Duration Of Migration Research Articles

Migration Patterns of Double-Crested Cormorants Wintering in the Southeastern United States

Abstract. Migration patterns of Double-crested Cormorants (Phalacrocorax auritus) wintering in the southeastern U.S. are poorly understood. Movement data were analyzed from 28 cormorants captured in Alabama, Arkansas, Louisiana and Mississippi and equipped with satellite transmitters. Four (three immature, one adult) cormorants did not migrate and stayed in the southeastern U.S. throughout the year. During spring, cormorants captured in Alabama migrated east of the Mississippi River and primarily west of the Appalachian Mountains. Cormorants from Arkansas, Louisiana and Mississippi migrated north along the Mississippi River Valley, the Missouri River Valley and/or the Ohio River Valley. The earliest departure for spring migration was 26 March, whereas the latest departure was 12 May. Adult cormorants departed for spring migration earlier than immature cormorants. The average departure date for fall migration was 1 October. Mean duration of spring migration was twelve days, and cormorants traveled an avera...

Summer and Migrational Movements of Satellite-Marked Double-Crested Cormorants from a Breeding Colony Managed by Egg-Oiling in Lake Ontario, USA

A two-year satellite telemetry study was initiated in May 2000 at a Double-crested Cormorant (Phalacrocorax auritus) breeding colony on Little Galloo Island (LGI) in eastern Lake Ontario, New York, USA, which is managed by egg-oiling. The objective was to describe cormorant (N = 26/year) movements, specifically during the period of reproductive management by egg-oiling and seasonally (breeding, migration and wintering). Egg-oiling at two-week intervals resulted in a hatch success on LGI of 5.7% for 2000 and 2001, combined. The majority (97%) of core use areas of marked cormorants contained LGI throughout three egg-oiling treatments (six weeks), and 71% still contained LGI by the end of the final (fourth) treatment (eight weeks). Of cormorants that moved during or after control activities, three remained in the vicinity of active breeding colonies for over three months. Cormorants initiated fall migration over a 16-week period ranging from 12 July to 29 October, with a mean departure date of 6 September (N = 24, SE = 8 days) over both years. Mean duration of fall migration was 34 days (N = 19, SE = 7 days, range = 108 days). Most (75%) cormorants captured at LGI migrated east of the Appalachian Mountains, and their winter range extended from southeastern Louisiana, along the coast of the Gulf of Mexico, to the southern portion of the Atlantic coast. Although three (13%) cormorants over both years relocated to other active colonies for long enough periods (over three months) to potentially raise young, this study indicates that control efforts did not result in complete abandonment of LGI. Egg-oiling was successful in reducing recruitment within breeding seasons, and within-breeding-season renesting attempts by cormorants in this study were limited and likely unsuccessful. Further evaluation and refinement of egg-oiling as a management tool will require multiyear monitoring of the LGI cormorant breeding colony.

Satellite Tracking on the Flyways of Brown-Headed Gulls and Their Potential Role in the Spread of Highly Pathogenic Avian Influenza H5N1 Virus

Brown-headed gulls (Larus brunnicephalus), winter visitors of Thailand, were tracked by satellite telemetry during 2008–2011 for investigating their roles in the highly pathogenic avian influenza (HPAI) H5N1 virus spread. Eight gulls negative for influenza virus infection were marked with solar-powered satellite platform transmitters at Bang Poo study site in Samut Prakarn province, Thailand; their movements were monitored by the Argos satellite tracking system, and locations were mapped. Five gulls completed their migratory cycles, which spanned 7 countries (China, Bangladesh, India, Myanmar, Thailand, Cambodia, and Vietnam) affected by the HPAI H5N1 virus. Gulls migrated from their breeding grounds in China to stay overwinter in Thailand and Cambodia; while Bangladesh, India, Myanmar, and Vietnam were the places of stopovers during migration. Gulls traveled an average distance of about 2400 km between Thailand and China and spent 1–2 weeks on migration. Although AI surveillance among gulls was conducted at the study site, no AI virus was isolated and no H5N1 viral genome or specific antibody was detected in the 75 gulls tested, but 6.6% of blood samples were positive for pan-influenza A antibody. No AI outbreaks were reported in areas along flyways of gulls in Thailand during the study period. Distance and duration of migration, tolerability of the captive gulls to survive the HPAI H5N1 virus challenge and days at viral shedding after the virus challenging suggested that the Brown-headed gull could be a potential species for AI spread, especially among Southeast Asian countries, the epicenter of H5N1 AI outbreak.

