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At a site in Buckinghamshire, England, in 1990–1992, numbers of Blackcaps peaked in late September, while Garden Warbler numbers declined steadily through the autumn. Both species showed an increase in mean weight through the autumn, due to the premigratory deposition of fat. About 30% of Blackcaps, but only 5% of Garden Warblers, weighed over 20g (ca. 25% fat). The results indicate that the heaviest 25% of Garden Warblers could have flown as far as north Portugal without refuelling, and the fattest 25% of Blackcaps as far as central‐southern Portugal. These results are discussed in relation to the two species’ migration strategies and patterns of occurrence at British bird observatories.

A farmland area in southern Sweden used for cereal production was turned into energy production by growing Salix. The breeding birds were censused in these fields after energy foresting had started and the first harvest was taken. The introduction of Salix virninalis in the fields showed to be favourable for species well adapted to bushy habitats like the marsh warbler. The habitat succession from the planted or harvested forest to the four, five years later mature forest is important too, as bird species prefer different growth stages of the brush forest. The whitethroat and the whinchat preferred the sprouts of the recently harvested areas, but the willow warbler and the garden warbler preferred the fully grown bushes preceeding the harvest. Introduction of Salix fields in an open farmland landscape will increase the number of bird species and for some species also the abundance. The biodiversity is improved if the harvest is asynchronous in different subareas. In terms of environment and fauna protection or improvement a limited increase of scattered energy producing Salix fields will probably be favourable, causing an increase in overall biological diversity.

The pectoral muscle is the biggest organ within a passerine bird. It provides flight locomotion and is known to act as a protein source during periods with increased protein demands or decreased protein availability. The mass of the flight muscle is dynamic and changes during juvenile growth, reproduction, seasonal acclimatization, fasting and migration. Thus, a tool that accurately and non-invasively quantifies this phenotypic flexibility in flight muscle mass is of interest to ornithologists. We provide a calibration and validation of a "muscle meter" device designed to accurately measure the shape of the flight muscle. For two species of different size, the European starling (Sturnus vulgaris) and the garden warbler (Sylvia borin), we compared the accuracy and precision of different linear regression models for predicting flight muscle mass. The multifactorial linear regression model with the most support for both species included “muscle meter score” (mmscore), tarsus length and body mass (m b), although a simpler model with mmscore and m b had as much support for predicting flight muscle mass of European starlings. A validation exercise revealed that flight muscle mass of these two species could be estimated with a relative error of about 3%. The muscle meter is a simple device, easy and quick to handle, that can reliably and non-invasively estimate flight muscle mass of captive and wild birds when used in conjunction with standard measurements of tarsus length and m b.

Migration remains one of the great mysteries of animal life. Small migratory birds rely on refuelling stopovers after crossing ecological barriers such as deserts or seas. Previous studies have suggested that fuel reserves may determine stopover duration but this hypothesis could not be tested because of methodological limitations. Here, we provide evidence that subcutaneous fat stores determine stopover duration by measuring the permanence of migratory garden warblers ( Sylvia borin ) on a small Mediterranean island during spring migration with telemetry methods. Garden warblers with large amounts of fat stores departed the island significantly sooner than lean birds. All except one fat bird left the island on the same evening after capture, with a mean total stopover estimate of 8.8 hours. In contrast, the mean estimated total stopover duration of lean birds was 41.3 hours. To our knowledge, this is the first study that measures the true minimum stopover duration of a songbird during migration.

The magnetic field sensors enabling birds to extract orientational information from the Earth's magnetic field have remained enigmatic. Our previously published results from homing pigeons have made us suggest that the iron containing sensory dendrites in the inner dermal lining of the upper beak are a candidate structure for such an avian magnetometer system. Here we show that similar structures occur in two species of migratory birds (garden warbler, Sylvia borin and European robin, Erithacus rubecula) and a non-migratory bird, the domestic chicken (Gallus gallus). In all these bird species, histological data have revealed dendrites of similar shape and size, all containing iron minerals within distinct subcellular compartments of nervous terminals of the median branch of the Nervus ophthalmicus. We also used microscopic X-ray absorption spectroscopy analyses to identify the involved iron minerals to be almost completely Fe III-oxides. Magnetite (Fe II/III) may also occur in these structures, but not as a major Fe constituent. Our data suggest that this complex dendritic system in the beak is a common feature of birds, and that it may form an essential sensory basis for the evolution of at least certain types of magnetic field guided behavior.

Migratory birds use stopover sites for resting and feeding. Breaks after prolonged flights may allow cooling down the muscles and save energy through hypothermia. We measured hypothermic abilities in two long-distance migratory songbirds (garden warbler, Sylvia borin, and icterine warbler, Hippolais polyglotta) at a stopover site during spring migration selecting (1) birds just arrived after a prolonged flight (morning) (2) birds that had been resting in the vegetation for several hours (afternoon) and (3) birds caught in the late afternoon and kept overnight in standard conditions (night). In the first two samples, body temperature was measured immediately, 30 and 180 min after capture. In the night sample, it was measured at 1 a.m. in birds awake and asleep, and at 7 a.m., when all birds were awake. Morning birds showed the highest values (39.7°C), dropping of about 3°C after 180 min. In the afternoon birds (2), the time course was similar, but values (38.5°C) were lower than that of morning birds of about 1°C. At night, asleep birds had lower temperature than awake birds, reaching up to 10°C less than daytime values, but recovering in the early morning. Such remarkable plasticity in thermogenic abilities during migration could allow small migrants to economize energy in emergency situations.

