Relative influence of fisheries and climate on the demography of four albatross species

Worldwide ecosystems are modified by human activities and climate change. To be able to predict future changes, it is necessary to understand their respective role on population dynamics. Among the most threatened species are top predators because of their position in the food web. Albatross populations are potentially affected by both human activities, especially longline fisheries, and climatic fluctuations. Based on long‐term data (1985–2006), we conducted through a comparative approach a demographic analysis (adult survival and breeding success) on four albatross species breeding on the Indian Ocean sub‐Antarctic Islands to assess the relative impact of climate and fisheries during and outside the breeding season. The study revealed that adult survival of almost all species was not affected by climate, and therefore probably canalized against climatic variations, but was negatively affected by tuna longlining effort in three species. Breeding success was affected by climate, with contrasted effects between species, with Southern Oscillation Index having an impact on all species but one. Differences in demographic responses depended on the foraging zone and season. In order to predict population trajectories of seabirds such as albatrosses, our results show the importance of assessing the relative influence of fishing and climate impacts on demography.     

Combined impacts of longline fisheries and climate on the persistence of the Amsterdam Albatross Diomedia amsterdamensis

Incidental capture of seabirds in longline fishing gear is a central issue in the conservation of many long-lived marine species. Despite growing evidence of climate-induced effects on population trends of long-lived species, climate change remains generally overlooked in most risk assessments of seabirds. Because variation in climate may interact with the detrimental effects of bycatch, considering climate is of great importance, especially in the context of ongoing global warming. This paper examines the combined effects of bycatch and climate change on the persistence of one of the world's rarest birds, the Amsterdam Albatross Diomedea amsterdamensis , which has a single population in the upland plateau of Amsterdam Island (Southeast Indian Ocean). Using continuous monitoring from 1983 onwards, we first estimated the relationship between climate and the species' demographic parameters. We then built a stochastic matrix population model to estimate the population growth rate and the probability that the population declines below the level recorded in 1983 of nine breeding pairs under different scenarios involving the joint effects of additional mortality caused by longline fisheries and climate change. The results suggest that the demography of the Amsterdam Albatross is influenced by climate in both breeding and wintering grounds and that these relationships may to some extent compensate for the impact of additive bycatch mortality. However, these compensatory effects would be negligible if the annual additional mortality exceeds around six individuals per year, suggesting that the resumption of longline fishery in the foraging range of the Amsterdam Albatross would rapidly put this species at risk of extinction.     

Effects of large-scale climatic fluctuations on survival and production of young in a Neotropical migrant songbird, the yellow warbler Dendroica petechia

Migrant songbirds are vulnerable to changes in climatic conditions on both the breeding and wintering grounds. For North American Neotropical migrants, the El Niño/Southern Oscillation (ENSO), via its effects on global precipitation and temperature, modulates the productivity of their temperate and tropical terrestrial ecosystems used during the course of their annual cycle. We evaluated how a densely nesting population of yellow warblers Dendroica petechia in a riparian forest in southern Manitoba, Canada, responded to the El Niño/Southern Oscillation (ENSO) between 1992 and 2001. Standardized mist netting was used to estimate apparent annual survival of adults and production of young. Both adult survival and the production of young were positively correlated with the Southern Oscillation Index (SOI). More specifically, values of both these demographic parameters were lowest during El Niño years and highest during La Niña years. These findings demonstrate the influence of climate on populations of Neotropical migrants in North America. The more frequent El Niños predicted to result from future global climate change could negatively affect populations of yellow warblers and other Neotropical migrants breeding in this region.     

Climatic conditions during outward migration affect apparent survival of an arctic top predator,the peregrine falcon Falco peregrinus

In long‐lived species, population growth rate is highly sensitive to changes in adult survival. Despite the growing concerns regarding recent climate changes, few studies have investigated the effect of climatic conditions on survival in long‐lived wildlife that are either resident or breed in the Arctic. In this study, we evaluated the effect of climate across the annual life cycle (breeding, outward migration, wintering, and inward migration) on apparent annual survival of arctic‐breeding peregrine falcons. From 1982 to 2008, peregrine falcons breeding near Rankin Inlet, Nunavut, Canada were monitored, in part, to assess apparent annual survival (the product of true survival and site fidelity) using re‐observations of marked individuals. Our study indicated that apparent annual survival of adult peregrine falcons was correlated with indices of climatic conditions during outward migration (i.e., flight from the Arctic breeding grounds). These climatic indices (fall NAO of the current year and fall NAO with a lag of one year) explained 35% of the temporal variation in apparent annual survival of peregrine falcons. Our results suggest that this top‐predator is vulnerable to weather‐related environmental conditions encountered during fall migration.     

