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Birds migrating different distances experience different temporal, energetic, physiological, and physical constraints throughout migration, which is reflected in their migration strategy. Consequently, we predict different behavioral decisions to similar environmental cues between short‐ and long‐distance migrants, which has been documented for autumn migration. Here, we focus on the question whether trade‐off decisions regarding departure, routing, and landing when alternating between migratory endurance flights and stopovers also differ during spring migration. As early arrivals at the breeding grounds should be ultimately favored regardless of migration distance, selection may favor more similar behavioral decisions in spring than in autumn. We radio‐tagged short‐ and long‐distance migratory songbirds at stopover sites along the German North Sea coast during spring and automatically tracked their migratory behavior using a large‐scale network of receiver stations. Once departed, birds could either cross the sea or detour along the coast. We corrected for spatially biased detection data, using a hierarchical multistate model to assess how birds respond to variation in environmental conditions in their day‐to‐day departure decisions and route selection. The day‐to‐day departure probability was higher in long‐distance migrants independently of the routing decision. Irrespective of migration distance, all species more likely departed under light winds and rainless conditions, while the influence of air pressure change and relative humidity was species‐specific. By accounting for detection probabilities, we estimated that about half of all individuals of each species crossed the sea but did not find differences between short‐ and long‐distance migrants. Offshore flights were more likely when winds blew offshore and began earlier within the night compared with onshore flights. Our results suggest that selection more similarly affects birds of different migration distances in spring than in autumn. These findings put the focus toward how ultimate mechanisms may shape departure and routing decisions differently between migration seasons. [ABSTRACT FROM AUTHOR]

Songbirds on migration spend a greater share of their travelling time at stopover sites in order to rest, recover and refuel compared to actively flying. In the German Bight of the North Sea, two subspecies of the northern wheatear split travelling routes, with Greenlandic/Icelandic breeders (subspecies leucorhoa) facing a long over‐sea flight and Scandinavian breeding birds (subspecies oenanthe) travelling further roughly along the coast. We used automated radio‐telemetry in spring to show that leucorhoa birds stayed significantly longer at a coastal stopover site and clearly selected for favourable weather, especially easterly winds, when resuming flights. Conditions for departures of individuals from the subspecies oenanthe were less obvious. They were more likely to depart on nights with southerly winds, often along with rising air temperatures, while air pressure dropped. Individuals of subspecies leucorhoa thus wait for optimal flying conditions to resume for longer flights, while oenanthe birds, with shorter distances ahead, seem to optimise time by leaving the stopover site more quickly. Our dataset thus confirms that songbirds optimise stopover based on their (sub)species‐specific migration patterns. [ABSTRACT FROM AUTHOR]

Many songbirds migrate twice a year to exploit seasonally available resources. These journeys are energetically demanding and energy reserves of these small birds are limited. Accordingly, most of the time migrating is spent during stopovers that serve to rest, replenish resources and recover. While external influences, like prevailing weather conditions and resource availability, are well studied with regard to stopover behaviour and departure decisions, studies on how birds' individual physiological condition and stopover decisions may be linked are scarce.We used a large‐scale radio‐telemetry network covering the German Bight (SE North Sea) to study how birds' immunological constitution at stopover may correlate with departure and flight behaviour in five species of short‐ to medium‐distance migratory songbirds. We measured markers of the innate (bacterial killing activity, lysozyme concentration, natural antibodies and complement titres) and acquired immune function (immunoglobulin Y) in the birds' plasma. After sampling, we tracked the birds' behaviour in terms of stopover duration as well as flight routes and flight distances within the telemetry network after departure.We found that stopover durations were positively related to natural antibodies and immunoglobulin Y across species and to the bacterial killing activity solely in song thrushes in spring, while no relations became apparent in fall. Flight distances were linked positively to immunoglobulin Y concentrations in both spring and fall, though not in all of the investigated species. Coastal and offshore‐oriented routes were taken independent of the birds' immune status.Our study for the first time shows that migratory behaviour of songbirds in the wild is correlated with their immune status, not only during but also beyond stopover. Furthermore, birds with increased complement titres and Immunoglobulin Y concentrations, either due to recent infection or greater investment in their immune function, took additional time at their stopover sites, probably to reach their breeding grounds in good condition. During the less time‐constrained fall season, stopovers were generally prolonged, independent from the birds' immune status and any delays taken to improve immune status are most likely not detrimental in terms of fitness. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The wind energy‐bat conflict is well documented for the onshore sector, with high numbers of casualties, specifically for migratory bat species. Offshore wind turbines might be a threat to bats as well, yet offshore bat migration is poorly documented. Accordingly, potential conflicts between bat conservation and offshore wind energy production are difficult to evaluate. Here, we used automated radio‐telemetry to track 50 km continuous offshore movements of two Nathusius' pipistrelles (Pipistrellus nathusii) within the Motus network. After crossing the marine waterbody, tagged bats traveled over several hundred kilometers along the coastline from Germany towards the Netherlands and Belgium. Our study highlights the possibility for migratory bats to collide with offshore and coastal wind turbines. Therefore, we plead for implementing pre‐ and post‐construction surveys and adequate mitigation schemes at offshore wind turbines in sensitive areas of the North and Baltic Sea if not already practised. [ABSTRACT FROM AUTHOR]

