Thomas Alerstam's research while affiliated with Lund University and other places
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Publications (186)
Great reed warblers, Acrocephalus arundinaceus,1 and great snipes, Gallinago media,2 exhibit a diel cycle in flight altitudes-flying much higher during the day than the night-when performing migratory flights covering both night and day. One hypothesis proposed to explain this behavior is that the birds face additional heating by solar radiation du...
Background
Long-distance migratory birds undergo complex annual cycles during which they must adjust their behaviour according to the needs and conditions encountered throughout the year. Yet, variation in activity throughout the entire annual cycle has rarely been studied in wild migratory birds.
Methods
We used multisensor data loggers to evalua...
Several factors affect the flight altitude of migratory birds, such as topography, ambient temperature, wind conditions, air humidity, predation avoidance, landmark orientation, and avoiding over-heating from direct sunlight.1-6 Recent tracking of migratory birds over long distances has shown that migrants change flight altitude more commonly and d...
High fliers
Migrating from hemisphere to hemisphere is a global strategy for many bird species. Despite allowing birds to track productivity, these long-distance movements bring them in contact with inhospitable regions such as deserts and oceans. Sjöberg et al. used geolocators to monitor flight in great reed warblers ( Acrocephalus arundinaceus )...
A wide variety of the barrier crossing strategies exist among migrating songbirds, ranging from strict nocturnal flights to non‐stop flights over a few days. We evaluate barrier crossing strategies in a nocturnally migrating songbird crossing the Mediterranean Sea and the Sahara Desert, the great reed warbler, exploring variation between the sexes...
Waders normally fly with their legs stretched out under the tail, with their feet pointing backwards. Whereas there are a few published records of waders flying with their legs folded forward (like a passerine), with legs and feet tucked in under the belly feathers, the causes and consequences of waders flying with folded legs are poorly understood...
The regular fluctuation of resources across the Globe guides movements of migratory animals. To ensure sufficient reproductive output and maintain viable population sizes, migratory animals should match arrival at breeding areas with local peaks in resource availability. It is generally assumed that breeding phenology dictates the timing of the ann...
The arctic tern Sterna paradisaea completes the longest known annual return migration on Earth, traveling between breeding sites in the northern arctic and temperate regions and survival/molt areas in the Antarctic pack‐ice zone. Salomonsen (1967, Biologiske Meddelelser, Copenhagen Danske Videnskabernes Selskab, 24, 1) put forward a hypothetical co...
Many flying animals, like birds feeding their young, make commuting flights between a central place and foraging areas in the surroundings. Such central place foraging (CPF) represents a special case of foraging theory. We use simple geometry and trigonometry to analyse CPF flight performance (a round-trip cycle of outward flight from the central p...
Stopovers play a crucial role for the success of migrating animals and are key to optimal migration theory. Variation in refuelling rates, stopover duration and departure decisions among individuals has been related to several external factors. The physiological mechanisms shaping stopover ecology are, however, less well understood. Here, we explor...
Billions of animals are adapted to a travelling life, making regular return migrations between more or less distant living stations on Earth by swimming, flying, running or walking (Figure 1). Extremely long migrations are completed annually by whales between calving areas in warmer waters and feeding areas at higher latitudes in either hemisphere....
Migration usually consists of intermittent travel and stopovers, the latter being crucially important for individuals to recover and refuel to successfully complete migration. Quantifying how sickness behaviours influence stopovers is crucial for our understanding of migration ecology and how diseases spread. However, little is known about infectio...
The development of migratory behaviour is a continuous process which is not only determined by genes, but also moulded by individual differences based on life-history variations occurring at each ontogenetic stage. Assessing consistency and plasticity in migratory traits between long distance (LDM) and short distance migratory (SDM) populations wit...
Birds use different compass mechanisms based on celestial (stars, sun, skylight polarization pattern) and geomagnetic cues for orientation. Yet, much remains to be understood how birds actually use these compass mechanisms on their long-distance migratory journeys. Here, we assess in more detail the consequences of using different sun and magnetic...
Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We track...
The use of accelerometers has become an important part of biologging techniques for large-sized birds with accelerometer data providing information about flight mode, wing-beat pattern, behaviour and energy expenditure. Such data show that birds using much energy-saving soaring/gliding flight like frigatebirds and swifts can stay airborne without l...
