The effects of hatching date on timing of autumn migration in partial migrants – an individual approach

Timing of spring migration and breeding and their interaction with climate change has been widely studied in recent years, but the possible changes in timing of autumn migration have gained less attention. This work focuses on autumn migration and provides the first multi‐species individual‐based study of how hatching date affects the autumn migration date and migration age by using nestling ring data and re‐trappings of the same individuals during the autumn migration at the Hanko Bird Observatory, Finland. We studied three potentially multibrooded passerines (great tit, blue tit and coal tit) and two single‐brooded birds of prey (goshawk, sparrowhawk), all partially migratory short‐distance migrants. Individuals from late broods migrated at a younger age in all tit species and also in hawks the late hatched individuals tended to migrate at a younger age than the early‐hatched individuals. Late‐hatched individuals migrated later than early‐hatched individuals in blue and coal tits, where the latest hatchers represented second brood individuals. Based on our results, the time from hatching to autumn migration is not constant even among individuals of the same population. Our study indicates that climate warming induced advancement of avian breeding may cause changes in the timing of autumn migration through the frequency of second broods.     

Body size and the adoption of a migratory tactic in brook charr

The presence of a conditional strategy based on size attained before migration and a sex-ratio at migration biased towards females were explored in a population of brook charr Salvelinus fontinalis in the Sainte-Marguerite River, Quebec Province, Canada, where anadromous and resident forms live sympatrically. Seaward migration in the system occurred at 1 and 2 years old. Comparisons between backcalculated size-at-age of migrant and resident fish revealed that smaller fish at age 1 year delay migration to the following year and that bigger fish either migrated at age 1 year or remained resident for the rest of their life-cycle. Slow growth was associated with migration later in life (age 2 years) at a bigger size, which is consistent with the hypothesis of a threshold size for migration. No difference in size at age 1 year between migrant and resident fish suggests that other factors, such as growth efficiency and the presence of heritability of the tactics, are involved. Overall the sex ratio was equal for migrant and resident fish, while an age-specific bias was found: more males migrated at age 1 year and more females at age 2 years. These differences suggest that different tactics are adopted by different sexes.     

Fall movements of Red‐headed Woodpeckers in South Carolina

Fall migration of Red‐headed Woodpeckers (Melanerpes erythrocephalus) can be erratic, with departure rates, directions, and distances varying among populations and individuals. We report fall migration departure dates, rates, and routes, and the size of fall home ranges of 62 radio‐tagged Red‐headed Woodpeckers in western South Carolina. Rates of fall migration differed among years; all radio‐tagged woodpeckers migrated in 2005 (15 of 15), none (0 of 23) migrated in 2006, and 54.2% (13 of 24) migrated in 2007. Of 28 woodpeckers that left their breeding territories, we relocated eight either en route or on their fall home ranges. These woodpeckers migrated short distances (4.3–22.2 km) south along the floodplain forest of a large creek. The variable migration patterns we observed indicate that Red‐headed Woodpeckers may best be described as facultative migrants. We determined the home range sizes of 13 woodpeckers in both seasons, regardless of whether they migrated, and fall home ranges were smaller (mean = 1.12 ha) than summer home ranges (mean = 3.23 ha). Fall‐winter movements of Red‐headed Woodpeckers were concentrated on mast‐producing oak (Quercus spp.) trees, which may have restricted home range sizes. The partial migration we observed in 2007 suggests that factors other than mast crop variability may also influence migration patterns because woodpeckers that year responded to the same annual mast crop in different ways, with some migrating and some remaining on breeding season home ranges during the fall.     

Patterns of migration between feeding and spawning sites in a coral reef surgeonfish

Many coral reef fishes exhibit regular localised migrations between feeding and spawning areas, but the factors affecting these migration patterns, such as the distance, frequency and spawning site fidelity are poorly understood. The aim of this study was to investigate the patterns of migration to spawning sites of the surgeonfish, Ctenochaetus striatus (Acanthuridae). We explored relationships amongst an individual’s size and sex, the distance and frequency it migrated from its feeding area to spawning sites, fidelity to particular spawning sites and the number of individuals that aggregated to spawn. In order to achieve this, 406 C. striatus were captured and tagged on inshore reefs in Kimbe Bay (5°30′S 150°6′E), New Britain, Papua New Guinea. Tagged individuals were consistently observed within spatially discrete but overlapping feeding areas (maximum diameter averaging <13 m). The mean distance migrated was 58 m (ranging from 2 to 291 m). No tagged individuals were witnessed spawning at more than one site. Whilst most individuals (n = 88) migrated to the spawning site that was closest to their feeding areas, those that migrated to sites further away (n = 9) always spawned at sites where the number of conspecifics aggregating was larger. Neither the size nor the sex of individuals limited migration distance. However, males migrated significantly more frequently than females (on average once every 2 days vs. once every 3 days), and migration frequency was positively correlated with size in females. Migration distance did not affect the frequency with which individuals spawned. Whether patterns of migration are determined by cost-benefit optimisation, tradition, or an alternative mechanism is unknown.     

