Premigratory Period Research Articles

Comparative Study of Winter Body Composition of Resident and Migrant Grey-Breasted Silvereyes

A comparative study of the winter body composition between resident and migrant birds was made on the partially migratory Tasmanian race of the Grey-breasted Silvereye (Zosterops I. lateralis). Each year some members migrate from Tasmania to winter on mainland sites, while other members remain in Tasmania year-round. Resident birds were those captured at Mt. Nelson, Tasmania, during midwinter; migrant birds were those captured during midwinter at Armidale, New South Wales, 1,500 km to the north. Nighttime winter temperatures at the two locations are very similar. Both residents and migrants showed diurnal increases in lipid content, but not in other major body components. Despite differences in photoperiod and feeding conditions at the winter grounds, lipid content accumulated in the late afternoon was similar (8% of live body mass) for residents and migrants. Fractional differences in major body components between residents and migrants were negligible, being less than 0.01 in all cases. Therefore, body composition is not related to whether an individual bird is a resident or a migrant. Low night temperatures alone do not explain why the species migrate from Tasmania to places like Armidale in New South Wales. The birds could migrate for reasons such as better food conditions, higher daytime temperatures, and longer daylength for foraging on the mainland. Received 14 January 1994, accepted 27 May 1994. INCLEMENT WEATHER and low food availability during winter are often implicated as the main forces in the evolution of bird migration (Co- hen 1967, Berthold 1975, Gauthreaux 1982). Small passetines breeding in temperate lati- tudes are of special interest because they have high metabolic rates and substantial increases in rates of energy expenditure when confronted with winter cold and diminishing food supplies (Dawson et al. 1983). In order to reduce ther- moregulatory costs in winter, many species have evolved adaptations that enable them to mi- grate to warmer regions. These include enlarge- ment of the pectoralis muscle (Lundgren and Kiessling 1988), flying at night (Moore and Ker- linger 1991), and substantial changes in body composition leading to massive fat accumula- tion (Ramenofsky 1990). The latter is known as migratory fattening, which normally develops in the premigratory period in which fat stores can more than double compared with the non- migratory period (e.g. Odum 1960, Berthold 1975, Dawson et al. 1983, Bairlein 1991). Birds that remain in their temperate breeding area in winter may reduce energy expenditure by

Development of migratory orientation in pied flycatchers in different magnetic inclinations

To examine whether magnetic orientation in young birds was affected by magnetic conditions in the region where they grew up, the orientation behaviour of pied flycatchers, Ficedula hypoleuca (Muscicapidae), hand-raised in Riga, Latvia (50 000 nT, 73° inclination), was compared with that of conspecifics hand-raised in Frankfurt a.M., Germany (46 000 nT, 66° inclination). Orientation was recorded during autumn migration in funnel cages in the local geomagnetic field under non-visual conditions. Birds that had been hand-raised in Germany without a view of the sky showed a unimodal tendency in their migratory direction, whereas in Latvia, the behaviour of birds raised under similar conditions was bimodal along the migratory axis. A second group of Latvian birds that had been exposed to a rotating planetarium sky prior to the tests also showed a unimodal preference. This suggests that celestial rotation observed during the pre-migratory period may play an important role in helping birds to decide which end of the magnetic axis points towards the wintering area.

Comparative diurnal and nocturnal foraging behaviour and energy intake of premigratory Grey Plovers Pluvialis squatarola and Whimbrels Numenius phaeopus in South Africa

Estimates of the energy budgets of nonbreeding waders (Charadrii) have frequently been hampered by ignorance of the birds' nocturnal activities. During the premigratory period (March), Grey Plovers Pluvialis squatarola and Whimbrels Numenius phaeopus at the Zwartkops estuary, South Africa, foraged throughout the nocturnal as well as the diurnal low‐tide period. Although both species continued to forage visually at night, they exhibited behavioural changes to compensate for the reduced visibility. Both species foraged more slowly at night, taking fewer steps per minute, and Grey Plovers paused for longer to search for prey. Prey items were sighted from shorter distances at night than during the day. Energy intake rates, however, did not differ significantly by day and night for either species, and both achieved over 40% of their daily low‐tide period intake at night. The energy intake rates and total daily intake of Grey Plovers, which fed exclusively on the study area, exceeded allometrically predicted values.

