Changes in the timing of spring and autumn migration in North American migrant passerines during a period of global warming

Butler (2003) used first arrival dates (FADs) of 103 migrant birds in northeastern USA and found that both long-distance migrants (LDMs; wintering south of the USA) and short-distance migrants (SDMs; wintering in the southern USA) arrived earlier in the second half of the 20th century than they had in the first, consistent with scenarios of global warming; the trend was stronger in SDMs. Using FADs to characterize migration systems can be problematic because they are data from one tail of a distribution, they comprise a mostly male population and they may not correlate well with the balance of the migration period. FADs also provide no information about autumn migration. This paper uses a banding dataset from Long Point Bird Observatory, Ontario, for 14 passerines for a period of global warming (1975–2000), taking these issues into account. The data were filtered to minimize effects of unequal netting effort (147 491 resulting records), and the passage dates then calculated in each season of each year for the 1st, 2nd and 3rd quartiles for regression analysis. Only two of 13 species analysed in the spring showed significantly earlier passage times, although the overall trend was towards earlier spring migration, especially among SDMs. Autumn responses were more prevalent, however, and in some cases more dramatic with six of 13 species showing delayed migration (four SDMs, two LDMs). Two LDMs exhibited earlier autumn migration. Where earlier spring migration occurred, both sexes appeared to contribute to the change. Where delayed migration occurred in autumn, both sexes and both adults and hatch-year birds appeared to contribute in at least some cases. The spring FAD results are consistent with those of Butler, but when the whole migration is considered, change is far from universal in spring and is in fact more substantial and complex in autumn.     

Annual and seasonal survival of trumpeter swans in the upper midwest

The reintroduction of trumpeter swans to the north central United States appears to be a conservation success story. For the most part, population management goals have been met or exceeded. The population cannot be considered self-sustaining, however, because 90% of the swans migrate short distances to wintering sites where supplemental feeding occurs. The remaining 10% migrate longer distances to areas where adequate open water and forage occur naturally. To determine how these 2 different wintering habits might affect mortality, we used mark-resight data gathered between 2000 and 2008 to estimate and compare annual survival rates for long- and short-distance migrant swans marked in Wisconsin. Apparent annual survival rates were similar for long- (0.81, SE = 0.019) and short- (0.81, SE = 0.022) distant adult migrants but were higher for long-distance sub-adult (0.86, SE = 0.036) migrants than for short-distance sub-adult migrants (0.7, SE = 0.046). We also estimated seasonal survival of long-distance migrants to determine if the migratory periods are a time of high mortality. We found little evidence for seasonal variation in survival and estimates for both migratory and non-migratory seasons were very high (>0.97). Overall, the results suggest that little mortality occurs during migration and long-distance migrants are able to survive at rates at least equal to, but probably higher than, short-distance migrants. © 2011 The Wildlife Society.     

Primary moult, body mass and migration of Grey Plovers Pluvialis squatarola in Britain

Long-distance migrants have evolved complex strategies for the timing of their annual moult, fattening and migration cycles. These strategies are likely to vary at different stages of a bird's life. Ringing data on 6079 Grey Plovers Pluvialis squatarola , caught on the Wash, England, between 1959 and 1996, were analysed to relate migratory strategies to patterns of primary moult and body mass changes. Adults returning from breeding grounds had a shorter and delayed primary moult (duration 90 days, starting date 19 August) in comparison with over-summering birds (duration 109 days, starting date 5 June). Three categories of migrant adults were identified on the basis of primary moult and body mass: (1) birds which did not moult, but increased body mass and migrated further south; (2) birds which moulted 1–3 inner primaries, suspended moult, increased body mass and migrated; and (3) birds which completed or suspended moult and wintered locally. In birds of the second category, timing of primary moult and body mass increase overlapped. Among wintering birds, 38% were in suspended moult. Ninety-six per cent of birds that suspended moult at the beginning of winter were males and almost all completed moult in spring. Grey Plovers which left Britain in autumn had an average body mass of 280 g, enough to reach southern Morocco without refuelling. Both wintering adults and first-year birds showed a prewinter body mass increase, peaking in December. Adults had a synchronized premigratory body mass increase in May, which suggested a negligible presence of African migrants. The average departure mass for spring migration, estimated at 316 g, would allow birds to fly non-stop to the Siberian breeding grounds in western Taymyr.     

