Trade-offs between shorter migration and warmer winters: carry-over effects of winter site choice in migratory shorebirds
José A. Alves1, Tomas G. Gunnarsson2,3, Daniel Hayhow1, Peter M. Potts4, William J. Sutherland5 & Jennifer A. Gill1
1 School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
2 University of Iceland, South Iceland Research Centre, Tryggvagata 36, IS-800 Selfoss, Iceland
3 Gunnarsholt, IS-851 Hella, Iceland
4 Solent Court Cottage, Chilling Lane, Warsash, Southampton SO31 9HF, UK
5 Department of Zoology, University of Cambridge, Downing St., Cambridge, CB2 3EJ
For migratory birds, timing of arrival on the breeding grounds can strongly influence breeding success through improved access to higher quality resources and breeding locations and increased numbers of potential breeding attempts. Previous studies have shown that arrival dates can be influenced by conditions during winter and/or on migration. For species that winter over large geographic and latitudinal ranges, individuals wintering in different parts of the range will encounter very different environmental conditions. The impact of these carry-over effects may therefore vary across the range, through trade-offs between winter site quality, costs of migration and the consequences for timing of arrival on the breeding grounds.
Icelandic black-tailed godwits (Limosa limosa islandica) breed almost exclusively in Iceland, but their winter distribution ranges from Britain and Ireland to the Iberian Peninsula. Individuals at different ends of the range are thus likely to experience very different environmental conditions and migration costs. Using an energetic model paramaterised for this species, we compare the net energetic benefits for Icelandic godwits wintering in three distinct sites encompassing the entire range. We then estimate the migratory costs during spring migration and assess the different wintering strategies by comparing individual arrival dates on the breeding grounds. We show that choice of winter location has huge implications for individual fitness during winter, and for strong carry-over effects into the breeding season. The inequalities in fitness arising from different wintering strategies have important implications for population dynamics and for the evolution of migratory systems.
Effect of endogenous and exogenous factors on departure decisions of sedge warblers, Acrocephalus schoenobaenus, from a stopover site during autumn migration.
Miren Andueza1, Juan Arizaga2, Eduardo J. Belda3, Emilio Barba1
1 “Cavanilles” Institute of Biodiversity and Evolutionary Biology, University of Valencia, C/ Catedrático José Beltrán 2, E-46980 Paterna, Spain.
2 Txingudi Ringing Station, Aranzadi Science Society, Alto de Zorroaga 11, E- 20014 Donostia-San Sebastián, Spain
3 IGIC, Politechnic University of Valencia, Crta. Nazaret-Oliva, s/n, E-46730 Gandía, Spain
Departure decision from a stopover site is an important aspect of bird migration, since it affects the speed and duration of the migratory journey. The factors that determine this decision can be exogenous (environmental factors) or endogenous (related with the internal circannual program). So far, the effect of these factors has been studied separately, although interactions among them are much expected. The aim of this study is the simultaneous analysis of both endo- and exogenous factors that are likely to determine the departure decisions of sedge warblers (Acrocephalus schoenobaenus) from a stopover site in northern Spain during the autumn migration period, and quantifying the relative importance of each factor in that decision. We included meteorology (rain and wind aloft, expressed as a tailwind component) and population density (expressed as number of sedge warblers captured/100 m of mist net) at the site as exogenous factors, and date, days of stay in the place, fuel load and age as endogenous factors. We estimated departure decision probability with Cormack-Jolly-Seber (CJS) models using program MARK. From the 107 models tested, only one had substantial support, according to the AIC criterion. Such model included a significant and additive effect of date, wind and population density in the area. As expected, sedge warblers were more likely to depart with high tailwind values and late in the season, but departure probability increased with decreasing population densities. The negative relationship between departure likelihood and population density was the opposite of what was expected. Possible explanations are discussed.
Current knowledge - future perspectives
Franz Bairlein
Institute of Avian Research, Wilhelmshaven, Germany
Migratory species are of particular challenge for effective conservation because of their reliance on not just intact breeding grounds but at least of similar importance on stopover sites and often far distant winter grounds. Long-distance and trans-Saharan migrants are of particular concern because their population declines during the last few decades are much more severe that those of within-Europe migrants and resident species, respectively.
For successful migration most of these long-distance migrants rely on internal energy reserves they have to accumulate before facing inhospitable areas such as sea and deserts with no feeding opportunities. In many species fuelling happens immediately before crossing ecological barriers or shortly after the obstacle to replenish used body reserves and to prepare for the continuation of migration and subsequent breeding. Thus, intact stopover sites are crucial for successful migration and overall fitness, respectively.
Habitat deterioration due to human practice and climate change will have severe impacts on staging, stopover ecology and fuelling in migratory birds, though the effects of these changes are still very speculative due to the lack of detailed studies and the uncertainty in climate models. The talk will summarize current knowledge and will emphasize several of the important issues we have to address for better understanding and effective conservation of migratory species in a changing world. Future focus should be in particular devoted to understanding spatial connectivity between breeding, stopover and wintering sites, and un-ravelling carry-over effects between the different annual life-history stages.
Silke Bauer & Lucas Jenni
Swiss Ornithological Institute
Getting to the Arctic on time: adaptive resource management of Horseshoe Crabs to protect migrating Red Knot
Nigel Clark, Phil Atkinson, Jacquie Clark, Simon Gillings & Rob Robinson
British Trust for Ornithology, Thetford, Norfolk, IP24 2PU, UK
Population-level responses of migratory birds to environmental change
School of Biological Sciences, University of East Anglia, Norwich, UK.