Migratory orientation of pied flycatchers: interaction of stellar and magnetic information during ontogeny

To study the interaction between magnetic compass and star compass during ontogeny, young pied flycatchers, Ficedula hypoleuca, were hand-reared, and after becoming self-sufficient were transferred into outdoor aviaries with full view of the sky. They were divided into three groups: controls experienced the sky while sitting in the local magnetic field; for group WSW, magnetic north was turned by 120 ° anticlockwise to geographical west-southwest; and for group ESE it was turned 120 ° clockwise to eastsoutheast. The birds remained in the aviary until the onset of the migratory season. They were then transferred indoors and tested in the local geomagnetic field without access to celestial cues. The controls showed a significant preference for the seasonally appropriate migratory direction. The group WSW was significantly oriented with a mean 119 ° clockwise from that of the controls. This is in agreement with the hypothesis that celestial cues during the pre-migratory period override any innate magnetic information and establish a new compass course with respect to the magnetic field. The orientation of the group ESE was significantly more scattered, and the mean does not fit the hypothesis mentioned above. Possible reasons for this difference in behaviour are discussed. If it reflects a true asymmetry of the orientation system, the sense of rotation of the sky, being an asymmetric factor, might be involved in the sense that a transfer of information from one system to the other might occur more easily in the direction of rotation than against it.

Changing priorities: the effect of pre-migratory fattening on the trade-off between foraging and vigilance

Many birds accumulate fat reserves prior to departure on long distance migration. Since there will be an increased food requirement during the pre-migratory period, it is to be expected that more time will be invested in foraging, at the expense of other activities. The allocation of time to anti-predatory behavior in migratory ruddy turnstones (adults) was found to decrease prior to migration (Fig. 1); non-migratory individuals (juveniles) showed no decrease over the same time period (Fig. 2). This is interpreted as a change in the optimal adult behavior, the cost of a reduced rate of resource accumulation outweighing the additional risk of predation which results from the decrease in vigilance.

Seasonal changes in the concentration of plasma prolactin in the migratory Canada goose ( Branta canadensis interior)

1. 1. Seasonal changes in the plasma prolactin level of the migratory Canada goose breeding in the Canadian subarctic region (Fort Churchill, Manitoba) and wintering in the southern USA (Swan Lake Refuge, Missouri) were studied. 2. 2. Peak prolactin level was observed in geese collected at Missouri in October, immediately after Fall migration (Fall postmigratory period). This was significantly higher than that in September (Fall premigratory period), July (moulting period) and March (Spring premigratory period). 3. 3. Prolactin levels in May (Spring postmigratory period) and June (incubating period) did not differ significantly from that of any other period.

Seasonal changes in circulating levels of luteinizing hormone and growth hormone in the migratory Canada goose

Seasonal changes in plasma levels of LH and GH in the Canada goose ( Branta canadensis interior) have been studied. The population examined breeds in the Canadian subarctic region (Fort Churchill, Manitoba) and winters in the southern United States (Swan Lake Refuge, Missouri). Peak levels of LH were observed during spring postmigratory (nest-building, early May) and nesting (incubating, early June) periods, while no significant differences were observed during the other periods studied. The highest levels of GH were observed during molting (late July) and the immediately following fall premigratory (early September) period.

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.

Involvement of thyroid gland in the development of migratory disposition in the redheaded bunting, Emberiza bruniceps

In the redheaded bunting Emberiza bruniceps, thyroidectomy inhibited premigratory fattening and nocturnal restlessness—two characteristics of avian migration—observed in caged birds during the premigratory period (March/April). Thyroxine (T 4) and triiodothyronine (T 3) administration in thyroidectomized birds stimulated locomotor activity and restored the loss in body weight. Annual variations in circulating thyroid hormone concentrations revealed a significant rise in T 3 T 4 ratio prior to spring migration in both years studied. This increase in circulating T 3 T 4 ratio may be associated with the development of migratory disposition in this bird. There was no increase in circulating T 3 T 4 ratio prior to autumnal migration, however, plasma T 4 increased significantly. Different thyroidal mechanisms are most likely involved in spring and fall migratory periods. While T 3 remained low throughout, apart from the characteristic spring rise, high T 4 levels in E. bruniceps were associated with periods of reproduction and molting, the latter coinciding partly with autumnal migration.

Glucose-6-phosphate dehydrogenase and 'malic' enzyme activities during adaptive hyperlipogenesis in migratory starling (Sturnus roseus) and white wagtail (Motacilla alba)

The changes in the activities of glucose-6-phosphate dehydrogenase and 'malic' enzyme in the liver and adipose tissue were studied in two migratory birds, viz., rosy pastor and white wagtail, which have different dietary habits during their post- and pre-migratory periods. Activities of both the enzymes in the liver of these birds increased during their premigratory period which correlated well with premigratory hyperlipogenesis. It is suggested that hyperphagia, diet, and hormones are involved in induction of the enzyme activities and premigratory hyperlipogenesis. Data on enzymatic studies indicate that 'malic' enzyme catalyzed reaction plays a major role in generation of NADPH2 and the liver is the main site for lipogenesis in these birds.