The migratory capacity of four Sylvia species was investigated during their initial phase of autumn migration in Sweden. Fat loads of individual birds were estimated by first determining approximately the fat‐free body masses for birds of different size (as judged from body mass ‐ fat index relationships). Individual fat loads varied considerably both inter‐ and intra‐specifically. The mean fat load (%fat mass of total body mass) of different species was: Lesser Whitethroat 9.3%, Whitethroat 7.2%, Garden Warbler 16.4% and Blackcap 13.2%. Comparatively low fat loads in the first two species may be because they probably commence their autumn migration in this area before the post‐juvenile moult is completed. Our results indicate that several autumn migrating Garden Warblers and Blackcaps stopping over at Gotland have the energetic capability to almost cross continental Europe without refuelling This contrasts with the Whitethroat and the Lesser Whitethroat of which many individuals would only be able to cro...

Goudswaard, K. & Wanink, J.H. 2000. Temporal and spatial variation in the occurrence of Palearctic warblers around Lake Victoria. Ostrich 71 (1 & 2): 210–212. Only one Palearctic warbler species, the Sedge Warbler, wintered at the south-eastem shores of Lake Victoria. Willow Warbler and Garden Warbler occurred mainly on passage, with peak values in the first lunar quarter, the period in which lakeflies would normally swarm. Higher warbler densities have been reported from the north-western shores. This agrees with our idea that the prevailing eastern winds will result in a higher availability of lakeflies to warblers at the western side of the lake.

Recopilación de observaciones sobre la Curruca mosquitera (Sylvia borin) realizadas durante varias salidas de campo a diferentes localidades de Valladolid, y a Burgos, entre el 10 de mayo de 1947 y el 26 de abril de 1952., Compilation of observations about the Garden Warbler (Sylvia borin) of many field trips to different localities of Valladolid, and Burgos, between the 10th of May of 1947 and the 26th of April of 1952.

Based on phenology, passage and median dates gathered from large number of study sites, we measured autumn and spring migration speeds of eleven long distance migratory passerines in four different ecogeographic sectors: Europe, desert, north-eastern and eastern Africa. Results demonstrate that, during the southward autumn migration, late-departing species, such as lesser whitethroat Sylvia curruca, garden warbler S. borin, spotted flycatcher Muscicapa striata, whitethroat S. borin, and willow warbler Phylloscopus trochilus cover their migration route with a slower average migration speed across Europe than do early migrating species. During spring migration, late-departing species (marsh warbler Acrocephalus palustris, garden warbler, spotted flycatcher, red-backed shrike Lanius collurio) across north-eastern Africa showed a higher speed than early migrating species. Our results show overall shorter migration duration estimates in spring than autumn. Sector-wise seasonal comparisons of duration indicate that migration journey in the African and desert sectors are covered in a relatively shorter time in spring than in autumn. Periods required to cover the distance between northern latitude breeding grounds and desert during both seasons were equivalent. published

We analyse 54 year long time series data on the numbers of common redstart (Phoenicurus phoenicurus), common whitethroat (Sylvia communis), garden warbler (Sylvia borin) and lesser whitethroat (Sylvia curruca) trapped in spring and autumn at Ottenby Bird Observatory, Sweden. The Ottenby time series could potentially serve as a reference on how much information on population change is available in count data on migrating birds. To investigate this, we combine spring and autumn data in a Bayesian state-space model trying to separate demographic signals and observation noise. The spring data are assumed to be a measure of the breeding population size, whereas the autumn data measure the population size after reproduction. At the demographic level we include seasonal density dependence and model winter dynamics as a function of precipitation in the Sahel region, south of the Sahara desert, where these species are known to spend the winter. Results show that the large fluctuations in the data restrict what conclusions can be drawn about the dynamics of the species. Annual catches are highly correlated between species and we show that a likely explanation for this is that trapping numbers are strongly dependent on local weather conditions. A comparative analysis of a related data set from the Courish Spit, Russia, gives rather different dynamics which may be caused by low information in the two data sets, but also by distinct populations passing Ottenby and the Courish Spit. This highlights the difficulty of validating results of the analyses when abundance indices derived by other methods or from other populations do not agree.

The true distribution of migrant species is rarely immediately apparent from the distribution of ring recoveries due to a heavy bias in regional recovery probabilities. For western Palearctic species, the recovery probability is especially low in Africa, but also varies within Europe. However, little work has been done to derive actual estimates of these recovery probabilities needed to infer the “true” underlying distribution. Here, we investigate the potential of using ringing data to estimate the seasonal distribution densities of migrant species. Using likelihoods based on a two point mixture distribution, the proportions of individuals wintering south of the Sahara are estimated using differences in recovery distributions among species in species groups where the location-specific probability of a ring recovery can be assumed to be essentially the same among species. We consider two such approaches. In the first, survival associated with a wintering area must be set constant across species. In the second, we assume the time series is long enough that a single binary response (recovered/not recovered) may be modeled independently of survival parameters. Under the first approach, we estimated the proportion of sub-Saharan migrants, together with 95% profile likelihood confidence intervals, for redstart as 0.84 [0.70,0.93], thrush nightingale 1.00 [0.49,1.00], garden warbler 0.95 [0.85;0.99], blackcap 0.60 [0.32;0.78], reed warbler 0.87 [0.72,0.95], and pied flycatcher 0.90 [0.76;0.97] using recovery data for birds ringed in Denmark and assuming that all robins winter north of Sahara. In the second approach, estimated proportions of sub-Saharan migrants were similar, but the confidence intervals were somewhat narrower. Although further work is required to examine the underlying assumptions, the models and analyses presented here provide a framework for making better use of existing ring recovery datasets to understand the “true” seasonal distribution patterns of European birds.

The fruit diets of Sylvia warblers, and some thrushes, were studied during 1989 at a coastal scrubland site, using faecal examination. Fruit feeding commenced as the earliest berries ripened in late July, but there were differences of timing between species. Amongst both warblers and thrushes, the larger species commenced earlier and ate more fruit. Almost all Blackcap and Garden Warbler faeces examined from early August contained some fruit remains, as did most Whitethroat faeces from mid-month. Mean fruit contents of faecal samples exceeded 80% infrequently, indicating that even the most frugivorous species always took other food, normally insects, to supplement their diet. Each species differed in their fruit diet: Blackcaps, and to a lesser extent Garden Warblers, ate Woody Nightshade berries in preference to Blackberries, as they are structurally adapted for feeding on the former plant. Only inexperienced juveniles of other species regularly chose the Nightshade berries. Elder berries, abundant from ...