Timing of spring migration in birds: long-term trends, North Atlantic Oscillation and the significance of different migration routes

We studied long-term trends and the yearly variation in mean spring passage time in 36 passerine bird species trapped at Ottenby Bird Observatory in south-eastern Sweden. Between the years 1952–2002, data were available for 22–45 years depending on species. Most long-distance migrant species passed progressively earlier over the study period (range: 2.5 days earlier to 0.7 days later per 10 years, with an average of 0.9 days earlier per 10 years). The annual variation in timing of migration in most species, regardless of migration distance, correlated negatively with the winter index of the North Atlantic Oscillation (NAO), a large-scale climate phenomenon influencing the climate in the North Atlantic region. Birds passed earlier after mild and humid winters, corresponding to the high phase of the NAO. This corroborates the pattern found at a nearby migration site with a comparable dataset (Helgoland, 600 km WSW of Ottenby). However, short/medium-distance migrant species at Ottenby, in contrast to the situation at Helgoland, have shown no general trend of earlier passage in recent years. This was probably a consequence of the shorter study period at Ottenby, which included only the last 22–32 years (41 years at Helgoland), when the NAO showed no significant trend. At the species-specific level, the long-term trends in passage time were similar at the two sites, and there was some congruence to the extent that a given species was affected by NAO. Long-distance migrants wintering south and south-east of the breeding grounds showed some of the strongest changes in long-term trends (passing progressively earlier) at Ottenby, and for some of these species passage time varied negatively with NAO. Obviously, and contrary to previous suggestions, variations in NAO also influence birds migrating through eastern Europe, although the direct or indirect mechanisms through which this is achieved are unknown.     

Winter habitat use by Loggerhead Shrikes (Lanius Ludovicianus) in Mexico: separating migrants from residents using stable isotopes

Several species of migrant birds overlap in range on their wintering grounds with non-migrant conspecifics or other species that occupy a similar niche. Very little is known whether such overlap results in competition and subsequent habitat segregation since it is usually impossible to separate resident from migrant individuals. The Loggerhead Shrike (Lanius ludovicianus) is a declining grassland species in North America that winters in the southern United States and Mexico. Using stable-hydrogen isotope (δD) analysis of feathers, we identified resident and migrant shrikes wintering in northeastern Mexico based on a latitudinal gradient in precipitation and feather δD values. Indicator species analyses showed that migrants occupied areas where bare ground was less available than those occupied by residents, a pattern which held when a more restricted set of birds from the extremes of the δD distribution were considered. This provides evidence for conspecific habitat segregation. Habitat differences were also found between sites occupied by shrikes and apparently suitable but unoccupied sites. Shrikes occupied more open sites that contained shorter tall shrubs and huisache (Acacia farneasiana) and fewer tall shrubs, mesquite (Prosopsis glandulosa) and huisache than unoccupied sites. The availability of suitable winter habitat and the potential competition between migrants and residents may be factors that influence the population dynamics of migrant shrikes in North America.     

Multiple Weather Factors Affect Apparent Survival of European Passerine Birds

Weather affects the demography of animals and thus climate change will cause local changes in demographic rates. In birds numerous studies have correlated demographic factors with weather but few of those examined variation in the impacts of weather in different seasons and, in the case of migrants, in different regions. Using capture-recapture models we correlated weather with apparent survival of seven passerine bird species with different migration strategies to assess the importance of selected facets of weather throughout the year on apparent survival. Contrary to our expectations weather experienced during the breeding season did not affect apparent survival of the target species. However, measures for winter severity were associated with apparent survival of a resident species, two short-distance/partial migrants and a long-distance migrant. Apparent survival of two short distance migrants as well as two long-distance migrants was further correlated with conditions experienced during the non-breeding season in Spain. Conditions in Africa had statistically significant but relatively minor effects on the apparent survival of the two long-distance migrants but also of a presumably short-distance migrant and a short-distance/partial migrant. In general several weather effects independently explained similar amounts of variation in apparent survival for the majority of species and single factors explained only relatively low amounts of temporal variation of apparent survival. Although the directions of the effects on apparent survival mostly met our expectations and there are clear predictions for effects of future climate we caution against simple extrapolations of present conditions to predict future population dynamics. Not only did weather explains limited amounts of variation in apparent survival, but future demographics will likely be affected by changing interspecific interactions, opposing effects of weather in different seasons, and the potential for phenotypic and microevolutionary adaptations.     