Synchrony in the downstream migration of smolts and upstream migration of adult Atlantic salmon in the subarctic River Utsjoki

Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001–2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300–0900 hours) and high sun (0900–1500 hours), while adults favoured the period of low sun (2100–0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2–3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups.     

The effect on cardiovascular risk factors of migration from rural to urban areas in Peru: PERU MIGRANT Study

Background

Mass-migration observed in Peru from the 1970s occurred because of the need to escape from politically motivated violence and work related reasons. The majority of the migrant population, mostly Andean peasants from the mountainous areas, tends to settle in clusters in certain parts of the capital and their rural environment could not be more different than the urban one. Because the key driver for migration was not the usual economic and work-related reasons, the selection effects whereby migrants differ from non-migrants are likely to be less prominent in Peru. Thus the Peruvian context offers a unique opportunity to test the effects of migration.

Methods/Design

The PERU MIGRANT (PEru's Rural to Urban MIGRANTs) study was designed to investigate the magnitude of differences between rural-to-urban migrant and non-migrant groups in specific CVD risk factors. For this, three groups were selected: Rural, people who have always have lived in a rural environment; Rural-urban, people who migrated from rural to urban areas; and, Urban, people who have always lived in a urban environment.

Discussion

Overall response rate at enrolment was 73.2% and overall response rate at completion of the study was 61.6%. A rejection form was obtained in 282/323 people who refused to take part in the study (87.3%). Refusals did not differ by sex in rural and migrant groups, but 70% of refusals in the urban group were males. In terms of age, most refusals were observed in the oldest age-group (>60 years old) in all study groups. The final total sample size achieved was 98.9% of the target sample size (989/1000). Of these, 52.8% (522/989) were females. Final size of the rural, migrant and urban study groups were 201, 589 and 199 urban people, respectively. Migrant's average age at first migration and years lived in an urban environment were 14.4 years (IQR 10–17) and 32 years (IQR 25–39), respectively. This paper describes the PERU MIGRANT study design together with a critical analysis of the potential for bias and confounding in migrant studies, and strategies for reducing these problems. A discussion of the potential advantages provided by the case of migration in Peru to the field of migration and health is also presented.     

Fertility of the Tibetans migrated to Northen India

This paper aims to study the fertility rate of the migrant Tibetans residing in Northern India and finding out the factors which are affecting the fertility level among them. Data are reported on age at menarche, age at marriage, first childbirth, use of contraception, widowhood, migration and on various fertility measures in the Tibetan of Northern India living at low and moderate altitude (600–2000 m), who have migrated from high altitude (4000 m above sea level) in Tibet. The migrant Tibetans reported a relatively lower fertility as compared to the high and moderate altitude populations. This lower fertility is mostly attributable to the use of contraception, the later mean age at marriage and first childbirth, and relatively high proportion of widows in the migrant Tibetans. However, the social as well as biological changes in population during migration should not be overlooked, which have a sufficient impact on fertility.     

Female‐biased migration of stream‐dwelling Dolly Varden in the Shiisorapuchi River, Hokkaido, Japan

The first evidence for female‐biased migration in a partially migratory stream‐dwelling salmonid the Dolly Varden Salvelinus malma , a phenomenon well known in sea‐run and lake‐run populations, is presented. Dolly Varden in the Shiisorapuchi River in central Hokkaido, Japan, used both tributaries, of which there are many, and the main stem, but spawned only in tributaries. The size structures of Dolly Varden (≥age 1 + years) in tributaries were unimodal (<100 mm fork length, L _F) during non‐spawning seasons but changed to bimodal during spawning seasons (lower mode <110 mm, upper mode >120 mm L _F). Mature individuals were observed in both modal groups. From the trapping and census data, the small group appeared to be tributary resident and the large group main stem migrant. Males were common in both resident and migrant components. Most females, however, migrated to the main stem to mature, indicating female‐biased migration.     