Large-scale environmental changes can provide the basis for the evolution of migratory behaviour, and changing environmental conditions may benefit species in some circumstances. However, current declines in many migratory bird populations may be occurring in response to on-going rapid and extensive changes in land use and resource availability. Understanding these responses to environmental changes is key to the development of appropriate conservation actions and policies, but the responses of migratory species can be particularly complex because the environmental pressures that they face may vary within and across the migratory range. The impact of environmental pressures in one season may be either exacerbated or moderated by the conditions experienced during other seasons in other parts of the migratory range. Using examples from a range of systems, I will explore the environmental changes currently influencing migratory bird populations, the factors influencing population-level responses to these changes and the importance of understanding the nature and influence of seasonal interactions in migratory systems.
Pacific traveller – the epic migration of the long-tailed cuckoo Eudynamys taitensis
Brian Gill1 & Mark Hauber2
1Auckland Museum, Private Bag 92018, Auckland, New Zealand
2Department of Psychology, Hunter College of the City University of New York, USA
Long-tailed Cuckoos (Eudynamys taitensis; 125 g) breed only in New Zealand, parasitising three species of endemic Mohoua (Pachycephalidae). After performing perhaps the most remarkable overwater migration of any land bird, cuckoos winter in a vast arc of Pacific islands extending 10,000 km from Palau (134.5°E) to Henderson Island (Pitcairn group; 128.3°W). Such an epic migration by so small a bird was originally doubted. After systematic collecting of birds on south Pacific islands by the Whitney South Sea Expedition (1920-32), a 1937 paper by Bogert established the bare details of the migration. Our study aims to reassemble data on the long-tailed cuckoo’s migration, using specimens and literature records. The sexes are alike, but immatures (spotted back, pale brown underparts) are readily distinguishable from adults (barred back, white underparts), allowing new analysis of migration dynamics in relation to age. Preliminary results show that many birds in the wintering grounds have intermediate plumage (are presumably moulting from immatures to adults). At the start of the breeding season (spring: October-December) practically all birds in New Zealand are in adult plumage. Immatures (from New Zealand) in museum collections are overwhelmingly restricted to late summer and autumn, showing that these are young of the most recent breeding season and have not retained immature plumage during a cycle of migration to the Pacific. Data also show that adults move north ahead of immatures in the autumn migration. One of the three hosts (yellowhead M. ochrocephala) is now critically endangered. This must mean that the populations of cuckoos adapted to parasitising yellowheads are endangered or extinct now, in proportion to the decline of their host. Certain Pacific islands to which the yellowhead-cuckoos migrated may now lack cuckoos.
Migratory birds and climatic change
Brian Huntley1, Michael Brooks2 & Nathalie Doswald1,3
1 School of Biological and Biomedical Sciences, Durham University, UK
2 Animal Demography Unit, University of Cape Town, South Africa
3 UNEP World Conservation Monitoring Centre, Cambridge, UK
Models were fitted to describe relationships between climate and the breeding and non-breeding distributions of 229 European breeding migratory birds, including 164 trans-Saharan migrants. The models were then used to simulate species’ potential breeding and non-breeding distributions for future climate scenarios.
To assess whether species may already be showing expected responses, data from two Southern African Bird Atlas Projects (SABAP1 and SABAP2) for 51 trans-Saharan migrants whose non-breeding ranges extend to southern Africa were used to estimate recent range changes in that region.
Simulations project a mean increase in extent of non-breeding ranges and a mean decrease in extent of breeding ranges. Both breeding and non-breeding ranges on average shift northwards, north-westward for breeding ranges and north-eastward for non-breeding ranges. Mean range centroid shift by 2025 is ca. 400 km for breeding and ca. 600 km for non-breeding ranges. These shifts result in projected ca. 25% mean increases in migratory distance. The greater shift in non-breeding range offsets the mean increase in extent resulting in mean overlaps of ca. 60% between present and future breeding and non-breeding ranges by 2025, decreasing to ca. 50% by 2085.
Those species whose non-breeding ranges extend to South Africa have mean projections very similar to those for all migrants. Comparison of SABAP2 and SABAP1 data shows that, over the 20 years between surveys, substantial changes have occurred. At 0·25° grid cell resolution (used by SABAP1) range extent in southern Africa has on average decreased by 50%, and the SABAP2 and SABAP1 ranges overlap by only 28% on average. Even when aggregated to the 1° grid used for modelling, mean range extent decrease is 35% and overlap only 53%. Centroids of ranges within southern Africa have shifted by a mean of ca. 90 km in a north-easterly direction. Mean rate of centroid shift, at ca. 4·5 km yr-1, is comparable to published results, but only ca. 35% of projected rates of centroid shift; this discrepancy also is comparable to that reported by previous studies.
Visual comparison of projected and observed range changes shows similar patterns for most species, 28 having a good or fair match between observed and projected patterns of change. Only 9 species show a poor match, the majority being species associated with wetlands. As in previous studies comparing model projections with observations, results indicate that model projections generally are robust and consistent with observations.
Amongst the implications of the projected changes in location of species’ breeding and non-breeding ranges is potential for species to change their migratory strategy in response to climatic change. Up to 40% of species that currently are exclusively trans-Saharan migrants have potential non-breeding areas north of the Sahara by 2025, whilst > 55% of short-distance migrants have increased areas that they potentially may occupy throughout both breeding and non-breeding seasons. Whilst such upheavals to migration strategies probably also occurred in the past in response to the climatic upheavals of the late-Quaternary, the rate of current changes appears to be out-stripping species’ ability to respond.