Changes in concentrations of hypothalamic gonadotrophin-releasing hormone (GnRH), pituitary and plasma LH, testicular mass, in-vitro release of testosterone, body mass and migratory activity were measured in male garden warblers (Sylvia borin) kept from November to June under a constant photoperiod of 12·8 h. Under such conditions garden warblers gradually change from the photorefractory to the photosensitive state and gonadal recrudescence then occurs. Hypothalamic GnRH content was low from December to March, but increased in April to reach the highest levels in June. The spontaneous increase in GnRH was paralleled by increases in pituitary LH content, testicular mass and in-vitro testosterone release. Body mass decreased 1 month and nocturnal activity 2 months before the spontaneous increase in GnRH. Ovine LH increased in-vitro testosterone release over basal release at all times. The results suggest that in garden warblers (1) changes in hypothalamic GnRH content can occur under constant photoperiodic condition, (2) the gradual change from the photorefractory to the photosensitive state is not characterized by a gradual increase in hypothalamic content of GnRH (cf. starlings), and (3) Leydig cells are capable of testosterone release even during the photorefractory state. Journal of Endocrinology (1991) 128, 339–345

Capsule: During the past 20 years, farmland specialist birds have declined in the Alps, especially below 1000 m asl. Aims: To investigate whether the altitudinal distribution of birds in the northern French Alps has changed over the last 20 years in relation to farming intensity and/or climate change. Methods: Two point-count surveys carried out in 1978-80 and 2001-02, at the same 316 spots along an elevational gradient of decreasing farming intensity, were compared. Account was taken of potential changes in species detectability over time. Potential differences between observers were also taken into account. Results: Most farmland specialist bird species decreased from the late 1970s onwards, but the decline was much stronger below 1000 m asl (70%) than above (20%). Such a pattern was not found in farmland generalists or woodland bird species. Conclusion: Specialist species probably suffered from changes in farming practices at low elevation following mechanization, rather than from climate change. Lowland farmland species are particularly threatened. Therefore, the Alps should no longer be considered as refuges for farmland species., Les espèces spécialistes des milieux agricoles ont fortement décliné au cours des 20 dernières années (1978-2000), en particulier en-dessous de 1000m d'altitude.

Protozoan coccidia are one of the most common intestinal parasites in birds. Ordinary coccidian detection and quantification techniques have proved to be inaccurate for wild passerines due to the existence of marked oocyst shedding rhythms throughout the day. Previous studies have suggested that these rhythms should be taken into account when analysing coccidian load and prevalence data, but their pattern and magnitude still remain poorly known. In this study we characterised shedding rhythms in the field by means of 406 samples of faeces taken from two species of passerines with different diets: the European Serin (a granivorous species), and the Garden Warbler (an insectivorous species). Both coccidian prevalence and load were two-phased, with maximums occurring in the afternoon. Oocyst elimination remained consistently high during the second half of the day, whereas prevalence peaked during the afternoon, lowering throughout the evening. This pattern was found in both species. We found a high repeatability of prevalence and intensity when differences between the morning and afternoon were statistically controlled. As a result, we suggest that sampling periods used in the analysis of coccidian prevalence and/or load studies should take into account these differences in times of shedding and be limited to the afternoon, otherwise a statistical control of this factor will be required.

Long-distance migratory birds often show little phenotypic variation in the timing of life-history events like breeding, molt, or migration. It has been hypothesized that this could result from low levels of heritable variation. If this were true, the adaptability of long-distance migratory birds would be limited, which would explain the vulnerability of this group of birds to environmental changes. The amount of phenotypic, environmental, and genetic variation in the onset of autumn migratory activity was assessed in two garden warbler (Sylvia borin) populations differing in breeding phenology and the length of the breeding season with the aim of investigating the effects of selection on the adaptability of long-distance migrants. High heritabilities and additive genetic variance components for the timing of autumn migration were found in both populations. Although genetic variation in the mountain population was lower than in the lowlands, this difference was not statistically significant. Moreover, no evidence was found for reduced levels of genetic variation in the garden warbler as compared to its sister species, the blackcap (S. atricapilla). Environmental variation, however, was markedly reduced in the garden warbler, suggesting that low levels of phenotypic variation typically found in long-distance migrants may be a consequence of environmental canalization of migratory traits. The buffering of environmental variation may be an adaptive response to strong stabilizing selection on the timing of migration. High environmental canalization of migration phenology in long-distance migrants could potentially explain low rates of immediate phenotypic change in response to environmental change. [KEYWORDS: heritability ; zugunruhe ; climate change ; adaptation ; canalization]

