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Moore, Joseph D., and David G. Krementz. "Migratory connectivity of american woodcock using band return data." Journal of Wildlife Management 81, no. 6 (2017): 1063–72. http://dx.doi.org/10.1002/jwmg.21269.
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Moran-Taylor, Michelle J. "Going North, coming South: Guatemalan migratory flows." MIGRATION LETTERS 6, no. 2 (2009): 155–64. http://dx.doi.org/10.33182/ml.v6i2.74.
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Understanding the return aspect of international migration is vital because returnees replete with new ideas, perceptions on life, and monies affect every dimension of social life in migrants’ places of origin. Yet, return migration remains uneven and an understudied aspect of migratory flows because migration scholars have privileged why individuals migrate, the underlying motivations for their moves abroad, and how migrants assimilate and succeed in their destinations abroad. Drawing on ethnographic research, this article addresses the migratory flows of Ladino and Mayan Guatemalans: those who go North, but in particular, those who come South. And in doing so, it highlights their similar and divergent responses towards migration processes.
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González, Betsabé Román, Eduardo Carrillo Cantú, and Rubén Hernández-León. "Moving to the ‘Homeland’." Mexican Studies/Estudios Mexicanos 32, no. 2 (2016): 252–75. http://dx.doi.org/10.1525/mex.2016.32.2.252.
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A growing number of minors have become part of the return migratory flow from the United States to Mexico. Based on a longitudinal study started in 2012, this article uses life-history narratives to analyze the return experiences of three children who arrived in the state of Morelos, Mexico, between 2010 and 2012. The findings presented here focus on a specific segment of the children’s migratory journey: leaving the United States, crossing the border and arriving in Morelos. The article contributes to the scholarship on children’s narratives of migration, which has been under-emphasized in traditional studies of United States-Mexico migration. Un número creciente de menores de edad forma parte del flujo migratorio de retorno de Estados Unidos a México. Con base en un estudio longitudinal iniciado en el 2012, este artículo hace uso de las historias de vida para analizar las experiencias de retorno de tres niños que llegaron al estado de Morelos, México, entre el 2010 y el 2012. Los resultados que se presentan están centrados en un segmento específico del recorrido migratorio de estos niños: partir de los Estados Unidos, cruzar la frontera y llegar a Morelos. Este artículo contribuye a los estudios migratorios centrados en la narrativa de los niños, la cual ha sido poco valorada en los estudios de migración entre Estados Unidos y México.
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Szente-Varga, Mónika, and Amadea Bata-Balog. "Return migration from Venezuela to Europe: Back to the Roots?" Estudos Internacionais: revista de relações internacionais da PUC Minas 9, no. 3 (2021): 75–95. http://dx.doi.org/10.5752/p.2317-773x.2021v9n3p75-95.
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The exodus from Venezuela increased in intensity until the Covid-19 pandemic. Arrivals in Europe were significantly lower than in Latin America, but also grew and displayed a shift in composition, including a decreasing percentage of people with European origins. This study investigates migration from Venezuela to Spain, Italy and Hungary, in the 21st century. It begins with a detailed theoretical framework and then examines the particular migratory flows. The analysis covers the major features of these migration moves, including antecedents, reasons and motivations, size, geographical distribution and indicators related to integration. Mixed methods are used, both qualitative and quantitative. Findings show that current emigration from Venezuela to Spain, Italy and Hungary can be considered as return migration because original flows existed in the 19th and 20th centuries, and actual counterflows not only incorporate descendants of immigrants but are also based on the existing migratory systems and networks between these countries.
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Alger, Samantha A., P. Alexander Burnham, Zachary S. Lamas, Alison K. Brody, and Leif L. Richardson. "Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size." PeerJ 6 (November 2, 2018): e5812. http://dx.doi.org/10.7717/peerj.5812.
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Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.
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Cormier, Renée L., Diana L. Humple, Thomas Gardali, and Nathaniel E. Seavy. "Migratory connectivity of Golden-crowned Sparrows from two wintering regions in California." Animal Migration 3, no. 1 (2016): 48–56. http://dx.doi.org/10.1515/ami-2016-0005.
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AbstractKnowledge of migratory connectivity is critical to understanding the consequences of habitat loss and climate change on migratory species. We used light-level geolocators to determine breeding locations and migratory routes of wintering Golden-crowned Sparrows (Zonotrichia atricapilla) in two regions of California, USA. Eight out of 9 birds tagged at coastal-wintering sites in Marin County went to breeding sites along the Gulf Coast of Alaska, while 7 out of 8 inland-wintering birds in Placer County migrated to interior sites in the Yukon, Northwest Territories, and British Columbia, Canada. Our estimate of the strength of migratory connectivity was relatively high (rm = 0.66). Coastal-wintering birds followed a coastal migration route while inland-wintering birds migrated inland. Coastalwintering birds migrated significantly farther than inland birds (3,624 km versus 2,442 km). Coastal birds traveled at a greater rate during spring migration (179 km/d) than did inland birds (118 km/d), but there was no statistical difference in the rate of fall migration (167 km/d and 111 km/d, respectively). Dates of arrival and departure, and duration of spring and fall migration, did not differ between groups, nor did return rates. Rates of return also did not differ between tagged and control birds. The distinct migration routes and breeding areas suggests that there may be more structuring in the migratory geography of the Golden-crowned Sparrow than in a simple panmictic population.
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Coss, Derek A., Kevin E. Omland, and Evangeline M. Rose. "Migratory return rates and breeding fidelity in Eastern Bluebirds (Sialia sialis)." Wilson Journal of Ornithology 131, no. 3 (2019): 598. http://dx.doi.org/10.1676/18-181.
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Jara, Laura, Carlos Ruiz, Raquel Martín-Hernández, et al. "The Effect of Migratory Beekeeping on the Infestation Rate of Parasites in Honey Bee (Apis mellifera) Colonies and on Their Genetic Variability." Microorganisms 9, no. 1 (2020): 22. http://dx.doi.org/10.3390/microorganisms9010022.
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Migratory beekeeping is a widely extended practice aimed at increasing the yield of products and pollination services of honey bee colonies. However, it represents a stress factor, as it facilitates the dissemination of diseases and may compromise the genetic identity of the colonies involved. To analyze the extent of these effects, pathogens infestation rate and genetic composition were monitored in a field experiment comparing stationary and migratory colonies sharing the same environmental conditions but differing in management (stationary vs. migratory) and genetic background. We studied the pathogens infestation rate (Varroa destructor, Nosema spp., and Deformed Wing Virus (DWV)) at four different times: before migratory operation, two weeks later, at the end of the migratory period, and two weeks after the return of the migratory hives. An increased incidence of V. destructor and Nosema ceranae and a lower DWV viral load were found in migratory colonies. Temporary changes in genetic diversity were detected regardless of colony type, suggesting that stressors other than management affect the genetic diversity of the colonies. Our study demonstrates that migratory practices have variable effects on the health and genetic diversity of honey bee colonies, which should be taken into account for the development of sustainable beekeeping.