Laboratory mice are predominantly used for one experiment only, i.e., new mice are ordered or bred for every new experiment. Moreover, most experiments use relatively young mice in the range of late adolescence to early adulthood. As a consequence, little is known about the day-to-day life of adult and aged laboratory mice. Here we present a long-term data set with three consecutive phases conducted with the same male mice over their lifetime in order to shed light on possible long-term effects of repeated cognitive stimulation. One third of the animals was trained by a variety of learning tasks conducted up to an age of 606 days. The mice were housed in four cages with 12 animals per cage; only four mice per cage had to repeatedly solve cognitive tasks for getting access to water using the IntelliCage system. In addition, these learner mice were tested in standard cognitive tests outside their home-cage. The other eight mice served as two control groups living in the same environment but without having to solve tasks for getting access to water. One control group was additionally placed on the test set-ups without having to learn the tasks. Next to the cognitive tasks, we took physiological measures (body mass, resting metabolic rate) and tested for dominance behavior, and attractivity in a female choice experiment. Overall, the mice were under surveillance until they died a natural death, providing a unique data set over the course of virtually their entire lives. Our data showed treatment differences during the first phase of our lifetime data set. Young learner mice showed a higher activity, less growth and resting metabolic rate, and were less attractive for female mice. These effects, however, were not preserved over the long-term. We also did not find differences in dominance or effects on longevity. However, we generated a unique and valuable set of long-term behavioral and physiological data from a single group of male mice and note that our long-term data contribute to a better understanding of the behavioral and physiological processes in male C57Bl/6J mice. [ABSTRACT FROM AUTHOR]

Even after decades of research, the migration of songbirds still holds numerous secrets. Distinct stopover and routing behavior of diurnally and nocturnally migrating songbirds has been stated in the 1960s, but empirical confirmation is yet lacking widely. We studied the behavior of individual diurnally migrating dunnocks and nocturnally migrating blackcaps by means of large‐scale automated radio‐telemetry. Birds were radio‐tagged during their stopover at the German North Sea coast. Our data indicate longer initial stopover duration in the diurnally migrating dunnocks, opposing the hypothesis of nocturnal migrants needing more time to recover due to their longer migratory flights. Nonetheless, dunnocks stopped over more often along their tracks as when compared to the nocturnally migrating blackcaps. Behavior en route did not differ as clearly between species challenging the general view of contrasting routings of diurnal and nocturnal migrants with regard to landscape and open water. Our results imply additional factors of relevance other than differences in species or daily migration timing per se. We discuss and highlight the need of detailed and individual based data to better understand stopover and routing behavior of songbirds in the environmental context. [ABSTRACT FROM AUTHOR]