The ability of many species of tiny, relatively short-lived birds to carry out migrations over thousands of kilometres has fascinated many researchers. This apparent ability is the more extraordinary because it is widely distributed amongst bird genera but migratory species often have close relatives that do not budge from home.New work by Claudia Mettke-Hofmann and Eberhard Gwinner at the Max Planck Research Centre for Ornithology in Andechs, Germany, (Proceedings of the National Academy of Sciences, published online) has looked at the cognitive abilities of two closely related species of warbler. The garden warbler migrates from Europe to sub-Saharan Africa each autumn and returns each spring whereas the Sardinian warbler is resident in the Mediterranean region. It might be an advantage, the researchers believe, if migratory species were able to remember places of food, shelter and other needs on their journeys. Previous neuroanatomic studies suggest that the size of the hippocampus, important for processing spatial information, in garden warblers that have undergone migration is larger than in pre-migration juvenile birds. No such difference was found in young and older Sardinian warblers.So the team captures young adults of both species and kept them in large aviaries. For the experiment they placed them in cages containing ‘rooms’ that contained one of two particular types of artificial vegetation with feeding bowls that did or did not contain food. After the tests the birds were returned to the aviaries. The researchers then re-exposed the birds to the different rooms over a period of days and months. They found a significant ability of the garden warblers to remember the rooms that contained food initially for up to 12 months in contrast to the Sardinian warbler, whose memory seemed to lapse after two weeks.Sedentary birds may be able constantly to update knowledge of their environment and do not need months-old memories to help them on their way. A migratory lifestyle, the researchers suggest, may have shaped the garden warbler's extended cognitive abilities.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Migration is a period of exceptionally high energy demands. To meet these demands during flight, energy is stored in the bird’s body. As fat is the prime fuel for migrating flights (Biebach 1996) many migratory birds therefore accumulate large amount of lipids in adipose tissue prior to and during migration at stopover. In small passerines, typically 73–82% of body mass gain is due to fat (Lindstrom and Piersma 1993) with maximum levels obtained by species crossing inhospitable areas such as sea and deserts with no feeding opportunities. The garden warbler, Sylvia borin, for example, a long-distance European migratory songbird wintering in tropical Africa, weighs about 16–18 g during the breeding and wintering seasons, but increases its body mass to up to 37 g just before leaving to cross the Sahara, in both autumn and spring (Bairlein 1991a), thus doubling fat-free body mass. Maximum fat deposition rates were found in small passerines with up to 10–15% change of lean body mass per day (Lindstrom 1991, this Vol.). Several migrant species also undergo protein accumulation prior to migration (Lindstrom and Piersma 1993; Klaassen and Biebach 1994), and protein is used during migration (Battley et al. 2000; Bauchinger and Biebach 2001). However, protein may not be used for energy purpose (Biebach 1996).

Acute pancreatic hormonal responses to oral glucose loads were investigated in garden warblers during the prolonged fast that follows their autumnal migratory fattening. Plasma glucose, free fatty acids, beta-hydroxybutyrate, insulin (INS), and glucagon (GLN) were measured prior to and 10 min after an oral glucose load in three groups of birds: One had food ad libitum, and the other two were either food restricted or food deprived down to a given (low) body mass level. Ten minutes after the glucose load, plasma glucose levels increased significantly in all three groups (range of mean values: basal, 15.1-16.0; glucose-stimulated, 19.1-23.7 mmol/L). A smaller increase in food-restricted/deprived groups was not statistically significant. Free fatty acid levels (1.0-1.5 mmol/L) after 10 min were unchanged, while beta-hydroxybutyrate decreased to similar levels in food-restricted/deprived and control groups (basal, 3.3-4.2; glucose-stimulated, 1.9-2.4 mmol/L). Insulin increased and glucagon decreased in response to oral glucose loads. However, initial levels and responses of plasma insulin to glucose were lower, and those of glucagon were higher in the food-restricted/deprived groups (INS, both 2.7; DeltaINS, 0.1-0.3 mIU/L; GLN, 2.8-3.3; DeltaGLN, 1.4-2.2 microg/L) than in the control group (means +/- SE; INS, 3.8 +/- 0.8; DeltaINS, 1.4 +/- 0.7 mIU/L; GLN, 2.5 +/- 0.5; DeltaGLN, 0.7 +/- 0.5 microg/L), resulting in similar increases in the insulin:glucagon ratio. Impaired insulin secretion may thus be compensated for by a greater glucagon response and the decreased glucose utilization rates of fasting garden warblers may result from insulin resistance and/or delayed glucose absorption.

The adaptive value of size changes in different organ and muscle groups was studied in red knots (Calidris canutus islandica) in relation to their migration. Birds were sampled on five occasions: at arrival in Iceland in May 1994, two times during subsequent refueling, at departure toward, and on return from, the high arctic breeding grounds. During their 24-d stopover in May, body mass increased from 144.3 to 214.5 g. Mass gains were lowest over the first week (0.85 g/d, only fat-free tissue deposited). Over the subsequent 10 d, average mass increased by 5.0 g/d (fat contributing 78%), and over the last week before takeoff, it increased by 2.0 g/d (fat contributing over 100% because of loss of lean components). There were no sex differences in body and fat mass gains. Over the first interval, lean masses of heart, stomach, and liver increased. During the middle 10 d, sizes of leg muscle, intestine, liver, and kidneys increased. Stomach mass decreased over the same interval. In the last interval before takeoff, the stomach atrophied further and the intestine, leg muscles, and liver became smaller too, but pectoral muscles and heart increased in size. Sizes of "exercise organs" such as pectoral muscle and heart were best correlated with body mass, whereas sizes of organs used during foraging (leg muscles) and nutrient extraction (intestine, liver) were best correlated with rate of mass gain. Kidneys changed little before takeoff, which suggests that they are needed as much during flight as during refueling.

Substrate utilization and regulatory mechanisms of metabolism were studied in migratory garden warblers by measuring plasma levels of glucose, free fatty acids (FFAs), beta-hydroxybutyrate, insulin and glucagon in response to oral glucose loads. Three different physiological states were examined: (a) the autumnal migratory period on a high and (b) on a fasted low body mass level, and (c) the postmigratory period with low body mass. Glucose tolerance was better in the postmigratory lean than fat condition. However, total food deprivation of 5-7 days with fat birds reaching their lean body mass further reduced the glucose utilization rate. Initial levels of FFAs were highest in the starved, intermediate in the fat and lowest in the lean condition. Changes in plasma FFAs during glucose tolerance tests were opposite to those of the glucose levels. Ten minutes after the glucose load plasma glucagon levels decreased and insulin increased. These effects were larger in the fat than in the postmigratory lean condition. There were no differences between sexes. It appears that during premigratory and migratory periods glucose utilization may be inhibited by a more favorable oxidation of fatty acids as would be predicted by the glucose fatty acid cycle. However, the inhibition of glucose utilization seems to be counterregulated by stronger responses of insulin and glucagon. These results may be important also in the consideration of food selection during premigratory periods and refueling abilities of birds crossing ecological barriers.