Variation in spring migration routes and breeding distribution of northern pintails Anas acuta that winter in Japan

In North America, spring migration routes and breeding distribution of northern pintails Anas acuta vary because some individuals opportunistically nest at mid‐latitudes in years when ephemeral prairie wetlands are available, whereas others regularly nest in arctic and sub‐arctic regions where wetland abundance is more constant. Less was known about migration routes and breeding distribution of pintails in East Asia. From 2007–2009 we marked 198 pintails on their wintering areas in Japan with satellite transmitters to: 1) document spring migration routes and summer distribution, 2) evaluate migratory connections and breeding season sympatry with North American pintails, and 3) determine if pintails used the same migration routes in fall as in spring. Most pintails (67%) migrated to the Kamchatka or Chukotka peninsulas in eastern Russia either directly from Japan or via Sakhalin Island, Russia. Remaining pintails primarily migrated to the Magadan region or Kolyma River Basin in eastern Russia via Sakhalin Island. The Chukotka Peninsula was the most common summer destination, with highest densities in the Anadyr Lowlands; a region also used by pintails that migrate from North America. One pintail migrated to St. Lawrence Island, Alaska, in spring and another briefly migrated to the western coast of Alaska in fall. Autumn migration routes generally mirrored spring migration although most pintails bypassed Sakhalin Island in fall. Compared to North American pintails, pintails that winter in Japan exhibited less variation in migration routes and breeding distribution, and nested at higher latitudes. In the Russian Far East there is no region with habitats comparable in extent to the ephemeral mid‐latitude wetlands of North America. Consequently, East Asian pintails mainly nest in arctic and sub‐arctic regions where annual consistency in wetlands promotes constancy in migration routes and breeding distribution. Breeding season sympatry between pintails from different continents results more from North American pintails migrating to eastern Russia than from Japanese pintails migrating to North America.     

Seasonal migration by a large forest ungulate: a study on takin (Budorcas taxicolor) in Sichuan Province, China

Migration in large mammals is a biological phenomenon that involves seasonal movements over a vertical or horizontal scale that encompasses distances of more than several home ranges. Takin are large bovid herbivores that conduct seasonal migrations. From 2006 to 2009, we utilized data from 9 GPS-collared animals and 22 trail event recorders to describe takin migration pattern at the level of both individuals and population. We found seasonal migration of takin over an elevation gradient which contained two migration cycles, with takin inhabiting the highest elevations in summer, lowest elevations in spring and autumn, and intermediate elevations during winter. These movements did not involve expansion of home range size but rather shifts in distribution. Habitat availability analysis based on five forest types indicated that takin showed significant monthly forest preferences. Based on both telemetry and trail monitors, mature forest with bamboo understory was the habitat favored by takin for more than 8 months of the year. Both methods also indicated that not all individuals migrated to the highest elevations during summer or the lowest elevations in winter. We also found that individual takin do not necessarily follow the same annual movement, as three out of the four animals with at least 2 years of data changed their migration pattern between years. Current protocols for annual surveys conducted at high-elevation meadows or low-elevation valleys are not adequate to detect all individuals. We suggest that surveys must include all potential habitats and include detection functions in order to accurately estimate takin numbers or relative changes in their density.     

Genetic and environmental correlations among serum lipids and apolipoproteins in elderly twins reared together and apart.

Genetic and environmental correlations among five serum-lipid measures were examined in the Swedish Adoption/Twin Study of Aging. The sample included 302 twin pairs; 146 of these twin pairs were separated at an early age and were reared apart. The lipid measures examined include total cholesterol, HDL-cholesterol, triglycerides, and apolipoproteins A-I and B. Genetic and environmental correlations were evaluated for two different age groups, formed by dividing the sample at the median. The younger group included individuals 41.8-65.4 years of age at the midpoint of testing, although only 24 individuals were < 50 years of age. The older group included all those > 65.4 years of age, up to age 87 years of age. Substantial genetic correlations were found within each age group, although there is no evidence for a single genetic factor common to all five lipids. The comparison of twins reared together with twins reared apart allowed estimation of the effects of shared rearing environment; however, shared rearing environment only appears to be a significant mediator of the phenotypic correlation between apolipoprotein B and cholesterol in the older group. Examination of the genetic and environmental covariances suggests that the relative contributions of genetic factors are lower in the older group. Nonshared environmental factors are relatively more important mediators of phenotypic correlations among the serum lipids in individuals > 65.4 years of age than they are for the younger group. Sex differences in the mediation of these serum lipids were not as clear.     

