Movement of juvenile migratory birds from settlement to adulthood across the non-breeding range.

Among migratory vertebrates, high levels of fidelity to non-breeding sites during adulthood are common. If occupied sites vary in quality, strong site fidelity can have profound consequences for individual fitness and population demography. Given the prevalence of adult site fidelity, the regions of the non-breeding range to which juveniles first migrate, and the scale of any subsequent movements, are likely to be pivotal in shaping distributions and demographic processes across population ranges.

Annual Schedule Adjustment by a Long-Distance Migratory Bird.

AbstractMatching the timing of annual cycle events with the required resources can have crucial consequences for individual fitness. But as the annual cycle is composed of sequential events, a delay at any point may be carried over to the subsequent stage (or more, in a domino effect) and negatively influence individual performance. To investigate how migratory animals navigate their annual schedule and where and when it may be adjusted, we used full annual cycle data on 38 Icelandic whimbrels () tracked over 7 years-a subspecies that typically performs long-distance migrations to West Africa.

Effects of pair migratory behavior on breeding phenology and success in a partially migratory shorebird population.

In migratory systems, variation in individual phenology can arise through differences in individual migratory behaviors, and this may be particularly apparent in partial migrant systems, where migrant and resident individuals are present within the same population. Links between breeding phenology and migratory behavior or success are generally investigated at the individual level. However, for breeding phenology in particular, the migratory behaviors of each member of the pair may need to be considered simultaneously, as breeding phenology will likely be constrained by timing of the pair member that arrives last, and carryover effects on breeding success may vary depending on whether pair members share the same migratory behavior or not.

Barriers and bridges for sustaining functional habitat networks: A macroecological system analysis of wet grassland landscapes.

This study aims at supporting the maintenance of representative functional habitat networks as green infrastructure for biodiversity conservation through transdisciplinary macroecological analyses of wet grassland landscapes and their stewardship systems. We chose ten north European wet grassland case study landscapes from Iceland and the Netherlands in the west to Lithuania and Belarus in the east. We combine expert experiences for 20-30 years, comparative studies made 2011-2017, and longitudinal analyses spanning >70 years.

Why do earlier-arriving migratory birds have better breeding success?

In migratory birds, early arrival on breeding sites is typically associated with greater breeding success, but the mechanisms driving these benefits are rarely known. One mechanism through which greater breeding success among early arrivers can potentially be achieved is the increased time available for replacement clutches following nest loss. However, the contribution of replacement clutches to breeding success will depend on seasonal variation in nest survival rates, and the consequences for juvenile recruitment of hatching at different times in the season.

Mechanisms driving phenological and range change in migratory species.

Many migratory systems are changing rapidly in space and time, and these changes present challenges for conservation. Changes in local abundance and site occupancy across species' ranges have raised concerns over the efficacy of the existing protected area networks, while changes in phenology can potentially create mismatches in the timing of annual events with the availability of key resources. These changes could arise either through individuals shifting in space and time or through generational shifts in the frequency of individuals using different locations or on differing migratory schedules.

Linking warming effects on phenology, demography, and range expansion in a migratory bird population.

Phenological changes in response to climate change have been recorded in many taxa, but the population-level consequences of these changes are largely unknown. If phenological change influences demography, it may underpin the changes in range size and distribution that have been associated with climate change in many species. Over the last century, Icelandic black-tailed godwits () have increased 10-fold in numbers, and their breeding range has expanded throughout lowland Iceland, but the environmental and demographic drivers of this expansion remain unknown.

Very rapid long-distance sea crossing by a migratory bird.

Landbirds undertaking within-continent migrations have the possibility to stop en route, but most long-distance migrants must also undertake large non-stop sea crossings, the length of which can vary greatly. For shorebirds migrating from Iceland to West Africa, the shortest route would involve one of the longest continuous sea crossings while alternative, mostly overland, routes are available. Using geolocators to track the migration of Icelandic whimbrels (Numenius phaeopus), we show that they can complete a round-trip of 11,000 km making two non-stop sea crossings and flying at speeds of up to 24 m s(−1); one of the fastest recorded for shorebirds flying over the ocean.

The Effects of Habitat Type and Volcanic Eruptions on the Breeding Demography of Icelandic Whimbrels Numenius phaeopus.

Distinct preference of species for habitats is most often driven by long term differences in demographic rates between habitats. Estimating variation in those rates is key for developing successful conservation strategies. Stochastic events can interact with underlying variation in habitat quality in regulating demography but the opportunities to explore such interactions are rare.

Ecosystem recharge by volcanic dust drives broad-scale variation in bird abundance.