Glucagon and insulin were measured by heterologous immunoassays in plasma samples of 17 garden warblers ( Sylvia borin ) kept under constant ad libitum or fasting–refeeding conditions during the migratory season from September to May. Plasma levels of key metabolic indicators (glucose, triglycerides, cholesterol, and free fatty acids) were measured every 2 weeks. Measurements of the two hormones concur with the general assumption of a higher glucagon:insulin ratio, indicating a more pronounced catabolism in birds than in mammals. The concentrations of both hormones varied (insulin: 0.7–7.7 μIU/ml, n = 66; glucagon: 0.4–4.5 ng/ml, n = 99), but differences between mean values per month were significant only for glucagon. Neither hormone titer correlated with either the seasonal or a fasting–refeeding-induced body mass cycle. However, there was a positive correlation between food intake, changes in body mass, and plasma triglycerides and insulin; in contrast, there was a negative relationship with the glucagon:insulin ratio. Glucagon showed only a small negative relationship to plasma glucose and cholesterol, but correlated directly more closely with plasma free fatty acids. The present data support the fact that glucagon is more lypolytic in birds than in mammals. Pancreatic hormones are suggested to participate in the regulation of premigratory hyperphagia and hyperlipemia.

Introduction: Two Workshops in Ornithology: A General Introduction: Dedication to Eberhard Gwinner: Ulf Bauchinger and Wolfgang Goymann. . I. Measurement of Hormones from Droppings and Egg Yolk of Birds:. 1. Introduction to the European Science Foundation Technical Meeting: Analysis of Hormones in Droppings and Egg Yolk of Birds: Wolfgang Goymann and Susanne Jenni-Eiermann. 2. Potential Impact of Nutritional Strategy on Noninvasive Measurements of Hormones in Birds: Kirk C. Klasing. 3. Measurement of Corticosterone Metabolites in Birds' Droppings: An Analytical Approach: Erich Mostl, Sophie Rettenbacher, and Rupert Palme. 4. Noninvasive Monitoring of Hormones in Bird Droppings: Physiological Validation, Sampling, Extraction, Sex Differences, and the Influence of Diet on Hormone Metabolite Levels: Wolfgang Goymann. 5. Measuring Fecal Glucocorticoid Metabolites in Mammals and Birds: The Importance of Validation: Chadi Touma and Rupert Palme. 6. Measuring Fecal Steroids: Guidelines for Practical Application: Rupert Palme. 7. A Noninvasive Technique to Evaluate Human-Generated Stress in the Black Grouse: Marjana Baltic, Susanne Jenni-Eiermann, Raphael Arlettaz, and Rupert Palme. 8. Measuring Corticosterone Metabolites in Droppings of Capercaillies (Tetrao urogallus): Dominik Thiel, Susanne Jenni-Eiermann, and Rupert Palme. 9. Noninvasive Measures of Reproductive Function and Disturbance in the Barred Owl, Great Horned Owl, and Northern Spotted Owl: Samuel K. Wasser and Kathleen E. Hunt. 10. Synthesis of Measuring Steroid Metabolites in Goose Feces: Katharina Hirschenhauser, Kurt Kotrschal, and Erich Mostl. 11. Sampling Effort/Frequency Necessary to Infer Individual Acute Stress Responses from Fecal Analysis in Greylag Geese (Anser anser): Isabella B. R. Scheiber, Simona Kralj, and Kurt Kotrschal. 12. Investigating Maternal Hormones in Avian Eggs: Measurement, Manipulation, and Interpretation: Ton G. G. Groothuis and Nikolaus Von Engelhardt. 13. Measuring Steroid Hormones in Avian Eggs: Nikolaus Von Engelhardt and Ton G. G. Groothuis. 14. Corticosterone in Chicken Eggs: S Rettenbacher, E Mostl, R Hackl, and R Palme. 15. Steroids in Allantoic Waste: An Integrated Measure of Steroid Exposure in Ovo: Z Morgan Benowitz-Fredericks, Alexander S. Kitaysky, and John C. Wingfield. . II. Optimality in Bird Migration: Adaptations for Long-Distance Migration in Birds? The Search for Adaptive Syndromes:. 16. Are There Specific Adaptations for Long-Distance Migration in Birds? The Search for Adaptive Syndromes: Outline of the European Science Foundation Workshop: Ulf Bauchinger, Christiaan Both, and Theunis Piersma. 17. Flexible Seasonal Timing and Migratory Behavior: Results from Stonechat Breeding Programs: Barbara Helm, Eberhard Gwinner, and Lisa Trost. 18. Are Long-Distance Migrants Constrained in Their Evolutionary Response to Environmental Change?: Causes of Variation in the Timing of Autumn Migration in a Blackcap (S. atricapilla) and Two Garden Warbler (Sylvia borin) Populations: Francisco Pulido and Michael Widmer. 19. Spatial Behavior of Medium and Long-Distance Migrants at Stopovers Studied by Radio Tracking: Nikita Chernetsov. 20. Ecomorphology of the External Flight Apparatus of Blackcaps (Sylvia atricapilla) with Different Migration Behavior: Wolfgang Fiedler. 21. Melatonin and Nocturnal Migration: Leonida Fusani and Eberhard Gwinner. 22. Phenotypic Flexibility of Skeletal Muscles during Long-Distance Migration of Garden Warblers: Muscle Changes Are Differentially Related to Body Mass: Ulf Bauchinger and Herbert Biebach. 23. Is There a "Migratory Syndrome" Common to All Migrant Birds?: Theunis Piersma, Javier Perez-Tris, Henrik Mouritsen, Ulf Bauchinger, and Franz Bairlein

We tested the hypothesis that experience of migration from Europe to tropical Africa by Garden Warblers is associated with changes in the relative volume of the hippocampus, a brain region thought to be involved in processing spatial information, including that used in navigation. Relative hippocampal volume was larger in birds at least one year old that had migrated to and from Africa, than in naive birds approx. 3 months old. Further comparisons between groups of differing age and experience of migration suggested that both experience and age during the first year have an effect of relative hippocampal volume. The increase in relative hippocampal volume was mainly due to a decrease in the size of the telencephalon; however, the comparison between young, naive birds and older, experienced birds also suggests a possible increase in absolute hippocampal volume. The latter is associated with an increase in number and density of neurons, whilst the former is associated with an increase in density but no change in total number of neurons. In a non-migratory close relative of the garden warbler, the Sardinian warbler, older birds had a smaller telencephalon but there was no change in hippocampal volume, which supports the view that changes in the hippocampus may be associated with migratory experience, whilst changes in the telencephalon are not.