Juvenile migration in brown trout: a consequence of energetic state

1. We explored the mechanisms determining age and size at juvenile migration in brown trout Salmo trutta L. A ¹³³Cs tracer methodology was used to estimate food consumption of juvenile brown trout in a Norwegian stream, and the energy budgets of early migrants and stream residents were compared.
2. Fast-growing brown trout migrated to the lake earlier and at a smaller body size than slower-growing individuals. The 2+ migrants were significantly larger than those that remained 1 or more years longer in the stream. The 3+ migrants were significantly larger than the 2+ migrants. Some fast-growing males matured in the stream, whereas all females left the stream before maturing sexually.
3. The food consumption and the energy budgets for 2+ migrants were more than four times higher than those of the resident 2+ fish. Total energy allocated to growth was also higher among migrants, and the total metabolic costs were five times higher among migrants than among resident fish.
4. The proportional energy allocation to growth among the 2+ migrants was much lower (about half) than that of those remaining longer in the stream. The reduction in the proportion of energy available for growth from age 1+ to 2+ was larger among migrants (88%) than among resident fish (68%). Reduction in the proportion of energy available for growth is a probable explanation for why migrations are initiated at age 2.
5. Our study supports the hypothesis that fast-growing individuals shift their niche earlier and at a smaller body size than slower-growing individuals because they maintain higher metabolic rates and are energetically constrained at a younger age by limited food resources than slow growers.     

Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts

Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3–6 days. Burrishoole and Conon fish migrated with a 15–19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na⁺, K⁺-ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter-strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na⁺, K⁺-ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon.     

Migration of lymphocytes through endothelial cell monolayers: augmentation by interferon-gamma

During normal lymphocyte recirculation and in chronic inflammation, lymphocytes emigrate from blood into the perivascular tissue. The mechanism of lymphocyte migration through the endothelial cell (EC) layer of blood vessels is poorly understood. To identify factors that control lymphocyte emigration, a method has been developed to measure human peripheral blood lymphocyte migration through monolayers of human umbilical vein EC and into nitrocellulose (NC) filters located below the EC monolayer. Counts were made of lymphocytes that had migrated into the NC filter using a particle counter. T lymphocytes attached to and migrated through EC monolayers in a T-cell-number- and time-dependent fashion. Migration required viable EC since lymphocytes failed to migrate through formaldehyde-fixed EC monolayers or monolayers of dermal fibroblasts. Interferon-gamma (IFN-gamma) markedly augmented the migration in a dose- and time-dependent manner when preincubated with the EC. When T lymphocytes were pretreated with IFN-gamma, no increase in migration was observed. Finally, IFN-gamma augmented the migration of T cells prebound to the EC, indicating that the IFN-gamma-enhanced migration was not due to increased binding of T cells to the EC, but rather to an action on the EC to facilitate subsequent migration.     

Patterns of migration and residency in coastal cutthroat trout Oncorhynchus clarkii clarkii from two tributaries of the lower Columbia River

Coastal cutthroat trout Onchorhynchus clarkii clarkii life-history variants, migration and freshwater residency were monitored using stationary passive integrated transponder (PIT) tag arrays in two tributaries of the Columbia River from 2001 to 2005 (Abernathy Creek, river kilometre, rkm 76) and from 2002 to 2005 (Chinook River, rkm 6). In 2001–2003 and 2002–2003 (Abernathy and Chinook, respectively), 300–500 coastal O. c. clarkii were captured in each tributary by electrofishing and implanted with 23 mm PIT tags. PIT arrays monitored movements from the initiation of tagging through the spring of 2005. Rotary screw traps were also operated on both tributaries. In Abernathy Creek, 28% of tagged individuals were observed through either active capture or passive interrogation. Of these, 32% were identified as migrants and 68% were identified as residents. In the Chinook River, 48% of tagged fish were observed subsequent to tagging; 92% of these fish were migrants and only 8% were resident. In both tributaries, a greater proportion of resident fish were in the upper reaches. The majority of migrants (78–93%) moved the spring following tagging. Migrants leaving at age 2+ years tended to grow faster than those that migrated at age 3+ years or residents. Patterns of growth or growth opportunities may influence both patterns of life-history expression and the timing of migration.     

Demography and social organization of free-ranging Lemur catta in the Beza Mahafaly Reserve,Madagascar

In 1987, a long-term study of the demography of Lemur catta was begun in southern Madagascar. Eighty-five ringtailed lemurs were captured, marked, and released. Adult age classes were estimated using patterns of dental attrition. Including young, 155 individuals from nine groups were identified and monitored over 18 months. The study population of the reserve remained stable, with a growth rate of 0.98. Group sizes ranged from nine to 22 individuals (mean 14). Home ranges were larger (32 ha) and population densities lower (135/km²) than those for previously studied populations, and there was a relationship between habitat quality (e.g., no. of large trees) and these factors. At the beginning of the study, there were more adult males than females, but the sex ratio reached 1.00 by the last census. Females first gave birth at 3 years of age, and 80% or more of the females gave birth in 2 consecutive years. Fifty-two percent of the infants died in the first year and, given preliminary findings, only 40% of those born reach adulthood. Age-specific fertility patterns were similar to those reported for anthropoid primates. Forty-seven percent of the adult males migrated or were missing within a year. This included 78% of the 3–4 year olds and 38% of older age classes. No females were observed to migrate. One group split during the study. Demographic patterns are discussed and related to patterns in other populations of ringtailed lemurs as well as in anthropoids.     