Most songbirds depart from stopover sites after sunset and migrate during the night. Several recent studies have reported larger variation in departure time than previously thought; yet, it is still unclear which factors govern departure timing. We investigated the departure timing of four species of nocturnally migrating songbirds using an automat...
We describe a method and device (< 1.2 g) for recording, processing and storing data about activity and location of individuals of free-living songbirds throughout the annual cycle. Activity level was determined every five minutes from five 100 ms samples of accelerometer data with 5 s between the sampling events. Activity levels were stored on an...
As the evolutionary responses to environmental change depend on selection acting on individual differences, disentangling within- and between-individual variation becomes imperative. In animal migration research, multiyear tracks are thus needed to estimate the individual consistency of phenotypic traits. Avian telemetry studies have recently provi...
The migration of the great snipe Gallinago media was previously poorly known. Three tracks in 2010 suggested a remarkable migratory behaviour including long and fast overland non-stop flights. Here we present the migration pattern of Swedish male great snipes, based on 19 individuals tracked by light-level geolocators in four different years. About...
Goal-oriented migrants travelling through the sea or air must cope with the effect of cross-flows during their journeys if they are to reach their destination [1-3]. In order to counteract flow-induced drift from their preferred course, migrants must detect the mean flow direction, and integrate this information with output from their internal comp...
1. Animals that use flight as their mode of transportation must cope with the fact that their migration and orientation performance is strongly affected by the flow of the medium they are moving in, i.e. by the winds. Different strategies can be used to mitigate the negative effects and benefit from the positive effects of a moving flow. The strate...
Departure decisions of how and when to leave a stopover site may be of critical importance for the migration performance of birds. We used an automated radiotelemetry system at Falsterbo peninsula, Sweden, to study stopover behaviour and route choice in free-flying passerines departing on flights across the Baltic Sea during autumn migration. In ad...
The nocturnal migration of many passerines starts after sunset and reaches peak intensity during the dark hours of the night. Birds destined for high arctic breeding grounds encounter a special situation, as they will experience continuous daylight when reaching the high latitudes during the final part of spring migration. How does this affect the...
By recording nocturnally migrating passerines with tracking radar we have investigated how coastlines affect the migrants’ flight paths. Birds could use coastlines as an orientation aid or as a reference cue to compensate for wind drift while migrating. However, on the small scale of Falsterbo Peninsula in southern Sweden, we found very little effe...
In order to compare the two species’ flight performance over the exposed and windy Falsterbo Peninsula, where thermal conditions seldom are very favorable, we used tracking radar to study flight parameters of sparrowhawks Accipiter ni-sus and common buzzards Buteo buteo during autumn migration. The results showed a clear difference between sparrowh...
Migrating birds are expected to fly at higher airspeeds when minimizing time rather than energy costs of their migratory journeys. Spring migration has often been suggested to be more time selected than autumn migration, because of the advantage of early arrival at breeding sites. We have earlier demonstrated that nocturnal passerine migrants fly a...
Narrow migration corridors known in diurnal, social migrants such as raptors, storks and geese are thought to be caused by topographical leading line effects in combination with learning detailed routes across generations. Here, we document narrow-front migration in a nocturnal, solitary migrant, the common cuckoo Cuculus canorus, using satellite t...
Information about when and where animals die is important to understand population regulation. In migratory animals, mortality might occur not only during the stationary periods (e.g. breeding and wintering) but also during the migration seasons. However, the relative importance of population limiting factors during different periods of the year re...
The timing of migration is generally considered of utmost importance for reproduction and survival, and timing is furthermore considered to be under strong genetic control. The individual timing of migration is presumably a result of a combination of genetic, phenotypic and environmental factors as well as some degree of randomness. However, potent...
Abstract It has been suggested that birds migrate faster in spring than in autumn because of competition for arrival order at breeding grounds and environmental factors such as increased daylight. Investigating spring and autumn migration performances is important for understanding ecological and evolutionary constraints in the timing and speed of...
Despite an overall advancement in breeding area arrival, one of the latest spring arrivals in northwest Europe since 1950 of several trans-Saharan songbird species occurred in 2011. Year-round tracking of red-backed shrikes and thrush nightingales revealed that the cause of the delay was a prolongation of stopover time during spring migration at th...
