Non-migratory Periods Research Articles

Genetic Control of Avian Migration: Insights from Studies in Latitudinal Passerine Migrants.

Twice-a-year, large-scale movement of billions of birds across latitudinal gradients is one of the most fascinating behavioral phenomena seen among animals. These seasonal voyages in autumn southwards and in spring northwards occur within a discrete time window and, as part of an overall annual itinerary, involve close interaction of the endogenous rhythm at several levels with prevailing photoperiod and temperature. The overall success of seasonal migrations thus depends on their close coupling with the other annual sub-cycles, namely those of the breeding, post-breeding recovery, molt and non-migratory periods. There are striking alterations in the daily behavior and physiology with the onset and end of the migratory period, as shown by the phase inversions in behavioral (a diurnal passerine bird becomes nocturnal and flies at night) and neural activities. Interestingly, there are also differences in the behavior, physiology and regulatory strategies between autumn and spring (vernal) migrations. Concurrent molecular changes occur in regulatory (brain) and metabolic (liver, flight muscle) tissues, as shown in the expression of genes particularly associated with 24 h timekeeping, fat accumulation and the overall metabolism. Here, we present insights into the genetic basis of migratory behavior based on studies using both candidate and global gene expression approaches in passerine migrants, with special reference to Palearctic-Indian migratory blackheaded and redheaded buntings.

Sustainability of the grazing and feeding resources for sheep during the non-migratory period in Jammu and Kashmir.

The objective of the study was to evaluate the sustainability of the grazing and feeding resources of the sheep in Kashmir, India. The study was conducted in the Ganderbal District of Kashmir to evaluate sustainability, along with the scenario of grazing pattern and feeding system of the sheep during the non-migratory period. The district was divided into three production zones based on altitude, i.e., zone I (high altitude), zone II (medium altitude), and zone III (low altitude). A total of 360 sheep farmers were interviewed from the three zones that consist of 9 blocks, with 40 sheep farmers interviewed from each block. Majority of the sheep farmers (75.00%) follow a semi-migratory type of production system, use forest, and low-mountain areas for grazing purposes (48.88%) and were having medium to high availability of grazing lands. The main feeding source available to majority of the sheep farmers (60.00%) was found to be crop residues and fodder grasses, with local markets (60.00%) and fellow farmers (71.11%) being the main source of procuring concentrates and fodders. Hybrid entropy and TOPSIS method were used for the evaluation of sustainability of grazing and feeding system in the area. The most influencing factors for sustainability of grazing pattern and feeding source were found to be production system followed and the major feed sources available respectively. Most of the variables included in the grazing system were ideally best in zone I and of feeding system were found to be ideally best in zone III. There is a need for improvement in the parameters of the grazing pattern in zone III, i.e., in low-altitude areas or planes where grazing lands are shrinking at an alarming rate. The parameters under the feeding system need due consideration in zone I, i.e., in the high altitudes where the socio-economic situation of the people is comparatively poor than the other two zones.

Sheep pastoralism in southern Karnataka

Present study was conducted to understand and document the migratory system followed, socio-economic status, management and healthcare practices adopted by pastoralists of southern Karnataka. In-person interview method with a structured questionnaire was used for collecting data from 25 shepherd groups on migration. Migration starts during December and continues for 6–8 months covering around 200 km. The breed is locally called Tumkur or Sira sheep which is not yet recognized as a separate breed. Migratory flock usually contains 1,000 to 1,200 sheep, 50 goats, 10 donkeys and 2–4 dogs. The average adult male to female ratio is 1 : 22. Sale of lambs and penning rental are the main sources of income. Sheep pastoralism is an established and effective way of utilizing the excess green cover in transient regions by the sheep from pasture deficient dry zones. Maintaining the social and community pasture and forest lands at their home place will be a benefit during the lean and non-migratory periods. Assessing the migratory paths, fodder and water resource and penning demand by the farmers on migratory tract will help policy makers to provide suitable interventions to curtail the problems of pastoralists. The traditional knowledge of shepherds should be documentedand validated for larger use. The pastoralists need to be educated and trained about the use of digital finance management, herd diversification, health management and government schemes to increase their profitability and standard of living.