Across the globe, deserts and volcanic eruptions produce large volumes of atmospheric dust, and the amount of dust is predicted to increase with global warming. The effects of long-distance airborne dust inputs on ecosystem productivity are potentially far-reaching but have primarily been measured in soil and plants. Airborne dust could also drive distribution and abundance at higher trophic levels, but opportunities to explore these relationships are rare.

Why is timing of bird migration advancing when individuals are not?

Recent advances in spring arrival dates have been reported in many migratory species but the mechanism driving these advances is unknown. As population declines are most widely reported in species that are not advancing migration, there is an urgent need to identify the mechanisms facilitating and constraining these advances. Individual plasticity in timing of migration in response to changing climatic conditions is commonly proposed to drive these advances but plasticity in individual migratory timings is rarely observed.

Relationships between Long-Term Demography and Weather in a Sub-Arctic Population of Common Eider.

Effects of local weather on individuals and populations are key drivers of wildlife responses to climatic changes. However, studies often do not last long enough to identify weather conditions that influence demographic processes, or to capture rare but extreme weather events at appropriate scales. In Iceland, farmers collect nest down of wild common eider Somateria mollissima and many farmers count nests within colonies annually, which reflects annual variation in the number of breeding females.

Sex-biases in distribution and resource use at different spatial scales in a migratory shorebird.

In migratory species, sexual size dimorphism can mean differing energetic requirements for males and females. Differences in the costs of migration and in the environmental conditions occurring throughout the range may therefore result in sex-biases in distribution and resource use at different spatial scales. In order to identify the scale at which sexual segregation operates, and thus the scale at which environmental changes may have sex-biased impacts, we use range-wide tracking of individually color-ringed Icelandic black-tailed godwits (Limosa limosa islandica) to quantify sexual segregation at scales ranging from the occupation of sites throughout the non-breeding range to within-site differences in distribution and resource use.

Costs, benefits, and fitness consequences of different migratory strategies.

The relative fitness of individuals across a population can shape distributions and drive population growth rates. Migratory species often winter over large geographic ranges, and individuals in different locations experience very different environmental conditions, including different migration costs, which can potentially create fitness inequalities. Here we used energetics models to quantify the trade-offs experienced by a migratory shorebird species at locations throughout the nonbreeding range, and the associated consequences for migratory performance, survival, and breeding habitat quality.

Sex promotes spatial and dietary segregation in a migratory shorebird during the non-breeding season.

Several expressions of sexual segregation have been described in animals, especially in those exhibiting conspicuous dimorphism. Outside the breeding season, segregation has been mostly attributed to size or age-mediated dominance or to trophic niche divergence. Regardless of the recognized implications for population dynamics, the ecological causes and consequences of sexual segregation are still poorly understood.

Rapid changes in phenotype distribution during range expansion in a migratory bird.

The capacity of species to track changing environmental conditions is a key component of population and range changes in response to environmental change. High levels of local adaptation may constrain expansion into new locations, while the relative fitness of dispersing individuals will influence subsequent population growth. However, opportunities to explore such processes are rare, particularly at scales relevant to species-based conservation strategies.

When density dependence is not instantaneous: theoretical developments and management implications.

Most organisms live in changing environments or do not use the same resources at different stages of their lives or in different seasons. As a result, density dependence will affect populations differently at different times. Such sequential density dependence generates markedly different population responses compared to the unrealistic assumption that all events occur simultaneously.

Why do female migratory birds arrive later than males?

1. In migratory birds males tend to arrive first on breeding grounds, except in sex-role reversed species. The two most common explanations are the rank advantage hypothesis, in which male-male competition for breeding sites drives stronger selection for early arrival in males than females, and the mate opportunity hypothesis, which relies on sexual selection, as early arrival improves prospects of mate acquisition more for males than for females.

Population-scale drivers of individual arrival times in migratory birds.

1. In migratory species, early arrival on the breeding grounds can often enhance breeding success. Timing of spring migration is therefore a key process that is likely to be influenced both by factors specific to individuals, such as the quality of winter and breeding locations and the distance between them, and by annual variation in weather conditions before and during migration.

Seasonal matching of habitat quality and fitness in a migratory bird.

When species occupy habitats that vary in quality, choice of habitat can be critical in determining individual fitness. In most migratory species, juveniles migrate independently of their parents and must therefore choose both breeding and winter habitats. Using a unique dataset of marked black-tailed godwits (Limosa limosa islandica) tracked throughout their migratory range, combined with analyses of stable carbon isotope ratios, we show that those individuals that occupy higher quality breeding sites also use higher quality winter sites.