In human psychological research, personality traits as well as cognitive traits are usually validated for both, their stability over time and contexts. While stability over time gives an estimate on how genetically fixated a trait can be, correlations across traits have the power to reveal linkages or trade − offs. In animals, these validations have widely been done for personality but not for cognitive traits. We tested guinea pigs in four consecutive discrimination tasks using four unique pairs of objects with two objects of the same form but different size in each pair. The same animals were tested twice each for three personality traits, i.e. boldness, aggression and sociopositive behaviour. The animals did not learn to “always choose the larger item” in the cognitive task but learned to discriminate the two objects of each stimulus pair anew, so that we did test for learning speed in four slightly different task setups. Performance over the four tasks was significantly repeatable as well as all tested personality traits. A stable linkage over time was found between sociopositive behaviour and learning performance, probably indicating an ecological relevance for a correlation between these two traits. Still, not all traits seem to be connected amongst each other, as in our case boldness and aggression are both not linked to individual learning performance. Future studies will hopefully further investigate the repeatability of various cognitive traits in several species and thus lead to a better understanding of the interdependence of personality and cognition. This will help to unravel which suites of traits facilitate individual life histories and hence improve our understanding of the emergence and maintenance of individual differences. [ABSTRACT FROM AUTHOR]

Highlights: [•] We tested for a long term impact of early environment on learning performance in zebra finches. [•] Birds that grew less due to early diet manipulation needed more trials to learn an association. [•] Early nutritional supply influenced cognitive performance lifelong in zebra finches. [Copyright &y& Elsevier]

Consistent individual differences in behaviour of animals, that is, personalities, are both widespread and widely studied, but very few studies also include cognitive traits in this context. Animal personality has recently been integrated into the pace-of-life-syndrome hypothesis, relating individual behavioural traits to life history. Variation in cognitive traits could be explained well by this theoretical framework. A risk-reward trade-off might lead to different cognitive types: Active birds that learn fast, take risks and probably have a fast lifestyle and less active, slow learning birds that are risk averse but thereby perform better in reversal learning as they probably pay more attention to external cues. We investigated the performance of zebra finches ( Taeniopygia guttata) in a cognitively challenging reversal learning task and linked this to two personality traits: activity and fearfulness. Male birds were better in reversal learning than females. While no personality-related differences occurred in the initial learning of our task, more active and fearful birds relearned the cue-reward association faster. While birds of different sex might have revealed different risk-taking strategies in the training, our findings do not reveal the expected direction of a risk-reward trade-off in the reversal learning. It seems likely that a more general and personality-related cognitive ability might improve performance across different tasks. The linkage between personality and cognition documented here could hence suggest that cognitive traits are indeed part of an overall pace-of-life syndrome. [ABSTRACT FROM AUTHOR]

Migratory songbirds may navigate by extracting positional information from the geomagnetic field, potentially with a magnetic-particle-based receptor. Previous studies assessed this hypothesis experimentally by exposing birds to a strong but brief magnetic pulse aimed at remagnetizing the particles and evoking an altered behaviour. Critically, such studies were not ideally designed because they lacked an adequate sham treatment controlling for the induced electric field that is fundamentally associated with a magnetic pulse. Consequently, we designed a sham-controlled magnetic-pulse experiment, with sham and treatment pulse producing a similar induced electric field, while limiting the sham magnetic field to a value that is deemed insufficient to remagnetize particles. We tested this novel approach by pulsing more than 250 wild, migrating European robins ( Erithacus rubecula ) during two autumn seasons. After pulsing them, five traits of free-flight migratory behaviour were observed, but no effect of the pulse could be found. Notably, one of the traits, the migratory motivation of adults, was significantly affected in only one of the two study years. Considering the problem of reproducing experiments with wild animals, we recommend a multi-year approach encompassing large sample size, blinded design and built-in sham control to obtain future insights into the role of magnetic-particle-based magnetoreception in bird navigation.