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Feng, H. Q., K. M. Wu, Y. X. Ni, D. F. Cheng, and Y. Y. Guo. "Return migration ofHelicoverpa armigera(Lepidoptera: Noctuidae) during autumn in northern China." Bulletin of Entomological Research 95, no. 4 (2005): 361–70. http://dx.doi.org/10.1079/ber2005367.
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AbstractThe autumn migration ofHelicoverpa armigera(Hübner) was observed with radar and two types of light-trap at Langfang, Hebei province, China in 2001 and 2002. The sudden increase in the proportion ofH. armigeramoths in the searchlight trap indicated migration into the area and catches increased 10-fold during the second half of the night due to the landing of migrants before dawn. The moths’ migratory flights took place at up to 2000 m above the ground, and moths flew differentially at times, and heights, when favourable (i.e. northerly) winds occurred. This facilitated the maximum displacement of moths towards the south during these ‘return’ migrations. The moths flew over the radar site at consistently high densities through the night, and the resulting flight durations ofc. 10 h, at displacement speeds of 30–33 km h−1, would allow moths emerging in the far northeast of China (i.e. Liaoning and Jilin provinces and the Inner Mongolia autonomous region) to migrate into northern China (Hebei, Shandong and Henan provinces). The association of the seasonal migratory movements ofH. armigerawith crops in northern China is briefly discussed.
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Espindola, Juan, and Mónica Jacobo-Suárez. "The ethics of return migration and education: transnational duties in migratory processes." Journal of Global Ethics 14, no. 1 (2018): 54–70. http://dx.doi.org/10.1080/17449626.2018.1498013.
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Sandoval, Rebeca, and Víctor Zúñiga. "¿Quiénes están retornando de Estados Unidos a México?" Mexican Studies/Estudios Mexicanos 32, no. 2 (2016): 328–56. http://dx.doi.org/10.1525/mex.2016.32.2.328.
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El artículo presenta una evaluación crítica de la producción académica que aborda la migración de retorno de Estados Unidos a México de 2008 a 2015. Los hallazgos muestran que la investigación se limita a estudiar el retorno de hombres adultos y su inserción en mercados laborales, así como el impacto económico y demográfico regional. Son casi inexistentes los trabajos sobre trayectorias, integración y experiencia migratoria de niños, jóvenes y mujeres, así como aquellos que toman en consideración las dinámicas familiares asociadas al retorno. Prevalecen las investigaciones deductivas de corte cuantitativo, a diferencia de las que abordan dimensiones cualitativas del fenómeno. The article presents a critical evaluation of the academic production on return migration from the United States to Mexico from 2008 to 2015. Our findings reveal that current research has been limited to studying the return of adult men and their insertion into labor markets, as well as the economic and demographic impacts of return. Analyses of migratory trajectories, integration, and experience of children, women and youth, and other studies with a focus on family dynamics are rare or virtually inexistent. Deductive and quantitative investigations still prevail, compared to those that prioritize the qualitative dimensions of the phenomenon.
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DREBY, JOANNA, SARAH GALLO, FLORENCIA SILVEIRA, and MELISSA ADAMS-CORRAL. "Nací Allá: Meanings of US Citizenship for Young Children of Return Migrants to Mexico." Harvard Educational Review 90, no. 4 (2020): 573–97. http://dx.doi.org/10.17763/1943-5045-90.4.573.
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In this essay, Joanna Dreby, Sarah Gallo, Florencia Silveira, and Melissa Adams-Corral use a transnational frame to explore the meanings of US citizenship for binational children and its importance to experiences of belonging. Drawing on interviews with children ages six to fourteen living with their Mexican-born parents in rural Puebla, their analysis shows that children view US citizenship as signaling their social location in a historically based migratory system and that the meaning of this social location on children’s daily lives differs given their transnational experiences, specifically the extent of US schooling they received. Migration thus engenders understanding of power and privilege among young children and influences how they negotiate among their peers. The authors argue that young children may exhibit “critical postures” arising from their migratory experiences. They conclude that schools on both sides of the border can view migrant children’s experiences and critical perspectives as assets that may provide more flexible spaces for learning and belonging.
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Borthwick, E. K. "Odysseus and the Return of the Swallow." Greece and Rome 35, no. 1 (1988): 14–22. http://dx.doi.org/10.1017/s0017383500028722.
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In an article in CP 80 (1985), 33–34, entitled ‘Odyssey 21.411: the Swallow's Call', Luis A. Losada drew attention to the apparent oddity that the sound of Odysseus' bow-string, as he twanged it after stringing it in the presence of the suitors, is compared to the note of the swallow, since, for the most part, the swallow's twittering cry, in terms of sound quality, is traditionally associated in much of later Greek literature with either barbarian unintelligibility, loquacity, or sometimes lamentation – none of which is at all appropriate here. He suggests instead that a ‘thematic connotation’ was alluded to by Homer – the migratory cycle and vernal return of the swallow, and concludes that ‘the swallow and its call might well be called a quintessential metaphor for the idea of returning…No more appropriate bird call exists – the singing bowstring heralds the hero'sreturn.’
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Stigter, E. "LIVELIHOODS UPON RETURN: Afghan Migratory Strategies - An Assessment of Repatriation and Sustainable Return in Response to the Convention Plus." Refugee Survey Quarterly 25, no. 2 (2006): 109–22. http://dx.doi.org/10.1093/rsq/hdi0129.
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Oklamd, F., J. Erkinaro, K. Moen, et al. "Return migration of Atlantic Salmon in the River Tana: Phases of migratory behaviour." Journal of Fish Biology 59, no. 4 (2001): 862–74. http://dx.doi.org/10.1111/j.1095-8649.2001.tb00157.x.
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Mackay, David W., and C. Ross Doughty. "Migratory salmonids of the Estuary and Firth of Clyde." Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 90 (1986): 479–90. http://dx.doi.org/10.1017/s0269727000005170.
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SynopsisThe paper describes the salmon and sea trout stocks of the rivers entering the sea via the Estuary and Firth of the Clyde including the Rivers Clyde, Leven, the Carts, the rivers of the Ayrshire coast and those entering via the sea lochs and from the Mull of Kintyre. Particular attention is paid to the recent return of salmonids to the Rivers Clyde and Cart, which have been denied to migratory species for over a century because of pollution in the upper Clyde Estuary. The changing environmental conditions, which have made the reappearance of migratory salmonids possible, are described and the future importance of the fishery assessed.
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Nichols, Rina K., Jessica Steiner, Lance G. Woolaver, Elaine Williams, Amy A. Chabot, and Ken Tuininga. "Conservation initiatives for an endangered migratory passerine: field propagation and release." Oryx 44, no. 2 (2010): 171–77. http://dx.doi.org/10.1017/s0030605309990913.