Migratory status determines resource selection by American Woodcock at an important fall stopover, Cape May, New Jersey

Abstract Migration is a period of high activity and exposure during which risks and energetic demand on individuals may be greater than during nonmigratory periods. Stopover locations can help mitigate these threats by providing supplemental energy en route to the animal’s end destination. Effective conservation of migratory species therefore requires an understanding of use of space that provides resources to migratory animals at stopover sites. We conducted a radio-telemetry study of a short-distance migrant, the American Woodcock (Scolopax minor), at an important stopover site, the Cape May Peninsula, New Jersey. Our objectives were to describe land-cover types used by American Woodcock and evaluate home range habitat selection for individuals that stopover during fall migration and those that choose to overwinter. We radio-marked 271 individuals and collected 1,949 locations from these birds (0–21 points individual–1) over 4 yr (2010 to 2013) to inform resource selection functions of land-cover types and other landscape characteristics by this species. We evaluated these relationships at multiple spatial extents for (1) birds known to have ultimately left the peninsula (presumed migrants), and (2) birds known to have remained on the peninsula into the winter (presumed winter residents). We found that migrants selected deciduous wetland forest, agriculture, mixed shrub, coniferous wetland forest, and coniferous shrub, while wintering residents selected deciduous wetland forest, coniferous shrub, and deciduous shrub. We used these results to develop predictive models of potential habitat: 7.80% of the peninsula was predicted to be potential stopover habitat for American Woodcock (95% classification accuracy) and 4.96% of the peninsula was predicted to be potential wintering habitat (85% classification accuracy). Our study is the first to report habitat relationships for migratory American Woodcock in the coastal U.S. and provides important spatial tools for local and regional managers to support migratory and winter resident woodcock populations into the future.

Phenotypic flexibility in migrating bats: seasonal variation in body composition, organ sizes and fatty acid profiles

Many species of bats migrate long distances, but the physiological challenges of migration are poorly understood. We tested the hypothesis that migration is physiologically demanding for bats by examining migration-related phenotypic flexibility. Both bats and birds are endothermic, flying vertebrates; therefore, we predicted that migration would result in similar physiological trade-offs. We compared hoary bats (Lasiurus cinereus) during spring migration and summer non-migratory periods, comparing our results with previous observations of birds. Migrating bats had reduced digestive organs, enlarged exercise organs, and fat stores had higher proportions of polyunsaturated fatty acids (PUFAs). These results are consistent with previous studies of migrating birds; however, we also found sex differences not typically associated with bird migration. Migrating female hoary bats increased the relative size of fat stores by reducing lean body components, while males maintained the same relative amount of fat in both seasons. The ratio of n-6 to n-3 PUFA in flight muscle membrane increased in migrating males and decreased in migrating females, consistent with males using torpor more frequently than females during spring migration. Enlarged exercise organs, reduced digestive organs and changes in adipose tissue composition reflect the elevated energetic demands of migration. Sex-specific patterns of fat storage and muscle membrane composition likely reflect challenges faced by females that migrate while pregnant. Our results provide some of the first insights into the physiological demands of bat migration and highlight key differences between bats and birds.

Food availability but not melatonin affects nocturnal restlessness in a wild migrating passerine

A large number of passerine species migrate at night, although most of them are diurnal outside the migratory seasons. This diurnal-to-nocturnal transition is a major life-history event, yet little is known about its physiological control. Previous work showed that during the migratory periods captive birds showing nocturnal migratory restlessness (Zugunruhe) have reduced concentrations of circulating melatonin at night compared to non-migratory periods. This suggested that the hormone melatonin, a main component of the avian circadian system, is involved in the expression of Zugunruhe. Other studies demonstrated that the relationship between low melatonin levels and Zugunruhe is not a seasonal correlation. When Zugunruhe was interrupted by exposing birds to a fasting-and-refeeding protocol, melatonin levels increased. Here we studied whether melatonin and food availability influence the intensity of Zugunruhe in wild migrating garden warblers (Sylvia borin) at a stopover site. Birds were held in recording cages overnight, with or without food available, and either bled to determine melatonin concentrations or treated transdermally with melatonin. We found that melatonin levels at night were correlated with the intensity of diurnal locomotor activity and with condition, but were not correlated with Zugunruhe. Similarly, the melatonin treatment did not have effects on Zugunruhe, whereas food availability increased it. Our study shows that the nocturnal melatonin levels in migrating warblers depend on food availability and are correlated with condition. In addition, it suggests that melatonin does not control Zugunruhe and might rather be involved in energy conservation and/or clock synchronization during migration.