Many animal taxa have been shown to possess the ability of true navigation. In this study we investigated the possibilities for geomagnetic bi-coordinate map navigation in different regions of the earth by analysing angular differences between isolines of geomagnetic total intensity and inclination. In ‘no-grid’ zones where isolines were running al...
Immature European Honey Buzzards Pernis apivorus are believed to remain in tropical Africa during the first years of their lives. We studied their movements during this period with the aid of satellite telemetry. After crossing the Sahara Desert on autumn migration, all six tracked young buzzards stopped at relatively northerly latitudes, between 9...
Regression coefficient and significance of the relationship between daily distance and latitude for each species by season.
(DOC)
Performance of migrating birds can be affected by a number of intrinsic and extrinsic factors like morphology, meteorological conditions and migration strategies. We compared travel speeds of four raptor species during their crossing of the Sahara desert. Focusing the analyses on this region allows us to compare different species under equivalent c...
Daily travelling hours (sample size, average and standard deviation) for each species by season.
(DOC)
Migratory birds are predicted to adapt their departure to wind, changing their threshold of departure and selectivity of the most favourable winds in relation to the mean, scatter and skewness of the wind regime. The optimal departure behaviour depends also on the importance of time and energy minimization during migration and on the ratio of cost...
Flight directions and routes of migrating birds are determined by the birds’
compass orientation, but also by effects of wind, social influence, responses to
topography and landmarks, and to navigation cues. We investigated the orientation
and routes taken by arctic shorebirds during autumn migration in southern
Sweden at three different sites situ...
Migratory movements in air or water are strongly affected by wind and ocean currents and an animal which does not compensate for lateral flow will be drifted from its intended direction of movement. We investigated whether arctic shorebirds during autumn migration in the region of South Sweden and the southern Baltic Sea compensate for wind drift o...
It has been suggested that time selection and precedence in arrival order are more important during spring than autumn migration. Migrating birds are expected to fly at faster airspeeds if they minimize duration rather than energy costs of migration, and they are furthermore expected to complete their journeys by final sprint flights if it is parti...
Metabolic rates may be informative of adaptations to migration or wintering at high latitudes and may therefore be particularly interesting in partial migrants requiring adaptations to both migration and residency. To study the extent of physiological adaptations in migratory and resident blue tits Cyanistes caeruleus during the period of autumn mi...
For organisms that fly or swim, movement results from the combined effects of the moving medium - air or water - and the organism's own locomotion. For larger organisms, propulsion contributes significantly to progress but the flow usually still provides significant opposition or assistance, or produces lateral displacement ('drift'). Animals show...
The small size of the billions of migrating songbirds commuting between temperate breeding sites and the tropics has long prevented the study of the largest part of their annual cycle outside the breeding grounds. Using light-level loggers (geolocators), we recorded the entire annual migratory cycle of the red-backed shrike Lanius collurio, a trans...
Using optimality perspectives is now regarded as an essential way of analysing and understanding adaptations and behavioural strategies in bird migration. Optimization analyses in bird migration research have diversified greatly during the two recent decades with respect to methods used as well as to topics addressed. Methods range from simple anal...
Nocturnal passerine migrants could substantially reduce the amount of energy spent per distance covered if they fly with tailwind assistance and thus achieve ground speeds that exceed their airspeeds (the birds’ speed in relation to the surrounding air). We analysed tracking radar data from two study sites in southern and northern Scandinavia and s...
Migratory land birds perform extreme endurance flights when crossing ecological barriers, such as deserts, oceans and ice-caps. When travelling over benign areas, birds are expected to migrate by shorter flight steps, since carrying the heavy fuel loads needed for long non-stop flights comes at considerable cost. Here, we show that great snipes Gal...
Vast numbers of insects and passerines achieve long-distance migrations between summer and winter locations by undertaking high-altitude nocturnal flights. Insects such as noctuid moths fly relatively slowly in relation to the surrounding air, with airspeeds approximately one-third of that of passerines. Thus, it has been widely assumed that windbo...
The exploration of animal migration has entered a new era with individual-based tracking during multiple years. Here, we investigated repeated migratory journeys of a long-distance migrating bird, the marsh harrier Circus aeruginosus, in order to analyse the variation within and between individuals with respect to routes and timing. We found that t...