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AbstractThe term ‘field propagation and release’ refers to the breeding of captive adults in large field enclosures, allowing them to raise their young, and then releasing those young from that location. This technique is currently being implemented in Canada as one of several recovery tools for the endangered eastern loggerhead shrike Lanius ludovicianus migrans. During 2001–2007 a total of 360 shrike fledglings were produced in field propagation enclosures and 301 were released from these enclosures. Annual return rates of birds released since 2004 are 2–6.6%. Seventeen released birds have been re-sighted, including 10 birds that have returned to the breeding grounds the following season to produce young with wild mates. The high annual return rate of release birds and the successful integration of these birds into the wild breeding population represent important milestones for the recovery of this population. The management technique we describe here has the potential to be applicable to other species that require natural habitat for breeding and/or are reliant on a suite of parent-learned behaviours that cannot be accommodated for or adequately replicated within intensive close captive-breeding or hand-rearing conditions.
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Yamamoto, Takashi, Akinori Takahashi, Katsufumi Sato, Nariko Oka, Maki Yamamoto, and Philip N. Trathan. "Individual consistency in migratory behaviour of a pelagic seabird." Behaviour 151, no. 5 (2014): 683–701. http://dx.doi.org/10.1163/1568539x-00003163.
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Many animals migrate between breeding and wintering areas; however, whether each animal behaves consistently in space and time between consecutive years is less well understood. Furthermore, previous breeding state (successful or failed) is often not considered when attempting to understand consistent individual differences in behaviour that are likely to impact upon the subsequent behaviour. Between 2006 and 2010, we used geolocators to track the migratory movements of a pelagic seabird, the streaked shearwater Calonectris leucomelas, with individuals () being followed for two years or more, including 23 birds that had chicks in two seasons and 23 birds in just one season. All individuals, except for one bird, migrated to the same broad wintering areas, and their migratory route as well as the centre of wintering distribution did not change in relation to the previous breeding outcomes. Migration schedules (dates of departure from the breeding colony, southward and northward migrations, and first return to the colony) did not differ significantly between years for individuals that had chicks during both years, while failed individuals left the breeding colony and appeared to start the southward migration at an earlier date than the previous successful year. Nonetheless, the timing of the southward migration was consistent within individuals, including both males and females, over successive years regardless of the previous breeding outcome, and also the timing of first return back to the colony for females that had chicks in the both previous years and eggs in the both following season. This may imply the existence of individual-specific broad time schedules, possibly a circannual rhythm, though ecological conditions might affect the exact timing of the actual departure event. Our results present evidence for high levels of individually consistent behaviour for this pelagic seabird outside the breeding season.
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Vilavedra, Dolores. "Women Who Leave: Uprooting and Return in Galician Literature." Humanities 11, no. 4 (2022): 98. http://dx.doi.org/10.3390/h11040098.
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The article considers the literary treatment of emigration in Galician fiction, through a review of the most recent work in the field. It looks in particular at the role of women (both authors and characters) and relates approaches here to the changes that have arisen as a result of Galician migratory flows over recent decades. It seeks to show how narrative fiction, a genre highly sensitive to social change, has the capacity to identify phenomena still barely visible in statistical accounts, and to act as a space for the re-signification of new individual and collective identities that are currently emerging within the context of globalization, thus contributing to the opening up of new possibilities relating to the kind of society that we want to become in the future.
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Huisman, Pieter. "From one-sided promotion of individual interests to integrated water management in the Rhine basin." Water Science and Technology 31, no. 8 (1995): 59–66. http://dx.doi.org/10.2166/wst.1995.0263.
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In autumn 1971, water pollution and poison incidents caused death in the Rhine. Aquatic life disappeared. The rulling opinion was: Clean up the waste water and life will return. It proved to be a half-truth. After treatment of waste water some organisms returned, others, particularly the migratory fish, did not. Barrages and weirs have decimated the migratory fish. Waste water gave only the final knock-out for these species. Slowly understanding arose for a harmonization between human interests and the ecosystem. In course of time the Rhine-states replaced the one-sided promotion of individual interests by the concept of integrated water management, a prerequisite for sustainable development. This contribution reflects the process of changing minds.
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Chatterji, Tuli. "Teaching The Penguin Book of Migration Literature." Radical Teacher 120 (August 18, 2021): 85–87. http://dx.doi.org/10.5195/rt.2021.892.
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The innovative four-point structure—Arrivals, Departures, Generations, and Return—of The Penguin Book of Migration Literature expands the purview established by previous anthologies of immigrant literature by mobilizing a classroom conversation where students’ own lived experiences of migratory crossings combine with the anthology’s narratives to both analyze texts and critique present national and global political climate.
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Franco Aguilar, José. "Mujeres mexicanas retornadas: reconfiguraciones en la dinámica familiar / Mexican women migrants returning. Reconfigurations in the family dynamics." Revista Trace, no. 80 (July 30, 2021): 234. http://dx.doi.org/10.22134/trace.80.2021.754.
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El presente artículo analiza los cambios o continuidades generados por mujeres mexicanas retornadas dentro de su dinámica intrafamiliar, derivados de su experiencia migratoria en EE. UU. El objetivo será la construcción de una tipología que discrimine la existencia de transformaciones dentro de dicha dinámica. En concreto, se exploran cuestiones intrínsecas en las familias que dan la pauta para contrastar situaciones. Particularmente, se estudian las siguientes dimensiones de análisis: trabajo doméstico, cuidado de los hijos, pautas de interacción familiar y concepción propia de la posición dentro del grupo doméstico. Los sujetos de análisis son veinte mujeres retornadas que tuvieron una residencia en EE. UU., quienes radican en una localidad rural, en el estado de Jalisco en México.Abstract: This article analyzes the changes and continuities in gender roles and family dynamics among migrant women returning from the United States. It considers the migratory experience as a potentially important factor influencing changes in gender dynamics within the family. The objective is to construct a typology that discriminates between existing changes in family dynamics and changes in gender roles resulting from the migratory experience. In order to provide a context to contrast situations, the article explores gender dynamics apparent in certain family dynamics, including housework, childcare, patterns of family interaction, and returning migrants’ conception of their position within the domestic group. The subjects of analysis are twenty returning migrant women from the United States who currently reside in a rural village in Jalisco, Mexico. Keywords: return migration; female return migration; family dynamics; rural area; Mexico. Résumé : Cet article analyse les changements et les continuités générés par les femmes mexicaines de retour de migration dans leur dynamique intra-familiale, comme résultats de leur expérience migratoire aux États-Unis. L’article propose de construire une typologie qui observe l’existence de transformations dans ces dynamiques. Plus précisément, les problèmes intrinsèques sont explorés au sein des familles et définissent la norme dans des situations contrastées. En particulier, sont analysées les dimensions suivantes : travail domestique, garde des enfants, modèles d’interaction familial et conception du rôle féminin dans le groupe domestique. Les sujets analysés sont vingt femmes de retour de migration qui ont résidé aux États-Unis et qui vivent actuellement dans une ville rurale de l’État de Jalisco au Mexique.Mots-clés : migration de retour ; femmes rapatriées ; dynamique intra-familiale ; zones rurales ; Mexique.
