Differences In Population Trends Research Articles

Ecological traits predict population trends of urban birds in Europe

The population dynamics of urban animals has been so far remarkably understudied. At the same time, urban species’ population trends can provide important information on the consequences of environmental changes in cities. We modelled long-term population trends of 93 bird species breeding in urban areas in 16 European countries as a function of species’ traits, characterising variability in their urbanization and ecology. We found that: (i) earlier colonisers have more negative population trends than recent colonisers; (ii) more urbanized open habitat species had more positive population trends than less urbanized open habitat species; (iii) highly urbanized birds breeding above the ground had more negative trends than highly urbanized ground breeders. These patterns can be explained by several processes occurring in cities as well as outside city borders. Namely, (i) pre-industrial colonisers might struggle to persist in rapidly changing urban areas, limiting their foraging and breeding opportunities of the birds. (ii) Open habitats are under pressure of intensive agricultural exploitation in rural areas, which may negatively affect populations of less urbanized birds. In contrast, urban areas do not experience such pressure keeping the trends of urbanized open habitat species more positive. (iii) Differences in population trends between highly urbanized ground and above-ground breeders suggest that the latter may lose their breeding opportunities in modern buildings that do not provide suitable breeding sites. Our results indicate that even once successful, city dwellers may not keep pace with changes in urban areas, but these areas may also provide suitable habitats for biodiversity.

Population dynamics in Taiwan from the Neolithic to early historic periods (5000–100 cal BP): Linking cultural developments and environmental change

To reconstruct population dynamics in Taiwan between 5000 and 100 cal BP, we analysed spatial-temporal changes in archaeological site abundance and size (area). The results suggest that population growth was discontinuous throughout the study region and that the main spatial differences in population trends were between eastern/northern and western Taiwan. Comparison of settlement data shows that population trends in Taiwan and different regions in continental China were partly parallel. We contrast these data with political, economic, settlement, and climatic developments in continental China, when considering possible factors that influenced these demographic relationships. In addition, we examined published palaeoenvironmental time series from the broader study region to explore human-environment interactions. This revealed that proxy records of human activities (agriculture, deforestation) correlate with the derived trends in site abundance and area. Furthermore, we hypothesise that the inferred sparse settlement in eastern Taiwan during 2700–1800 cal BP is related to climate change. An increase in seasonal rainfall and high-intensity precipitation events in late summer and autumn, due to long-term changes in summer monsoon precipitation and El Niño–Southern Oscillation intensity, likely resulted in unfavourable hydrological conditions for crop cultivation in this part of the study region.

Trophic selectivity of the barnacle goose and the white-fronted goose in the area of reproductive concentration

Against the backdrop of intense transformation of the Arctic environment and biota, differences in population trends of massive and widespread herbivores in the Arctic are of great interest. In this regard, the main goal of our work was a comparative assessment of the trophic selectivity of the barnacle goose and the white-fronted goose under conditions of the largest reproductive concentration, characterizing the role of competition in the dynamics of their populations. It has been shown that the differences in the quantitative ratio of plants eaten by these species are not sufficient to avoid competition, and that the most selective, i.e. The food of the barnacle goose is sensitive to quality and energy-consuming. However, its status as a relatively weak competitor belies the exponential growth of its population in the study area and the entire Arctic population. We believe that differences in the population dynamics of the barnacle goose and the white-fronted goose are currently not due to competition during reproductive concentrations, but to the influence of anthropogenic and climatic factors far beyond the breeding range.

Contrasting bottom-up effects of warming ocean on two king penguin populations.

Breeding success is often correlated with climate, but the underlying bottom-up mechanisms remain elusive-particularly in marine environments. Consequently, conservation plans of many species often consider climate change as a unilateral threat, ignoring that even nearby populations can show contradicting trends with climate. Better understanding the relationship between climate and environment at different scales can help us interpret local differences in population trends, ultimately providing better tools to evaluate the global response of a species to threats such as global warming. We studied a growing king penguin population nesting at Kerguelen island (Southern Indian Ocean), hosting one of the largest colonies in the world. We used a unique dataset of foraging, breeding success, and climate data spanning over 25 years to examine the links between climate, marine environment, and breeding success at this colony. The results were then compared to the neighboring population of Crozet, which experienced the steepest decline for this species over the past few decades. At Crozet, penguins experienced lower breeding success in warmer years due to productive currents shifting away from the colony, affecting foraging behavior during chick rearing. At Kerguelen, while chick mass and survival experienced extreme variation from year to year, the annual variation was not associated with the position of the currents, which varied very little compared to the situation in Crozet. Rather than being affected by prey distribution shifts, we found evidence that chick provisioning in Kerguelen might be influenced by prey abundance, which seem to rather increase in warmer conditions. Furthermore, warmer air temperature in winter increased chick survival rate, likely due to reduced thermoregulation cost. Investigating the mechanisms between climate and fitness allowed us to predict two different fates for these populations regarding ongoing global warming.

