproductive success when deciding if or how far to disperse between years, and temporary emigration rates also did not vary based on reproductive success the previous year. Instead, variables other than prior individual or neighbour nest success influenced Rosss goose nest site selection and colony fidelity. The number of Rosss geese nesting at MCR increased at an average rate of 11.4% per year from 20032007, despite no increase (0%) from 2006 to 2007. Vital rate information gathered during this time suggests that immigration may have contributed to this growth; however, with few assumptions it can be concluded that MCR is a sustainable population. As a result, studies of geese breeding at MCR provide evidence that arctic geese are capable of successfully colonizing nesting areas great distances beyond historic range.
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The role of dispersal in population dynamics of breeding Ross's geeseDrake, Kiel L. 27 April 2006
Spatial variation in density of organisms can lead to challenges in estimation of population size. Associated vital rates responsible for this variation also may vary geographically and in response to local ecological conditions, with the result that subunits of a metapopulation may have different trajectories. Both temporal and spatial variation in population size occurs not only as a result of additions through birth and deletions through death, but also from gains and losses arising from immigration and emigration, respectively. Although virtually all organisms have evolved mechanisms for dispersal, the role of movement in population dynamics has received far less attention than have contributions from recruitment and losses to mortality. I used mark-recapture techniques to make inferences about the role of movement in local population dynamics of Rosss Goose (Chen rossii) colonies by estimating rates of movement between breeding subpopulations in the Queen Maud Gulf metapopulation. I also assessed decision-based philopatry (i.e., the role of previous nesting outcome; sensu Hoover 2003) and a potential cost of reproduction to female geese through experimental manipulation of nesting success. <p>Previous nest fate influenced intra-colony dispersal as failed nesters moved further between consecutive nest sites, but inter-colony movement was not affected by previous nest fate. Regardless of previous nest fate, Rosss Geese did not exhibit philopatry to nest sites, or to breeding territories, suggesting that philopatry occurs at a larger spatial scale. Breeding success accounted for a detectable, but only small amount of variation (<11%) in dispersal distance within colonies. I suggest that temporal variation in habitat availability favors flexibility in settling patterns by geese in a changing matrix of habitat availability, governed largely by receding snow cover. Such flexibility is necessary for nesting as early as possible, because recruitment is strongly linked to timing of breeding by arctic-nesting geese. Colonial philopatry may be important not only for favorable nesting but also for access to high-quality feeding areas adjacent to colonies. Such feeding areas represent a predictable food resource important not only to growing goslings, but also adult survival regardless of the outcome of their breeding attempt. <p>I concluded from experimental manipulation that successful reproduction was encumbered with a cost to survival of females. I argue that such a cost of breeding is more likely to be incurred when climatic conditions during incubation are harsh, and when the breeding population is larger. <p>I did not find evidence for geographic variation in survival, but rates of philopatry varied markedly among colonies. The substantial exchange of females among breeding colonies (1) underscores the potential for dispersal to alter breeding distribution, (2) demonstrates that the influence of immigration on colony-specific rates of population growth was nontrivial, and (3) provides behavioral evidence for extensive gene flow resulting from female dispersal. Estimates of emigration and survival from my studies were used in combination with those for fecundity parameters and colony-specific population growth rates (lambda) to interpolate the role of immigration from a simple balance equation. During years for which rates of movement were estimated, immigration constituted 9-20% of lambda at the Karrak Lake colony, suggesting that movement was an important contribution to population growth.