Survivorship across the annual cycle of a migratory passerine,the willow flycatcher

Annual survivorship in migratory birds is a product of survival across the different periods of the annual cycle (i.e. breeding, wintering, and migration), and may vary substantially among these periods. Determining which periods have the highest mortality, and thus are potentially limiting a population, is important especially for species of conservation concern. To estimate survival probabilities of the willow flycatcher Empidonax traillii in each of the different periods, we combined demographic data from a 10‐year breeding season study with that from a 5‐year wintering grounds study. Estimates of annual apparent survival for breeding and wintering periods were nearly identical (65–66%), as were estimates of monthly apparent survival for both breeding and wintering stationary periods (98–99%). Because flycatchers spend at least half the year on the wintering grounds, overall apparent survivorship was lower (88%) on the wintering grounds than on the breeding grounds (97%). The migratory period had the highest mortality rate, accounting for 62% of the estimated annual mortality even though it comprises only one quarter or less of the annual cycle. The migratory period in the willow flycatcher and many other neotropical migrants is poorly understood, and further research is needed to identify sources of mortality during this crucial period.     

Comparing the seasonal survival of resident and migratory oystercatchers: carry‐over effects of habitat quality and weather conditions

Events happening in one season can affect life‐history traits at (the) subsequent season(s) by carry‐over effects. Wintering conditions are known to affect breeding success, but few studies have investigated carry‐over effects on survival. The Eurasian oystercatcher Haematopus ostralegus is a coastal wader with sedentary populations at temperate sites and migratory populations in northern breeding grounds of Europe. We pooled continental European ringing‐recovery datasets from 1975 to 2000 to estimate winter and summer survival rates of migrant and resident populations and to investigate long‐term effects of winter habitat changes. During mild climatic periods, adults of both migratory and resident populations exhibited survival rates 2% lower in summer than in winter. Severe winters reduced survival rates (down to 25% reduction) and were often followed by a decline in survival during the following summer, via short‐term carry‐over effects. Habitat changes in the Dutch wintering grounds caused a reduction in food stocks, leading to reduced survival rates, particularly in young birds. Therefore, wintering habitat changes resulted in long‐term (>10 years) 8.7 and 9.4% decrease in adult annual survival of migrant and resident populations respectively. Studying the impact of carry‐over effects is crucial for understanding the life history of migratory birds and the development of conservation measures.     

Disentangling the effects of environmental conditions on wintering and breeding grounds on age‐specific survival rates in a trans‐Saharan migratory raptor

Migratory species are subject to environmental variability occurring on breeding and wintering grounds. Estimating the relative contribution of environmental factors experienced sequentially during breeding and wintering, and their potential interaction, to the variation of survival is crucial to predict population viability of migratory species. Here we investigated this issue for the Montagu's harrier Circus pygargus, a trans‐Saharan migrant. We analysed capture–recapture data from a 29‐year long monitoring of wing‐tagged offspring and adults at two study sites in France (Rochefort‐RO and Maine‐et‐Loire‐ML). The study period covers a climatic shift occurring in the Sahel with increasing rainfall following a period of droughts (Sahel greening). We found that harriers’ adult survival in RO (between 1988 and 2005) varied over time and was sensitive to the interaction between the amount of rainfall in the Sahel and the annual mean breeding success, two proxies of prey availability. The occurrence of adverse conditions on breeding and wintering grounds in the same year decreased survival from 0.70–0.77 to 0.48 ± 0.05. Juvenile survival in RO was slightly more sensitive to conditions in Europe than in the Sahel. Unexpectedly, lower survival rates were found in years with higher mean breeding success, suggesting compensatory density feedbacks may operate. By contrast, adult survival in ML, monitored between 1999 and 2017, was higher compared to RO (0.76 ± 0.03 versus 0.66 ± 0.02), remained constant and unaffected by any proxy of prey availability. This difference seems consistent with the fact that harriers in ML experienced better and especially less variable environmental conditions during breeding and wintering seasons compared to RO. Overall, we showed that survival of a migratory bird is sensitive to the level of variability in environmental conditions and that adverse conditions on wintering grounds can amplify the negative effects of conditions during the previous breeding season on birds’ survival.     