Protein Requirements of an Omnivorous and a Granivorous Songbird Decrease During Migration

ABSTRACT. Many songbirds are seasonally frugivorous and eat primarily fruit during migration and insects or seeds during nonmigratory periods. Previous work has suggested that most wild fruits may have inadequate protein for birds. Assessing the nutritional adequacy of fruit requires knowing the protein requirements of birds in relation to the composition of available fruits. We tested predictions of two hypotheses: (1) interspecific differences in protein requirements of birds are related to their foraging strategy; and (2) protein requirements of birds increase with demand, for example during migratory periods of the annual cycle. We measured the protein requirements of the omnivorous Hermit Thrush (Catharus guttatus) and the granivorous White-throated Sparrow (Zonotrichia albicollis) during nonmigratory and migratory stages of the annual cycle and compared the results with published estimates for other songbird species. In the nonmigratory state both species ate less, lost body mass, and had more negat...

Seasonal influences on sleep and executive function in the migratory White-crowned Sparrow (Zonotrichia leucophrys gambelii)

BackgroundWe have previously shown that the White-crowned Sparrow (WCS) decreases sleep by 60% during a period of migratory restlessness relative to a non-migratory period when housed in a 12 h light: 12 h dark cycle. Despite this sleep reduction, accuracy of operant performance was not impaired, and in fact rates of responding were elevated during the migratory period, effects opposite to those routinely observed following enforced sleep deprivation. To determine whether the previously observed increases in operant responding were due to improved performance or to the effects of migration on activity level, here we assessed operant performance using a task in which optimal performance depends on the bird's ability to withhold a response for a fixed interval of time (differential-reinforcement-of-low-rate-behavior, or DRL); elevated response rates ultimately impair performance by decreasing access to food reward. To determine the influence of seasonal changes in day length on sleep and behavioral patterns, we recorded sleep and assessed operant performance across 4 distinct seasons (winter, spring, summer and fall) under a changing photoperiod.ResultsSleep amount changed in response to photoperiod in winter and summer, with longest sleep duration in the winter. Sleep duration in the spring and fall migratory periods were similar to what we previously reported, and were comparable to sleep duration observed in summer. The most striking difference in sleep during the migratory periods compared to non-migratory periods was the change from discrete day-night temporal organization to an almost complete temporal fragmentation of sleep. The birds' ability to perform on the DRL task was significantly impaired during both migratory periods, but optimal performance was sustained during the two non-migratory periods.ConclusionsBirds showed dramatic changes in sleep duration across seasons, related to day length and migratory status. Migration was associated with changes in sleep amount and diurnal distribution pattern, whereas duration of sleep in the non-migratory periods was largely influenced by the light-dark cycle. Elevated response rates on the DRL task were observed during migration but not during the short sleep duration of summer, suggesting that the migratory periods may be associated with decreased inhibition/increased impulsivity. Although their daily sleep amounts and patterns may vary by season, birds are susceptible to sleep loss throughout the year, as evidenced by decreased responding rates following enforced sleep deprivation.

Changes in brain gene expression during migration in the white-crowned sparrow

Long-term recordings of seasonal sleep patterns in captive white-crowned sparrows ( Zonotrichia leucophrys gambelii) have shown that these birds markedly reduce sleep time during the migratory period relative to the non-migratory period. It was also found that, despite this sleep reduction, sparrows showed no evidence of neurobehavioral deficits in a standard operant task used to assess the effects of sleep loss. In this study, we performed an extensive microarray analysis of gene expression in the sparrow telencephalon during the migratory season (M), relative to a 78-h period of enforced sleep restriction during the non-migratory season (SR), and a 6-h period of normal wakefulness during the non-migratory season (W). Of the estimated 17,100 transcripts that were reliably detected, only 0.17% changed expression as a function of M (relative to both SR and W), and 0.11% as a function of SR (relative to both M and W). Brain transcripts whose expression increased during M include the facilitated glucose transporter GLUT1, the presenilin associated rhomboid-like protein PARL, and several members of the heat shock protein family, such as HSP70, HSP90, GRP78 and BiP. These data suggest that migration is associated with brain cellular stress and enhanced energetic demands.

