Oenanthe Oenanthe Research Articles

The role of ketogenesis in the migratory fattening of the northern wheatear Oenanthe oenanthe.

The fuelling capacity of migratory birds and their ability to avoid health conditions derived from the subsequent fat overload are exceptional among vertebrates. In this work, we screen the expression of the genes involved in the production of ketone bodies (KB) in the liver of northern wheatears (Oenanthe oenanthe) during the development and resolution of migratory fattening. Thirteen genes were found to be regulated among the migratory stages. Based on the dynamics of gene expression, we concluded that KB play a versatile role in wheatears' energy metabolism homeostasis. The ketogenic pathway can adaptively: (i) provide carbon equivalents for lipogenesis, speeding up fuelling; (ii) replace glucose during long-distance flights using lipids as the substrate; (iii) act as a floodgate to avoid steatosis; and (iv) might provide a metabolic solution to defatting in captive birds.

Changes in fat mass affect the motivation to migrate in northern wheatears

To fuel their migratory endurance flights, most birds accumulate large quantities of fat prior to departure. It therefore seems logical that the decision to depart on a migratory flight depends on fuel stores, at least to some extent; very small fuel stores prohibit migratory endurance flight. However, studies linking migrants' estimated fuel stores (or sometimes actual fat stores) to departure likelihood or to migratory restlessness measured in captive birds (an accurate proxy for migrants' motivation to depart from stopover) have provided inconsistent results. Fuel stores are not static though, but highly dynamic. Instead of investigating fuel stores at a given time, we therefore focussed on quantifying the dynamic process of fuelling and how it affects migrants' motivation to depart. We did so by temporarily caging wild northern wheatears Oenanthe oenanthe at a stopover site during autumn migration. Birds were kept under controlled conditions, receiving ad libitum food. Changes in fat mass (measured by quantitative magnetic resonance) and migratory restlessness were closely monitored. We found that the change in fat mass was a good predictor of the change in migratory restlessness. Individuals accumulating little fat did not show much change in their restlessness, while individuals accumulating much fat showed a strong increase in restlessness. Our study therewith provides clear support for the idea that fat stores affect birds' motivation to migrate, and shows that for migrating birds, increasing fat stores are an important cue to depart from stopover. Fat accumulation affected the change in migratory restlessness in the same manner for relatively lean and relatively fat birds. Additionally, food intake or changes therein did not explain the change in migratory restlessness we observed. We therefore hypothesize that the fat tissue itself signals changes in energetic state, likely through production and release of hormones, affecting birds' motivation to migrate.

Historical links between breeding Northern Wheatears Oenanthe oenanthe and European Rabbits Oryctolagus cuniculus warrens in southeast England

ABSTRACT A former breeding population of Northern Wheatears Oenanthe oenanthe in the downs of southern England is frequently mentioned in early modern sources from 1529 to 1772 CE. The south of England also seems to have been the first inland area in Britain where European Rabbits Oryctolagus cuniculus were successfully kept away from the coast. There is textual evidence that Northern Wheatears were exploiting newly established Rabbit warrens as nests and foraging sites.

A Revised and Improved Version of the Northern Wheatear (Oenanthe oenanthe) Transcriptome

This work presents an updated and more complete version of the transcriptome of a long-distance migrant, the Northern Wheatear (Oenanthe oenanthe). The improved transcriptome was produced from the independent mRNA sequencing of adipose tissue, brain, intestines, liver, skin, and muscle tissues sampled during the autumnal migratory season. This new transcriptome has better sequencing coverage and is more representative of the species’ migratory phenotype. We assembled 20,248 transcripts grouped into 16,430 genes, from which 78% were successfully annotated. All the standard assembly quality parameters were improved in the second transcriptome version.

Female-Biased Adult Sex Ratio in Relation to Sex-Specific Adult and First-Year Survival, Fledgling Sex Ratio and Dispersal in a Migratory Passerine