Oil pollution and climate have wide-scale impacts on seabird demographics

Oil spills often spell disaster for marine birds caught in slicks. However, the impact of oil pollution on seabird population parameters is poorly known because oil spills usually occur in wintering areas remote from breeding colonies where birds may be distributed over a wide area, and because it is difficult to separate the effects of oil pollution from the effect of natural environmental variation on seabird populations. Using a long-term data set we show that over-winter survival of adult common guillemots (Uria aalge) is negatively affected by both the incidence of four major oil-spills in their wintering grounds and high values of the North Atlantic Oscillation (NAO) index. After controlling for the effect of the NAO index, we show that winter mortality of adult guillemots is doubled by major oil pollution incidents. Our results demonstrate that oil pollution can have wide-scale impacts on marine ecosystems that can be quantified using populations of marked individuals to estimate survival.     

High within‐winter and annual survival rates in a declining Afro‐Palaearctic migratory bird suggest that wintering conditions do not limit populations

For migratory birds, it is necessary to estimate annual and overwinter survival rates, identify factors that influence survival, and assess whether survival varies with age and sex if we are to understand population dynamics and thus inform conservation. This study is one of the first to document overwinter and annual survival from the wintering grounds of a declining Afro‐Palaearctic migrant bird, the Whinchat Saxicola rubetra. We monitored a population of marked individuals for which dispersal was low and detectability was high, allowing accurate estimates of survival. Annual survival was at least 52% and did not differ significantly across demographic groups or with habitat characteristics or residency time in the previous winter. Overwinter survival was very high and monthly survival at least 98% at some sites. Although winter residency varied spatially and with age, lower residency did not correlate with reduced annual survival, suggesting occupancy of multiple wintering sites rather than higher winter mortality of individuals with shorter residency. Our results suggest that mortality occurs primarily outside the wintering period, probably during migration, and that wintering conditions have minimal influence on survival. The similarity between survival rates for all age and sex classes when measured on the wintering grounds implies that any difference in survival with age or sex occurs only during the first migration or during the post‐fledging stage, and that selection of wintering habitat, or territory quality, makes little difference to survival in Whinchats. Our findings suggest that the wintering grounds do not limit populations as much as the migratory and breeding stages, with implications for the conservation of declining Afro‐Palaearctic migrants more widely.     

Survival during the Breeding Season: Nest Stage,Parental Sex,and Season Advancement Affect Reed Warbler Survival

Avian annual survival has received much attention, yet little is known about seasonal patterns in survival, especially of migratory passerines. In order to evaluate survival rates and timing of mortality within the breeding season of adult reed warblers (Acrocephalus scirpaceus), mark-recapture data were collected in southwest Poland, between 2006 and 2012. A total of 612 individuals (304 females and 308 males) were monitored throughout the entire breeding season, and their capture-recapture histories were used to model survival rates. Males showed higher survival during the breeding season (0.985, 95% CI: 0.941–0.996) than females (0.869, 95% CI: 0.727–0.937). Survival rates of females declined with the progression of the breeding season (from May to August), while males showed constant survival during this period. We also found a clear pattern within the female (but not male) nesting cycle: survival was significantly lower during the laying, incubation, and nestling periods (0.934, 95% CI: 0.898–0.958), when birds spent much time on the nest, compared to the nest building and fledgling periods (1.000, 95% CI: 1.00–1.000), when we did not record any female mortality. These data (coupled with some direct evidence, like bird corpses or blood remains found next to/on the nest) may suggest that the main cause of adult mortality was on-nest predation. The calculated survival rates for both sexes during the breeding season were high compared to annual rates reported for this species, suggesting that a majority of mortality occurs at other times of the year, during migration or wintering. These results have implications for understanding survival variation within the reproductive period as well as general trends of avian mortality.     