Circulating Levels of Thyroxine (T₄) and Triiodothyronine (T₃) in the Migratory Canada Goose

Changes in circulating levels of thyroxine (T₄) and triiodothyronine (T₃) in the migratory Canada goose (Branta canadensis interior) during the different periods of its yearly life cycle in both its breeding and wintering grounds were investigated. Total plasma T₄ level ranged from a minimal value of 1.156 μg/dl in the fall postmigratory period to a maximal value of 1.737 μg/dl in the spring postmigratory period. The T₄ values during spring postmigratory period and breeding (1.700 μg/dl) were significantly higher than those in the spring premigratory (1.175 μg/dl), fall premigratory (1.327 μg/dl), and the fall postmigratory periods. The T₄ level during molt was significantly higher than that during the spring premigratory period and the fall postmigratory period but was not significantly different from that in the other periods. The peak level in plasma T₃ (330.62 ng/dl) observed in the spring premigratory phase was significantly higher than that in all other periods, and the trough T₃ level (71.72 ng/dl) noted in the fall premigratory period was significantly lower than that in all the other periods. No significant variations in T₃ levels were noted during the spring postmigratory, breeding, molt, and the fall postmigratory periods. The T₃ level was at its peak in the spring premigratory period when the ambient temperature was 20-25 C and daily photoperiod 11.5 h. However, the T₄ levels were highest in the spring postmigratory and breeding periods when the ambient temperatures were from -12 to -3 C and from -3 to 0 C and the photoperiods 16 h and 18 h, respectively. It is concluded that the high T₄ levels during these periods are indicative of the influence of the lower ambient temperatures and greater day lengths on the activity of the thyroid and the activity of the animal. The hypertrophy of the pectoral muscles in the spring pre- and postmigratory periods may be attributed to increased thyroidal activity. No definite relationship of thyroidal activity to molt was discernible, however.

Seasonal changes in serum free fatty acid level in the migratory Canada goose.

The changes in the serum level of free fatty acids (FFA) in the migratory Canada goose (Branta canadensis interior) breeding in Ft. Churchill (Manitoba, Canada) and wintering in Swan Lake (Missouri, U.S.A.), were studied during the different periods of its yearly life cycle. The lowest serum FFA level was noted during the spring premigratory phase (early March) at Swan Lake, and the highest during moult (early August) at Ft. Churchill. Serum FFA level during the spring postmigratory period (early May at Ft. Churchill) was significantly higher than that during the spring premigratory period and the breeding period (early at Ft. Churchill). No signigicant difference in FFA levels was noted between the fall premigratory (early September at Ft. Churchill) and the fall postmigratory (mid-October at Swan Lake) periods. The significance of the seasonal variations in serum FFA level is discussed in relation to the cyclic physiological events taking place in the bird.

Moult, flight muscle “hypertrophy” and premigratory lipid deposition of the juvenile Willow warbler, Phylloscopus trochilus

In England juvenile Willow warblers undergo premigratory lipid deposition in August. Prior to this there is a moult of the juvenile plumage which results in a reduction in both the glycogen content and the wet weight of the pectoralis muscles, the latter reflecting a decrease in the lipid‐free dry weight. Muscle lipid levels are apparently unaffected by this moult. The decrease in the weight of the lipid‐free dry fraction of the body extends also to components other than these muscles at this time. A correlation between the wet weight and the glycogen content of the pectoralis muscles suggests that cold stress may be the cause of the low glycogen levels found in the middle of the moult; part of this increased demand for thermogenesis may be due to lower body insulation brought about by feather loss during the moult. The muscle “hypertrophy” found in the premigratory period is simply a return to pre‐moult weights.The uniformity of total body weights during and after the moult indicates that at the end of this moult the water fraction of the body decreases in weight. The pectoralis muscles of juvenile Willow warblers are not fully grown on fledging; these unmoulted birds may also have higher body lipid levels than during the following moult.