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Wynn, Joe, Oliver Padget, Henrik Mouritsen, Joe Morford, Paris Jaggers, and Tim Guilford. "Magnetic stop signs signal a European songbird’s arrival at the breeding site after migration." Science 375, no. 6579 (2022): 446–49. http://dx.doi.org/10.1126/science.abj4210.
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Although it is known that birds can return to their breeding grounds with exceptional precision, it has remained a mystery how they know when and where to stop migrating. Using nearly a century’s worth of Eurasian reed warbler ( Acrocephalus scirpaceus ) ringing recoveries, we investigated whether fluctuations in Earth’s magnetic field predict variation in the sites to which birds return. Ringing recoveries suggest that magnetic inclination is learned before departure and is subsequently used as a uni-coordinate “stop sign” when relocating the natal or breeding site. However, many locations have the same inclination angle. Data from populations with different migratory directions indicate that birds solve this ambiguity by stopping at the first place where the right inclination is encountered on an inherited return vector.
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Gómez, Jesús, Chantel I. Michelson, David W. Bradley, et al. "Effects of geolocators on reproductive performance and annual return rates of a migratory songbird." Journal of Ornithology 155, no. 1 (2013): 37–44. http://dx.doi.org/10.1007/s10336-013-0984-x.
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Kauffer, Edith. "The Mexico–Guatemala Border During COVID-19: From Open Border to New Assemblage?" Borders in Globalization Review 2, no. 1 (2020): 66–69. http://dx.doi.org/10.18357/bigr21202019890.
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The dynamics at the Mexican–Guatemalan border drastically changed from the beginning of the COVID-19 pandemic. This paper deals with these transformations and tries to evidence a new assemblage that has resulted. The rationale that prevailed until the beginning of 2020 between Mexico and Guatemala was a south-north selective open border derived from migratory controls applied to travelers according to their citizenship and their US or Canadian migratory status. From March until October, 2020 the pandemic gave birth to a new north-south rationale organized around a selective closure: the Guatemalan border was totally closed except to Guatemalans that were allowed to return to their country. On the Mexican side, communitarian, municipal, and local boundaries were established to curb the spread of COVID-19.
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Cousineau, Jean-Michel. "La mobilité interprovinciale de la main-d’oeuvre au Canada : le cas de l’Ontario, de la Nouvelle-Écosse et du Nouveau-Brunswick." Articles 55, no. 4 (2009): 501–15. http://dx.doi.org/10.7202/800848ar.
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This paper studies the migratory flows between Ontario and two Atlantic provinces of Canada, from 1960-61 to 1975-76. Search theory is used as the theoretical framework and leads to predictions as to the influence on interprovincial migratory flows of three economic variables: relative wages, employment opportunities, and unemployment insurance (UI). Proxies for these theoretical variables are used in an ordinary least squares regression based on pooled time series and cross-section data on interprovincial migration in Canada (Family Allowances' data base). The model performs poorly in explaining short term variations in the interprovincial migration rates, and the expected return migration from Ontario to New Brunswick and Nova Scotia due to UI changes in 1971 is not found. However, the model performs relatively well in explaining long term interprovincial migration flows and the 1970's reversal of the net migratory flows between Central Canada (Ontario) and the Atlantic provinces considered. Higher unemployment rates in Ontario, improved relative wages in New Brunswick and Nova Scotia as well as the UI revisions of 1971 explain a significant part of the observed change.
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Coppack, Timothy, Simon F. Becker, and Philipp J. J. Becker. "Circadian flight schedules in night-migrating birds caught on migration." Biology Letters 4, no. 6 (2008): 619–22. http://dx.doi.org/10.1098/rsbl.2008.0388.
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Many species of migratory birds migrate in a series of solitary nocturnal flights. Between flights, they stop to rest and refuel for the next segment of their journey. The mechanism controlling this behaviour has long remained elusive. Here, we show that wild-caught migratory redstarts ( Phoenicurus phoenicurus ) are consistent in their flight scheduling. An advanced videographic system enabled us to determine the precise timing of flight activity in redstarts caught at a northern European stopover site during their return trip from Africa. Birds were held captive for three days in the absence of photoperiodic cues (constant dim light) and under permanent food availability. Despite the absence of external temporal cues, birds showed clear bimodal activity patterns: intense nocturnal activity alternating with diurnal foraging and resting periods. The onset of their migratory activity coincided with the time of local sunset and was individually consistent on consecutive nights. The data demonstrate that night-migrating birds are driven by autonomous circadian clocks entrained by sunset cues. This timekeeping system is probably the key factor in the overall control of nocturnal songbird migration.
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Komolkin, Andrei V., Pavel Kupriyanov, Andrei Chudin, Julia Bojarinova, Kirill Kavokin, and Nikita Chernetsov. "Theoretically possible spatial accuracy of geomagnetic maps used by migrating animals." Journal of The Royal Society Interface 14, no. 128 (2017): 20161002. http://dx.doi.org/10.1098/rsif.2016.1002.
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Many migrating animals, belonging to different taxa, annually move across the globe and cover hundreds and thousands of kilometres. Many of them are able to show site fidelity, i.e. to return to relatively small migratory targets, from distant areas located beyond the possible range of direct sensory perception. One widely debated possibility of how they do it is the use of a magnetic map, based on the dependence of parameters of the geomagnetic field (total field intensity and inclination) on geographical coordinates. We analysed temporal fluctuations of the geomagnetic field intensity as recorded by three geomagnetic observatories located in Europe within the route of many avian migrants, to study the highest theoretically possible spatial resolution of the putative map. If migratory birds measure total field intensity perfectly and take the time of day into account, in northern Europe 81% of them may return to a strip of land of 43 km in width along one of coordinates, whereas in more southern areas such a strip may be narrower than 10 km. However, if measurements are performed with an error of 0.1%, the strip width is increased by approximately 40 km, so that in spring migrating birds are able to return to within 90 km of their intended goal. In this case, migrating birds would probably need another navigation system, e.g. an olfactory map, intermediate between the large-scale geomagnetic map and the local landscape cues, to locate their goal to within several kilometres.
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Martínez, Rafael Viruela. "The Romanian Migrants in Spain. An Exceptional Migratory Flow." International Review of Social Research 1, no. 1 (2011): 31–59. http://dx.doi.org/10.1515/irsr-2011-0002.
Texte intégralRésumé :
Abstract The Romanian population is the most important foreign population in Spain. Romanian migrants are characterized by their large number (about 800.000 residents and 268.000 contract workers) and their rapid growth. The economic and labour motivation for migration determines their geographical distribution, with high numbers of Romanian migrants in cities and in areas of agricultural, industrial and tourist industries. However, a high proportion of Romanian migrants also live in small towns and rural areas. Most of them were already illegal migrants when Romania entered the EU and they became EU citizens. From January 1st 2009, these once illegal migrants now have full freedom of employment in Spain. They adapt to circumstances of each period of time, in order to enter or to remain in the Spanish labour market. Most work in construction and agriculture as well as domestic services, trade, tourism and industries. The current economic crisis and the resulting unemployment have raised the issue of return migration to Romania.