Can a ‘wintering area effect’ explain population status of Swainson's hawks? A stable isotope approach

It has been suggested that declines in breeding populations of Swainson's hawks ( Buteo swainsoni ) in California, Oregon, and Nevada may be due to differential mortality of hawks on their wintering grounds. Although massive mortality incidents reported on the wintering grounds partially support this suggestion, there are no data showing differential use of wintering areas by breeding populations of Swainson's hawks. We used stable-hydrogen isotope analysis of feathers to determine whether large flocks of hawks wintering in Argentina consisted of a mixture of individuals from across the North American breeding range or consisted of individuals from discrete breeding populations. We found that flocks of wintering Swainson's hawks consisted of a mixture of individuals. The lack of connectivity between populations of breeding and wintering hawks suggests that high wintering mortality, either natural or human-induced, is unlikely to have direct consequences on a single breeding area in North America. The demographic effects of winter mortality should be 'diluted' across the entire breeding range of Swainson's hawks.     

Effects of flyway‐wide weather conditions and breeding habitat on the breeding abundance of migratory boreal waterbirds

Anthropogenic habitat loss and climate change are among the major threats to biodiversity. Bioclimatic zones such as the boreal and arctic regions are undergoing rapid environmental change, which will likely trigger changes in wildlife communities. Disentangling the effects of different drivers of environmental change on species is fundamental to better understand population dynamics under changing conditions. Therefore, in this study we investigate the synergistic effect of winter and summer weather conditions and habitat type on the abundance of 17 migratory boreal waterbird species breeding in Finland using three decades (1986–2015) of count data. We found that above‐average temperatures and precipitations across the western and northern range of the wintering grounds have a positive impact on breeding numbers in the following season, particularly for waterbirds breeding in eutrophic wetlands. Conversely, summer temperatures did not seem to affect waterbird abundance. Moreover, waterbird abundance was higher in eutrophic than in oligotrophic wetlands, but long term trends indicated that populations are decreasing faster in eutrophic than in oligotrophic wetlands. Our results suggest that global warming may apparently benefit waterbirds, e.g. by increased winter survival due to more favourable winter weather conditions. However, the observed population declines, particularly in eutrophic wetlands, may also indicate that the quality of breeding habitat is rapidly deteriorating through increased eutrophication in Finland which override the climatic effects. The findings of this study highlight the importance of embracing a holistic approach, from the level of a single catchment up to the whole flyway, in order to effectively address the threats that waterbirds face on their breeding as well as wintering grounds.     

Carry‐over effects provide linkages across the annual cycle of a Neotropical migratory bird,the Louisiana Waterthrush Parkesia motacilla

Population limitation models of migratory birds have sought to include impacts from events across the full annual cycle. Previous work has shown that events occurring in winter result in some individuals transitioning to the breeding grounds earlier or in better physical condition than others, thereby affecting reproductive success (carry‐over effects). However, evidence for carry‐over effects from breeding to wintering grounds has been shown less often. We used feather corticosterone (CORT_f) levels of the migratory Louisiana Waterthrush Parkesia motacilla as a measure of the physiological state of birds at the time of moult on the breeding territory to investigate whether carry‐over effects provide linkages across the annual cycle of this stream‐obligate bird. We show that birds arriving on wintering grounds with lower CORT_f scores, indicating reduced energetic challenges or stressors at the time of moult, occupied higher quality territories, and that these birds then achieved a better body condition during the overwinter period. Body condition, in turn, was important in determining whether adult birds returned the following winter, with birds in better condition returning at higher rates. Together these data suggest a carry‐over effect from the breeding grounds to the wintering grounds that is further extended with respect to annual return rates. Very few other studies have linked conditions during the previous breeding season with latent effects during the subsequent overwintering period or with annual survival. This study shows that the effects of variation in energetic challenges or stressors can potentially carry over from the natal stream and accumulate over more than one life‐history period before being manifested in reduced survival. This is of particular relevance to models of population limitation in migratory birds.     