Stable-hydrogen isotope turnover in red blood cells of two migratory thrushes: application to studies of connectivity and carry-over effects

ABSTRACT Understanding turnover rates of stable isotopes in metabolically active tissues is critical for making spatial connections for migratory birds because samples provide information about pre-migratory location only until the tissue turns over to reflect local values. We calculated stable-hydrogen isotope (δ2H) turnover rate in the red blood cells of two long-distance migratory songbirds, Bicknell's Thrushes (Catharus bicknelli) and Swainson's Thrushes (Catharus ustulatus), using samples collected at a breeding site in New Brunswick, Canada. Blood from both species captured early in the breeding site was more positive in δ2H than blood sampled later in the summer, but did not match blood values for wintering Bicknell's Thrushes. An asymptotic exponential model was used to estimate turnover of red blood cell δ2H and yielded a half-life estimate of 21 days and 14 days for Bicknell's and Swainson's thrushes, respectively. Red blood cells of both species approached the local breeding site value one month after the first individuals were detected at the site. For Bicknell's Thrushes, estimated δ2H in blood at arrival (−72‰) was closer to blood collected at wintering sites (mean −61‰) than to expected breeding site δ2H (−120‰). Discrimination values calculated for red blood cells collected at the breeding site for both species were greater than expected based on studies using keratin. Turnover during migration currently limits the use of blood sampled early in the breeding season for connectivity/carry-over effect studies. However, direct tracking technology such as geolocators can provide information about migration duration, timing, and stopovers that can be used to improve isotopic turnover equations for metabolically active tissues.

Migrations of Common Snook from a Tidal River with Implications for Skipped Spawning

AbstractCommon snook Centropomus undecimalis support a recreational fishery that contributes greatly to Florida's economy and have been the subject of many diverse studies in which aspects of their life history, reproductive biology, and fishery dynamics have been defined. The current stock assessment contains assumptions based on historical reproductive schedules measured at the population level during the early 1990s. Recent research, however, suggests our understanding of habitat residency and spawning schedules may be overly generalized. We used acoustic telemetry to study the movements and migrations of common snook from the tidal reaches of the Caloosahatchee River, a major tributary of Charlotte Harbor, for 3 years (2005–2007). During this period, 60% of the tagged snook left the study area during at least one spawning season, presumably to enter higher salinity waters where they spawn. The onset and duration of these annual migrations are similar to those reported in previous reproductive studies of snook, but individual dynamics varied. Unexpectedly, 40% of tagged snook remained within the monitored portion of the river for up to three spawning seasons, providing initial evidence for skipped spawning. These detailed data indicate differential individual contributions to total spawning biomass. If further investigation confirms skipped spawning in common snook and shows similar rates of skipped reproduction throughout the snook population, this information should be incorporated into future stock assessments.

OC-089 Transient hiatus hernia during transient lower oesophageal sphincter relaxations

IntroductionIn hiatus hernia there is proximal displacement of the gastro-oesophageal junction (GOJ) relative to the crural diaphragm impairing barrier function. Fluoroscopic studies have indicated proximal migration of the GOJ during...

THE ROLE OF FAMILY SUPPORT AND OTHER FACTORS IN RETURNING HOME

The present study focuses on the effect of social and other support from the family in the place of origin of migrants and how it impacts upon migrants’ propensity to return. The study uses longitudinal data from a project in Northeastern Thailand called the Nang Rong Project. The analysis shows that monetary support from the family left behind has a significant effect on migrants’ propensity to return home. Household strategies of migration have played an important role in explaining migration in the Nang Rong setting. At the individual and household level, education, occupation and household size were strongly associated with migrants’ propensity to return to their original village. Among the social support variables, duration of migration has significant effects on migrants’ likelihood of returning home. Three variables—marital status, wealth index and whether the person came with an immediate family member—were found to have weak associations with the dependent variable. A major finding from this study was that migrants who have higher education are more likely to stay at the destination.

Coyotes, Migration Duration, and Remittances

The migration of Mexican immigrants to the U.S. is one of the largest bilateral migration flows in the world and remittances from these immigrants represent a crucial source of income for Mexican households. As the United States tightens controls on illegal migration, this may impact both migration durations and remittances. Tighter borders increase crossing costs, often because migrants need to pay smugglers (coyotes). Using data from the Mexican Migration Project, we find that higher crossing costs increase the probability of remitting, the remittance rate and the duration of stay as undocumented workers pay off the crossing debt. If immigrants did not incur these crossing debts then more of their earnings could be spent in the United States or by their households in Mexico on productive activities and durations in the U.S. might be lessened at the margin. This suggests some potential gain to both the U.S. and Mexican economies through expanding guest worker programs and consequently reducing the hiring of coyotes.