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Montoya Zavala, Erika Cecilia, Martha Cecilia Herrera García, and Anna Ochoa O'Leary. "Foto-voz como Técnica de Investigación en Jóvenes Migrantes de Retorno. Trayectorias migratorias, identidad y educación." Empiria. Revista de metodología de ciencias sociales, no. 45 (January 15, 2020): 15. http://dx.doi.org/10.5944/empiria.45.2020.26303.
Texte intégralRésumé :
El objetivo de este artículo es describir de manera general la técnica de investigación Foto-voz y valorar si ampliar los alcances de esta técnica, al tema de migración de retorno, nos ayuda a comprender el rol que juegan las trayectorias migratorias, el lenguaje, el estigma y la identidad en las aspiraciones educacionales de los jóvenes de retorno en la Universidad Autónoma de Sinaloa (UAS). Asimismo, es nuestro objetivo presentar los principales hallazgos en las tres categorías de análisis propuestas: las trayectorias migratorias, el estigma- identidad, y las aspiraciones educativas de los jóvenes retornados. Utilizamos el instrumento de la Foto-Voz, la cual es una técnica de investigación cualitativa, de muestreo intencional y de acción participante. Participaron jóvenes de retorno, jóvenes sin experiencia migratoria y profesores y profesoras de la Facultad de Estudios Internacionales y Políticas Públicas de la UAS en Culiacán, Sinaloa, en un taller de fotografía donde expresan sus experiencias migratorias, su identidad y sus aspiraciones educativas por medio de fotos y pequeñas narrativas. Se reclutaron 15 participantes, por medio de invitación directa, difusión de información del taller de fotografía y por medio de bola de nieve. Dentro de los resultados podemos destacar que ampliar el alcance de Foto-voz al tema de migración de retorno de jóvenes, tiene utilidad al proporcionar a los y las recién llegadas herramientas para expresar su identidad (todavía incomprensible para ellos) con representaciones simbólicas a través de fotografías. Sus testimonios reflejan una introspección y un esfuerzo de autoconocimiento sobre sus sentimientos y perspectivas. Con esta técnica identificamos y priorizamos situaciones de exclusión e inclusión en las trayectorias migratorias y en el proceso de inmersión en la universidad de los jóvenes retornados.The objective of this article is to describe in a general way the Photo-voice research tecnique and assess whether extending the scope of this tecnique to the issue of return migration helps us to understand the role played by migratory trajectories, language, stigma and identity in the educational aspirations of returning youth at the Autonomous University of Sinaloa (UAS). Likewise, it is our objective to present the main findings in three categories of analysis: migratory trajectories, stigma-identity, and the educational aspirations of young returnees. Methodology: Foto-Voz is a technique of qualitative research, non-representative sampling and participatory action. Participated in a photography workshop: young people of returned, young people without migratory experience and professors from the Faculty of International Studies and Public Policies of the UAS in Culiacán, Sinaloa, where they express their migratory experiences and their educational aspirations through photos and small narratives. 15 participants were recruited, through direct invitation, dissemination of information from the photography workshop and by a snowball. Findings: Extending the scope of the Fotovoz to the issue of return migration of young people, is useful in providing newcomers with tools to express their identity (still incomprehensible to them) with symbolic representations through photographs. Their testimonies reflect an introspection and an effort of self-knowledge about their feelings and perspectives. Under this methodology we identify and prioritize situations of exclusion and inclusion in migratory trajectories and in the process of immersion in the university of the young returned.
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Potvin, D. A., P. W. Crawford, S. A. MacDougall-Shackleton, and E. A. MacDougall-Shackleton. "Song repertoire size, not territory location, predicts reproductive success and territory tenure in a migratory songbird." Canadian Journal of Zoology 93, no. 8 (2015): 627–33. http://dx.doi.org/10.1139/cjz-2015-0039.
Texte intégralRésumé :
In territorial animals occupying environments that vary in quality over the landscape, high-quality individuals are predicted to monopolize high-quality territories. Thus, in many cases it may be difficult to disentangle the relative effects of individual quality from those of territory quality on long-term fitness. We used a 9-year field data set from a migratory population of Eastern Song Sparrows (Melospiza melodia melodia (A. Wilson, 1810)) to evaluate the relative contributions of male song quality (as measured by song repertoire size) and territory location to fitness components including annual reproductive success, overwinter return rates, and between-year territory tenure. Song repertoire size did not predict territory location, allowing us to evaluate territory location and song quality separately. Song repertoire size, but not territory location, predicted annual reproductive success. Moreover, males with larger repertoires moved smaller distances between subsequent breeding seasons, suggesting more successful territory tenure. There was no effect of either repertoire size or territory location on overwinter return. We conclude that intrinsic male phenotype, indicated by song repertoire size, is an important predictor of male fitness, independent of breeding-territory location in this migratory population, and that the value of specific territories may depend largely on previous experience.
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Marco-Rius, Francisco, Graciela Sotelo, Pablo Caballero, and Paloma Morán. "Insights for planning an effective stocking program in anadromous brown trout (Salmo trutta)." Canadian Journal of Fisheries and Aquatic Sciences 70, no. 7 (2013): 1092–100. http://dx.doi.org/10.1139/cjfas-2013-0084.
Texte intégralRésumé :
Brown trout (Salmo trutta) is a salmonid species with a high socio-economic value related with recreational fishing. Because of that, stocking programs have been developed in many populations, although they have focused on resident populations. To explore which factors promote migratory behaviour when implementing stocking actions, 28 brown trout artificial crosses were carried out in a noncommercial hatchery, and the returning success of their offspring was further evaluated. Return rate was examined according to male phenotype (anadromous versus resident), mean egg size, parents’ similarity at major histocompatibility complex (MHC) class II β-gene, and stocking procedure. At the end of the experiment, 35 of the captured returning adults (9.4%) belonged to 14 of those crosses. Return success shows a significant effect (p = 0.0016) by parental MHC similarities, stocking procedure, and male phenotype. Our results indicate that planting fertilized eggs in nursery areas of the river, together with the selection of anadromous males as brood stock and mate pairs with higher similarity at the MHC locus, can be an appropriate option to increase the migratory part of trout populations. In addition, nursery areas can allow an important decrease in the cost per stocked individual, being 32 times less expensive than the cost per hatchery-reared individual.
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González García, Inmaculada. "Immigration In Spain: Migratory Routes, Cooperation With Third Countries and Human Rights in Return Procedures." Paix et Securite Internationales, no. 7 (2019): 201–30. http://dx.doi.org/10.25267/10.25267/paix_secur_int.2019.i7.06.
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González García, nmaculada. "Immigration In Spain: Migratory Routes, Cooperation With Third Countries and Human Rights in Return Procedures." Paix et Securite Internationales, no. 7 (2019): 201–30. http://dx.doi.org/10.25267/paix_secur_int.2019.i7.06.