Differential adult survival at close seabird colonies: The importance of spatial foraging segregation and bycatch risk during the breeding season

Marine megafauna, including seabirds, are critically affected by fisheries bycatch. However, bycatch risk may differ on temporal and spatial scales due to the uneven distribution and effort of fleets operating different fishing gear, and to focal species distribution and foraging behavior. Scopoli's shearwater Calonectris diomedea is a long‐lived seabird that experiences high bycatch rates in longline fisheries and strong population‐level impacts due to this type of anthropogenic mortality. Analyzing a long‐term dataset on individual monitoring, we compared adult survival (by means of multi‐event capture–recapture models) among three close predator‐free Mediterranean colonies of the species. Unexpectedly for a long‐lived organism, adult survival varied among colonies. We explored potential causes of this differential survival by (1) measuring egg volume as a proxy of food availability and parental condition; (2) building a specific longline bycatch risk map for the species; and (3) assessing the distribution patterns of breeding birds from the three study colonies via GPS tracking. Egg volume was very similar between colonies over time, suggesting that environmental variability related to habitat foraging suitability was not the main cause of differential survival. On the other hand, differences in foraging movements among individuals from the three colonies expose them to differential mortality risk, which likely influenced the observed differences in adult survival. The overlap of information obtained by the generation of specific bycatch risk maps, the quantification of population demographic parameters, and the foraging spatial analysis should inform managers about differential sensitivity to the anthropogenic impact at mesoscale level and guide decisions depending on the spatial configuration of local populations. The approach would apply and should be considered in any species where foraging distribution is colony‐specific and mortality risk varies spatially.     

Spatial heterogeneity in mortality and its impact on the population dynamics of Eurasian woodcocks

Spatial heterogeneity, especially in mortality risk, is a major factor shaping population dynamics. Here we study the impacts of spatial heterogeneity in hunting pressure on the demography of Eurasian woodcock Scolopax rusticola, a relatively long-lived migratory game bird. We develop capture–recapture–recovery models in which both seasonality and spatial variation in hunting pressure are accounted for, and fit them to individual-based data collected across the French wintering range (>44000 banded individuals) as well as recoveries from spring stopovers and breeding grounds in Europe. Our results quantify spatial variation in survival probability in the wintering areas. They highlight the role of source-sink dynamics involving juvenile settlement decisions, as well as the importance of mortality outside the winter quarters. We also discuss the impact of spatial heterogeneity for demographic parameter estimation and data collection at the range scale.     

Foraging movements of the Shy Albatross Diomedea cauta breeding in Australia; implications for interactions with longline fisheries

Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedea cauta breeding at two sites off Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island foraged over the Australian continental shelf or slope waters off northwest Tasmania, while those from Pedra Branca foraged between the colony and the southeastern edge of the continental shelf. The distances travelled by the birds and the duration of their foraging trips varied during the breeding cycle and tended to decrease as eggs approached hatching. Adults which were tracked near the end of the breeding season (March-April, n = 7 birds) deserted their chicks prematurely, and while dispersing further than incubating or brooding birds, they remained over the continental shelf and slope waters off southeast Australia. Home range analyses indicated 41% overlap between foraging zones of birds during successive breeding stages. Dispersal during the postbreeding period extended the foraging zones with less overlap between individuals (10% for Albatross Island and 19% for Pedra Branca). The recent contraction of the Japanese Southern Bluefin Tuna longline fishery to the south and east coasts of Tasmania has resulted in extensive overlap with adult Shy Albatrosses from Pedra Branca, but appears to pose a minimal threat to adult birds from Albatross Island. Coupled with the concomitant increase in the Australian domestic tuna longlining industry, adult Shy Albatrosses from southern Tasmania (Pedra Branca and the Mewstone) are vulnerable to incidental capture through out their annual cycle.     

Effects of Climate Change and Fisheries Bycatch on Shy Albatross (Thalassarche cauta) in Southern Australia