A quantitative histochromatographic regional study of certain free amino acids in the brain of a migratory starling during pre- and post-migratory phases

1. 1. Changes in the levels of certain free amino acids in the different parts of the brain of a migratory starling ( Sturmus roseus) wintering in India, were studied histochromatographically, during the pre- and post-migratory periods. 2. 2. The level of glutamic acid was higher in the premigratory period (February, March, April) than in the postmigratory period (August, September) in all the regions of the brain investigated. Cerebrum was found to contain the highest level of glutamic acid reaching the peak in February and the medulla oblongata the lowest with trough in April. 3. 3. The level of tyrosine in all the regions was higher in the premigratory period than in the postmigratory period. The highest level of tyrosine was seen in the optic lobes with peak in February with pars nervosa showed the lowest with trough in September. 4. 4. Threonine was considerably higher in the postmigratory than in the premigratory period. In most regions of the brain there was a gradual decrease in the level of threonine towards migration time. Generally, pars nervosa and cerebrum showed fairly high levels of threonine and optic lobes the lowest. 5. 5. There was also a gradual decrease in phenylalanine towards migration time. Phenylalanine was highest in the optic lobes with the peak in August. 6. 6. Considerable increase in the levels of cysteine and cystine too was seen in the median eminence and pars nervosa towards migration. 7. 7. The physiological significance of the above changes is discussed in relation to migration.

Some Morphological and Biochemical Changes in Steelhead Trout During the Parr–Smolt Transformation

This study was initiated to determine changes in chemical composition, coefficient of condition, and body morphology for juvenile steelhead trout from premigratory through postmigratory periods, January through July. Winter-run steelhead trout, originating from Big Creek and the Sandy River, in Oregon, were used as experimental animals.A discriminant analysis indicated that coefficient of condition and fork length were nearly as powerful in separating smolts from parr as were 10 morphological measurements.The parr–smolt transformation in winter steelhead is size-dependent and characterized by a marked decrease in body depth and coefficient of condition. Changes in depth measurements and coefficient of condition provided the most meaningful measure of morphological change at the time of parr–smolt transformation.During the migratory period, lipid content was substantially lower than in the premigratory period for migrant-sized fish (≥ 160 mm) but remained relatively constant in nonmigrants (≤ 159 mm) throughout all periods. Seasonal changes in moisture and protein levels occurred in the larger fish, although moisture and protein content for the smaller fish remained relatively constant. The amount of ash did not change within a size group.The coefficient of condition of migrant-sized fish declined continuously from February through May but increased in June and July. The mean coefficient of condition for nonmigrants declined from December through February, but remained relatively stable from March through June, with an upward trend in July.

Ecologic Aspects of Lipid Deposition in Some Postbreeding Arctic Birds

A series of 112 arctic birds representing five species (golden plover, western sandpiper, arctic tern, redpoll, and Lapland Longspur) was taken near Cape Thompson, Alaska, for lipid studies. The birds were collected in 1960 during the postbreeding and autumnal premigratory period of late summer. Relevant data on life history, distribution, migration, and molt are presented. Extractions of body lipids revealed that there was no significant increase in lipid deposits in any of the species except a few adult western sandpipers. Possible correlations among lipid levels, timing of migration, and migratory paths are discussed.

CAPACITY FOR FATTY ACID OXIDATION BY THE BREAST MUSCLE OF THE STARLING (STURNUS ROSEUS) IN THE PRE- AND POST-MIGRATORY PERIODS.

Studies on the capacity for fatty acid oxidation by the breast muscle homogenate of the migratory starling Sturnus roseus in the pre- and post-migratory periods were carried out, using sodium butyrate as the substrate. It was observed that the oxygen uptake due to the added butyrate in the manometric system during the premigratory period was considerably lower than that in the post-migratory period. During the premigratory period there was more oxygen uptake due to malate oxidation than in the complete system with added butyrate for fatty acid oxidation. The significance of the diminished capacity for fatty acid oxidation in the premigratory period is discussed.

Haematopoietic nodules as centres of fat synthesis in the liver of the migratory starling, astor roseus

ABSTRACT A histological and histochemical study of the haematopoietic nodule in the liver of Pastor roseus was made from October to April. The formation and development of the haematopoietic nodule by aggregation of lymphocytes and monocytes was found to be a continuous process, in which new nodules are formed regularly. The older nodules after a certain period of high activity show a considerable decline in the activity of blood-cell formation. The fully formed haematopoietic nodules give rise to different types of blood-cells—erythrocytes, granular leucocytes, lymphocytes, and monocytes. During the pre-migratory period the lymphocytes and monocytes were found to be more numerous in the nodules. It is likely that the number of erythrocytes increases during migration and that the formation of different types of blood-cells depends upon demand. It is concluded that fat is synthesized in the lymphocytes, monocytes, and free-moving reticulo-endothelial cells, but that this synthesis is mainly carried by the reticulo-endothelial cells. The phagocytes may also be the carriers of fat, and it is suggested that they are later modified into fat-cells in the fat-depot. Haematopoiesis in this bird is a normal phenomenon occurring in the liver in all seasons and is not a pathological condition.