The science and the art of international action planning for migratory birds
Tim Jones
DJEnvironmental, Harpers Mill, Sterridge Valley, Berrynarbor, Ilfracombe, Devon, EX34 9TB, United Kingdom
International collaboration to develop and implement action plans for the conservation of migratory birds has developed enormously over the last 30 years. There is no ‘one-size-fits-all’ approach, with a variety of models being followed for different groups/species and in different regions of the world. Some action plans have been developed within intergovernmental frameworks, such as the Convention on Migratory Species (CMS) and its daughter Agreements. Other processes have been much more informal and primarily non-governmental in nature. Action plans may cover singles species, certain populations of a species, or whole groups of species. They may extend to entire flyways covering many countries, or be restricted to bilateral cooperation.
Much of the early work focused on waterbirds, especially Anatidae and Scolopacidae but increasingly action plans are being drawn up to cover species from other families, including migratory seabirds, raptors and passerines.
Whatever the model of action plan followed, writing the plan – and even agreeing it with the key stakeholders – is just the first step. Implementation is the acid test. Experience shows that successful international action planning needs:
- a strong science base
- a clear platform/mechanism for collaboration
- a participatory process
- effective leadership and coordination
- adequate and stable resourcing
- clear objectives, targets and indicators of success
- effective monitoring and evaluation
- periodic review
It is particularly important to recognise that scientific and technical merit alone are insufficient to deliver a successful action plan, and that neither ‘soft’ nor binding international law can guarantee implementation. The ‘art’ of international action planning depends on integrating these more tangible characteristics with cooperation, commitment, enthusiasm, mutual respect and shared will. International NGOs such as BirdLife International, Wetlands International (and their predecessor organizations) have played a key role in helping to ensure that these disparate elements are brought together in a way capable of delivering concrete conservation outcomes.
Examples will be drawn inter alia from the International Single Species Action Plans (SSAPs) for Lesser White-fronted Goose Anser erythropus and Sociable Lapwing Vanellus gregarius, both established under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), in the framework of the CMS and adopted by the Range States in 2008 and 2004 respectively (the latter plan currently undergoing revision); as well as from bilateral and multilateral processes in the Americas and Asia-Pacific.
What we know about raptor migration within South America
Matias A. Juhant
University of Maribor, Slovenia
Although South America has the world’s richest avifauna, the migration of birds within the continent is largely unknown. Raptors are a good example of how little we know. Most studies of raptor migration have been made in North America, Europe and Asia, while few studies have been made in South America. Ninety-six species of raptors are found in the continent, 43 of which migrate in part of their range (45%). Five species are complete migrants, 22 partial migrants and 16 irruptive or local migrants. These migratory species correspond to three migration systems: Nearctic-Neotropical; Intratropical; and Austral-Neotropical. The raptor migration in South America is confusing and complex because there are three types of migration systems, and there are not enough data available. We do not have data to answer the most basic question, like when the different raptor species leave from and arrive from their breeding areas? And which are the main wintering and bottlenecks areas in South America? Only eight raptor species that migrate in the continent were studied by satellite tracking. Thirty-five watchsites are in the continent, but only two of them have available data for at least one full season-count. In this presentation, I will review our current knowledge of raptor migration in South America focusing in the Nearctic-Netropical and Austral-Neotropical migration systems, and I will suggest points where we should focus our research.
Evolution does not optimize - should we?
Hanna Kokko
Australian National University, Canberra, Australia
Modelling of partial migration in birds has progressed from simple graphical representations to sophisticated analyses that use evolutionary invasion analysis to determine how the success of the two strategies (stay year round on the breeding grounds, or migrate) can become frequency dependent. Here I build two models to relax two assumptions commonly made in models and often violated in nature: that individuals do not vary in any trait other than their migratory propensity, and that the prior residence effect (which grants priority access of good habitats to non-migrants) operates at maximum strength. The same framework can incorporate and merge aspects of various hypotheses proposed to explain partial migration (dominance, body size, arrival timing, and limited foraging opportunities), and shows that either small (subdominant) or large (dominant) individuals may emerge as the more likely migrants; the latter case occurs when it is easy for socially dominant migrants to win back prime breeding locations upon their arrival. The dynamics of territory acquisition is shown to be an important and understudied topic, as variations in the relative importance of prior residency versus resource holding power can shift a population from complete migration to complete year-round residency. These models also highlight exceptions to a tacit assumption in discussions of evolution of migration under climate change, which is that populations can decline if genetic adaptation or phenotypic plasticity do not occur fast enough. Competition can also yield the opposite pattern where adaptation itself leads to a population decline.
Mini biography: Hanna Kokko is a professor at Australian National University and an Australian Laureate Fellow. She is interested in linking individual level behaviours to their population dynamic consequences, and has studied a wide range of examples of this kind, from sexual selection to studies of sustainable harvesting. She has also authored a textbook on modelling methods in biology (Cambridge University Press).
Can we study the winter distribution of Aquatic Warblers with feather isotope analyses?
Steffen Oppel1, Deborah J. Pain1,2, Jeremy Lindsell1, Lars Lachmann1,3, Ibrahima Diop4, Cosima Tegetmeyer5, Paul F. Donald1, Guy Anderson1, Christopher G. R. Bowden1, Franziska Tanneberger5, Martin Flade6
1 Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, U.K.