The impacts of climate change on marine species are often compounded by other stressors that make direct attribution and prediction difficult. Shy albatrosses (Thalassarche cauta) breeding on Albatross Island, Tasmania, show an unusually restricted foraging range, allowing easier discrimination between the influence of non-climate stressors (fisheries bycatch) and environmental variation. Local environmental conditions (rainfall, air temperature, and sea-surface height, an indicator of upwelling) during the vulnerable chick-rearing stage, have been correlated with breeding success of shy albatrosses. We use an age-, stage- and sex-structured population model to explore potential relationships between local environmental factors and albatross breeding success while accounting for fisheries bycatch by trawl and longline fisheries. The model uses time-series of observed breeding population counts, breeding success, adult and juvenile survival rates and a bycatch mortality observation for trawl fishing to estimate fisheries catchability, environmental influence, natural mortality rate, density dependence, and productivity. Observed at-sea distributions for adult and juvenile birds were coupled with reported fishing effort to estimate vulnerability to incidental bycatch. The inclusion of rainfall, temperature and sea-surface height as explanatory variables for annual chick mortality rate was statistically significant. Global climate models predict little change in future local average rainfall, however, increases are forecast in both temperatures and upwelling, which are predicted to have detrimental and beneficial effects, respectively, on breeding success. The model shows that mitigation of at least 50% of present bycatch is required to offset losses due to future temperature changes, even if upwelling increases substantially. Our results highlight the benefits of using an integrated modeling approach, which uses available demographic as well as environmental data within a single estimation framework, to provide future predictions. Such predictions inform the development of management options in the face of climate change.     

The interacting effects of food,spring temperature,and global climate cycles on population dynamics of a migratory songbird

Although long‐distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black‐throated blue warbler (Setophaga caerulescens), a double‐brooded long‐distance migrant, we used Pradel models to analyze 25 years of mark–recapture data collected in New Hampshire, USA. We assessed the effects of spring temperature (local weather) and the El Niño Southern Oscillation index (a global climate cycle), as well as predator abundance, insect biomass, and local conspecific density on population growth in the subsequent year. Local and global climatic conditions affected warbler populations in different ways. We found that warbler population growth was lower following El Niño years (which have been linked to poor survival in the wintering grounds and low fledging weights in the breeding grounds) than La Niña years. At a local scale, populations increased following years with warm springs and abundant late‐season food, but were unaffected by spring temperature following years when food was scarce. These results indicate that the warming temperature trends might have a positive effect on recruitment and population growth of black‐throated blue warblers if food abundance is sustained in breeding areas. In contrast, potential intensification of future El Niño events could negatively impact vital rates and populations of this species.     

Differences in shifts of wintering and breeding ranges lead to changing migration distances in European birds

Studies on the impact of climate change on the distributions of bird species in Europe have largely focused on one season at a time, especially concerning summer breeding ranges. We investigated whether migratory bird species show consistent range shifts over the past 55 yr in both breeding and wintering areas or if these shifts are independent. We then analyzed whether patterns in changing migration distances of Finnish breeding birds could be explained by habitat use, phylogeny or body size. We used long‐term datasets from the Finnish ringing centre to analyze the mean wintering latitudes of 29 species of Finnish breeding birds, then used breeding distribution data to make predictions as to whether certain species were migrating shorter or longer distances based on the comparative shifts in the wintering and breeding grounds. Our data reveal species‐specific differences in changing migration distances. We show that for many species, long‐term shifts in wintering ranges have not followed the same patterns as those in the breeding range, leading to differences in migration distances over time. We conclude that species are not adjusting predictably to climate change in their wintering grounds, leading to changing migration distances in some, but not all, species breeding in Finland. This research fills an important gap in the current climate change biology literature, focusing on individuals’ entire life histories and revealing new complexities in range shift patterns.     

Survival of Breeding Pacific Common Eiders on the Yukon-Kuskokwim Delta,Alaska

ABSTRACT Populations of Pacific common eiders (Somateria mollissima v-nigrum) breeding in Alaska, USA, have declined markedly over the past 40 years. We studied survival of adult female Pacific common eiders using capture—recapture of nesting hens at 3 sites on the Yukon-Kuskokwim Delta (YKD), Alaska from 1994 to 2004. We used data consisting of 268 recapture events from 361 uniquely marked individuals to investigate temporal, geographic, and environmental variation in adult female survival. Our results suggest apparent annual survival of adult eiders from the YKD was high (0.892, SE = 0.022) and spatially and temporally invariant (σ² = 0.005), a pattern consistent with other long-lived marine birds. Moreover, our results suggest adult survival may be functionally fixed for Pacific common eiders, and at the present, adult survival may be relatively unresponsive to environmental or management perturbations. Our data did not support hypothesized variation in survival relative to mortality factors such as predation on breeding grounds, physiologic costs of reproduction, and wintering conditions. Although changes in adult survival likely have a large potential effect on prospective population growth, our results suggest viable management actions aimed at increasing survival may be extremely limited.