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Vivas-Romero, María, and Ababela O. Sánchez Martínez. "Tracing Migrant-Mothers’ ‘Return’ Narratives in the Mexico-United States and Peru-Belgium Migratory-Circuits." Revista Trace, no. 71 (January 9, 2017): 166. http://dx.doi.org/10.22134/trace.71.2017.59.
Texte intégralRésumé :
¿Qué estrategias emplean las madres migrantes para retornar al país de origen? ¿Cómo influye en la decisión de retornar el acceso a la protección social de sus hijos ciudadanos binacionales? Por medio de esta contribución respondemos a estas preguntas, partiendo desde el análisis comparativo de las carreras migratorias de dos madres en contextos radicalmente diferentes. Argumentamos que la decisión del retorno de estas madres migrantes y las estrategias empleadas para hacerlo dependen del acceso a la protección social que tienen sus hijos binacionales y de sus percepciones subjetivas sobre cómo ser “buenas madres”. Esta comparación transatlántica muestra de qué forma diferentes contextos nacionales, culturas del cuidado y de la maternidad, dan origen a diversos modelos de movilidad internacional para estas mujeres y sus familias.
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de Lucas, Javier. "Migration, law, democracy: identifiyng where the risk is." SOCIOLOGIA DEL DIRITTO, no. 2 (December 2009): 139–50. http://dx.doi.org/10.3280/sd2009-002009.
Texte intégralRésumé :
- This paper focuses on migration, law and democracy in order to identify where risk lies. The author concentrates on studying a recent case, the Directive on the Return of so-called illegal immigrants (sans papiers) approved by the European Parliament on 18 June 2008. The usual point of view, that of the dominant discourse, maintains that today's migratory movements constitute one of the structural factors that justify the definition of our societies as the "Risk Society". According to this point of view, the migratory flows entail a risk for social cohesion and even a destabilising potential for both democracy and the rule of law. The risk is illustrated by the menacing image of invasion threatening at our doors, hence the classical argument of the "demographic bomb" as the resource of poor countries. The author's thesis sustains that it is precisely our responses, in the form of migratory policy tools, that constitute a risk factor. Some of these tools, including this Directive, have become destabilising elements of the rules of the game and, moreover, of the values of the rule of law and of democracy.
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Castro-Santos, Theodore, and Benjamin H. Letcher. "Modeling migratory energetics of Connecticut River American shad (Alosa sapidissima): implications for the conservation of an iteroparous anadromous fish." Canadian Journal of Fisheries and Aquatic Sciences 67, no. 5 (2010): 806–30. http://dx.doi.org/10.1139/f10-026.
Texte intégralRésumé :
We present a simulation model in which individual adult migrant American shad ( Alosa sapidissima ) ascend the Connecticut River and spawn, and survivors return to the marine environment. Our approach synthesizes bioenergetics, reproductive biology, and behavior to estimate the effects of migratory distance and delays incurred at dams on spawning success and survival. We quantified both the magnitude of effects and the consequences of uncertainty in the estimates of input variables. Behavior, physiology, and energetics strongly affected both the distribution of spawning effort and survival to the marine environment. Delays to both upstream and downstream movements had dramatic effects on spawning success, determining total fecundity and spatial extent of spawning. Delays, combined with cues for migratory reversal, also determined the likelihood of survival. Spawning was concentrated in the immediate vicinity of dams and increased with greater migratory distance and delays to downstream migration. More research is needed on reproductive biology, behavior, energetics, and barrier effects to adequately understand the interplay of the various components of this model; it does provide a framework, however, that suggests that provision of upstream passage at dams in the absence of expeditious downstream passage may increase spawning success — but at the expense of reduced iteroparity.
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James, Michael C., Ransom A. Myers, and C. Andrea Ottensmeyer. "Behaviour of leatherback sea turtles, Dermochelys coriacea , during the migratory cycle." Proceedings of the Royal Society B: Biological Sciences 272, no. 1572 (2005): 1547–55. http://dx.doi.org/10.1098/rspb.2005.3110.
Texte intégralRésumé :
Leatherback sea turtles, Dermochelys coriacea , undertake broad oceanic movements. While satellite telemetry has been used to investigate the post-nesting behaviour of female turtles tagged on tropical nesting beaches, long-term behavioural patterns of turtles of different sexes and sizes have not been described. Here we investigate behaviour for 25 subadult and adult male and female turtles satellite-tagged in temperate waters off Nova Scotia, Canada. Although sex and reproductive condition contributed to variation in migratory patterns, the migratory cycle of all turtles included movement between temperate and tropical waters. Marked changes in rates of travel, and diving and surfacing behaviour, accompanied southward movement away from northern foraging areas. As turtles approached higher latitudes the following spring and summer, they assumed behaviours consistent with regular foraging activity and eventually settled in coastal areas off Canada and the northeastern USA. Behavioural patterns corresponding to various phases of the migratory cycle were consistent across multiple animals and were repeated within individuals that completed return movements to northern waters. We consider the potential biological significance of these patterns, including how turtle behaviour relates to predator avoidance, thermoregulation and prey distribution.
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Broderick, Annette C., Michael S. Coyne, Wayne J. Fuller, Fiona Glen, and Brendan J. Godley. "Fidelity and over-wintering of sea turtles." Proceedings of the Royal Society B: Biological Sciences 274, no. 1617 (2007): 1533–39. http://dx.doi.org/10.1098/rspb.2007.0211.
Texte intégralRésumé :
While fidelity to breeding sites is well demonstrated in marine turtles, emerging knowledge of migratory routes and key foraging sites is of limited conservation value unless levels of fidelity can be established. We tracked green ( Chelonia mydas , n =10) and loggerhead ( Caretta caretta , n =10) turtles during their post-nesting migration from the island of Cyprus to their foraging grounds. After intervals of 2–5 years, five of these females were recaptured at the nesting beach and tracked for a second migration. All five used highly similar migratory routes to return to the same foraging and over-wintering areas. None of the females visited other foraging habitats over the study period (units lasted on average 305 days; maximum, 1356 days), moving only to deeper waters during the winter months where they demonstrated extremely long resting dives of up to 10.2 h (the longest breath-holding dive recorded for a marine vertebrate). High levels of fidelity and the relatively discrete nature of the home ranges demonstrate that protection of key migratory pathways, foraging and over-wintering sites can serve as an important tool for the future conservation of marine turtles.
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Hagan, Jacqueline Maria, Ricardo Martinez-Schuldt, Alyssa Peavey, and Deborah M. Weissman. "Family Matters: Claiming Rights across the US-Mexico Migratory System." Journal on Migration and Human Security 6, no. 2 (2018): 167–80. http://dx.doi.org/10.1177/2331502418777456.