Long-term population declines in Danish trans-Saharan migrant birds

Capsule Long-distance migrant birds show less favourable trends than sedentary/short-distance species.

Aims To use breeding bird surveys to contrast population trends amongst common species according to their migration pattern.

Methods Changes in abundance of 62 Danish breeding sedentary, short-distance (Europe/North Africa) or long-distance (trans-Saharan) migrants were described by fitting log linear regression models to point-count census data gathered during 1976–2005.

Results Trans-Saharan migrants declined by 1.3% per annum during this period, while short-distance migrants and sedentary species increased by 1.4% and 1.0% per annum, respectively. There were no significant decadal declines amongst species using different summer breeding habitats, except for wetlands, and there was no consistent variation in trends associated with wintering regions or habitats or diet.

Conclusions More information is urgently needed on diet, feeding ecology, habitat requirements, winter distribution and intra-African movements of the commoner European summer visitors to identify causes of the declines and highlight when in the annual cycle detrimental effects occur. Studies linking individuals on their breeding, staging and wintering grounds are especially needed. Danish trends resemble those from elsewhere in Europe, confirming that restoration to favourable conservation status requires inter-continental action to meet European and global targets to reduce or halt biodiversity loss.     

Spring arrival response to climate change in birds: a case study from eastern Europe

This paper analyses the dependence of the first spring arrival dates of short/medium- and long-distance migrant bird species on climate warming in eastern Europe. The timing of arrival of the selected species at the observation site correlates with the North Atlantic Oscillation (NAO) index, air temperature, atmospheric pressure, precipitation and wind characteristics. A positive correlation of fluctuations in winter and spring air temperatures with variations in the NAO index has been established in eastern Europe. Positive winter NAO index values are related to earlier spring arrival of birds in the eastern Baltic region and vice versa—arrival is late when the NAO index is negative. The impact of climate warming on the bird’s life cycle depends on local or regional climate characteristics. We tested the hypothesis that differences in climate indices between North Africa and Europe can influence the timing of spring arrival. Our results support the hypothesis that differences in first spring arrival dates between European populations occur after individuals cross the Sahara. We assume that the endogenous programme of migration control in short/medium-distance migrants synchronises with the changing environment on their wintering grounds and along their migration routes, whereas in long-distance migrants it is rather with environmental changes in the second part of their migratory route in Europe. Our results strongly indicate that the mechanism of dynamic balance in the interaction between the endogenous regulatory programme and environmental factors determines the pattern of spring arrival, as well as migration timing.     

Consequences of the settlement of migrant European Robins Erithacus rubecula in wintering habitats occupied by conspecific residents

In wintering areas where migrant birds meet sedentary conspecifics, early settlement of local residents in the best habitat patches might reduce the availability of suitable sites for arriving migrants. We studied how sympatric migratory and sedentary European Robins Erithacus rubecula occupy two wintering habitats of different quality (forests and shrublands) in southern Spain, and how such a distribution affects individuals of each population sector. In September, before migrants arrived, Robins were only found in forests, and they had already saturated these habitats, so that rather than increasing Robin abundance in these habitats, the arrival of migrants caused a massive occupation of the previously vacant shrublands. During the winter, we captured Robins and identified them as migrants or residents using a discriminant function based on morphological traits. Residents always predominated in forests, and migrants in shrublands, but through the winter around 35% of residents (mainly juveniles) moved to shrublands, having been replaced by some migrants in forests. Although food was more abundant in shrublands, Robins had better body condition in forests, suggesting that other factors determined habitat preferences (e.g. shelter availability or food diversity, which were higher in forests). In addition, we observed a greater variance in body mass relative to body size in forests, suggesting that energy management was less constrained in this habitat (for example owing to a lower exposure to predators or a higher food predictability). Our results suggest that sedentary Robins benefit from an early occupation of the best habitats in the wintering grounds, forcing migrants to colonize apparently less suitable sites. This would explain the persistence of these small southern populations despite the yearly flooding of the area by huge numbers of migrant conspecifics.     