Duration and Rate of Spring Migration of Kirtland's Warblers

Abstract The duration of migration of the endangered Kirtland's Warbler (Setophaga kirtlandii) has not been previously documented. We estimated the average duration of spring migration for five male Kirtland's Warblers by observing uniquely color-banded individuals at or near both the beginning and end of spring migration in Eleuthera, The Bahamas, and Michigan, respectively. We estimated the average duration of spring migration for these five individuals to have been no more than 15.8 days (range 13–23 days) and the average distance traveled to have been 144.5 km/day (96.1–169.1 km/day).

Mapping the migratory routes and wintering areas of Lesser Kestrels Falco naumanni: new insights from satellite telemetry

Recent improvements in satellite tracking, such as the miniaturization of transmitters, have enabled the study of movements of an increasing number of bird species. The Lesser Kestrel Falco naumanni has been the subject of numerous studies but detailed information on its migration routes and wintering areas is still lacking. Here, we provide a detailed description of migration routes, timing of migration and wintering areas of Lesser Kestrels. Five adults fitted with satellite transmitters in southeastern Spain were tracked during autumn and spring migration journeys and on their wintering grounds. The overall migration duration was longer in spring than in autumn, although birds also showed longer stopovers in this season and hence the number of travelling days was lower. Lesser Kestrels covered longer daily distances in spring due to a higher frequency of nocturnal migration, rather than differences in flight speed, which did not differ between seasons. Wintering areas of Lesser Kestrels from the same breeding colony were widely spaced throughout the western Sahel along the borders of Mauritania, Mali and Senegal, approximately 2800 km from their breeding sites. The autumn migration duration of Lesser Kestrels derived from recent studies using geolocators was underestimated compared with that recorded by satellite telemetry. Given the current rapid habitat loss in the Sahel, a better understanding of migratory routes and wintering areas of other populations of this species would be important to assess its influence on population trends.

Labour Market Activity, Occupational Change and Length of Stay in the Gulf

This paper analyses the relationship between migration duration and occupational changes, using the case of Indian expatriates in the Gulf States. De jure, permanent migration to a Gulf state is almost impossible, leaving a (renewable) temporary work visa the only option available for Indian migrants. De facto, however, ‘temporary’ stay can last for years or even decades, and thus, questions about the factors influencing the timing of return become relevant. This analysis, based on two rounds of the Kerala Migration Survey (KMS 2008 and 2009), aims to deepen our understanding about the relationship between return migration, labour market activity and occupational change among Indian expatriates returning from the Gulf region. In particular, we investigate whether the length of stay in the Gulf depends on migrants’ occupational trajectories before, during, and after the migration experience. We find some significant effects of transitions in labour market activity on the length of stay abroad. In particular, the prospect of acquiring an occupation which entails upward social mobility (mainly in the public sector or self-employment) seems to be associated with a shorter stay in the Gulf states, whereas the prospect of post-return labour market drop-out significantly increases migration duration.

Migrating husbands and changing cardiovascular risk factors in the wife: a cross sectional study in Asian Indian women

ObjectiveThe authors studied the influence of migration of husband on cardiovascular risk factors in Asian Indian women.MethodsPopulation-based studies in women aged 35–70 years were performed in four urban and five...

Comparative effects of migrants’ remittances on composition of recipient household income in two small, island economies

We use unique household survey data from Fiji and Tonga to estimate and compare the combined impact of migration and remittances on the composition of household income. A two-step methodology is followed employing a migration prediction model followed by the estimation of a Three Stage Least Squares (3SLS) remittances and income equation system. We find that remittances contribute to growth in productive capital and entrepreneurial activity in the longer-established migrant economy, but have yet to impact on business activity in the more recently remittances-oriented economy, despite it having a more developed, market economy. In the latter case, remittances seem more linked to supporting consumption through supplementing low wage income. These findings suggest that the duration and intensity of remittance-driven migration, and the structure of economic activity within a community are important in understanding the influences of migration and remittances on household resource allocation and production decisions.