Texte intégralRésumé :
The Immigration and Nationality Act of 1952 (INA) created an immigration system favoring the immigration of spouses, children, and parents of US citizens, thereby establishing family unity as the cornerstone of US immigration policy. Despite this historical emphasis on family unity, backlogs and limited visas for non-immediate relatives of US citizens and legal permanent residents, the militarization of the US-Mexico border, punitive measures for those who enter without inspection, such as the forced separation of children from their parents at the US border, and an aggressive policy of deportation have made it more difficult for members of Mexican binational families to unify. How do members of Mexican binational families manage the hardships that result from US immigration policies that prolong and force family separation? Immigrants and return migrants alike may not be aware of their rights and the legal remedies that exist to enforce them. Structural barriers such as poverty, legal status, fear of deportation, lack of proficiency in English, and lack of familiarity with government bureaucracies no doubt prevent many migrants in the United States and return migrants in Mexico from coming forward to request legal assistance and relief in the courts. Despite these barriers, when it comes to family matters, members of some Mexican binational families can and do assert their rights. In this article, we analyze an administrative database of the Department of Legal Protection of the Mexican consular network that documents migrant legal claims resulting from family separation, along with findings from 21 interviews with consular staff and community organizations in three consular jurisdictions — El Paso, Raleigh, and San Francisco — to investigate the sociolegal processes of claims. Our investigation centers on the mediating role the Mexican state — via its consular network — has developed to assist binational families as they attempt to assert their rights and resolve child support and child custody problems resulting from prolonged and forced family separation. We find that the resolution of binational family claims in part depends on the institutional infrastructure that has developed at local, state, and federal levels, along with the commitment and capacity of the receiving and sending states and the binational structures they establish. These binational structures transcend the limitations of national legal systems to achieve and implement family rights and obligations across borders.
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Keiser, Jeffrey T., Charles W. S. Ziegenfus, and Daniel A. Cristol. "Homing Success of Migrant Versus Nonmigrant Dark-Eyed Juncos (Junco Hyemalis)." Auk 122, no. 2 (2005): 608–17. http://dx.doi.org/10.1093/auk/122.2.608.
Texte intégralRésumé :
Abstract Within a population, the evolution of migratory behavior is accompanied by a suite of physiological, behavioral, and cognitive adaptations. Spatial memory is associated with the hippocampus in mammals and birds; in some cases, hippocampal neuroanatomy correlates with differences in behavior. In a recent study, a migratory subspecies of sparrow, the Dark-eyed Junco (Junco hyemalis hyemalis), performed better on room-scale spatial memory tests than did a nonmigratory conspecific. Migrants collected after migration also possessed greater hippocampal neuron density, which suggests a neurological basis for differences in spatial memory and a link between migratory behavior and enhanced spatial memory. It is likely that homing behavior, like migration, relies to some extent on spatial memory. In some instances, spatial memory performance has generalized across spatial scales, with pronounced differences at larger scales. We tested whether differences in spatial memory between migrants and nonmigrants, previously observed at a room scale, were detectable at a landscape scale; specifically, we investigated whether differences in homing ability could be detected after displacements of 1–40 km. We found no difference in number of returning individuals or in duration of return. Our results suggest that homing in this species may not rely on aspects of spatial memory that differed in aviary tests.
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Crook, David A., Wayne M. Koster, Jed I. Macdonald, et al. "Catadromous migrations by female tupong (Pseudaphritis urvillii) in coastal streams in Victoria, Australia." Marine and Freshwater Research 61, no. 4 (2010): 474. http://dx.doi.org/10.1071/mf09170.
Texte intégralRésumé :
Understanding migratory requirements is critical for the conservation of diadromous fishes. Tupong (Pseudaphritis urvillii) are diadromous fishes found in freshwater and estuarine regions of south-eastern Australia. Previous studies have hypothesised that mature female tupong undertake downstream spawning migrations from freshwater to the estuary or sea, with a compensatory return of juveniles, and possibly spent fish, back upstream. We applied acoustic telemetry to test this hypothesis. We tagged 55 female tupong in two river systems in Victoria, Australia, and tracked movements for 4- to 6-month periods over 2 years. Thirty-one fish undertook rapid downstream migrations and then appeared to move through the estuary and out to sea between May and August in each year. Migration was associated with relatively high river discharges, and movement from the estuary to the sea tended to occur most frequently during intermediate moon phases. Low rates of movement between September and April suggested that tupong inhabited restricted home ranges outside of the spawning season. The apparently disparate migratory patterns of female (catadromous) and male (non-diadromous) tupong are rare amongst fishes globally. Differential exertion of a range of selective pressures may have resulted in the evolution of sexual differences in migratory modes in this species.
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Zhang, Gang, Dany Shoham, David Gilichinsky, Sergei Davydov, John D. Castello, and Scott O. Rogers. "Evidence of Influenza A Virus RNA in Siberian Lake Ice." Journal of Virology 80, no. 24 (2006): 12229–35. http://dx.doi.org/10.1128/jvi.00986-06.
Texte intégralRésumé :
ABSTRACT Influenza A virus infects a large proportion of the human population annually, sometimes leading to the deaths of millions. The biotic cycles of infection are well characterized in the literature, including in studies of populations of humans, poultry, swine, and migratory waterfowl. However, there are few studies of abiotic reservoirs for this virus. Here, we report the preservation of influenza A virus genes in ice and water from high-latitude lakes that are visited by large numbers of migratory birds. The lakes are along the migratory flight paths of birds flying into Asia, North America, Europe, and Africa. The data suggest that influenza A virus, deposited as the birds begin their autumn migration, can be preserved in lake ice. As birds return in the spring, the ice melts, releasing the viruses. Therefore, temporal gene flow is facilitated between the viruses shed during the previous year and the viruses newly acquired by birds during winter months spent in the south. Above the Arctic Circle, the cycles of entrapment in the ice and release by melting can be variable in length, because some ice persists for several years, decades, or longer. This type of temporal gene flow might be a feature common to viruses that can survive entrapment in environmental ice and snow.
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Le Bris, Arnault, Jonathan A. D. Fisher, Hannah M. Murphy, et al. "Migration patterns and putative spawning habitats of Atlantic halibut (Hippoglossus hippoglossus) in the Gulf of St. Lawrence revealed by geolocation of pop-up satellite archival tags." ICES Journal of Marine Science 75, no. 1 (2017): 135–47. http://dx.doi.org/10.1093/icesjms/fsx098.
Texte intégralRésumé :
Abstract Characterizing migratory behaviours contributes to the sustainable management of marine fishes by resolving stock structure and identifying the timing and locations of events within fish life cycles. The migratory behaviour of Atlantic halibut (Hippoglossus hippoglossus) in the Gulf of St. Lawrence (GSL), Canada was characterized over an annual cycle using pop-up satellite archival tags (n = 15). Daily probability density functions of individual halibut positions were estimated using a geolocation model specifically developed to track demersal fish species in the GSL. Reconstructed migration routes (n = 8) revealed that Atlantic halibut displayed seasonal migrations, moving from deeper offshore waters in the winter to shallower nearshore waters in the summer. Variability in migratory behaviours was observed among individuals tagged at the same location and time. One individual resided year round in the vicinity of the tagging site, three individuals displayed homing behaviour, and four individuals did not return to the tagging site. The identification of presumed spawning rises for two individuals suggested that spawning of Atlantic halibut occurred in the GSL. Although based on a limited number of individuals, these results suggest that Atlantic halibut in the GSL forms a philopatric population, supporting the current separate management of this stock from the adjacent Scotian Shelf and southern Grand Banks stock.