The phenology mismatch hypothesis: are declines of migrant birds linked to uneven global climate change?

1.  Migrant bird populations are declining and have been linked to anthropogenic climate change. The phenology mismatch hypothesis predicts that migrant birds, which experience a greater rate of warming in their breeding grounds compared to their wintering grounds, are more likely to be in decline, because their migration will occur later and they may then miss the early stages of the breeding season. Population trends will also be negatively correlated with distance, because the chances of phenology mismatch increase with number of staging sites.
2.  Population trends from the Palaearctic (1990–2000) and Nearctic (1980–2006) were collated for 193 spatially separate migrant bird populations, along with temperature trends for the wintering and breeding areas. An index of phenology mismatch was calculated as the difference between wintering and breeding temperature trends.
3.  In the Nearctic, phenology mismatch was correlated with population declines as predicted, but in the Palaearctic, distance was more important. This suggests that differential global climate change may be responsible for contributing to some migrant species' declines, but its effects may be more important in the Nearctic.
4.  Differences in geography and so average migration distance, migrant species composition and history of anthropogenic change in the two areas may account for the differences in the strength of the importance of phenology mismatch on migrant declines in the Nearctic and Palaearctic.     

Dispersal and migration of juvenile African Black Oystercatchers Haematopus moquini

African Black Oystercatchers Haematopus moquini are sedentary as adults. However, colour-ringing of more than 700 juveniles has revealed complex post-fledging movements that vary geographically. Young from the western part of the breeding range either remain within 150 km of their natal site or migrate 1500–2000 km to one of five discrete nursery areas on the Namib Desert coast of central and northern Namibia, and southern Angola. These nurseries all lie north of the species' breeding range. We calculate that 36–46% of all juveniles born in South Africa migrate to nurseries. Birds return to their natal sites from nurseries at 2–3 years old, but never migrate again. Juveniles from the eastern part of the range undertake 'diffusion dispersal', regularly up to 1000 km, but these journeys mostly end within the breeding range, where there are no nurseries. Very few eastern birds reach nurseries. There is no evidence that movements of western birds are density-dependent responses to hatching date, but long-distance migrants are significantly heavier as chicks than are short-distance dispersers. We hypothesize that a genetic basis exists to these movements, possibly triggered by body condition, that could account not only for the highly dichotomous behaviour of western birds, but also for the intermediate behaviour of eastern birds.     

Dispersal and migration of juvenile African Black Oystercatchers Haematopus moquini

African Black Oystercatchers Haematopus moquini are sedentary as adults. However, colour-ringing of more than 700 juveniles has revealed complex post-fledging movements that vary geographically. Young from the western part of the breeding range either remain within 150 km of their natal site or migrate 1500–2000 km to one of five discrete nursery areas on the Namib Desert coast of central and northern Namibia, and southern Angola. These nurseries all lie north of the species' breeding range. We calculate that 36–46% of all juveniles born in South Africa migrate to nurseries. Birds return to their natal sites from nurseries at 2–3 years old, but never migrate again. Juveniles from the eastern part of the range undertake 'diffusion dispersal', regularly up to 1000 km, but these journeys mostly end within the breeding range, where there are no nurseries. Very few eastern birds reach nurseries. There is no evidence that movements of western birds are density-dependent responses to hatching date, but long-distance migrants are significantly heavier as chicks than are short-distance dispersers. We hypothesize that a genetic basis exists to these movements, possibly triggered by body condition, that could account not only for the highly dichotomous behaviour of western birds, but also for the intermediate behaviour of eastern birds.     