An assessment of people living by coral reefs over space and time.

Human populations near ecosystems are used as both a proxy for dependency on ecosystems, and conversely to estimate threats. Consequently, the number of people living near coral reefs is often used in regional coral reef management, evaluation of risk at regional and global scales, and even considerations of funding needs. Human populations and their statistics, are ever-changing and data relating to coral reefs have not been updated regularly. Here, we present an up-to-date analysis of the abundance, and density of people living within 5-100 km of coral reef ecosystems along with population proportion, using freely available data sets and replicable methods. We present trends of changes in human populations living near coral reefs over a 20-year time period (2000-2020), divided by region and country, along with socio-economic denominations such as country income category and Small Island Developing States (SIDS). We find that across 117 coral reef countries there are currently close to a billion people living within 100 km of a coral reef (~13% of the global population) compared with 762 million people in 2000. Population growth by coral reefs is higher than global averages. The Indian Ocean saw a 33% increase in populations within 100 km of a coral reef and 71% at 5km. There are 60 countries with 100% of their population within 100 km of coral reefs. In SIDS, the proportion of the total population within 100 km of a coral reef is extremely high: 94% in 2020. Population density 5-10km from coral reefs is 4× the global average. From 5 to 100 km, more people from lower-middle-income countries live by coral reefs than any other income category. Our findings provide the most up-to-date and extensive statistics on the regional and nation-level differences in population trends that play a large role in coral reef health and survival.

Reproductive success of the wood warbler Phylloscopus sibilatrix varies across Europe

Differences in population trends across a species' breeding range are ultimately linked to variation in demographic rates. In small songbirds, demographic rates related to fecundity typically have strong effects on population trends. Populations of a forest songbird, the wood warbler Phylloscopus sibilatrix, have been declining in many but not all regions of the European breeding range. We investigated if clutch size, hatching rate, nest survival and number of fledglings vary across Europe, and if nest survival is related to differences in the regionally dominant nest predator class (birds versus mammals). From 2009 to 2020, we monitored 1896 nests and used cameras at a subsample of 645 nests in six study regions: the United Kingdom (mid‐Wales, Dartmoor, the New Forest), Germany (Hessen), Switzerland (Jura mountains) and Poland (Białowieża National Park). Number of fledglings was lowest in the New Forest (1.43 ± CI 0.23), intermediate in Jura (2.41 ± 0.31) and Białowieża (2.26 ± 0.24) and highest in mid‐Wales (3.02 ± 0.48) and Dartmoor (2.92 ± 0.32). The reason for low reproductive success in the New Forest, Jura and Białowieża was low nest survival, and large clutch sizes in Białowieża did not compensate for high nest losses. High reproductive success in mid‐Wales and Dartmoor was due to high nest survival and large clutch sizes. Overall predation rates were similar everywhere despite variation between the regions in the dominant nest predator class. Unsuccessful nests in mid‐Wales were mainly predated by birds; in Dartmoor, the New Forest, Hessen and Jura similarly by birds and mammals; and in Białowieża exclusively by mammals. Regional reproductive success does not match the population trends recently reported for the wood warbler in the six study regions (i.e. high reproduction ≠ positive trend). Annual survival may be a decisive factor, but it is difficult to quantify for a nomadic species such as the wood warbler that rarely returns to the same breeding locations.