Bird Community Dynamics and Habitat Associations in Karst, Mangrove andPterocarpusForest Fragments in an Urban Zone in Puerto Rico

Puerto Rico's forest cover decreased to less than 10% in the early 1900's leaving few forest patches available for migrant and resident birds. In this process of deforestation karst hills and coastal wetlands have been some of the most severely modified forest types; however, we know little about their bird community dynamics and their relation with habitat variables. To address this issue we studied bird species composition and habitat characteristics in karst forest and two coastal forested wetlands (mangrove and Pterocarpus forest) in the Caribbean island of Puerto Rico. In each forest type, we conducted 10 point counts monthly for two years and characterized habitat variables. We performed a non-metric multidimensional scaling (NMS) ordination and a multi-response permutation procedure (MRPP) for each year to determine the similarity of bird species composition among monthly censuses and the relation between species composition and habitat variables. This ordination technique grouped censuses into three groups: karst forest, Pterocarpus and mangrove in the migratory period, and Pterocarpus and mangrove in the non-migratory period. The high tree species richness in the karst forest, and the presence of standing water in coastal wetlands were the most important habitat variables associated with the different bird communities. Our results demonstrate that the karst and coastal wetlands forests, even if they are small patches surrounded by a mixed matrix of pasture and urban settlements may be important habitat for both residents and migrants, and suggest that the protection and restoration of these habitats should be high management and conservation priorities.

FLIGHT CALLS OF WOOD-WARBLERS ARE NOT EXCLUSIVELY ASSOCIATED WITH MIGRATORY BEHAVIORS

Wood-warblers (Parulidae) have species-specific flight calls given day and night in migration. These vocalizations are believed to maintain flocks and to stimulate migratory activity during migration. However, anecdotal evidence suggests that warblers also give flight calls during non-migratory periods. I examined use of flight calls during the nesting, fledgling, and wintering periods in 23 species of warblers to clarify the seasonal pattern of occurrence for this type of vocalization. Flight calls recorded during migratory and non-migratory periods were similar. The Nashville Warbler (Vermivora ruficapilla) was the only species that gave flight calls during the nesting period and it did so rarely. Half of the species surveyed during fledgling periods and nearly half (47.8%) of the species surveyed during wintering periods gave flight calls. Calls per minute rates during the nesting period were an order of magnitude lower than in the fledgling and wintering periods. Flight calls are most common during migration but this vocalization in warblers is not limited to migratory periods. Flight calls may have functions additional to those during migration.

Lymphoid distribution in the migratory gull Larus ridibundus

We studied the distribution of lymphocytes in the main lymphoid tissues (blood, spleen and thymus) of the gull Larus ridibundus, searching for variations that might depend on the migratory cycle. We also looked for sex- and age-associated differences in lymphoid redistribution. In L. ridibundus, lymphocytes are the most commonly observed leukocyte subpopulation in blood. Moreover, changes in the distribution of lymphocytes in the lymphoid tissue occur, depending on the migratory period. The proportion of these cells in spleen is greater in the post-migratory and pre-migratory periods compared to the non-migratory period. The percentages of circulating lymphocytes are high in the pre-migratory period, but depletion occurs in the post-migratory period. In contrast, the age or the sex of the animals did not confer any major differences on the lymphoid distribution.