Range‐wide patterns of migratory connectivity in the western sandpiper Calidris mauri

Understanding the population dynamics of migratory animals and predicting the consequences of environmental change requires knowing how populations are spatially connected between different periods of the annual cycle. We used stable isotopes to examine patterns of migratory connectivity across the range of the western sandpiper Calidris mauri. First, we developed a winter isotope basemap from stable‐hydrogen (δD), ‐carbon (δ¹³C), and ‐nitrogen (δ¹⁵N) isotopes of feathers grown in wintering areas. δD and δ¹⁵N values from wintering individuals varied with the latitude and longitude of capture location, while δ¹³C varied with longitude only. We then tested the ability of the basemap to assign known‐origin individuals. Sixty percent of wintering individuals were correctly assigned to their region of origin out of seven possible regions. Finally, we estimated the winter origins of breeding and migrant individuals and compared the resulting empirical distribution against the distribution that would be expected based on patterns of winter relative abundance. For breeding birds, the distribution of winter origins differed from expected only among males in the Yukon‐Kuskokwim (Y‐K) Delta and Nome, Alaska. Males in the Y‐K Delta originated overwhelmingly from western Mexico, while in Nome, there were fewer males from western North America and more from the Baja Peninsula than expected. An unexpectedly high proportion of migrants captured at a stopover site in the interior United States originated from eastern and southern wintering areas, while none originated from western North America. In general, we document substantial mixing between the breeding and wintering populations of both sexes, which will buffer the global population of western sandpipers from the effects of local habitat loss on both breeding and wintering grounds.     

Spring migration phenology of birds in the Northern Prairie region is correlated with local climate change

ABSTRACT In apparent response to recent periods of global warming, some migratory birds now arrive earlier at stopover sites and breeding grounds. However, the effects of this warming on arrival times vary among locations and species. Migration timing is generally correlated with temperature, with earlier arrival during warm years than during cold years, so local variation in climate change might produce different effects on migration phenology in different geographic regions. We examined trends in first spring arrival dates (FADs) for 44 species of common migrant birds in South Dakota (1971–2006) and Minnesota (1964–2005) using observations compiled by South Dakota and Minnesota Ornithologists’ Unions. We found significant trends in FAD over time for 20 species (18 arriving earlier and two later) in South Dakota and 16 species (all earlier) in Minnesota. Of these species, 10 showed similar significant trends for both states. All 10 of these species exhibited significantly earlier arrival, and all were early spring migrants, with median FADs before 10 April in both states. Eighteen of the 44 species showed significant negative correlations of FADs with either winter (December–February) or spring (arrival month plus previous month) temperatures in one or both states. Interestingly, spring temperatures in both South Dakota and Minnesota did not warm significantly from 1971–2006, but winter temperatures in both states warmed significantly over the same time period. This suggests that the warmer winters disproportionately affected early spring migrants, especially those associated with aquatic habitats (seven of the 10 species showing significantly earlier spring arrival in both states). The stronger response to climate change by early spring migrants in our study is consistent with the results of several other studies, and suggests that migrants, especially early migrants, are capable of responding to local temperature conditions experienced on wintering grounds or along the migration route.     

Perspectives on Palaearctic and Nearctic bird migration; comparisons and overview of life-history and ecology of migrant passerines

In this paper we compare ecological attributes of tropical migrant passerines from the Nearctic and western Palaearctic, focusing particularly on habitat association patterns during both breeding and wintering seasons. Three regions were compared: Europe, western and eastern North America. Breeding bird census data from 32 studies (each including at least four stages of forest succession) were used to assess the association patterns of breeding habitats among tropical migrants. For each species we calculated an index of habitat diversity and habitat preference.
Tropical migrants preferred earlier successional stages than other birds in Europe. The opposite was true in eastern North America. In eastern North America, tropical migrants tended to be associated with a smaller range of serai stages than other passerine species. In their winter quarters, Palaearctic migrants live primarily in open habitats, such as savannas, whereas eastern Nearctic migrants make more frequent use of evergreen forests. Migrants from western North America show the greatest match between breeding and wintering habitats.
We relate the results to the taxonomy and probable history of contemporary avifaunas and vegetation formations of the Old and New World. Taxonomically, tropical migrants from different parts of the Holarctic are less closely related to each other than residents and short-distance migrants. Tropical and temperate avifaunas are more closely related to each other in the New World than in the Old World. Conservation implications of the between-continent differences are briefly discussed.     