2 Wildfowl and Wetlands Trust, Slimbridge, Gloucestershire GL2 7BT, U.K.
3 Polish Society for the Protection of Birds (OTOP), Ul. Odrowąża 24, 05-270 Marki, Poland
4 Parc National des Oiseaux du Djoudj, BP80, St Louis, Senegal
5 Institute of Botany and Landscape Ecology, University of Greifswald, Grimmer Str. 88, 17487 Greifswald, Germany
6 Brandenburg State Office for Environment, Dept. Large Protected Areas and Regional Development, Tramper Chaussee 2, 16225 Eberswalde, Germany
Stable isotope analysis of feathers can be useful in the study of seasonal interactions and migratory connectivity in birds. For the Palaearctic-African migration system, however, the lack of isotope data from feathers of known origin in Africa renders the geographic assignment of birds captured on European breeding grounds to potential wintering areas problematic. Rectrices of the threatened aquatic warbler (Acrocephalus paludicola) grown in Africa were sampled across six European countries to assess whether birds in different breeding populations shared similar isotopic signatures and so were likely to have wintered in the same region in Africa. Freshly grown feathers of aquatic warblers collected at the only known wintering site in Senegal showed high variation in carbon, nitrogen, and hydrogen isotope ratios. Due to similarly high variation in isotope ratios of African-grown feathers within all breeding populations, it was not possible to determine whether different populations wintered in different regions. However, isotope signatures of 20% of birds captured on European breeding grounds fell outside the range of those captured in Senegal, suggesting a wider wintering distribution than is currently known. We therefore assessed whether the origin of these feathers could be estimated by trying to establish isotopic gradients across sub-Saharan West Africa. Feathers of three ecologically similar surrogate species were sampled from wetlands across a 3000 km east-west and a 2000 km north-south transect. Within-site variation in feather isotope ratios was frequently larger than the difference predicted by gradients across West Africa. Thus, predicting the origin of individual feathers using single-isotope gradients was not reliable. The large within-site variability of feather isotope ratios of a habitat specialist species like the aquatic warbler indicates that using feather isotope ratios will require large sample sizes from many locations, and may thus not be an efficient tool in identifying wintering areas of Palaearctic-African migrants.
Directions in modelling partial migration: how adaptation can cause a population decline and why the rules of territory acquisition matter.
Urbanisation effects on migration behaviour of short-distance migratory birds
Studying birds in the context of the annual cycle: carry-over effects and seasonal interactions
Peter P. Marra
Smithsonian Conservation Biology Institute, Migratory Bird Center, National Zoological Park, WAshington DC, US
Migratory animals spend different periods of the annual cycle in geographically disparate places. For all such species, these periods are inextricably linked, such that events in one period are likely to influence events in subsequent periods that take place, in some cases, thousands of miles away. This simple fact has enormous implications for how we study and interpret facets of both the ecology and the evolution of migratory species. Such a perspective is equally important for the implementation of conservation strategies of migratory birds. Indeed, the conditions and selective pressures at winter locations are likely to affect individual performance during migration and breeding, and vice versa. Such events are likely to occur both within and between generations and thus will influence both ecological events as well as evolutionary processes. For example, the size and composition of summer populations are likely to be strongly influenced by events on the wintering grounds and simple mathematical models illustrate the effects of density-dependence on population dynamics. Events on wintering grounds are also likely to affect arrival time, body condition and reproductive readiness of individual birds on the breeding grounds. These parameters are likely to have important consequences for breeding behavior and success, natal dispersal and annual survival. In addition, the evolution of body size and plumage quality and color are all likely examples of trade-offs that can act throughout the year to drive individual traits. Unfortunately, although the importance of many of these ‘seasonal interactions’ has long been recognized, they remain poorly understood within most bird migration systems largely for two reasons. First, the majority of research on migratory birds is still focused on a single season, breeding, leaving us with an inadequate understanding of the fundamental natural history and ecology of migrant birds during other parts of their annual cycle. This is despite the fact that most migratory birds spend the majority of the year on their non-breeding grounds. Second, we have a poor understanding of migratory connectivity - how individual birds and populations are connected between specific breeding and non-breeding (migration and winter) locations.
The playing field, however, is changing rapidly. New scientific tools and techniques allow for unprecedented advances in the pace and magnitude of data collection, analysis, and modelling of animal movement. The use of satellite transmitters, geolocators, stable isotope analysis and genomics are advancing our ability to track animals throughout the annual cycle, allowing for significant improvements in our understanding of migratory connectivity and seasonal interactions. In this keynote address, I will describe through several specific examples how understanding seasonal interactions, such as carry-over effects, will greatly improve our fundamental understanding of migratory bird biology. Furthermore, I will emphasize that if we hope to implement effective conservation strategies and policies to protect wildlife species, it will be essential to study all biological phenomena in the context of the entire annual cycle.
Can we use stable isotope analyses to trace the migration of Atlantic seabirds?
Militão T.1*, González-Solís J.1,
Institut de Recerca de la Biodiversitat i Departament de Biología Animal (Vertebrats), Universitat de Barcelona. Avinguda Diagonal 645. 08028 Barcelona, Spain
Tracking devices, such as geolocators, are revealing many new aspects of the migratory dynamics of seabirds but it is often unfeasible to use them in large numbers, on non-breeding birds or on small species. In these occasions intrinsic markers, such as the analysis of stable isotope ratios on feathers, can be a useful alternative to trace migratory movements. However, in contrast with the terrestrial environment we still have insufficient sea baseline knowledge for linking isotopic signatures of different feathers to movements amongst distinct water masses. In this study we determined the carbon and nitrogen signatures on feathers from tracked birds to link specific water masses in the Atlantic Ocean to the isotopic signals in feathers. We sampled and analysed the1st primary, 8th and 13th secondary and 6th rectrice feathers in three seabird species: the great (Puffinus gravis from Gough Island), the Manx (P. Puffinus from Iceland) and the Cory’s (Calonectris diomedea borealis from Canary Islands) shearwaters. These species breed in different archipelagos but share several feeding grounds throughout the Atlantic (e.g. the Arctic Atlantic or the Patagonian shelf) in different periods of their annual cycle. Stable isotope signatures in different feathers corresponded well with the areas in which we inferred that they were grown. Thus, stable isotope analysis of feathers is a powerful tool to trace the migratory movements of seabirds in the Atlantic.