Using tracking radars, we investigated the variability of flight directions of long-distance nocturnal passerine migrants
across seasons (spring versus autumn migration) and sites at the southern (56° N) and northern (68° N) ends of the Scandinavian
Peninsula (Lund versus Abisko). Whilst most migrants at Lund are on passage to and from breeding sit...
Individuals differ consistently in their behavioural reactions towards novel objects and new situations. Reaction to novelty is one part of a suit of individually consistent behaviours called coping strategies or personalities and is often summarised as bold or shy behaviour. Coping strategies could be particularly important for migrating birds exp...
Wind and ocean currents may potentially have important effects on travelling animals, as an animal which does not respond to lateral flow will be drifted from its intended direction of movement. By analysing daily movements of migrating ospreys Pandion haliaetus and marsh harriers Circus aeruginosus, as recorded by satellite telemetry, in relation...
We investigated the orientation in relation to wind of common swifts, Apus apus, during nocturnal spring and autumn migration. Swifts are highly adapted to a life in the air, showing wind-dependent orientation during nocturnal roosting flights, and may be expected to be more efficient in their wind drift/compensation behaviour than nocturnal passer...
Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. He...
We investigated the risk associated with crossing the Sahara Desert for migrating birds by evaluating more than 90 journeys across this desert by four species of raptors (osprey Pandion haliaetus, honey buzzard Pernis apivorus, marsh harrier Circus aeruginosus and Eurasian hobby Falco subbuteo) recorded by satellite telemetry. Forty per cent of the...
Bird migration was recorded by tracking radar and visual observations in the Beringia region. The data were subdivided into seven areas extending from north of Wrangel Island southeastward toward the Bering Strait and then northwestward off the coast of Alaska to Point Barrow. The studies, which took place during a ship-based expedition between 30...
Many migratory bird species fly mainly during the night (nocturnal migrants), others during daytime (diurnal migrants) and still others during both night and day. Need to forage during the day, atmospheric structure, predator avoidance and orientation conditions have been proposed as explanations for the widespread occurrence of nocturnal migration...
We have studied the nocturnal flight behaviour of the common swift (Apus apus L.), by the use of a tracking radar. Birds were tracked from Lund University in southern Sweden during spring migration, summer roosting flights and autumn migration. Flight speeds were compared with predictions from flight mechanical and optimal migration theories. Durin...
1. Since the early 1990s, an increasing proportion of barnacle geese, Branta leucopsis, bound for breeding sites in the Russian Arctic delay their departure from the wintering quarters in the Wadden Sea by 4 weeks. These late-migrating geese skip spring stopover sites in the Baltic traditionally used by the entire population. 2. Individual geese fr...
Comúnmente se considera que la migración parcial es una etapa transitoria entre la migración y la residencia, y se desconoce en gran medida si los migrantes parciales tienen en cuenta las condiciones climáticas durante la migración. Para evaluar si los migrantes parciales difieren de los migrantes regulares en sus respuestas al clima, comparamos la...
Bird migration was recorded by tracking radar and visual observations in the Beringia region. The data were subdivided into seven areas extending from north of Wrangel Island southeastward toward the Bering Strait and then northwestward off the coast of Alaska to Point Barrow. The studies, which took place during a ship-based expedition between 30...
Autumn migration of adult Eurasian hobbies Falco subbuteo from Europe to southern Africa was recorded by satellite telemetry and observed routes were compared with randomly simulated routes. Two non-random features of observed routes were revealed: (i) shifts to more westerly longitudes than straight paths to destinations and (ii) strong route conv...
Several different factors may determine where species range limits are located within regions of otherwise continuously available habitat and suitable climate. Within the Arctic tundra biome many bird species are migratory and their breeding distributions are affected by migration routes that are in turn limited by factors such as suitable winter h...
Alerstam T. 2008. Complex timing of Marsh Harrier Circus aeruginosus migration due to pre-and post-migratory movements. Ardea 96(2): 159–171. We tracked three juvenile and 14 adult Marsh Harriers Circus aerugi-nosus from southern Sweden via satellite to investigate migration strate-gies. Four individuals were tracked for at least two years. All thr...