RESTRICTED MOVEMENT IN STREAM FISH: THE PARADIGM IS INCOMPLETE, NOT LOST

The “restricted-movement paradigm” (RMP) states that adult fish in streams are sedentary and spend most of their lives in short (20–50 m) reaches of stream. In mark–recapture studies, however, many fish initially marked are often never recaptured. As well, turnover rates of individuals in the home section (where fish were originally marked) can be high when marked fish moving out are rapidly replaced by unmarked ones. Recent challenges to the RMP have been based on the inference that high turnover indicates high mobility. However, when the home section is small many individuals may leave (high turnover) but not move far away (low displacement). I present two models for the frequency distribution of displacement distances: one represents populations as homogeneous ensembles with a single mobility parameter; the second represents populations as a mixture of stationary and mobile individuals. Both readily distinguish the turnover and displacement components of movement and show that high turnover rate is compatible with low displacement. The models were then fit to dispersal curves for six species of stream salmonids in 27 populations. Empirical estimates of turnover rate were high (median: 0.53), variable among populations (range: 0.15–0.78), but unrelated to displacement distance. Median displacement was <100 m for 24 populations and was typically <50 m. The proportion of mobile individuals was low in most populations (median: 19%) and exceeded 50% in only five of the populations. Brook trout, a species central to studies critical of the RMP, appeared to be exceptionally mobile relative to other salmonids. The compatibility of high turnover rates with short displacement distances and the finding that median displacement was usually limited support the notion that restricted movement is the norm in populations of stream salmonids during nonmigratory periods. However, the finding of considerable intra- and interspecific heterogeneity in the extent of movement underscores the potential importance of the mobile component to population processes. By providing an analytical framework that yields quantitative measures of different components of movement and allows for standardized comparisons, these models can bring needed rigor to analysis and design in movement studies.

Impact of Photoperiod on the Sexual Behavior of the Black Cutworm Moth (Lepidoptera: Noctuidae)

Abstract We tested the hypothesis that changes in photoperiod alone are responsible for the delay in the onset of sexual maturity that has been previously observed in natural populations of the migratory black cutworm, Agrotis ipsilon (Hufnagel), moth.We hypothesized that under short days, which occur at the onset of the spring and fall migrations, the first age at which males and females engage in sexual communication would be later than under long days typical of nonmigratory periods. Individuals were kept at 25°C from egg to adult under three photoregimes that they encounter in nature at different latitudes: 12:12 (L:D) h (late March and late September), 14:10 (L:D) h, and 16:8 (L:D) h. As predicted, the mean age at which females first called (i. e., released pheromone) was earlier under long-day than under short-day photoregimes, but this trend was not significant. The percentage of females that called over a 6-d-period was similar among photoregimes but it varied with age. There was no interaction be...

Cooperative defence and other benefits among exposed spiny lobsters: inferences from group size and behaviour

Caribbean spiny lobsters show strikingly coordinated queuing behaviour and resting, outward-facing radial formations, especially during mass migrations when large numbers cross shelter-poor substrate in daylight. The close association of individual lobsters during these behaviours could be due to chance or some benefit of association such as dilution (and associated selfish-herd effects), group vigilance, cooperative defence, and/or drag reduction during migration. To infer probable beneficial functions, we examined the frequency distributions of individuals and groups using a seven-year set of field data and additional behavioural observations in large seawater enclosures. Group size distributions were not significantly aggregated in dens during the non-migratory period but became highly aggregated during migration. The group size distributions of lobsters initially leaving dens and those observed moving in the open were statistically different from one another, indicating that group sizes at each of these steps in the migration are not simply the result of previous group sizes. The distribution of group sizes suggests that, during movement in the open, dilution, vigilance, cooperative defence, and/or drag reduction may all favour the formation of queues. During resting in the open, dilution, vigilance, and cooperative defence may continue to favour individuals that remain in formation within the group.

Seasonal and diel transitions in physiology and behavior in the migratory dark-eyed junco

Body mass, fat stores, activities of lipogenic and lipolytic enzymes, and plasma corticosterone were measured throughout seasonal and diel transitions from fall through spring encompassing the non-migratory stages of early and mid winter, the prealternate molt, and the spring migratory stage in captive dark-eyed juncos to determine the physiological mechanisms underlying adaptations for migration. On a seasonal basis, lipid enzymes and corticosterone varied little throughout the stages even though the birds underwent dramatic alterations in mass, fat deposition, behavior, and activation of the reproductive axis. By contrast, diel changes were found in lipogenesis, lipolysis, muscle lipoprotein lipase, and plasma corticosterone when comparing birds in the two phases of spring migration—active flight and resting, as during times of stopover. In these two phases of migration, coordination of the lipogenic and lipolytic systems appear to maximize storage of fatty acids during rest and delivery/utilization during flight. Diel patterns of corticosterone revealed fairly consistent peaks during the night time (23:00) throughout the nonmigratory period. The profile of this pattern altered during the migratory period with variation between the flight and resting phases. In sum, the results from these captive studies offer a new approach for studying the regulation of migratory physiology in free-living birds.