Shifts in breeding phenology in the willow warbler: implications for population trends
Catriona A. Morrison1, Robert A. Robinson2, Jacquie A. Clark2, David I. Leech2 & Jennifer A. Gill1
1School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
2British Trust for Ornithology, The Nunnery, Thetford, IP24 2PU, UK
Over the past 40 years there have been large declines in the abundance of many long-distance Afro-Palaearctic migrants which breed in Europe. While changing rainfall patterns in the Sahel region of Africa have been linked to lowered overwinter survival for some long-distance migrants, changes in productivity may also be implicated in these population declines, particularly as the population trends for several species appear to vary through the breeding range. As many of these species breed at temperate latitudes, seasonal variation in resource availability means that timing of breeding can be a key driver of productivity and ability to fine tune timing of breeding in response to these changes may play a key role in a population’s dynamics. Since the 1970s, the breeding dates of many temperate breeding bird species have advanced, and the extent of these changes has been linked to both wintering and breeding ground cues. Using data from the BTO Breeding Bird Survey and the Birdwatch Ireland Countryside Bird Survey, we show that population trends for one of Europe’s most abundant Afro-Palaearctic migrants, the willow warbler, Phylloscopus trochilus, are highly variable across Britain and Ireland. We then use data from the BTO Nest Record Scheme to investigate the extent of changes in seasonality of willow warbler breeding productivity across the UK and how these interact with changes in timing of breeding to influence patterns of population trends. Our findings suggest that advancements in laying date may be buffering population declines in some regions, but constraints on advancement of laying date may be exacerbating population declines elsewhere.
The Ecology of bird migration patterns
Ian Newton
Centre for Ecology & Hydrology, Benson Lane, Crowmarsh Gifford, Wallingford, OX10 8BB, UK
Migration in birds is often defined as a regular return movement between breeding and wintering areas. It is evident mainly in seasonal environments, whether driven by temperature or rainfall, in which food varies predictably between abundant and scarce during the course of a year. In such seasonal environments, two types of bird migratory behaviour have long been recognised, now most commonly called obligate and facultative. In obligate migration, all main aspects are viewed as under firm internal (genetic) control, with limited scope for year-to-year variation. Obligate migrants thus typically show a high degree of annual consistency in the timing, directions and distances of their migrations. For the most part, each individual behaves in the same way year after year, migrating at similar dates and for similar distances. Obligate migrants often leave their breeding areas before food-supplies collapse, their movements being ‘anticipatory’. Typically, they exploit foods which are predictably absent in the breeding areas during winter. Individuals tend to return to the same breeding areas each year, and often to the same wintering areas. Examples include those insectivorous species, such as the Pied Flycatcher and Common Cuckoo, which migrate long distances to winter in the tropics.
In contrast, facultative migration is viewed more as a direct response to prevailing conditions, especially food supplies, and the same individual may migrate in some years but not in others. It occurs in populations whose food supplies in breeding areas vary greatly from one winter to another, according to weather or other variables. Within a population, depending on prevailing conditions, the proportions of individuals that leave the breeding range, the dates they leave and the distances they travel, can vary greatly from year to year, as can the rates of progress on migration. This type of migration is typical of many partial migrants, but is most evident in so-called irruptive migrants that depend on inconsistent food sources: for example, finches that depend on sporadic tree-seed crops, or owls that depend on peaks in rodent populations.
It will be argued that the nature of migration varies with the types of food supplies to which different bird species are exposed. Regular (obligate) migration is associated with food supplies that are predictable in time and space, and is consistent in timing, direction and distance from year to year; whereas irregular (facultative) migration is associated with food supplies that – to varying degrees – are unpredictable in time and space; and is variable in timing, direction and distance from year to year. In its most extreme form, facultative migration is manifest as irruptions, and individual participants show little or no site fidelity from year to year. Both systems are adaptive, the one to conditions in which resource levels are predictable in space and time, and the other to conditions in which resource levels are unpredictable. They are best viewed not as distinct types, but as representing opposite ends of a continuum in bird migratory behaviour.
Large scale patterns of demography in Palearctic warblers
Rob Robinson, Sarah Eglington and Ali Johnston
British Trust for Ornithology, Thetford, Norfolk, IP24 2PU, UK
Over the last couple of decades there has been increasing concern over the adverse biological impacts of changing climates. Migrant species are thought to be especially vulnerable as these may be impacted by changes in multiple areas (breeding, non-breeding, stopover) and their ability to adapt to phenological change may be constrained by their need to move between breeding and non-breeding areas in response to increasingly asynchronous cues used to time these migratory journeys. Several studies have recently correlated population declines with response to increasing temperature, and further changes have been predicted using a range of climate envelope models. However, in order to fully understand the nature of these changes we need to quantify the demographic mechanisms that underlie them. We use data generated by a large-scale monitoring scheme that uses constant effort ringing to quantify changes in productivity and survival of a suite of migrant Afro-Palaearctic warblers to assess the demographic impacts of the changing climate across western Europe.
Who is who? – Olivaceous Warblers in West Africa
Volker Salewski
University of Osnabrück, Department of Behavioural Biology, Barbarastr. 11, 49076 Osnabrück, Germany
Since ornithologists correlated crashes of breeding populations of Palearctic-African long-distance migrants with droughts in the African winter quarters in the late 1960s, the awareness that the understanding of the population dynamics of migrants has to consider conditions experienced during the entire annual cycle have to be taken into account grew rapidly. This is expressed by the growing number of publications that correlate population changes as well as demographic factors like survival and/or reproduction with conditions experienced on migration or in the non-breeding staging areas. There is growing awareness that the protection of migrants needs the implementation of integrative conservation strategies taking breeding areas as well as non-breeding areas into account.