The garden warbler Sylvia borin is a long-distance migrating bird that travels exclusively at night. During the migratory seasons caged warblers develop intense nocturnal activity which may become even more intense than that during the day. It is demonstrated that in spite of dramatic seasonal changes in the 24-h pattern of locomotor activity measured in caged garden warblers, the corresponding pattern of plasma melatonin changed only very little. As in other species melatonin levels were generally low during the day (below 50 pg/ml) and high at night (350 to 650 pg/ml). A slight reduction in the nocturnal melatonin peak (from 650 pg/ml to between 350 and 400 pg/ml) observed during the autumn and spring migratory seasons, was possibly due to an increased light perception of the birds moving around while being exposed to dim night lights. In general the results show that the 24-h plasma melatonin profiles of these birds are rather robust and that locomotor activity does not depend in a simple and direct way on plasma melatonin levels.

Avian long-distance migration involves the storage and expenditure of very large fuel loads. Birds may double in weight before take-off on flights of many 1000 km, and they may lose half their body mass over the subsequent few days that such trips take. Recent studies indicate that in addition to the storage and depletion of fat, the muscles and belly organs also undergo considerable changes in size in the course of such migrations. Such intraindividual and repeatedly reversed changes in stores and organ sizes represent a class of phenotypic plasticity called 'phenotypic flexibility'. Using preliminary comparative data for different populations of Bar-tailed Godwits Limosa lapponica, and several other shorebird species adding variation to the migration strategies sampled (Golden Plover Pluvialis apricaria, Ruff Philomachus pugnax, Red Knot Calidris canutus and Bristle-thighed Curlew Numenius tahitiensis), the thesis is developed that the size of the organs carried during take-off represent evolutionary compromises between their functions during the storage, flight and post-arrival phases of migration. In all cases fat-free tissue along with fat is deposited during fuel storage, but the proportions vary a great deal between similarly sized species. Just before departure on long-distance flights, exercise organs (pectoral muscle and heart) tend to show hypertrophy and nutritional organs (stomach, intestine and liver) tend to show atrophy. Reductions in nutritional organs appear most pronounced in (sub-) species that are about to overfly barren oceans with few or no opportunities for emergency landings. Migrant birds seem to show a great deal of adaptive flexibility, and the study of this flexibility may shed light on (presently unknown) physiological mechanisms as well as on correlated ecological constraints on bird migration.

Bird species distributions in 151 woods (0.02-30 ha) in a lowland arable landscape in eastern England were investigated using logistic regression analysis. Of 31 species included in the study, only Marsh Tit Parus palustris, Nightingale Luscinia megarhynchos and Chiffchaff Phylloscopus collybita failed to breed in woods of

Fall migratory restlessness (Zugunruhe) of caged first year Garden Warblers Sylvia borin is partly endogenously preprogrammed and it has been suggested that the pattern of Zugunruhe reflects a mechanism that determines the time course and possibly the distance of migration. The question arose of how migrating birds cope with interruptions induced by adverse weather conditions or the need to refuel. Here we have tested the hypothesis that birds compensate for interruptions by adding migratory activity to other nights. An experimental group of 13 Garden Warblers was subjected to repeated schedules of food withdrawal and re-feeding. This treatment resulted in a significant increase in the number of nights without Zugunruhe as compared with the performance of 12 control birds that received food ad libitum. The overall amount of fall Zugunruhe of the experimental birds was reduced correspondingly suggesting that birds did not compensate. This conclusion is corroborated by the finding that those experimental birds in which the treatment induced most interruptions showed the smallest overall amount of Zugunruhe. The results suggest that if a migratory time program determines migratory distance in first year migrants, the wintering area may be relatively variable unless other factors determine its exact position.

Garden Warblers appear to be equipped with a migratory strategy which matches the problems arising from migration very well. They are equipped with innate endogenous programmes which determine the seasonal events for migration (for reviews see Berthold 1984, Gwinner 1986). They exhibit strong habitat preferences in resting areas which are likely to be endogenously controlled and which allow the specimens to be well accommodated in the various migratory stopoverareas (Bairlein 1981). They possess physiological and behavioural adaptations in their nutrition which guarantee optimal fattening up prior to migratory flights. Garden Warblers apparently avoid the risk of dehydration during long nonstop flights across the Sahara by crossing the desert in stages with regular stopovers at suitable sites rather than in one long hop.

1. 1. Intake of food, protein, fat and carbohydrates and their fecal output and the birds' weights were recorded during different feeding trials with specific nutrient reduced diets in the old-world long-distance migratory garden warbler. 2. 2. The birds' body weights were affected by low dietary protein as well as low dietary fat levels. 3. 3. Low dietary protein and fat levels were associated with significant changes in daily gross and net food intake and in the efficiency of food and nutrient utilization. 4. 4. Birds fed on diets with low nutrient levels for an extended length of time recovered in weight after an initial weight loss. They obviously compensated the restricted nutrient levels primarily by increasing the daily food intake and by changing the efficiency of food and nutrient utilization. 5. 5. Effects of restricted dietary nutrient levels on body weight and adaptation depended on the previous composition of the food. 6. 6. The average daily net fat intake was much higher than the average daily net protein intake, both for maintenance of a constant body weight and for successful regain of weight. 7. 7. The data were further discussed with respect to the role of a fruit diet in omnivorous passerine birds.