Historical reconstruction of the population dynamics of southern right whales in the southwestern Atlantic Ocean

Understanding the recovery of whale populations is critical for developing population-management and conservation strategies. The southern right whale (SRW) Eubalena australis was one of the baleen whale species that has experienced centuries of exploitation. We assess here for the first time the population dynamics of the SRW from the southwestern Atlantic Ocean at the regional level to measure numerically the effect of whaling and estimate the population trend and recovery level after depletion. We reconstructed the catch history of whaling for the period 1670–1973 by an extensive review of different literature sources and developed a Bayesian state-space model to estimate the demographic parameters. The population trajectory indicated that the pre-exploitation abundance was close to 58,000 individuals (median = 58,212; 95% CI = 33,329–100,920). The abundance dropped to its lowest abundance levels in the 1830s when fewer than 2,000 individuals remained. The current median population abundance was estimated at 4,742 whales (95% CI = 3,853–6,013), suggesting that the SRW population remains small relative to its pre-exploitation abundance (median depletion P2021 8.7%). We estimated that close to 36% of the SRW population visits the waters of the Península Valdés, the main breeding ground, every year. Our results provide insights into the severity of the whaling operation in the southwestern Atlantic along with the population´s response at low densities, thus contributing to understand the observed differences in population trends over the distributional range of the species worldwide.

Men's decrease and women's increase in harmful alcohol use from the 2014 to 2018 national surveys in Taiwan: A harbinger for an emerging national trend in East Asia?

Gender differences in alcohol use have narrowed in Western societies, but that in Asia has been less investigated. By comparing the 2014 and 2018 waves of the national survey in Taiwan, we aimed to examine the gender differences in population trends in past-month alcohol use, binge drinking, and harmful alcohol use. The national survey enrolled 17,837 participants in 2014 and 18,626 participants in 2018. Binge drinking was defined as having ≥5 drinks on one occasion in the past month, and harmful alcohol use as having an Alcohol Use Disorders Identification Test score of ≥8. There were significant decreases from 2014 to 2018 in the population's prevalence of past-month alcohol use, binge drinking, and harmful alcohol use. However, males and females had different trends: males showed significant reductions in all three alcohol use behaviours (a decrease of 3.79%, 1.59%, and 2.60%, respectively), while females exhibited a significant rise in harmful alcohol use (from 1.32% to 1.72%), particularly among those aged 18-29 years. There was gender convergence in alcohol use in Taiwan, mainly due to men's decrease and women's increase in harmful alcohol use. Our findings have important implications for the intervention and prevention of the problematic use of alcohol in East Asia.

The Asian Woollyneck Ciconia episcopus: A Review of its Status, Distribution and Ecology

The Asian Woollyneck Ciconia episcopus is a stork found throughout Asia whose international conservation status is currently being considered for reclassification from vulnerable to near-threatened. However, much of what is known about this species is fragmented across observational reports and small studies making a comprehensive assessment of population trends difficult. Here, we bring together all available published information to see what is known and what research questions still need answering in order to make reliable assessments of regional population trends and identify probable drivers of decline. Despite the species likely being extinct in the extremes of its former range and evidence of dramatic declines in Southeast Asia, Asian Woollyneck appears to be stable or increasing in India, Sri Lanka and Nepal. Observations of its preferred foraging and nesting habitats in South versus Southeast Asia show some obvious differences that may explain regional variations in population trends. In South Asia the bird is common in open grasslands and agricultural areas, while in Southeast Asia it is mostly observed in forested areas. Also, reports of the Asian Woollyneck nesting on cell phone towers is increasing in South Asia. However, because of a severe lack of reporting from Southeast Asia, it is unclear if or how these regional differences in population trends and habitat use are linked. Structured surveys and studies into the Asian Woollyneck foraging, nesting and movement ecology are urgently needed to understand the extent and drivers of decline in Southeast Asia. Therefore, researchers should focus future studies on population trends across the species' range, and aim to identify the local factors influencing recent changes in population growth. Without such knowledge, reassessment of its conservation status may be premature.

Population Viability Analysis of Yangtze Finless Porpoise in the Yangtze Main Steam Suggesting that a Total Ban on Productive Fishing could be Decisive

Background: China is paying more attention to ecological systems within the Yangtze River has provided great opportunities to the conservation of the Yangtze finless porpoise (YFP). The rapid population decline of YFP in the main steam appears to have slowed, but the infrequent movement of porpoises represents a considerable threat to the long-term viability of this species in this region. We studied the population viability of YFP in the Yangtze main steam, based on published ecological and genetic information.Methods: Vortex model was used to analyze the population viability of the YFP. The simulations were started from the year 2017 when the initial population size was 445 animals in baseline scenario. We examined the population viability for the species under demographic fluctuations and conservation scenarios.Result: Baseline model showed the probability of extinction was 0.245; deterministic growth rate was -0.023; stochastic growth rate was -0.036. Sensitivity analysis showed differences in population trends between the baseline and each alternative scenario and the most sensitive parameters were the percentage of females breeding and mortality rates. Under different conservation scenarios, the population of the YFP in the main stream will increase by 11.0%-181.2% in 100 years.