However, for a number of Palearctic-African migrants crucial information about migration such as migration routes and the location of non-breeding staging areas are still missing. In some cases this is due to the unobtrusive behaviour or the habitat use of the respective species. In case of the “Olivaceous Warblers” the lack of knowledge is mainly due to the difficulties to distinguish between several species and subspecies of which there are even African resident populations overlapping with non-breeding areas of Palearctic migrants.
The “Olivaceous Warblers” have recently been split and the genus renamed from Hippolais to Iduna. Two species are currently recognized: the Western Olivaceous Warbler I. opaca (monotypic) and Eastern Olivaceous Warbler I. pallida with the subspecies pallida, reiseri, elaeica and laeneni. All species and subspecies are difficult to separate in the field and even in the hand. Therefore, few details are known about migration and non-breeding areas of these different taxa.
In recent years, enhanced fieldwork, aided by better knowledge with respect to identification, helped to shed some light on the distribution, migration and non-breeding areas of at least some of these taxa. The Western Olivaceous Warbler has a scattered breeding distribution on the Iberian Peninsula and in north-western Africa. It spends the non-breeding season in sub-Saharan Africa mainly in the Sudan savanna zone and in the northern Guinea savanna zone. Migration through Mauritania occurs mainly during August and September and during March-May. The westernmost subspecies of the Eastern Olivaceous Warbler I. p. reiseri occurs further west than previously thought and concentrations of singing males reach unknown high densities in south-eastern Morocco. Migration of birds of unknown origin through central-Mauritania probably takes place mainly in September and during March and April, but some individuals may spend the non-breeding season there. Further non-breeding areas were recently identified in the valley of the Senegal River in north-eastern Senegal.
Despite the enhanced information with respect to migration and locality of the non-breeding staging areas of the various taxa of “Olivaceous Warblers” our knowledge is still fragmentary. As this is also due to the low density of ornithological projects and birdwatchers in the area, new technologies like stable isotope analyses or the application of geolocators may be paramount for a better understanding of “Olivaceous Warbler” migration ecology.
EU Species Action Plan for the Corncrake
Norbert Schäffer & Boris Barov
RSPB, The Lodge, Sandby, Beds, SG19 2DL, UK
The Corncrake (Crex crex) has long been classified by BirdLife International and the International Union for the Conservation of Nature (IUCN) as a globally threatened species (category "vulnerable") because of the rapid decline in its numbers in Western and Central Europe. Here we have seen that even large Corncrake populations can disappear within only a few years as a result of land use, in particular the poor timing of mowing in permanent grassland. Better data gathered in the 1990s from Eastern European countries, particularly from European Russia, showed that the world population of Corncrakes was much larger than thought for a long time. In addition, and more relevant to its status on the global Red Data Book, the collapse of agriculture in many Eastern European Countries, including Russia, resulted in an abandonment of many meadows and, through this, to a rapid increase in Corncrake numbers from the end of the 1990s. Consequently, the Corncrake was down-listed to the category "near threatened" in 2004 and finally to "least concern" in 2010 (BirdLife, 2010).
In the EU, the Corncrake is still seen as a priority species. As for all other EU priority species, the EU funded the development of a EU Species Action Plan in the 1990s. Species Action Plans were seen as the backbone of species protection work in the EU. In a parallel process, the Convention on Migratory Birds (CMS), the Bern Convention and the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) also developed Single Species Action Plans for threatened species. Compiled by the key experts for each individual species, EU Species Action Plans summarise the current conservation-relevant knowledge of the biology and ecology of each species. The Plans also describe the threats to the species, set recovery objectives and suggest conservation actions. Today, there are 54 Species Action Plans for priority species and subspecies in the EU, and most of those adopted before or soon after 2000 have been reviewed at least once.
The EU adopted a SAP for the Corncrake in 1996 (Crockford et al. 1996), which was consequently expanded to cover the non-EU range and endorsed by the CMS (2000). In 2006, the original EU SAP was replaced by the current International Single Species Action Plan (Koffijberg & Schaffer, 2006), commissioned by AEWA. The EU SAP underwent implementation reviews in 2001 and 2004.
Today, we have more than 15 years of working experience with the EU Species Action Plan for the Corncrake as well as other bird species. Over this period, we have learned what makes such a plan successful and where the limitations are. In our talk, we will briefly present the Species Action Plan for the Corncrake and describe our experience with this tool – both good and bad. Based on this, we will make recommendations for the further development of this tool.
The impact of increased food availability on reproduction in a long-distance migratory bird
Adam Seward1, 2, Rob Thomas1, Colin Beale3, Lucy Gilbert2 and Hefin Jones1
1Cardiff School of Biosciences, Cardiff University, Cardiff, CF10 3AX, UK
2Macaulay Land Use Research Institute, Macaulay Drive, Craigiebuckler, Aberdeen, AB15 8QH, UK
3Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK
Climate change has major implications for ecosystems and populations. The unevenness of climate change across the planet presents particular challenges to long-distance migratory birds because they have to time their migrations to coincide with food availability at locations hundreds or thousands of kilometres apart. Since 2008, we have been conducting feeding experiments to simulate a climate-linked change in food availability of a migratory bird, investigating the effects on breeding productivity, body mass regulation and annual survival.
Assessing the migration routes of the Sociable Lapwing Vanellus gregarius using historical records and satellite telemetry
RD Sheldon1, J Kamp2, M Koshkin3, PF Donald2
1RSPB Scotland, 2 Lochside View, Edinburgh Park, Edinburgh, EH12 9DH, United Kingdom.