The relative number of adult males to females in a population, the adult sex ratio (ASR), is an important demographic variable in populations, which plays a role in, for instance, mating systems and viability of populations. The origins of variation in ASR between populations are often unclear. A skewed ASR in a local population may result from a skewed sex ratio among fledglings, sex differences in survival or dispersal or a combination of these. Meta-analyses show that ASRs across bird species are mostly male-biased and that male-biased survival is the main contributor to this bias. Here, we examine the origins of a female-biased ASR in a small population (3–24 breeding females in 2007–2017) of a passerine, the Northern Wheatear Oenanthe oenanthe. Because 95% of all fledglings were sexed, 88% of the individuals were colour-banded and because this species is highly philopatric, we could accurately examine: (1) fledgling sex ratio, (2) sex-specific first year and adult apparent survival and (3) sex-specific dispersal. It appeared that survival was not sex-biased for either age cohort but that fledgling sex ratio was male-biased, especially so among late broods. In addition, natal dispersal out of the breeding population was likely male-biased, in contrast to the general pattern of female-bias in avian dispersal. So, perhaps females are more common in our relict population solely because more males disperse from the population than females, without being compensated by male-biased fledgling sex ratio or survival and without compensation from immigrating males. Likely, the population sex ratio (including both adults and young) at the end of the breeding season is male-biased, because of a pronounced male-biased sex ratio among fledglings from late nests. Perhaps this male-bias induces prospecting young males to settle elsewhere to avoid competition next year, but at the same time convinces prospecting females to settle particularly in this area.

Why we should care about movements: Using spatially explicit integrated population models to assess habitat source-sink dynamics.

Assessing the source–sink status of populations and habitats is of major importance for understanding population dynamics and for the management of natural populations. Sources produce a net surplus of individuals (per capita contribution to the metapopulation > 1) and will be the main contributors for self‐sustaining populations, whereas sinks produce a deficit (contribution < 1). However, making these types of assessments is generally hindered by the problem of separating mortality from permanent emigration, especially when survival probabilities as well as moved distances are habitat‐specific.To address this long‐standing issue, we propose a spatial multi‐event integrated population model (IPM) that incorporates habitat‐specific dispersal distances of individuals. Using information about local movements, this IPM adjusts survival estimates for emigration outside the study area.Analysing 24 years of data on a farmland passerine (the northern wheatear Oenanthe oenanthe), we assessed habitat‐specific contributions, and hence the source–sink status and temporal variation of two key breeding habitats, while accounting for habitat‐ and sex‐specific local dispersal distances of juveniles and adults. We then examined the sensitivity of the source–sink analysis by comparing results with and without accounting for these local movements.Estimates of first‐year survival, and consequently habitat‐specific contributions, were higher when local movement data were included. The consequences from including movement data were sex specific, with contribution shifting from sink to likely source in one habitat for males, and previously noted habitat differences for females disappearing.Assessing the source–sink status of habitats is extremely challenging. We show that our spatial IPM accounting for local movements can reduce biases in estimates of the contribution by different habitats, and thus reduce the overestimation of the occurrence of sink habitats. This approach allows combining all available data on demographic rates and movements, which will allow better assessment of source–sink dynamics and better informed conservation interventions.

Time available for moulting shapes inter- and intra-specific variability in post-juvenile moult extent in wheatears (genus Oenanthe)

Moult is a vital and endogenously controlled process in the avian life. However, birds may modulate their feather renovation properties, such as the extent of moult, based on exogenous factors. Despite the large body of knowledge about moult patterns, numerous questions remain unclear. In this study, we aimed to improve our knowledge about the factors that affect variation in the extent of the post-juvenile moult in passerines by performing inter- and intra-specific comparative analyses. We assessed the effect of internal and external factors on passerines’ moult by comparing post-juvenile moult extent among 16 wheatear species (genus Oenanthe) from the Palearctic Ecozone. The tested factors included migration distance used as a proxy of time available for moulting and habitat type. We also explored the relationship between the extent of the moult, migration distance, and sex in the Northern Wheatear Oenanthe oenanthe across a latitudinal gradient in Western Europe. The results indicate that post-juvenile moult extent in wheatears was negatively related to migration distance, such that species with shorter migration distances moult extensively compared to long-distance migratory species. In contrast, the extent of post-juvenile moult in the Oenanthe genus was not related to preferred habitat type (arid or non-arid) of the species. Migration distance was also related to post-juvenile moult extent in the Northern Wheatear, with fewer renewed feathers in northern populations. However, the extent of the post-juvenile moult did not differ between sexes. Thus, our results support that time constraints affect moult extent in long-distance migratory species and populations.

Temperature change is an important departure cue in nocturnal migrants: controlled experiments with wild-caught birds in a proof-of-concept study.