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Underwater observations of fish attractors in a final cut coal mine lakeRold, Robert E. 03 June 2011 (has links)
Two types of fish attractors, brush attractors made of cedar trees and Berkley and Company's Fish-Hab modules, were placed in a final cut coal mine lake and evaluated for fish concentrating effectiveness. Dives were conducted biweekly and numbers and species of fish at attractors were recorded. Data were then evaluated using Analysis of Variance tests.A total of 623 fish were recorded on attractors during the eight dives made from July 21 to October 24, 1986. Brush attractors held 485 fish or 78% of the total. Module attractors concentrated 105 fish (17%) and 33 fish (5%) were observed in the control areas. Brush attractors concentrated nearly five times as many fish as the modules and 15 times as many fish as the control area. The modules concentrated over three times as many fish as the control area. Results indicated there was no significant difference (0.05) in numbers of fish attracted by brush and modules with an Analysis of Variance With Repeated Measures test but density of individual species was not considered. Furthur analysis of attractors by date and specie over the study period using a One-Way Analysis of Variance revealed that brush attractors concentrated significantly (0.05) more fish than modules in mid to late summer, but not in the early fall. Modules were much less effective at concentrating fish and were never significantly different than the control areas.Scuba diving worked well as a method of evaluation for the attractors. Water clarity was adequate for visual observations and fish did not display a fright response or leave when the diver approached. At no time was there difficulty in identifying or counting fish greater than 10 cm.Ball State UniversityMuncie, IN 47306
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The role of dispersal in population dynamics of breeding Ross's geeseDrake, Kiel L. 27 April 2006 (has links)
Spatial variation in density of organisms can lead to challenges in estimation of population size. Associated vital rates responsible for this variation also may vary geographically and in response to local ecological conditions, with the result that subunits of a metapopulation may have different trajectories. Both temporal and spatial variation in population size occurs not only as a result of additions through birth and deletions through death, but also from gains and losses arising from immigration and emigration, respectively. Although virtually all organisms have evolved mechanisms for dispersal, the role of movement in population dynamics has received far less attention than have contributions from recruitment and losses to mortality. I used mark-recapture techniques to make inferences about the role of movement in local population dynamics of Rosss Goose (Chen rossii) colonies by estimating rates of movement between breeding subpopulations in the Queen Maud Gulf metapopulation. I also assessed decision-based philopatry (i.e., the role of previous nesting outcome; sensu Hoover 2003) and a potential cost of reproduction to female geese through experimental manipulation of nesting success. <p>Previous nest fate influenced intra-colony dispersal as failed nesters moved further between consecutive nest sites, but inter-colony movement was not affected by previous nest fate. Regardless of previous nest fate, Rosss Geese did not exhibit philopatry to nest sites, or to breeding territories, suggesting that philopatry occurs at a larger spatial scale. Breeding success accounted for a detectable, but only small amount of variation (<11%) in dispersal distance within colonies. I suggest that temporal variation in habitat availability favors flexibility in settling patterns by geese in a changing matrix of habitat availability, governed largely by receding snow cover. Such flexibility is necessary for nesting as early as possible, because recruitment is strongly linked to timing of breeding by arctic-nesting geese. Colonial philopatry may be important not only for favorable nesting but also for access to high-quality feeding areas adjacent to colonies. Such feeding areas represent a predictable food resource important not only to growing goslings, but also adult survival regardless of the outcome of their breeding attempt. <p>I concluded from experimental manipulation that successful reproduction was encumbered with a cost to survival of females. I argue that such a cost of breeding is more likely to be incurred when climatic conditions during incubation are harsh, and when the breeding population is larger. <p>I did not find evidence for geographic variation in survival, but rates of philopatry varied markedly among colonies. The substantial exchange of females among breeding colonies (1) underscores the potential for dispersal to alter breeding distribution, (2) demonstrates that the influence of immigration on colony-specific rates of population growth was nontrivial, and (3) provides behavioral evidence for extensive gene flow resulting from female dispersal. Estimates of emigration and survival from my studies were used in combination with those for fecundity parameters and colony-specific population growth rates (lambda) to interpolate the role of immigration from a simple balance equation. During years for which rates of movement were estimated, immigration constituted 9-20% of lambda at the Karrak Lake colony, suggesting that movement was an important contribution to population growth.
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