2RSPB, The Lodge, Sandy, Bedfordshire SG19 2DL. United Kingdom.
3Association for the Conservation of Biodiversity in Kazakhstan, ul. Beibitshilik, 18, office 203, 01000 Astana, Republic of Kazakhstan.
The Sociable Lapwing Vanellus gregarius is a Critically Endangered long-distance migrant that has undergone a large decline in range and population size over the last century. With the extinction of the species in Ukraine and south-western Russia, the breeding population of the Sociable Lapwing is now concentrated in Kazakhstan. Detailed work on the species’ habitat selection and breeding ecology suggests that the population is not currently limited by habitat availability or productivity on the breeding grounds, but could be limited by factors operating on either the migration routes or the wintering grounds.
Sociable Lapwings migrate to wintering sites in Africa, the Arabian Peninsula and India. A database of historical and recent sightings has been established to identify key staging areas along the migration routes and wintering grounds. This has identified eastern and western migratory routes. Subsequent targeted survey work by a network of Birdlife partners has resulted in the identification of a number of important new sites. Key stopover sites have been discovered in the Manych wetlands in south-western Russia, where daily counts in excess of 1000 birds have been recorded in September 2009 and 2010. In Ceylanpinar, eastern Turkey a record flock of 3200 birds was observed in October 2007. Hunting of Sociable Lapwings has been confirmed in Syria and Iraq and has been identified as the key threat to the conservation of the species.
Since 2007, a number of adult Sociable Lapwings have been fitted with satellite tags to further aid our understanding. Key findings include tracking birds to the wintering quarters in India and Sudan where flocks comprising up to 35 birds have been recorded. A new important stopover site in Uzbekistan has been confirmed. There is a strong spatial and temporal correlation between the historical sightings within our database and the routes followed by satellite tagged birds. To help gain more information and support for conservation work across the species’ range, Birdlife International has recently launched a web-site that allows visitors to follow the migration of satellite tagged Sociable Lapwings. The site allows birdwatchers and conservationists to report their sightings, which are added to the database and in some cases followed up by additional surveys where possible. A key discovery of a wintering flock of 90+ birds has been reported in Oman through the web site.
The combined approach of literature review of historical sightings, satellite tracking and public participation is providing a wealth of information that is driving conservation efforts for this Critically Endangered migratory species. We suggest that compiling historical records can be an effective method for tracking the migratory routes of poorly known species.
Hundreds of ringers and one million of Swallows: large-scale joint efforts to unravel the journeys of a symbol of migration.
Fernando Spina
Italian Ringing Centre ISPRA, Via Cà Fornacetta, 9 I-40064 Ozzano Emilia (BO), Italy
With its huge breeding quarters, the Barn Swallow Hirundo rustica has been a symbol of bird migration since ancient times. Thanks to its habit of nesting in human dwellings, this aerial insectivore is also one of the few bird species man has always affectionately respected across continents and cultures. The herald of spring, the Swallow however raises our deepest concern due to widespread declines in large parts of its European range. Its colonial breeding habits and gregarious roosting behaviour outside the breeding season make the Swallow an ideal species to monitor through ringing, either of chicks and breeding adults at the colonies, as well as roosting birds. Huge roosts across the vast wintering quarters have been intensively monitored in Africa, ranking the Swallow as the most ringed Palaearctic visitor in the continent. However, despite widespread interest, many gaps in our knowledge especially of the pre-migratory strategies of this species were still to be recorded when EURING (The European Union for Bird Ringing, www.euring.org) launched a large-scale ringing project on this species in 1997 (EURING Swallow Project, ESP). Intensified marking activities at the colonies allowed to locate previously unknown migratory routes and wintering ranges for some of the European populations. Differently from what previously proposed by several Authors based on the aerial feeding habits of the Swallow, intensive pre-migratory fattening strategies have been described, similarly to e.g., several species of long-distance warblers. The trade-offs between post-breeding body moult and fat accumulation have been analysed and will be illustrated. In the framework of optimal migration theories, pre-migratory strategies in fat accumulation were investigated in detail across a vast latitudinal gradient, showing progressive accumulation of reserves while approaching the crossing on important ecological barriers like the Mediterranean Sea and Sahara desert. Data on physical conditions at the onset of barrier crossing as recorded in first-year inexperienced birds have confirmed population-specific fattening strategies. These relate to the distance to cover across ecological barriers never experienced before, indicating an important role of the latter in modelling pre-migratory strategies. The vast amount of data collected through the ESP have also significantly improved the geographical coverage of winter reports from Africa, allowing novel connectivity analyses.
Migratory bird conservation at the flyway scale: approaches to practical implementation in Africa-Eurasia
Tim Stowe1, Leon Bennun2, Nicola Crockford1, Richard Grimmett2, Vicky Jones2 and Danaë Sheehan1
1Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL
2BirdLife International, Wellbrook Court, Cambridge CB1 3SX
Birds’ migratory journeys cross many national boundaries. International collaboration is therefore key for the conservation of migratory birds. There are more than 30 international, flyway-based instruments with this aim, the only one with global remit being the UN Convention on Migratory Species (CMS) . Only some flyways are reasonably well covered by such instruments. Along with the Americas, Africa-Eurasia probably has the best coverage, key instruments being the CMS Waterbird Agreement (AEWA) and Bird of Prey Memorandum of Understanding; no similar instrument exists for passerines and other landbirds of that flyway.
While international agreement is an important start, implementation at national and regional levels remains a severe challenge. Many migratory bird populations are in decline with 14% of 2,274 migratory species globally threatened or near-threatened with extinction.