Prevalence of psychiatric morbidity at Mobile Health Clinic in an urban community in North India

ObjectiveThe objective was to estimate the prevalence of psychiatric morbidity amongst patients attending Mobile Health Clinic (MHC) in an urban community in South Delhi. MethodsAdult subjects were recruited by systematic random sampling at outpatient MHC. Primary Care Evaluation of Mental Disorder Patient Health Questionnaire (PHQ) was used for screening, and Mini International Neuropsychiatric Interview (M.I.N.I.) was used for the confirmation of diagnosis of psychiatric disorder of all PHQ-positive and 20% of PHQ-negative patients. Association of selected sociodemographic factors with psychiatric morbidity was also assessed. ResultsIn total, 350 subjects were recruited, out of which 92 (26.3%) [95% confidence interval (CI) 21.7–31.0] were found to be PHQ positive. M.I.N.I. was administered to 141 subjects (92 PHQ positives and 52 PHQ negatives). Total estimated magnitude of psychiatric morbidity by M.I.N.I. was 25.4% (95% CI 20.9–29.9). Depression (15.7%) was observed to be the most common psychiatric disorder followed by generalized anxiety disorder (11.1%) and phobic disorders (10.1%). Suicidal ideation was reported by 37 (10.6%) patients. Literate status [odds ratio (OR)=0.43] and duration of migration >20 years to study area (OR=1.27) were found to be significantly associated with psychiatric morbidity. ConclusionIn resource-poor country like India, high psychiatric morbidity at MHC justifies the use of MHC for providing outreach mental health services in difficult areas.

Sex-specific differences in migratory movements of adult paddlefish above Fort Peck Reservoir, Montana, USA

Spring spawning migrations of paddlefish Polyodon spathula into the River Missouri above Fort Peck Reservoir, Montana were investigated with radio-telemetry during 2006–2009. Selected migration characteristics (total movement, rate of movement, maximum upriver ascent, duration of the migration, upriver residence time and spawning periodicity) were compared between sexes and among years. Paddlefish exhibited sexual dimorphisms in selected measures of migratory behavior. Females typically moved at a faster rate (mean, 13.4 km/ day for females versus 10.1 km/day for males) and remained in the river a shorter time (mean, 40 days) than did males (mean, 45 days). Females and males exhibited similar total movements, upriver residence times and mean maximum ascents. Spawning periodicity was shorter for males (mean, 1.5 years) than females (mean, 2.3 years). Total movement, movement rate, mean duration of the spawning migration and upriver residence time of both sexes differed among years. Results from this study indicate that certain analyses of paddlefish migrations and migratory behavior should be undertaken separately for female and male fish.

Left-Behind Children and Return Decisions of Rural Migrants in China

This paper examines how left-behind children influence return migration in China. We first present a simple illustrative model based on Dustmann (2003) that incorporates economic and non-economic motives for migration duration (or intentions to return), among which are parents' concerns about the well-being of their left-behind children. We then propose two complementary empirical tests based on data we collected from rural households in Wuwei county (Anhui province) in fall 2008.We first use a discrete-time proportional hazard model to estimate the determinants of migration duration for both on-going migrants with an incomplete length of duration and return migrants with a complete length of duration. Second, we apply a binary Probit model to study the return intentions of on-going migrants. Both models yield consistent results regarding the role of left-behind children as a significant motive for return. First, left-behind children are found to draw their parents back to the village, the effect being stronger for pre-school children. Second, sons are found to play a more important role than daughters in reducing migration duration.

The annual cycle of a trans-equatorial Eurasian–African passerine migrant: different spatio-temporal strategies for autumn and spring migration

The small size of the billions of migrating songbirds commuting between temperate breeding sites and the tropics has long prevented the study of the largest part of their annual cycle outside the breeding grounds. Using light-level loggers (geolocators), we recorded the entire annual migratory cycle of the red-backed shrike Lanius collurio, a trans-equatorial Eurasian-African passerine migrant. We tested differences between autumn and spring migration for nine individuals. Duration of migration between breeding and winter sites was significantly longer in autumn (average 96 days) when compared with spring (63 days). This difference was explained by much longer staging periods during autumn (71 days) than spring (9 days). Between staging periods, the birds travelled faster during autumn (356 km d(-1)) than during spring (233 km d(-1)). All birds made a protracted stop (53 days) in Sahelian sub-Sahara on southbound migration. The birds performed a distinct loop migration (22 000 km) where spring distance, including a detour across the Arabian Peninsula, exceeded the autumn distance by 22 per cent. Geographical scatter between routes was particularly narrow in spring, with navigational convergence towards the crossing point from Africa to the Arabian Peninsula. Temporal variation between individuals was relatively constant, while different individuals tended to be consistently early or late at different departure/arrival occasions during the annual cycle. These results demonstrate the existence of fundamentally different spatio-temporal migration strategies used by the birds during autumn and spring migration, and that songbirds may rely on distinct staging areas for completion of their annual cycle, suggesting more sophisticated endogenous control mechanisms than merely clock-and-compass guidance among terrestrial solitary migrants. After a century with metal-ringing, year-round tracking of long-distance migratory songbirds promises further insights into bird migration.