The decision-making process of migrating birds at stopover sites is a complex interplay of the innate migration program and both intrinsic and extrinsic factors. While it is well studied how variation in precipitation, wind and air pressure influence this process, there is less evidence of the effects of temperature changes on the departure decision. Thus, we lack knowledge on how the predicted changes due to global climate change in temperature alone may affect the decision-making process during migration. Aiming to fill parts of this gap, we conducted a proof-of-concept study by manipulating the ambient temperature of temporarily confined wild-caught migrant songbirds under constant feeding conditions. In spring, departure probability increased with a 20°C rise in temperature for both a medium-distance migrant (European robin, Erithacus rubecula) and a long-distance migrant (northern wheatear, Oenanthe oenanthe), and in autumn, departure probabilities of the long-distance migrant both decreased with a 20°C rise and increased with a 20°C drop. Consequently, the temperature is an important departure cue influencing the decision-making process of migrating songbirds. Incorporating causal relationships between changes in temperature and departure probability in migration models could substantially improve our ability to predict the effects of climate change on the phenology of migratory birds.

The Shetland Bird Survey: population trends for widespread breeding birds 2002–2019

ABSTRACT Capsule Population trends are estimated for the first time for 12 species based on Shetland Breeding Bird Survey data collected between 2002 and 2019. Aim To provide population trends for a selection of commoner breeding waders and passerines on the Shetland Isles, the most northerly region of the UK, which has historically been under-represented in national bird monitoring schemes. Methods One hundred and forty-five self-selected 1-km2 squares were surveyed between 2002 and 2019 using similar methods to the BTO/JNCC/RSPB Breeding Bird Survey (BBS), the main breeding bird monitoring scheme in the UK. Results Over 17 years, Eurasian Oystercatcher Haematopus ostralegus, Northern Lapwing Vanellus vanellus, and Common Redshank Tringa totanus populations declined whilst Eurasian Curlew Numenius arquata and Common Snipe Gallinago gallinago showed no significant changes in their population trends. For passerines, Common Skylark Alauda arvensis and Northern Wheatear Oenanthe oenanthe populations declined, whilst Common Starling Sturnus vulgaris, Common Blackbird Turdus merula, and House Sparrow Passer domesticus increased. Winter Wren Troglodytes troglodytes and Meadow Pipit Anthus pratensis showed no significant population changes. Comparisons with BBS trends for the UK and for Scotland are provided. For Eurasian Curlew, Common Starling, and House Sparrow, trends were more favourable in Shetland than elsewhere in UK. Conclusion The Shetland Breeding Bird Survey provides useful trends for several bird species, which include important breeding numbers of Winter Wren and Common Starling (both endemic subspecies), as well as nationally important wader populations. We recommend increasing the number of survey squares sampled each year, which would increase the precision of population estimates. The inclusion of a random or stratified element to square selection would help to ensure that these trends are representative of the wider region.

Can Mitogenomes of the Northern Wheatear (Oenanthe oenanthe) Reconstruct Its Phylogeography and Reveal the Origin of Migrant Birds?

The Northern Wheatear (Oenanthe oenanthe, including the nominate and the two subspecies O. o. leucorhoa and O. o. libanotica) and the Seebohm’s Wheatear (Oenanthe seebohmi) are today regarded as two distinct species. Before, all four taxa were regarded as four subspecies of the Northern Wheatear. Their classification has exclusively been based on ecological and morphological traits, while their molecular characterization is still missing. With this study, we used next-generation sequencing to assemble 117 complete mitochondrial genomes covering O. o. oenanthe, O. o. leucorhoa and O. seebohmi. We compared the resolution power of each individual mitochondrial marker and concatenated marker sets to reconstruct the phylogeny and estimate speciation times of three taxa. Moreover, we tried to identify the origin of migratory wheatears caught on Helgoland (Germany) and on Crete (Greece). Mitogenome analysis revealed two different ancient lineages that separated around 400,000 years ago. Both lineages consisted of a mix of subspecies and species. The phylogenetic trees, as well as haplotype networks are incongruent with the present morphology-based classification. Mitogenome could not distinguish these presumed species. The genetic panmixia among present populations and taxa might be the consequence of mitochondrial introgression between ancient wheatear populations.