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Abdulle, S. A., and K. C. Fraser. "Does wind speed and direction influence timing and route of a trans-hemispheric migratory songbird (purple martin) at a migration barrier?" Animal Migration 5, no. 1 (2018): 49–58. http://dx.doi.org/10.1515/ami-2018-0005.
Texte intégralRésumé :
Abstract The influence of weather on the departure decisions and routes of migratory birds can now be further investigated with the use of direct tracking methods. We tested hypotheses for migration departure decisions and flight trajectories by determining the influence of wind speed and direction at the Yucatan peninsula in spring on departure date, migratory route, and longitude of arrival at the northern Gulf coast of a trans-hemispheric migratory songbird, purple martin (Progne subis). Birds were equipped with geolocators at their breeding colony and 36 were recaptured upon return after spring migration. While southerly tailwinds with low wind speeds prevailed at the Yucatan during the period of passage, we found that daily wind speed and direction were still important predictors of departure date. However, wind conditions at departure did not predict longitude of arrival at the US gulf coast after crossing the gulf. Birds appeared to favour the shortest distance across the Gulf of Mexico, aided by consistent tailwinds, but may have corrected for wind drift so as to land at a longitude near 88°, reflecting the shortest distance across from the Yucatan staging areas. Considering their use prior to departure, high quality roost sites at the Yucatan peninsula would be important conservation targets for this declining aerial insectivore.
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Pagel, R. Kyle, Elena H. West, Andrew W. Jones, and Henry M. Streby. "Variation in individual autumn migration and winter paths of Great Lakes red-headed woodpeckers (Melanerpes erythrocephalus)." Animal Migration 7, no. 1 (2020): 9–18. http://dx.doi.org/10.1515/ami-2020-0002.
Texte intégralRésumé :
AbstractMigratory movements of facultative migrants are poorly understood due to their irregular and often unpredictable occurrence. However, tracking such movements is important for understanding population dynamics, informing annual cycle conservation plans, and identifying possible cues of facultative migration. We used pinpoint GPS tags to track autumn and winter movements of migratory red-headed woodpeckers (Melanerpes erythrocephalus) to better understand migration frequency, timing, and routes for birds breeding in managed oak savanna systems in the North American Great Lakes region. Proportions of individuals migrating differed between the two sites, with 72% of the Ohio population migrating, while no individuals in the Minnesota population migrated. Of the Ohio birds that migrated, their movements were highly variable in distance and direction but generally occurred south of the breeding site. Wintering sites ranged from 111 – 218 km from the breeding site. Cover types occupied during migration and wintering were almost exclusively small patches of closed-canopy hardwood forest within agricultural matrices. We documented one-time movements in migratory and non-migratory individuals during the year that have not previously been described in facultative migrants. We found no evidence of a harness or marker effect on proportions of individuals migrating, migration return rates, or annual survival regardless of migration.
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Heggberget, Tor G., Finn Økland, and Ola Ugedal. "Distribution and migratory behaviour of adult wild and farmed Atlantic salmon (Salmo salar) during return migration." Aquaculture 118, no. 1-2 (1993): 73–83. http://dx.doi.org/10.1016/0044-8486(93)90282-4.
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Branch, Carrie L., Dovid Y. Kozlovsky, Rebecca Croston, Angela Pitera, and Vladimir V. Pravosudov. "Mountain chickadees return to their post-natal dispersal settlements following long-term captivity." Behaviour 153, no. 5 (2016): 551–67. http://dx.doi.org/10.1163/1568539x-00003363.
Texte intégralRésumé :
There is little work investigating the relationship between environmental changes and associated hippocampal effects on animal homing. We took advantage of previous studies in which wild, non-migratory mountain chickadees spent six months in captivity prior to being released. Over the following three years, 45.8% of the birds were resighted, and in all cases birds were identified less than 300 m from their initial capture locations at their respective elevation, despite previous studies documentingca30% captivity-related reduction of the hippocampus. Reproductive success of birds that spent six months in captivity did not differ from control birds that did not experience captivity. Our findings suggest that chickadees are highly site faithful and can return to their original capture location after spending time in captivity. Our results also have important implications for animal welfare practices as birds held in captivity bred successfully and may not need to be sacrificed following captivity.
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Wells, Alan, Christal E. Grierson, Laura Marshall, et al. "Physiological consequences of “premature freshwater return” for wild sea-run brown trout (Salmo trutta) postsmolts infested with sea lice (Lepeophtheirus salmonis)." Canadian Journal of Fisheries and Aquatic Sciences 64, no. 10 (2007): 1360–69. http://dx.doi.org/10.1139/f07-107.
Texte intégralRésumé :
The physiological consequences of premature migratory return to freshwater for wild sea-run brown trout (Salmo trutta) smolts infested with sea lice (Lepeophtheirus salmonis) were investigated in the laboratory. Osmoregulatory, metabolic, and stress markers were analysed in order to assess the potential consequences of transfer to freshwater, 19 days after the challenge with L. salmonis. Infestation intensity was significantly reduced following transfer to freshwater, and mortality rates were markedly higher in infested fish maintained in seawater vs. fish that were transferred to freshwater. Significant sea lice effects, consistent across a number of physiological markers, were apparent once L. salmonis developed to the mobile stages. Plasma chloride, lactate, and cortisol all were significantly higher than control values, and liver glycogen concentration was significantly reduced in infested fish in seawater. After return to freshwater, these physiological measures returned to control levels, but significant lice effects persisted for fish maintained in seawater. Premature return of infested sea-run brown trout to freshwater does, therefore, confer significant short-term physiological benefits across a range of osmoregulatory, metabolic, and stress markers.
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Pasallo Zepeda, María de Jesús, and Ana María Méndez Puga. "Reflexiones de inclusión educativa: un estudio con familias de retorno." Tequio 1, no. 1 (2017): 57–62. http://dx.doi.org/10.53331/teq.v1i1.7948.
Texte intégralRésumé :
The difficult economic situation that cross Mexican families, the consequences of anti-immigrant policies and the economic crisis in the United States have caused changes in migratory patterns. The gradual increase, during the last years of returnees, is linked to the increase of groups of people interested in the education of their children. This article seeks to create axes of analysis and reflection to promote the school inclusion of migrant children’s return, the same that are derived from the qualitative study, from the perspective of Ethnography in which they worked with fifteen return migrant children, ten parents and eighteen professors. The results show that returning children, across borders, are generating knowledge that enable them to join the here and there, but school is not aware of this, so that is intended to show some reflections generated by this dynamic.