For globally threatened birds, the approach of implementing internationally approved species action plans through species working groups in the framework of CMS and AEWA is proving successful for species such as Aquatic Warbler and Sociable Lapwing.
Identification and conservation of a network of key sites– Important Bird Areas - can benefit many migrants, particularly waterbirds and soaring birds. In Africa-Eurasia, the ‘Wings over Wetlands’ project developed the Critical Site Network tool, which presents information on key sites in a flyways context, levels. Its modular training kit addresses capacity gaps for migratory waterbird conservation, management and monitoring. Implementation is provided by the project “Strengthening networks for the conservation of migratory birds and their habitats along the west coast of Africa”.
For soaring birds, infrastructural development at key sites, unsustainable hunting and land degradation pose major threats that are best tackled at the policy level. In north-east Africa and the Middle East the GEF/UNDP/BirdLife ‘Soaring Birds Project’ is working to mainstream migratory bird conservation considerations into policy decisions across economic sectors, especially the energy sector with a focus on wind energy developments.
However, big conservation challenges are posed by passerines and other landbirds that migrate on a broad front. A third of the 188 passerine species that use the Africa-Eurasia Flyway are in decline for reasons that are poorly understood, though habitat degradation appears to play a major role. A recent RSPB/BTO/Cambridge University study has collated expert opinion to identify the key Sahelian habitats for terrestrial migrant birds, critical land management practices, the social and economic drivers responsible for these and opportunities for policy intervention to influence land cover to benefit migrant birds.
European resources for migratory bird research and conservation are still focused on work that can be carried out in Europe, despite the conservation challenges and knowledge gaps elsewhere in the flyway. The need for cross-regional collaboration has never been greater.
Studying long-distance migration of raptors
Kasper Thorup
Natural History Museum of Denmark, University of Copenhagen, Denmark
For many years, the study of behavioural ecology in migratory birds has been hampered by the problems associated with following free-flying birds over long distances. The possibilities for tracking the sometimes even global journeys undertaken by migrating birds are still very limited. Nevertheless, the use of satellite telemetry has provided a wealth of information on the migration routes, stopovers and wintering grounds of long-distance migrants that are otherwise very difficult to study. However, the method also opens up for studying behaviours during migration. So far, the study of migratory behaviours has only been possible for a small part of the migration and in many cases even been restricted to the lab, where the consequences of different behaviours are almost impossible to evaluate. Here, I show how satellite tracking of several long-distance raptor species, ospreys, honey buzzards, peregrines and marsh harriers, has been successfully applied to study a number of migratory behaviours in the wild: wind drift, daily travel decisions and orientation cue use. These studies have provided new insights to nature of the migratory orientation system and, with the rapidly decreasing weight of transmitters, satellite telemetry remains a most promising line for future studies of migratory behaviour.
Juliet A. Vickery1, Nathaniel Anorbah2, Philip W. Atkinson3, Christopher M. Hewson3, Mark Hulme3, Aly Issa4, Oumar Issa4, Ernestina Mensah-Pebi2, Christopher J. Orsman1 and Danaë K. Sheehan1.
1 Royal Society for the Protection of Birds, Sandy, Bedfordshire, SG19 2DL, UK.
2 Ghana Wildlife Society, PO Box 13252, Accra, Ghana.
3 British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU, UK.
4 Naturama, 01 BP 6133, Ouagadougou, Burkina Faso.
There is widespread concern about the declines in Palaearctic-African migrant birds. The extent to which these declines may be driven by changes in the African wintering habitats remains unclear, although there is growing evidence that current declines, in UK breeding populations at least, are greatest amongst species that winter in the humid zones of West Africa and that populations of species that winter in the Sahel are now stable. Habitat degradation, drainage and agricultural intensification have all increased in the wintering areas over the period of population declines, but their effects on these species’ wintering habitats are largely unknown. In part, this is because our understanding of the implications of present and future land use change for Afro-Palearctic migrant birds is limited by the paucity of detailed information regarding their specific habitat requirements in the region.
Here, we present new field data on Palaearctic-African migrant birds and their habitats in west Africa collected in Burkina Faso and Ghana along a north-south transect from dry Sahelian woodland in Burkina Faso to lowland tropical forest in Ghana. Data were gathered from point counts surveys at 5 discrete locations along this transect on 4 occasions between October and March 2009/2010, with repeat counts in Jan-Feb 2011. We use these data to quantify seasonal patterns of distribution and habitat use and to look at how possible causes for the population declines (e.g. habitat degradation) may be impacting on populations of migrants wintering in West Africa.
Ellie Yohannes
Max Planx Institute for Ornithology, Germany
Stable isotope analysis is an increasingly valuable tool in avian migration studies. Advances and potential of the approach has been very successful in the exploring nutrient sources and allocation for reproduction, in particular the role of capital vs. income breeding. We explored the relationship between laying date and resource use for reproduction in the pectoral sandpiper (Calidris melanotos) breeding in the Alaskan arctic by contrasting carbon isotope (δ13C) values of the local diet and of maternal plasma, cellular blood, feather and claw with those of the eggs produced. By comparing maternal feather δ13C, claw δ13C and feather δD, we examined whether non-breeding season events influenced the use of resources for egg production through variation in arrival time and clutch initiation date. Female pectoral sandpipers originating from moulting areas characterized by higher δD signatures were more likely to arrive and start laying earlier, and they used stored resources for reproduction.
Using feather samples gathered from Asia and Africa, I will discuss how the analyses of the stable isotope composition of feathers provide significant insights into the understanding of the spatial structure of bird migration pattern between these continents. This technique also shows promise as a measure of nutritional and physiological stress in wild animals. I will show some examples supported by laboratory experiments and discuss assumptions that should be considered before applying this technique in the field.