A database on visible diurnal spring migration of birds (Central Europe: Lake Constance)

Millions of birds migrate each year between breeding grounds and overwintering areas. Migration behavior is influenced by a number of factors: day length, physiological and genetic factors, the magnetic compass, population dynamics, and weather and climatic conditions. Historical and current data on avian migration are of broad scientific value. Most of information on avian migration is presented in form of summary statistics (e.g., duration of migration, number of individuals, trend line over years) in published studies, but original data sets are not readily available. Here, we describe the first open-source archive on visible diurnal spring migration in Central Europe. The database comprises the records of a systematic field study, which covers 35541 records of migrating birds for more than 138000 specimens of 96 species. Data were collected during the spring periods of 1984, 1985, and 1986. Bird census was conducted at the tip of the Hori peninsula in Lake Constance, Germany (north of the Alps: 47°41′...

Migration strategy of a flight generalist, the Lesser Black-backed Gull Larus fuscus

Migrating birds are believed to minimize the time spent on migration rather than energy. Birds seem to maximize migration speed in different ways as a noteworthy variation in migration strategies exists. We studied migration strategies of a flight mode and feeding generalist, the Lesser Black-backed Gull Larus fuscus, using GPS-based satellite telemetry. We expected the gulls to achieve very high overall migration speeds by traveling via the shortest direct route, traveling during a large part of the day and night, and making few and short stopovers. Fourteen individuals were tracked between the Dutch breeding colony and the wintering sites in England, southern Europe and northwest Africa. The gulls did not travel via the shortest possible route but made substantial detours by their tendency to follow coasts. Although the gulls traveled during most of the day, and sometimes during the night, they did not achieve long daily distances (177 and 176 km/day in autumn and spring, respectively), which is explained by the gulls stopping frequently on travel days to forage. Furthermore, due to frequent and long migratory stopovers, their overall migration speed was among the lowest recorded for migratory birds (44 and 98 km/day, in autumn and spring, respectively). A possible explanation for the unexpected frequent stopovers and low migration speeds is that gulls do not minimize the duration of migration but rather minimize the costs of migration. Energy rather than time might be important for short-distance migrating birds, resulting in very different migration strategies compared with long-distance migrants.

Study on effects of duration of migration to high-altitude on cerebral hemodynamics and their ethnic differences

Objective To study the effects of duration of migration from sea-level to high-altitude on cerebral hemodynamic parameters and their ethnic differences.Methods This randomized comparative study recruited 5 groups of healthy male subjects which were native Hans at sea-level (NHS),Han migrants from sea-level to high-altitude (HMSH,where HMSH-a for residence duration of 4 days,HMSH-b for 1 year,and HMSH-c for 5 years),and native Tibetans at high-altitude (NTH).Color duplex Doppler sonography (CDDS) was used to measure bilateral vertebral and internal carotid arterial diameters,mean flow velocities.The heart rate,arterial blood pressure,and arterial oxygen saturation were also recorded simultaneously,and in combination,hemoglobin was measured to assess total cerebral blood flow (TCBF),total cerebrovascular resistance (TCVR),and total cerebral oxygen supply (TCOS).Results After migration to high-altitude,Hans' TCVR and TCBF maintained the level of NHS after transient changes during early stage (P<0.05),and the TCBF was markedly higher than that of NTH (P<0.05);while the blood pressure and TCOS increased abruptly (P<0.05) at the beginning and kept for a relatively long time at a constant level which were higher than those of NTH all the time (P<0.05).Conclusions Han migrants can acclimate to high-altitude by adaptive change of cerebral blood flow over a short time and maintain a constant adaptability which is always weaker than that of native Tibetans.CDDS can be used for non-invasive measurement of actual cerebral blood flow,and is of good value in the study on high-altitude-related cerebral hemodynamics. Key words: Ultrasonography; Altitude; Hypoxia; Brain; Hemodynamic phenomena