Biology subjects

Schmaljohann, H.

Publications and source records attributed to Schmaljohann, H..

5 recordsLinked to original sources

bioRxiv2026

The road to nowhere: geolocation-by-genotype traces large-scale yellow-browed warbler vagrancy to central Siberia

Vagrant animals - individuals found far outside their normal range - offer powerful natural experiments for understanding migratory mechanisms. The yellow-browed warbler (Phylloscopus inornatus) provides perhaps the best-yet example, typically migrating from Siberia to South/Southeast Asia yet found in increasingly large numbers in Western Europe. This represents a strikingly unresolved evolutionary puzzle: why do so many migrants consistently move in almost the complete wrong direction? A critical first step toward solving this enigma is determining where these birds come from. If vagrants came from the proximal western range edge this would imply simple disorientation, whilst a more easterly origin could imply large-scale reverse misorientation. Here, we develop a geolocation-by-genotype algorithm for low-coverage whole-genome resequencing data collected from feathers. Our method identifies spatially informative SNPs; clusters them to account for covariance in allele frequency through space; and employs a bootstrapped maximum-likelihood framework to estimate spatial origin with uncertainty. Applied to more than 80 European-caught birds, our results place their origin in central Siberia (118{degrees}E; 89-134{degrees}E [95% CI]); over 2000km east of the western range edge. These results suggest mass misorientation in a near-reverse direction, and highlight the yellow-browed warbler as an exceptional system for probing the mechanism, ontogeny and evolution of migration.

animal behavior and cognition↗

bioRxiv2026

Stopover departure decisions and movement patterns of migratory bats during autumn migration

Migrating bats alternate between stopover periods and directed flights. When departing from a stopover site, bats select the night, the specific time within the night, and the flight direction to resume migration. Despite their ecological importance, the factors shaping these stopover departure decisions remain poorly understood. To identify the intrinsic and environmental factors driving departure decisions and movement patterns, we tagged Nathusius pipistrelles Pipistrellus nathusii at three coastal locations in the Netherlands and tracked 178 individuals during autumn migration, using the MOTUS Wildlife Tracking System. We examined movement patterns and analysed departure probability in relation to a set of individual and environmental covariates in a Bayesian capture-recapture model in state-space formulation. Additionally, we modelled within-night variation in departure timing. Seasonal patterns were strongly influenced by reproductive behaviour, with decreased migration probability during the mating period. Regardless of their seasonal timing, bats departed under moderate tailwinds and dry conditions, optimizing energy efficiency, while avoiding crosswinds and cloud cover, enhancing navigational safety. Most individuals departed shortly after sunset, whereas headwinds delayed nocturnal departure. Movement patterns were diverse, including migration towards lower latitudes, coastal barrier movements, and long-distance roundtrips, suggesting the use of multiple movement strategies. Our study demonstrates that migration patterns in bats emerge from the interaction between intrinsic factors and external conditions, and highlights the importance of both energy efficiency and safety in shaping stopover departure decisions. The presence of multiple movement strategies complicates predictions of spatiotemporal occurrence, emphasising the need to account for behavioural variability in conservation planning, for example in the context of wind energy developments.

ecology↗

bioRxiv2023

Dispersal in Kentish plovers (Charadrius alexandrinus): Adult females perform furthest movements

Dispersal is an important behavioural process that plays a significant role in, among others, speciation, population viability, and individual fitness. Despite progress in avian dispersal research, there are still many knowledge gaps. For example, it is of interest to study how movement propensity (i.e., nomadic vs. philopatric) relates to age- and/or sex-specific patterns of dispersal. Here, we investigated the role of sex and life-stage on natal (i.e., displacement between birth site and first breeding site) and breeding dispersal (i.e., displacement between sequential breeding sites) in the Kentish plover (Charadrius alexandrinus). This small and inconspicuous wader is characterised by flexible mating behaviour that includes monogamy, and serial polygyandry. Using a continent-wide dataset of ringing and re-encounter data throughout the species range in Europe, we found that adult females generally dispersed further than adult males between seasons, but we detected no sex-difference in natal dispersal distances and no general difference between natal and breeding dispersal distances. Furthermore, females were the main group exhibiting long-distance breeding dispersal, which we defined as breeding movements greater than [≥]108 km (i.e., upper 10% percentile of our dataset). Our work detected two females breeding in the Mediterranean before dispersing and breeding at the North Sea in the subsequent year, distances of 1,290 and 1,704 km, respectively - this represents the longest known breeding dispersal within the genus Charadrius. The long-distance dispersal records we identified are consistent with low genetic differentiation between mainland populations shown in previous work. The dispersive nature of the Kentish plover is likely attributed to its breeding behaviour: polyandrous females exhibit extensive mate searching and habitat prospecting. We recommend that the dispersal traits of Kentish plover be incorporated into the species conservation and management planning to more accurately inform models of population connectivity and metapopulation dynamics.

animal behavior and cognition↗

bioRxiv2022

Inherited geomagnetic signposts can maintain migratory detours in changing geomagnetic landscapes

BackgroundFor many migratory species, inexperienced (naive) individuals reach remote nonbreeding areas independently using one or more inherited compass headings and, potentially, magnetic signposts to gauge where to switch between compass headings. Inherited magnetic-based migratory orientation programs have not yet been assessed as a population-level process, particularly where strong geomagnetic spatial gradients or long-term shifts could create mismatches with inherited magnetic headings. In particular, it remains unstudied whether and how, under natural selection, inherited headings and signposts could potentially adapt to long-term geomagnetic shifts. MethodsTo address these unknowns, we modelled bird migration using an evolutionary algorithm incorporating global geomagnetic data (1900-2023). Modelled population mixing incorporated both natal dispersal and trans-generational inheritance of magnetic headings and signposts, the latter including intrinsic (stochastic) variability. Using the model, we assessed robustness of signposted and non-signposted trans-hemispheric songbird migration across a rapidly magnetically-shifting Nearctic breeding region (mean 34{degrees} declination shift) via Europe to Africa. ResultsModel-evolved magnetic-signposted migration was (i) overall successful throughout the 124-year period, with 60-90% mean successful arrival across a broad range in plausible compass precision, (ii) through reduced trans-Atlantic flight distances, up to twice as successful compared with non-signposted migration, but (iii) to avoid evolving unsustainable open-ocean flights, intrinsic variability in inheritance of magnetic headings was required (model-evolved {sigma} {approx} 2.6{degrees} standard error in inherited headings). ConclusionsOur study supports the potential long-term viability of inherited magnetic migratory headings and signposts, and illustrates more generally how inherited migratory programs can both mediate and constrain evolution of routes, in response to global environmental change.

ecology↗

bioRxiv2022

A magnetic pulse does not affect free-flight navigation behaviour of a medium-distance songbird migrant in spring

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. This aims at re-magnetising particles to alter the internal representation of the external field prior to a navigation task. While pulsing provoked deflected bearings in laboratory experiments, analogous studies with free-flying songbirds yielded inconsistent results. Here, we pulsed European robins (Erithacus rubecula), being medium-distance migrants, at an offshore stopover site during spring migration and monitored their free-flight behaviour with a regional-scale tracking system. We found no pulse effect on departure probability, nocturnal departure timing, or departure direction, in agreement with results on a long-distance migrant released at the same site in autumn. This necessitates a reassessment of the importance of geomagnetic maps for migratory decisions for free-flying birds. Summary statementMagnetic pulse pre-treatment disturbs geomagnetic map usage of birds in lab environments. However, our free-flying birds show no effect, suggesting geomagnetic map information is less important in the natural environment.

animal behavior and cognition↗