Microclimate affects the distribution of grassland birds, but not forest birds, in an Alpine environment

Predictions derived from species distribution models (SDMs) are strongly influenced by the spatial scale at which species and environmental data (e.g. climate) are gathered. SDMs of mountain birds usually build on large-scale temperature estimates. However, the topographic complexity of mountain areas could create microclimatic refuges which may alter species distributions at small spatial scales. To assess whether fine-scale data (temperature and/or topography) improve model performance when predicting species occurrence, we collected data on presence–absence of bird species, habitat and fine-scale temperature at survey points along an elevational gradient in the Alps (NW Italy). Large-scale temperature data, and both large- and fine-scale topography data, were extracted from online databases for each point. We compared species models (fine-scale vs large-scale) using an information-theoretic approach. Models including fine-scale temperature estimates performed better than corresponding large-scale models for all open habitat species, whereas most forest/ecotone species showed no difference between the two scales. Grassland birds such as Northern Wheatear Oenanthe oenanthe and Water Pipit Anthus spinoletta were positively associated with warmer microclimates. These results suggest that alpine grassland species are potentially more resistant to the impact of climate change than previously predicted, but that indirect effects of climate change such as habitat shifts (forest- and shrub encroachment at high elevations) pose a major threat. Therefore, active management of alpine grassland is needed to maintain open areas and to prevent potential habitat loss and fragmentation. SDMs based solely on large-scale temperatures for open habitat species in the Alps should be re-assessed.

Diel variation in corticosterone and departure decision making in migrating birds

Animals usually show distinct periods of diel activity and non-activity. Circulating baseline levels of glucocorticoid hormones (corticosterone and cortisol) often peak just before or at the transition from the non-active to the active period of the day. This upregulation of glucocorticoids may function to mobilize stored energy and prepare an animal for increased activity. Usually, the alternation of active and non-active periods is highly predictable; however, there is one group of animals for which this is not always the case. Many otherwise diurnal birds show nocturnal activity during the migration seasons. Nocturnal migratory flights are alternated with stopover periods during which the birds refuel and rest. Stopovers vary in length, meaning that nocturnal migrants are inactive in some nights (when they continue their stopover) but extremely active in other nights (when they depart and fly throughout the night). This provides an ideal natural situation for testing whether glucocorticoids are upregulated in preparation for an increase in activity, which we used in this study. We found that in northern wheatears (Oenanthe oenanthe), corticosterone levels peaked in the few hours before sunset in birds departing from stopover that night, and, importantly, that this peak was absent in birds continuing stopover. This indicates that corticosterone is upregulated in the face of an increase in energy demands, underlining corticosterone's preparative metabolic function (energy mobilization). The timing of upregulation of corticosterone also gives a first insight in when during the day nocturnally migrating birds decide whether or not to resume migration.

Transcriptome signatures in the brain of a migratory songbird

Most of the birds's adaptations for migration have a neuroendocrine origin, triggered by changes in photoperiod and the patterns of Earth's magnetic field. Migration phenomenology has been well described in the past decades, yet the genetic structure behind it remains terra incognita. We used RNA-Seq data to investigate which biological functions are linked with the seasonal brain adaptations of a long-distance trans-continental migratory passerine, the Northern Wheatear (Oenanthe oenanthe).We sequenced the wheatear's transcriptomes at three different stages: lean birds, a characteristic phenotype before the onset of migration, during fattening, and at their maximal migratory body mass. We identified a total of 15,357 genes in the brain of wheatears, of which 84 were differentially expressed. These were mostly related to nervous tissue development, angiogenesis, ATP production, innate immune response, and antioxidant protection, as well as GABA and dopamine signalling. The expression pattern of differentially expressed genes is correlated with typical phenotypic changes before migration, such as hyperphagia, migratory restlessness, and a potential increment in the visual and spatial memory capacities. Our work points out, for future studies, biological functions found to be involved in the development of the migratory phenotype —a unique model to study the core of neural, energetic and muscular adaptations for endurance exercise.Comparison of wheatears' transcriptomic data with two other studies with similar goals shows no correlation among the trends in the gene expression. It highlights the complexity and diversity of adaptations for long-distance migration in birds.

