Causes and Consequences of Partial Migration in a Passerine Bird

Hegemann, Arne; Marra, Peter P.; Tieleman, B. Irene

doi:10.1086/682667

Cited by 73 publications

(102 citation statements)

References 77 publications

(124 reference statements)

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“…On one hand, migration is generally thought to confer benefits in the form of increased annual survival (by achieving beneficial non‐breeding conditions), but costs in terms of decreased fecundity or time for reproduction (Greenberg and Marra ). Accordingly, migrants have higher survival than residents in some within‐species comparisons (Gillis et al , Hegemann et al ). On the other hand, migration is seen as a dangerous endeavour, and so this danger should increase with the scale and duration of migration.…”

Section: Are Long‐jump Migrants Close To the Edge?mentioning

confidence: 99%

Extreme migration and the individual quality spectrum

Conklin

Senner

Battley

et al. 2017

Journal of Avian Biology

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Costs of migration, in terms of time, energy, and mortality risk, have a strong theoretical and empirical foundation in the study of birds. We expect these costs to be most severe for extreme long‐distance migratory landbirds, whose demanding annual routines (e.g. non‐stop flights > 8000 km and return journeys > 30 000 km) may approach their maximum physiological capabilities. To explore whether this is true, we review evidence in long‐jump migratory shorebirds (Scolopacidae), focusing most on the prototypical example, the Alaska‐breeding bar‐tailed godwit Limosa lapponica baueri. Contrary to expectations, these and similar birds demonstrate high adult survival, little evidence for elevated mortality during migration, no apparent minimisation of non‐stop flight distances, and low inter‐ and intra‐individual variation in migration performance. Two key aspects of extreme migrants may explain these findings: 1) a counter‐intuitively conservative annual‐cycle strategy, which minimises risks and enables dissipation of carry‐over effects before fitness consequences arise; and 2) selection pressure during early life, which quickly removes low‐performing individuals from the population. We hypothesise that these two factors, applicable to extreme strategies in a wide range of taxa, act to truncate the range of individual quality in a population, and decrease the prevalence and detectability of carry‐over effects. Testing these hypotheses is challenging, as it requires comparative studies of demography and individual quality spectra along a continuum of extremeness. However, it has important potential implications for interpreting individual variation, designing studies of cross‐seasonal interactions or costs of migration, and recognising early‐warning signs of population decline. For example, the most extreme shorebird migrations rely on abundant but difficult‐to‐access resources; the high minimum individual performance required for survival predicts that degradation of these resource hot‐spots will propel rapid population collapse, rather than incremental declines in condition or performance. Therefore, in extreme migrants, we may paradoxically view populations as operating close to the edge, even while individuals are not.

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Section: Are Long‐jump Migrants Close To the Edge?mentioning

confidence: 99%

Extreme migration and the individual quality spectrum

Conklin

Senner

Battley

et al. 2017

Journal of Avian Biology

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“…For instance, new insights about the causes and consequences of the existence of partial migration have been gained for skylarks ( Alauda arvensis ), where wintering strategies are more related to structural body size and immune functions than to the more classical control mechanisms such as genetic dimorphism or age‐ and sex‐dependent conditions (Hegemann et al . ).…”

Section: Introductionmentioning

confidence: 97%

Animal tracking meets migration genomics: transcriptomic analysis of a partially migratory bird species

et al. 2017

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Seasonal migration is a widespread phenomenon, which is found in many different lineages of animals. This spectacular behaviour allows animals to avoid seasonally adverse environmental conditions to exploit more favourable habitats. Migration has been intensively studied in birds, which display astonishing variation in migration strategies, thus providing a powerful system for studying the ecological and evolutionary processes that shape migratory behaviour. Despite intensive research, the genetic basis of migration remains largely unknown. Here, we used state-of-the-art radio-tracking technology to characterize the migratory behaviour of a partially migratory population of European blackbirds (Turdus merula) in southern Germany. We compared gene expression of resident and migrant individuals using high-throughput transcriptomics in blood samples. Analyses of sequence variation revealed a nonsignificant genetic structure between blackbirds differing by their migratory phenotype. We detected only four differentially expressed genes between migrants and residents, which might be associated with hyperphagia, moulting and enhanced DNA replication and transcription. The most pronounced changes in gene expression occurred between migratory birds depending on when, in relation to their date of departure, blood was collected. Overall, the differentially expressed genes detected in this analysis may play crucial roles in determining the decision to migrate, or in controlling the physiological processes required for the onset of migration. These results provide new insights into, and testable hypotheses for, the molecular mechanisms controlling the migratory phenotype and its underlying physiological mechanisms in blackbirds and other migratory bird species.

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“…It follows, therefore, that in partially migratory populations residency may offer complementary fitness benefits to those offered by migration (Lundberg, ; Zúñiga et al, ). In the case of conditional strategies, these may refer to individual states such as sex or body condition (Hegemann, Marra, & Tieleman, ; Warkentin, James, & Oliphant, ), or external conditions, such as population density (Grayson & Wilbur, ) or environmental conditions (Chapman et al, ; Lack, ; Lundberg, ; Meller et al, ). Additionally, the prevalence of each strategy within a population may itself influence the relative fitness benefits conferred by either (Kokko, ; Lundberg, ).…”

Section: Introductionmentioning

confidence: 99%

Fitness consequences of different migratory strategies in partially migratory populations: A multi‐taxa meta‐analysis

Buchan

Gilroy

Catry

et al. 2019

Journal of Animal Ecology

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Partial migration—wherein migratory and non‐migratory individuals exist within the same population—represents a behavioural dimorphism; for it to persist over time, both strategies should yield equal individual fitness. This balance may be maintained through trade‐offs where migrants gain survival benefits by avoiding unfavourable conditions, while residents gain breeding benefits from early access to resources. There has been little overarching quantitative analysis of the evidence for this fitness balance. As migrants—especially long‐distance migrants—may be particularly vulnerable to environmental change, it is possible that recent anthropogenic impacts could drive shifts in fitness balances within these populations. We tested these predictions using a multi‐taxa meta‐analysis. Of 2,939 reviewed studies, 23 contained suitable information for meta‐analysis, yielding 129 effect sizes. Of these, 73% (n = 94) reported higher resident fitness, 22% (n = 28) reported higher migrant fitness, and 5% (n = 7) reported equal fitness. Once weighted for precision, we found balanced fitness benefits across the entire dataset, but a consistently higher fitness of residents over migrants in birds and herpetofauna (the best‐sampled groups). Residency benefits were generally associated with survival, not breeding success, and increased with the number of years of data over which effect sizes were calculated, suggesting deviations from fitness parity are not due to sampling artefacts. A pervasive survival benefit to residency documented in recent literature could indicate that increased exposure to threats associated with anthropogenic change faced by migrating individuals may be shifting the relative fitness balance between strategies.

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Causes and Consequences of Partial Migration in a Passerine Bird

Cited by 73 publications

References 77 publications

Extreme migration and the individual quality spectrum

Extreme migration and the individual quality spectrum

Animal tracking meets migration genomics: transcriptomic analysis of a partially migratory bird species

Fitness consequences of different migratory strategies in partially migratory populations: A multi‐taxa meta‐analysis

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