Using citizen science to assess drivers of Common House Martin Delichon urbicum breeding performance

Many hirundine (swallows and martins) species are declining throughout their ranges. The Common House Martin Delichon urbicum is a migratory hirundine that breeds throughout Europe but has shown recent declines in some parts of the UK, particularly in the south. We conducted a large‐scale citizen science survey to assess how the breeding performance of House Martins, measured by the number of attempted broods and nest success, is influenced by nest‐specific, landscape and weather factors. Pairs in eastern parts of the UK started breeding earlier than those in the west, and breeding performance was higher in eastern regions. There was no effect of latitude on either aspect of breeding performance, so our measures of breeding performance alone do not help to explain differences in population trends across the UK. The probability of attempting multiple broods and producing successful nests was higher in previously used nests than in newly built nests, and in artificial nests than in natural nests. Nests built on plastic soffits of buildings were less likely to be multi‐brooded and less likely to be successful compared with other materials. Suggested conservation measures therefore include discouraging the removal of old nests and encouraging the installation of artificial nests, particularly on buildings with plastic soffits. This study provides comprehensive insight into the breeding biology of House Martins, and although our findings do not show conclusively that breeding performance is the sole driver of population trends, they go some way to explain declines in House Martins and ultimately provide information that may help conserve this species.

What are the competitive effects of invasive species? Forty years of the Eurasian collared-dove in North America

Eurasian collared-doves (Streptopelia decaocto; hereafter ‘collared-doves’) have spread throughout North America since they first colonized Florida in the early 1980s. Here I test for adverse effects of this introduced species on four confamilial potential competitor dove and pigeon species using data from the breeding season (North American Breeding Bird Survey; BBS) and the winter (Audubon Christmas Bird Count; CBC). Within sites of both sets of surveys, correlations between populations of collared-doves and all four potential competitor species have generally been either nonsignificant or positive, indicating a lack of adverse competitive effects due to collared-doves. Similarly, there were no significant differences in population trends of any of the four species in sites where collared-doves were present compared to those where they were not, and there have been no significant declines in population trends of the four species driven by differences in collared-dove abundance in areas where the latter were present. Overall, analyses revealed no negative effects of collared-doves on populations of these potential competitors. Evidence thus far supports a ‘passenger’ rather than a ‘driver’ role for collared-doves in North America, although future monitoring of potential competitor species is warranted, especially if collared-dove populations continue to increase.

The paradox of endangered European rabbits regarded as pests on the Iberian Peninsula: trends in subspecies matter

The European rabbit Oryctolagus cuniculus faces a paradoxical situation in its native range on the Iberian Peninsula. While many populations have declined sharply due to a new variant of the rabbit haemorrhagic disease virus (RHDV-b), others remain healthy. The latter populations, which flourish mostly on farmland, cause significant crop damage. We explored if this difference could be related to the existence of the 2 rabbit subspecies (O. c. algirus and O. c. cuniculus) that coexist allopatrically on the Iberian Peninsula. Potential differences in population trends between rabbit subspecies may also be relevant in assisting the conservation of endangered rabbit-dependent predators which mainly occur in the distribution area of O. c. algirus. To test this, we assessed rabbit trends after the outbreak of RHDV-b by an online questionnaire to the senior administrative officers of all provincial official game departments throughout peninsular Spain (n = 47). A generalized negative trend was reported by officers in the distribution area of O. c. algirus, while a more stable or even positive trend was reported in the distribution area of O. c. cuniculus. We point to the need for establishing a long-term rabbit population monitoring programme on the Iberian Peninsula to further confirm the observed patterns, but also to contribute to evidence-based management decision-making. Our results suggest a need to apply different management systems for each rabbit subspecies.