Garden warblers breeding in central Europe and wintering in tropical and southern Africa show characteristic changes in flight direction during their fall migration: they initially leave their breeding grounds in a southwest direction but then change to S or SSE in southern Spain or northern Africa. Since it had been demonstrated in previous studies that several features of this species' migratory activity are dependent on endogenous timing processes, the hypothesis was proposed that the changes in migratory direction are also endogenously controlled. To test this hypothesis a total of 59 garden warblers were handraised and subsequently kept under constant temperature and photoperiodic conditions throughout the fall migratory season. At regular intervals the birds were moved to circular orientation cages in which they were tested for directional preferences in their nocturnal migratory restlessness. In these orientation cages the birds had no view of the sky, but were exposed to the local magnetic field of the earth. The analysis of data from 404 nights in which birds showed migratory restlessness revealed a significant concentration of the mean directions in the southern sector of the cage. Moreover the birds showed a counterclockwise shift in the preferred direction from SW or SSW to S or SSE, corresponding with the directional shift in freeliving garden warbler migration. These results suggest that the changes in migratory direction occurring in this species are due, at least in part, to spontaneous endogenous changes in the preferred direction relative to external orienting cues, probably of the earth's magnetic field.

1. Two groups of garden warblers, a western Palaearctic long-distance migratory passerine bird species, were kept under controlled laboratory conditions and their weights were recorded almost daily for up to 18 and 30 months, respectively. 2. All specimens exhibited spontaneous, regular body weight fluctuations with an average periodicity of about 18 days and an amplitude of up to 32% of the corresponding initial body weight. The period length of the cycle was influenced by the seasonal level of body weight due to migratory fattening as well as by the nutritional composition of the diet. 3. This is the first time that such spontaneous cyclic, body weight fluctuations with almost a semimonthly period are described for a bird species. 4. Since no obvious external zeitgeber seems to exist for these rhythms in body weight they appear to be endogenously controlled. 5. It is suggested that the observed infradian cycle in body weight may be an expression of an internal metabolic regulatory process in order to set up to species-specific fixed body weight. 6. The adaptive value of such infradian body weight variations is discussed in relation to the bird's migratory behavior.

1. Most migratory birds breeding in the northern hemisphere show regular changes in the direction of their migratory flights from roughly south in autumn to roughly north in spring. To test the hypothesis that these changes are primarily controlled by endogenous physiological changes, we carried out experiments with the garden warbler, Sylvia borin. 2. Eleven birds were hand-raised and subsequently kept under a constant 12-h photoperiod and constant temperature conditions throughout their first fall and spring migratory seasons. At regular intervals, the birds were tested in circular orientation cages for directional preferences of their nocturnal migratory restlessness. During the tests, the birds were exposed to the local magnetic field of the earth, but had no view of the sky. 3. Birds showed a significant preference for a southerly direction in autumn and for a northerly direction in spring (Figs. 2 and 3). These results support the hypothesis that the reversal of the migratory direction results from spontaneous changes in the preferred direction relative to external orienting cues that are controlled by an endogenous circannual clock.

Vertikale Verteilung von Monchs- und Gartengrasmucken in der Vegetation. — In Norditalien liesen sich jahreszeitliche Unterschiede in der vertikalen Verteilung von Monchsgrasmucken mit Hilfe standardisierter Netzfange feststellen. Im Herbst kann sich aus der Ahnlichkeit des Verteilungsmusters zwischen Garten- und Monchsgrasmucke interspezifische Konkurrenz ergeben. Die gefundenen Verteilungsmuster gleichen solchen aus Gegenden mit ganz anderer Artenzusammensetzung der Vegetation.

The comparative study of the ontogeny of behaviour should be of evolutionary interest, as in the morphological characters. Here some reported data of observations of this sort are extracted for comparison from the works of Barrand (Great Tit, Chaffinch), Blase (Red-backed Shrike), Kuroda (Grey Starling), Messmer (European Blackbird. Original was not available) and Sauer (Garden Warbler).Twenty four behaviour items classified into sight development, physical behaviours (preening, etc.), self protection (crouching, fleeing, etc.), social behaviours (aggressiveness, juvenile song, juvenile nesting, etc.) and food getting (oriented gaping, pecking, species-specific use of bill, self foraging and drinking, etc.) were selected for comparison.It could tentatively be concluded that: 1. The duration from hatching to self foraging does not differ much by species with different habits and duration of nestling life. This should there-fore be the evolutionary basic Passerine character. 2. The hole and open nesters would have developed later adaptively. The nestling life was lengthened in the hole nesters (about 20 days) and shortened in the open nesters (10-15 days) as the result of natural selection against predators, but the basic growth pace was not changed. Thus hole nest chicks that stay longer in the nest are fed by parents shorter time after flying since they are well grown and open nest chicks fly precociously and are fed longer (Thus they retain incomplete adaptation against the danger of predation when flying). 3. This difference of the nestling period caused the difference in the timing of physiological and behavioural growth of early nestling life, such as eye-opening, lateral sight, preening and self protection, etc. These were accerelated in open nest chicks so as they have developed by the time of their precocious flying from the nest. 4. But, this accerelation of the occurrence of behaviours seems to have not influenced the basic timing of the final completion of self foraging. However, at the time when self foraging becomes established species-specific use of the bill (and feet) occurs similarly at around 20-25 days after hatching irrespective of the difference of habit by species. 5. The social habits occur first as an aggressiveness against each other (head forward posture, maintenance of individual distance) at different period by species (this occurs early at about 20 days in strongly territorial species), but always after or when the self foraging is established. 6. These species-specific behaviours (4 and 5) which occur latest during the ontogeny should be the ethological characters which have evolved recently.