Phenotypic consequences of nonrandom migration in the Jirels of Nepal

The phenotypic structure of human populations is shaped by a number of factors such as population size and marital migration. This paper examines the impact of migration on the between-village phenotypic differentiation of the Jirels, a tribal group of eastern Nepal. Data on stature and five cranial measurements for 526 individuals (males and females) are utilized to illustrate the patterns of phenotypic variation. A permutation method is used to generate the phenotypic consequences of random migration constrained to observed levels of movement. The results suggest that Jirel migration is nonrandom and that it produces higher levels of phenotypic differentiation than would result from a random migration process.     

The growth history of anadromous white-spotted charr in northern Japan: a comparison between river and sea life

Anadromous white-spotted charr Salvelinus leucomaenis in a natural river in northern Japan migrated to the sea mainly at age 3+ years. Sea-run charr grew faster than parr, particularly as first time migrants. Sea-run charr repeated seaward migration up to three times; the observed maximum age was 5+ years old. The likelihood ratio test identified significant differences in asymptotic size and individual growth variability between parr and sea-run charr. Sea-run charr had an asymptotic size ( L ^∞) twice as large as parr, while the growth parameter ( K ) was similar between sea-run and parr. Growth variability was higher for parr than for sea-run charr.     

Correlates of timing of spring migration in birds: a comparative study of trans-Saharan migrants

The evolution of migratory strategies in birds is likely to have been influenced by ecological as well as socio-sexual factors in both wintering and breeding areas. In this comparative study, we analysed timing of spring passage of 38 long-distance migratory bird species that winter south of the Sahara desert and breed in Europe, in relation to wintering and breeding latitudes, moult strategy, nesting site (open vs. cavity), and sexual dimorphism in size and coloration, which may reflect intensity of sexual selection. We employed a large data set consisting of more than 190 000 individuals ringed during spring migration in the Mediterranean Sea. We found that the species that migrated earlier were those wintering farther north, nesting in cavities and showing the largest degree of sexual size dimorphism (SSD). However, sexual dichromatism was not related to migration date. Among passerine species, moulting wing-feathers in Africa delayed migration. We found no support for the energetic constraint hypothesis, which proposes that early arrival selects for large male size, since early arriving species were not larger than late arriving ones. Thus, the observed associations suggest that variation in migration schedules at the interspecific level may have evolved in relation to ecological factors and SSD, possibly reflecting the intensity of mating competition.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 199–210.     

The gut microbiome composition and degradation enzymes activity of black Amur bream (Megalobrama terminalis) in response to breeding migratory behavior

Black Amur bream (Megalobrama terminalis), a dominant species, resides in the Pearl River basin, known for its high plasticity in digestive ability. During spawning season, M. terminalis individuals with large body size and high fertility undergo a spawn migratory phase, while other smaller individuals prefer to settlement over migration. It is well known that gut microbial community often underpins the metabolic capability and regulates a wide variety of important functions in fish. However, little was known about how the gut microbiomes affect fish breeding migration. To investigate the variations in the gut microbiome of M. terminalis during the migration, we used high‐throughput 16S rRNA gene sequencing to reveal the distinct composition and diversity of the whole gut microbiome of migrated and nonmigrated population during period of peak reproduction, respectively. Our results indicated that nonmigrated population in estuary had a higher alpha diversity than that of migrated population in main stem. Additionally, an obvious abundant taxa shift between the gut microbiota community of nonmigrated and migrated M. terminalis was also observed. Change of dominant gut taxa from nonmigrated to migrated population was thought to be closely related to their degradation enzymes. Our results suggested that amino acid metabolism and lipid metabolism in migrated population were higher than that in nonmigrated population, providing a line of evidence for that M. terminalis change from partial herbivorous to partial carnivorous diet during breeding migration. We further concluded that, in order to digest foods of higher nutrition to supply energy to spawning migration, M. terminalis regulate activities of the gut microbiome and degradation enzymes, considered to be a key physiological strategy for reproduction.