Differential responses to expansion and crisis? The role of urban‐rural divides in long‐term demographic dynamics

AbstractEconomic downturns in advanced countries may influence demographic dynamics, increasing regional differences in population trends and consolidating social divides in accessible and marginal regions. The present study proposes a quantitative framework analysing the latent impact of economic expansions and recessions on regional population dynamics in Greece. Selected indicators (population density, contribution of natural balance and migration balance to total population growth, gross fertility rate and crude birth rate, crude marriage rate, births per marriage, and crude mortality rate) were used to distinguish long‐term transitional processes (1956‐2017) from short‐term dynamics characterising the most recent economic expansion (2000‐2008) and recession (2009‐2017) in Greece. Indicators were calculated separately for Attica, a metropolitan region centred on Athens, where more than 30 per cent of country population was (and still is) settled, and the rest of Greece, allowing a detailed analysis of socio‐demographic dynamics in urban and rural areas. Results of this study indicate that regional population trends in Greece were influenced by a combination of factors reflecting long‐term transitional forces, urbanisation/suburbanisation processes, and short‐term impact of economic downturns.

Evidence for multiple drivers of aerial insectivore declines in North America

AbstractAerial insectivores (birds that forage on aerial insects) have experienced significant population declines in North America. Numerous hypotheses have been proposed for these declines, but current evidence suggests multiple factors could be operating in combination during their annual migratory cycles between breeding and nonbreeding areas. Potential drivers include decreased prey abundance, direct or indirect impacts of environmental contaminants, habitat loss, phenological changes due to warming climate, and conditions on migratory stopover or wintering grounds. While no single threat appears to be the cause of aerial insectivore declines, existing evidence suggests that several of these factors could be contributing to the declines at different times in the annual lifecycle. Breeding productivity for most of these species does not appear to be limited by overall prey abundance, contaminants, or habitat loss, which suggests that similar issues on nonbreeding grounds or carryover effects could play important roles. However, a better understanding of the importance of prey quality throughout the lifecycle is critically needed. Based on current evidence, we propose that changes in availability of high-quality prey, with variability across breeding and nonbreeding grounds, reduce various combinations of fledging success, post-fledging survival, and nonbreeding season body condition of aerial insectivores, resulting in species and geographic differences in population trends. We encourage others to use this hypothesis as a starting point to test specific mechanisms by which availability of high-quality prey influences demographic parameters. We suggest that future research focus on defining prey quality, monitoring insect abundance in conjunction with birds, comparing demographic models across local populations experiencing different population growth rates, and using tracking technology to document important migratory and nonbreeding areas. Considerable research progress already has been made, but additional research is needed to better understand the complex web of potential causes driving aerial insectivore declines.

An Analysis of the Interactions Between Weather and Land Use on Midwestern Gamebird Populations Using Historical Data: A Preliminary Report

Concern surrounding species’ abilities to cope with a changing climate and variable land use presents opportunities to look forward toward solutions while investigating historical trends to assess the interaction of land use and weather. Uncertainty surrounding population responses to increased severity and frequency of severe weather associated with climate change presents challenges for making informed management decisions for a suite of already declining bird populations, including huntable populations of socially and economically important game birds, such as northern bobwhite (Colinus virginianus). Historical data are a rich resource for developing a priori hypotheses and models predicting species’ responses to climate change and continued variation in land use. We are utilizing 30 years of historical data to model the responses of northern, ring-necked pheasant (Phasianus colchicus), and wild turkey (Meleagris gallopavo) to land use change and weather within a gradient of land use and climate in Nebraska, Kansas, Iowa, and Missouri. Mixed models incorporating agricultural acreages, relative abundances of gallinaceous birds from the annual Breeding Bird Survey, and historical precipitation and temperature data built at the county-level will illuminate broad scale trends and enable us to draw conclusions about future population responses. We are finding expected differences in population trends between states within a climatic gradient, and varied responses to temperature and precipitation among gallinaceous species, where different annual periods are more or less crucial for different species despite similar life history characteristics. We expect that further modeling will continue to elucidate critical thresholds for birds in the Great Plains in terms of weather and habitat, allowing us to make strong recommendations to managers preparing to deal with the implications of climate change.