Rapid change in host use of the common cuckoo Cuculus canorus linked to climate change

Parasites require synchrony with their hosts so if host timing changes with climate change, some parasites may decline and eventually go extinct. Residents and short-distance migrant hosts of the brood parasitic common cuckoo, Cuculus canorus, have advanced their phenology in response to climate change more than long-distance migrants, including the cuckoo itself. Because different parts of Europe show different degrees of climate change, we predicted that use of residents or short-distance migrants as hosts should have declined in areas with greater increase in spring temperature. Comparing relative frequency of parasitism of the two host categories in 23 European countries before and after 1990, when spring temperatures in many areas had started to increase, we found that relative parasitism of residents and short-distance migrants decreased. This change in host use was positively related to increase in spring temperature, consistent with the prediction that relative change in phenology for different migrant classes drives host-use patterns. These findings are consistent with the hypothesis that climate change affects the relative abundance of different host races of the common cuckoo.     

THE WINTERING AND MIGRATION OF PALAEARCTIC PASSERINES AT KAMPALA, SOUTHERN UGANDA

Palaearctic passerines were observed and trapped over three seasons near Kampala, in southern Uganda. Passage migration and wintering are described.
Only 11 species were encountered at all frequently. Three of these were common as passage migrants only, the rest remained in numbers throughout the northern winter. Most migrants reached Kampala during October and November, but the majority of Acrocephalus warblers appeared later. Spring departure commenced at the end of March, and continued throughout April. Autumn passage was in progress from late September to December, but appreciable spring movement was confined to a period of a few weeks only.
Ringing revealed that most wintering warblers were highly sedentary, and that a high proportion of surviving birds returned to the same site in successive winters. No fewer than 12–5% of the 220 Acrocephalus warblers ringed during 1966/67 were retrapped during the following season.
Wing measurements were recorded for most migrants trapped. Plumage details were noted, and representative specimens of several species were subsequently compared with museum series. It was concluded that most migrant passerines which occurred at Kampala were of eastern origin.
Migration times were compared with those recorded for some other areas. The spring movement from southern Uganda to the Middle East tends to be more rapid than the return journey. Some species apparently spend weeks or even months of the autumn in northeast Africa before reaching the equator,     

Bird migration times, climate change, and changing population sizes

Past studies of bird migration times have shown great variation in migratory responses to climate change. We used 33 years of bird capture data (1970–2002) from Manomet, Massachusetts to examine variation in spring migration times for 32 species of North American passerines. We found that changes in first arrival dates – the unit of observation used in most studies of bird migration times – often differ dramatically from changes in the mean arrival date of the migration cohort as a whole. In our study, the earliest recorded springtime arrival date for each species occurred 0.20 days later each decade. In contrast, the mean arrival dates for birds of each species occurred 0.78 days earlier each decade. The difference in the two trends was largely explained by declining migration cohort sizes, a factor not examined in many previous studies. We found that changes in migration cohort or population sizes may account for a substantial amount of the variation in previously documented changes in migration times. After controlling for changes in migration cohort size, we found that climate variables, migration distance, and date of migration explained portions of the variation in migratory changes over time. In particular, short-distance migrants appeared to respond to changes in temperature, while mid-distance migrants responded particularly strongly to changes in the Southern Oscillation Index. The migration times of long-distance migrants tended not to change over time. Our findings suggest that previously reported changes in migration times may need to be reinterpreted to incorporate changes in migration cohort sizes.     

Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.     

Flying in the face of climate change: a review of climate change, past, present and future

The distribution and abundance of birds is known to depend critically upon climate variability at a range of temporal and spatial scales. In this paper we review historical changes in climate in the context of what is known about climate variability over the last millennium, with particular reference to the British Isles. The climate of Britain is now warmer than it has been in at least 340 years, with the 1990s decade 0.5 °C warmer than the 1961–1990 average. In addition, the frequency of cold days (mean temperature below 0 °C), particularly during March and November, has declined and there has been a marked shift in the seasonality of precipitation, with winters becoming substantially wetter and summers becoming slightly drier. Current understanding is that the rate of future warming is likely to accelerate with more frequent and more intense summer heatwaves, milder winters, an increase in winter rainfall, an increased risk of winter river floods, and an increase in mean sea-level and associated coastal flooding. All of these aspects of climate change are likely to impact on coastal birds. A range of potential future climate scenarios for the British Isles are presented derived from recently completed global climate model experiments. For migrant bird species, changes in the British climate have also to be seen within the context of remote climate change in both the breeding and the overwintering grounds.