Oxidative damage to lipids is rapidly reduced during migratory stopovers

Abstract Most migrating birds need to stopover in between flights in order to refuel. Lately, additional purposes of stopover have been suggested, including physiological recovery from metabolically demanding migratory flight. One apparently unavoidable, but harmful physiological effect of migratory flight is increased oxidative damage to lipids and proteins. We here, for the first time, tested whether migrating birds are able to reduce their oxidative damage during stopover. To be able to collect longitudinal data on a large number of individual birds, we temporarily caged wild northern wheatears, a long‐distance migrant which does not suffer stress when caged during migration. Around noon on the first and third day at stopover, the birds were blood‐sampled to determine malondialdehyde (MDA) concentration, a commonly used marker of oxidative damage to lipids. We found that MDA concentrations significantly decreased during stopover, a result unchanged when correcting for the peroxidizability of the substrate. The extent of the decrease was unrelated to the amounts of food consumed or of fuel accumulated. Our findings support the hypothesis that stopovers serve reduction of oxidative damage, warranting re‐thinking of how birds accomplish their migrations. They also highlight the need to include physiological recovery as a driver of the (temporal) organization of migration. A free Plain Language Summary can be found within the Supporting Information of this article.

Stopover departure decisions in songbirds: do long-distance migrants depart earlier and more independently of weather conditions than medium-distance migrants?

BackgroundSongbirds following distinct migration strategies (e.g. long- vs. short- to medium-distance migrants) often differ in their speed of migration during autumn and, thus, are assumed to face different time constraints. During migration, most songbird species alternate migratory flights with stopover periods. Many of them restrict these migratory flights to the night, i.e., they are nocturnal migrants. At stopover, nocturnal migrants need to select a specific night (night-to-night decision) and time of night (within-night decision) to resume migration. These departure decisions, which largely determine the speed of migration, are jointly affected by a set of intrinsic and extrinsic factors, i.e., departure cues. Here we aim to assess whether the set of intrinsic and extrinsic factors and the magnitude of their respective effects on stopover departure decisions differs between nocturnally migrating songbird species, depending on their migration strategy and associated time constraints.MethodsWe radio-tracked migrating Northern Wheatears (Oenanthe oenanthe; long-distance migrant), European robins (Erithacus rubecula) and Common Blackbirds (Turdus merula; both medium-distance migrants) during autumn stopover and analysed their night-to-night and within-night departure timing in relation to intrinsic and extrinsic factors.ResultsSpecies generally differed in their departure timing on both temporal scales, with shortest stopovers and earliest nocturnal departures in the long-distance migrant. Some factors, such as day of year, fuel load, cloud cover and crosswind, had consistent effects on stopover departure decisions in all three species. However, species differed in the effects of tailwind assistance, change in atmospheric pressure and air temperature on their stopover departure decisions. Whereas night-to-night decisions were affected by these extrinsic factors in either both or one of the medium-distance migrants, such effects were not found in the long-distance migrant.ConclusionsOur results suggest that the general timing of departures in songbirds is affected by the species-specific migration strategy and associated time constraints. Further, they imply that the assessment and usage of specific extrinsic factors, i.e., weather conditions, as departure cues is adjusted based on this migration strategy, with the long-distance migrants being least selective at departure. Other intrinsic and extrinsic factors, however, seem to be used as departure cues independent of migration strategy.

Reindeer carcasses provide foraging habitat for insectivorous birds of the alpine tundra

On August of 2016, almost an entire herd (n = 323) of wild tundra reindeer (Rangifer tarandus) was killed by lightning on Hardangervidda in southern Norway. While conducting fieldwork for another study in 2017, we opportunistically registered the occurrence and behaviour of birds on carcasses from this mass die-off. Several passerine species other than corvids were observed actively foraging on arthropods, such as blowfly (Calliphoridae sp.) adults and larvae, which are typically associated with carcass decomposition. We quantified observations of those birds, and described their foraging behaviour at the carcass site. In decreasing order of abundance, five passerine species were observed taking arthropods at the site: Meadow Pipit (Anthus pratensis), Northern Wheatear (Oenanthe oenanthe), Common Reed Bunting (Emberiza schoeniclus), Bluethroat (Luscinia svecica,), and Lapland Bunting (Calcarius lapponicus). Systematic surveys of passerines utilizing carcass sites would further our understanding of how such resources may affect behaviour and life history of various bird species.

Factors influencing plasticity in the arrival-breeding interval in a migratory species reacting to climate change.