Migrating birds flexibly adjust their individual migratory decisions, i.e. departing, routing and landing, based on intrinsic (e.g. energy stores) and extrinsic (e.g. landscape features and weather) factors modulating the endogenous stimuli. So far, these decisions have mostly been studied separately. Notably, we lack information on which factors landing decisions during active flight are based on. Therefore, we simultaneously recorded all three decisions in free-flying long-distance migratory songbirds in a coastal stopover area via regional-scale radio-telemetry and related them to the prevailing weather. Birds departed under favourable weather conditions resulting in specific nights with increased departure probability. Once departed, birds could either fly offshore or take a route along the coast, which was predicted by wind support. Radio-tracking revealed that departed individuals more likely interrupted their migratory endurance flight under overcast or headwind conditions. Studying departure, routing and landing decisions in concert, we highlight the importance of weather as a common driver across all migratory decisions. By radio-tracking individuals between stopovers, we provide evidence that avoidance of adverse weather conditions is an important function of stopover. Understanding how birds adjust migratory decisions and how they affect the timing of migration and survival is key to link migration performance to individual fitness., (© 2023 The Authors.)

Current evidence suggests that migratory animals extract map information from the geomagnetic field for true navigation. The sensory basis underlying this feat is elusive, but presumably involves magnetic particles. A common experimental manipulation procedure consists of pre-treating animals with a magnetic pulse, with the aim of re-magnetising particles to alter the internal representation of the external field prior to a navigation task. Although pulsing provoked deflected bearings in caged songbirds, analogous studies with free-flying songbirds yielded inconsistent results. Here, we pulsed European robins (Erithacus rubecula) at an offshore stopover site during spring migration and monitored their free-flight behaviour with a regional-scale network of radio-receiving stations. We found no pulse effect on departure probability, nocturnal departure timing departure direction or consistency of flight direction. This suggests either no use of the geomagnetic map by our birds, or that magnetic pulses do not affect the sensory system underlying geomagnetic map detection., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)

Naïve migrants reach their wintering grounds following a clock-and-compass strategy. During these inaugural migrations, birds internalise, among others, cues from the Earth's magnetic field to create a geomagnetic map, with which they navigate to destinations familiar to them on subsequent migrations. Geomagnetic map cues are thought to be sensed by a magnetic-particle-based receptor, which can be specifically affected by a magnetic pulse. Indeed, the orientation of experienced but not naïve birds was compromised after magnetic pulsing, indicating geomagnetic map use. Little is known about the importance of this putative magnetoreceptor for navigation and decision-making in free-flying migrants. Therefore, we studied in unprecedented detail how a magnetic pulse would affect departure probability, nocturnal departure timing, departure direction and consistency in flight direction over 50-100 km in experienced and naïve long-distant migrant songbirds using a large-scale radio-tracking system. Contrary to our expectations and despite a high sample size ( n total = 137) for a free-flight study, we found no significant after-effect of the magnetic pulse on the migratory traits, suggesting the geomagnetic map is not essential for the intermediate autumn migration phase. These findings warrant re-thinking about perception and use of geomagnetic maps for migratory decisions within a sensory and ecological context.

With each trajectory taken during the ontogeny of an individual, the number of optional behavioural phenotypes that can be expressed across its life span is reduced. The initial range of phenotypic plasticity is largely determined by the genetic material/composition of the gametes whereas interacting with the given environment shapes individuals to adapt to/cope with specific demands. In mammalian species, the phenotype is shaped as the foetus grows, depending on the environment in the uterus, which in turn depends on the outer environment the mother experiences during pregnancy. After birth, a complex interaction between innate constitution and environmental conditions shapes individual lifetime trajectories, bringing about a wide range of diversity among individual subjects. In laboratory mice inbreeding has been systematically induced in order to reduce the genetic variability between experimental subjects. In addition, within most laboratories conducting behavioural phenotyping with mice, breeding and housing conditions are highly standardised. Despite such standardisation efforts a considerable amount of variability persists in the behaviour of mice. There is good evidence that phenotypic variation is not merely random but might involve individual specific behavioural patterns consistent over time. In order to understand the mechanisms and the possible adaptive value of the maintenance of individuality we review the emergence of behavioural phenotypes over the course of the life of (laboratory) mice. We present a literature review summarizing developmental stages of behavioural development of mice along with three illustrative case studies. We conclude that the accumulation of environmental differences and experiences lead to a "mouse individuality" that becomes increasingly stable over the lifetime.