Seasonal variation of hepatic EROD activity in flounder ( Platichthys flesus) in the Dutch Wadden Sea

The use of hepatic 7-ethoxyresorufin O-deethylase (EROD) activity in flounder ( Platichthys flesus) as a potential biomarker of marine pollution by organic chemicals (as indicated by hepatic PCB-153 concentration) was investigated in the Dutch Wadden Sea in 1989 and 1990. Particular attention was paid to the seasonal variation. The results indicate that EROD activity was reasonably stable during the year, except for a period in January–February when a marked peak occurred. This peak coincided with the absence of mature flounder from the sampling area probably due to the spawning migration. Generally a good relationship existed between hepatic EROD activity and PCB-153 concentration, with one exception. During the period January–April 1990 a peak in PCB-153 concentration occurred immediately after the observed peak in EROD activity. It is concluded that the best period for monitoring EROD activity in flounder is the summer, corresponding to the non-migratory period of the species.

Seasonal variations in extrathyroidal conversion of thyroxine to tri-iodothyronine and migratory disposition in redheaded bunting

Thyroid gland has been shown to be involved in the migratory disposition in redheaded bunting, Emberiza bruniceps, ( Chandola & Pathak, 1980 a,b; Pathak & Chandola, 1982). Extrathyroidal conversion of thyroxine (T4) to triiodothyronine (T3) was now studied in thyroidectomised buntings by measuring the appearance of plasma T3 (RIA) 4h after an injection of 2.5ug I-T4 during non-migratory (January), spring pre-migratory (March) and post-migratory (June) periods of the year. A significantly high peripheral conversion of T4-T3 was recorded during pre-migratory period compared to non-migratory and postmigratory periods. This suggests that the increase in circulating T3 T4 ratio observed in buntings prior to spring migration could be to a certain extent, the result of an enhanced peripheral monodeiodination of T4. The inhibition of extrathyroidal conversion of exogenously administered I-T4 into T3 in thyroidectomised buntings (by propylthiouracil) prevented the T4-induced fattening significantly during non-migratory period (January). Same dose of PTU failed to inhibit T4-induced fattening as well as peripheral monodeiodination of T4 in thyroidectomised birds in spring premigratory period. This indicates that the T4-effects on fattening may be brought about by its conversion to T3, and also that the peripheral deiodinating enzyme systems in this bird may be comparatively more active during spring premigratory period than that during nonmigratory period. The results argue for a role of T3 in premigratory fattening, a characteristic of migratory disposition in birds. Also the seasonal variations in peripheral conversion of T4-T3 may be of great adaptive significance in seasonal breeders where energy requiring events like migratory fattening (and reproduction and molting-all influenced by thyroid status) must be temporally spaced across the year.

The effect of insulin, glucagon and prolactin on lipid synthesis and related metabolic activity in migratory and non-migratory finches

1. 1. The effects of insulin, glucagon and prolactin on lipid synthesis were investigated in house sparrows ( Passer domesticus) and white-crowned sparrows ( Zonotrichia leucophrys gambelii). 2. 2. The incorporation of glucose-U-C 14 and acetate-1-C 14 into abdominal fat pad lipid was measured in in vitro and in vivo experiments. 3. 3. None of these hormones accelerated lipid synthesis, even though lipogenesis is sensitive to changes in carbohydrate metabolism (i.e. glucose uptake) in this tissue. 4. 4. Insulin, a potent stimulator of lipid synthesis in mammalian adipose tissue, had no effect on the metabolism of finch fat pads. 5. 5. Glucagon and prolactin inhibited the synthesis of fatty acids from acetate. Only glucagon has the necessary potency to be of physiological significance. 6. 6. It is hypothesized that a relatively high glucagon output inhibits lipid synthesis during non-migratory periods. During migratory periods the output of glucagon falls, allowing lipid synthesis to proceed at a more rapid rate.