Climate change is profoundly affecting the phenology of many species. In migratory birds, there is evidence for advances in their arrival time at the breeding ground and their timing of breeding, yet empirical studies examining the interdependence between arrival and breeding time are lacking. Hence, evidence is scarce regarding how breeding time may be adjusted via the arrival‐breeding interval to help local populations adapt to local conditions or climate change. We used long‐term data from an intensively monitored population of the northern wheatear (Oenanthe oenanthe) to examine the factors related to the length of 734 separate arrival‐to‐breeding events from 549 individual females. From 1993 to 2017, the mean arrival and egg‐laying dates advanced by approximately the same amount (~5–6 days), with considerable between‐individual variation in the arrival‐breeding interval. The arrival‐breeding interval was shorter for: (a) individuals that arrived later in the season compared to early‐arriving birds, (b) for experienced females compared to first‐year breeders, (c) as spring progressed, and (d) in later years compared to earlier ones. The influence of these factors was much larger for birds arriving earlier in the season compared to later arriving birds, with most effects on variation in the arrival‐breeding interval being absent in late‐arriving birds. Thus, in this population it appears that the timing of breeding is not constrained by arrival for early‐ to midarriving birds, but instead is dependent on local conditions after arrival. For late‐arriving birds, however, the timing of breeding appears to be influenced by arrival constraints. Hence, impacts of climate change on arrival dates and local conditions are expected to vary for different parts of the population, with potential negative impacts associated with these factors likely to differ for early‐ versus late‐arriving birds.

Breeding populations of a declining farmland bird are dependent on a burrowing, herbivorous ecosystem engineer

In recent decades, numerous farmland birds have experienced considerable population declines. The loss of nutrient-poor habitats with short vegetation due to land-use intensification, abandonment or nitrogen deposition helps account for this decrease. Soil-disturbing ecosystem engineers can naturally create short and sparsely vegetated swards with beneficial effects for biodiversity.The aim of this study is to examine the influence of the European rabbit (Oryctolagus cuniculus) as an ecosystem engineer on breeding populations of the severely declining northern wheatear (Oenanthe oenanthe) on the East Frisian Islands (Lower Saxony, northern Germany). Rabbits were found to have had a considerable influence on the structure of the dune grassland, the main breeding habitat of the wheatear: high rabbit abundance resulted in greater burrow density and more bare ground. Wheatears were also more abundant on islands with larger rabbit populations. At the plot level, wheatear abundance increased with burrow density and the cover of potential foraging habitats (short vegetation). In addition, the likelihood of nest-building increased with burrow density and decreased with vegetation height.We thoroughly investigated the dependence of the northern wheatear on large populations of the ecosystem engineer European rabbit. Through their digging and grazing activities, rabbits create two key resources for breeding wheatears: (i) sufficient burrows as potential nesting sites and (ii) the availability of short vegetation as foraging habitats.

Not just fuel: energy stores are correlated with immune function and oxidative damage in a long-distance migrant.

In many animals, catabolic and anabolic periods are temporally separated. Migratory birds alternate energy expenditure during flight with energy accumulation during stopover. The size of the energy stores at stopover affects the decision to resume migration and thus the temporal organization of migration. We now provide data suggesting that it is not only the size of the energy stores per se that may influence migration scheduling, but also the physiological consequences of flying. In two subspecies of the northern wheatear Oenanthe oenanthe, a long-distance migrant, estimated energy stores at a stopover during autumn migration were positively related with both constitutive innate and acquired immune function, and negatively related with oxidative damage to lipids. In other words, migrants’ physiological condition was associated with their energetic condition. Although time spent at stopover before sampling may have contributed to this relationship, our results suggest that migrants have to trade-off the depletion of energy stores during flight with incurring physiological costs. This will affect migrants’ decisions when to start and when to terminate a migratory flight. The physiological costs associated with the depletion of energy stores may also help explaining why migrants often arrive at and depart from stopover sites with larger energy stores than expected. We propose that studies on the role of energy stores as drivers of the temporal organization of (avian) migration need to consider physiological condition, such as immunological and oxidative states.

Stopover departure decisions in autumn are not associated with constitutive immune function in Northern Wheatears Oenanthe oenanthe

Stopover periods in between migratory flights determine the speed of migration and as such may affect birds’ fitness. The decision to leave a stopover site is affected by, for example, energy stores and weather conditions. We investigated whether immunological state influences autumn stopover departure decisions in Northern Wheatear (Oenanthe oenanthe), a nocturnal long-distance migrant. We measured three parameters of constitutive immune function: microbial killing capacity, haptoglobin, and total immunoglobulins. None of them explained variation in departure probability, minimum stopover duration, or departure time within the night. Thus, we did not find an effect of the birds’ immunological state on stopover departure decisions.