1. 1. Ten juvenile Garden Warbler Sylvia borin were maintained in controlled laboratory conditions and their blood sugar concentrations were determined regularly. 2. 2. The concentrations of blood glucose were higher during the migratory periods both in autumn and in spring. 3. 3. The study reveals a seasonal rhythm in the blood glucose levels in a migratory songbird. 4. 4. The laboratory data are supported by data of wild birds trapped at different times.

Migrating spotted flycatchers, resting and feeding in an oasis, have longer stopover periods when fat reserves on arrival are low. In the laboratory migratory activity could likewise be suppressed by a combination of two factors: low fat reserves and the possibility of feeding.

1 Intake of food, fat, protein and carbohydrates and their fecal output were recorded during the annual body weight cycle of the garden warbler, and old-world longdistance migratory bird species, and the efficiencies of food and nutrient utilization, defined as the ratio (intake-fecal output)/intake, were calculated. 2. Gross food intake and food and nutrient utilization differed significantly between different phases of the birds' body weight cycle. 3. During premigratory fattening, both in “autumn” and “spring”, food intake and utilization of fat, protein and carbohydrates were significantly higher than during the low body weight prefattening periods. 4. The increase in efficiency of nutrient utilization accounted for about 1/3 and the increase in gross food intake about 2/3 of all surplus energy for hyperlipogenesis in the premigratory periods of the garden warbler. 5. The seasonal changes in efficiency of food and nutrient utilization seem to be driven by a circannual timing mechanism.

During autumn migration, Pied Flycatchers (Ficedula hypoleuca) like many other migrating bird species, have to change their initial migratory direction on reaching Portugal and south Spain from SW to SE to reach their central African wintering area (Zink 1977). While this Zugknick seems to be endogenously controlled in other bird species like the Garden Warbler (Sylvia borin, Gwinner and Wiltschko 1978), it was not to observed in Pied Flycatchers. While these birds were tested in the local geomagnetic field (0.46 Gauss, mN 360°, 66° Incl) without visual cues no change in the migratory direction or in orientation from the initial direction to SW after the 10th of October was observed, although Pied Flycatchers are able to orient with respect to the earth magnetic field (Beck and Wiltschko 1981). So it is fell that this bird species needs an external factor to change their migratory direction. The present experiments will prove whether the variation of inclination and force of the earths magnetic field along the migratory path of the Pied Flycatchers serves as this factor.

Ecological divergence between Blackcaps and Garden Warblers appears to be incomplete. They resemble each other closely in morphology and their foraging behaviour and food (in the breeding season) are at least broadly similar. Nevertheless, they are sympatric and occur together in a wide range of habitats although Garden Warblers are proportionately commoner in lower, denser vegetation. The two species are strongly interspecifically territorial where they occur together. However, Blackcaps are more interspecifically aggressive than Garden Warblers and are clearly dominant to them in interactions. Blackcaps respond just as strongly to playback of Garden Warbler song as they do to that of Blackcap song. They sometimes intrude into Garden Warbler territories and seek- out and chase the territory holders. In contrast, with rare exceptions, any Garden Warblers which intrude into Blackcap territories are attacked and chased until they leave the area. Also, during song playback experiments, Garden Warblers approach the loudspeaker less closely in response to Blackcap song than they do to Garden Warbler song. Many Blackcaps arrive on the breeding grounds before the earliest Garden Warblers do. A removal experiment, in which such established Blackcaps were systematically removed, showed that some of them had been keeping-out potential Garden Warbler settlers, since the latter then readily established territories and bred in a large part of the Blackcap-free zone. Normally, Garden Warblers have their territories outside Blackcat>-occupied habitat, partly because they are prevented by the aggressiveness of the Blackcaps from settling elsewhere. However, observation and song playback experiments have shown that, once established, Garden Warblers do defend their territories against both conspecifics and Blackcaps. Blackcaps have recently increased dramatically in Britain and Garden Warblers have decreased simultaneously. However, although Blackcaps can limit the local breeding densities of Garden Warblers in any one year, it is not yet clear whether Blackcap numbers are a significant factor in determining the total sizes of Garden Warbler populations.

The effects of community dynamics in birds on the optimisation of their migratory strategies is a neglected area. For three years, we captured migrating warblers on autumn passage at a coastal site in western Britain. We used canonical correspondence analysis (CCA) to assess spatio-temporal patterns of occurrence, and principal components analysis (PCA) to assess morphological variation. We calculated Euclidean distance in ordination and morphological space to assess separation between species pairs, and used Monte-Carlo simulations to assess the probability of pattern occurring by chance. Ordination revealed five species-groups separated by habitat type and time of passage. Reed Warbler Acrocephalus scirpaceus and Sedge Warbler A. schoenobaenus (Group 1) occurred in wet habitats and peaked simultaneously. In drier habitats with scrub, a first wave of Blackcap Sylvia atricapilla (Group 2) significantly preceded Grasshopper Warbler Locustella naevia, Willow Warbler Phylloscopus trochilus, Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca (Group 3), which in all but one case (Lesser Whitethroat) significantly preceded Garden Warbler Sylvia borin (Group 4); peak numbers of Chiffchaffs Phylloscopus collybita and a second wave of Blackcaps (Group 5) occurred later still. Age effects were found only in Acrocephalus, with adults peaking before juveniles. For seven out of eight pairings within genera, separation in time of passage increased significantly in species that were morphologically similar. The only exception was Blackcap and Lesser Whitethroat which differed substantially in both passage time and morphology. Monte-Carlo simulations showed that chance was unlikely to be responsible for ordination patterns, nor for inter-specific variation in passage time and its relationship with species morphology. These data provide annually consistent evidence that migrating sylviid warblers are separated ecologically by habitat use, time of passage and morphology: we cannot refute the hypothesis that community dynamics have influenced niche use and autumn migratory strategy. We call for further tests of the ‘migrant interaction’ hypothesis in other geographical locations and taxa, particularly where migrants are allopatric and interact ecologically only on migration.