Using habitat-specific population trends to evaluate the consistency of the effect of species traits on bird population change

Many species are undergoing rapid population declines, while other species have increased. Previous work has related population change to species traits to elucidate the drivers of population change. However, this assumes that these drivers operate consistently across habitats. We use national-scale monitoring data on UK bird abundance from 1994–2012 to calculate habitat-specific population trends, allowing us to evaluate whether the effect of species traits was consistent between habitats. Although we found significant interactions with habitat for traits relating to migratory behaviour, diet, nest site and habitat specialisation, the direction of these trait effects was generally consistent between habitats. This suggests that large-scale processes operating across habitats are responsible for many changes in bird populations, although processes operating within habitats can modulate the effect of these drivers. Despite this, differences in population trends between habitats remain when variation in population trends due to species identity is accounted for, indicating that some habitat effects do occur. By identifying the scale at which drivers of population change operate, it is possible to target conservation actions more directly. Population declines were most evident in woodland and urban habitats, and we suggest that these habitats should be the focus of increased research and conservation effort if declines evident in many bird species are to be reversed.

Estimating sex-specific abundance in fawning areas of a high-density Columbian black-tailed deer population using fecal DNA

The recent development of fecal-genetic capture-mark-recapture (CMR) methods has increased the feasibility of estimating abundance of forest-dwelling ungulates that are difficult to survey using visual methods. Unless genetic markers differentiating sex are incorporated into such studies, however, genetic CMR approaches risk missing sex-specific differences in population trends. We developed a single-reaction genetic assay for sex and individual identification, including 10 microsatellites and an SRY marker, and applied it in the context of a post-fawning CMR study of Columbian black-tailed deer (Odocoileus hemionus columbianus) in forested habitat of coastal California during 2011 and 2012. We measured sex-specific abundance and sex ratios in high-quality summer habitats encompassing 4 distinct fawning areas. We detected a significant interaction between sex and year, indicating different trends in the abundance of males and females. We also detected a significant decline in abundance of females between years (P = 0.045), which agreed with independent telemetry-based estimates, and significant differences in female abundance among fawning areas (P = 0.020) but no significant differences in the abundance of males for either variable (F1–3,20 < 0.710, P > 0.410). When sex was not considered in the analysis, we found no significant differences in abundance between the 2 years, suggesting that differing trends between the 2 sexes obscured the female-specific patterns. We estimated average local (i.e., on the high-quality summer ranges) density ( D ^ ) for females at 41.0 (± 5.9) deer/km2 in 2011 and 29.1 (± 6.8) deer/km2 in 2012, and local density of males at 15.7 (± 3.0) deer/km2 across the 2 study years. Accordingly, sex ratios differed between years (95% CI = 3.0–4.2 F:M ratio in 2011, 2.0–2.3 F:M ratio in 2012). Incorporating sex and individual markers into a single assay provided a cost-effective means of applying CMR estimation based on fecal DNA to a high-density ungulate population in a forested ecosystem and emphasized the importance of explicitly modeling sex in abundance estimation. © 2014 The Wildlife Society.

Migratory connectivity of Palaearctic–African migratory birds and their responses to environmental change: the serial residency hypothesis

In most long‐distance migratory birds, juveniles migrate without their parents and so are likely to lack detailed knowledge of where to go. This suggests the potential for stochasticity to affect their choice of wintering area at a large scale (&gt; 1000 km). Adults, in contrast, may re‐use non‐breeding sites that promote their survival, so removing uncertainty from their subsequent migrations. I review the evidence for large‐scale stochastic juvenile site selection followed by adult site fidelity, and then develop a ‘serial‐residency’ hypothesis based on these two traits as a framework to explain both the migratory connectivity and the population dynamics of migrant birds and how these are affected by environmental change. Juvenile stochasticity is apparent in the age‐dependent effects of weather or experimental displacement on the outcome of migration and in the very wide variation in the destinations of individuals originating from the same area. Adults have been shown to be very faithful to their wintering grounds and even to staging sites. The serial residency hypothesis predicts that migrants that show these two traits will rely on an individually unique but fixed series of temporally and spatially linked sites to complete their annual cycle. As a consequence, migratory connectivity will be apparent at a very small scale for individuals, but only at a large scale for a population, and juveniles are predicted to occur more often at less suitable sites than adults, so that survival will be lower for juveniles. Migratory connectivity will arise only through spatial and temporal autocorrelation with local environmental constraints, particularly on passage, and the distribution and age structure of the population may reflect past environmental constraints. At least some juveniles will discover suitable habitat that they may re‐use as adults, thus promoting overall population‐level resilience to environmental change, and suggesting value in site‐based conservation. However, because migratory connectivity only acts on a large scale, any population of migrants will contain individuals that encounter a change in suitability somewhere in their non‐breeding range, so affecting average survival. Differences in population trends will therefore reflect variation in local breeding output added to average survival from wintering and staging areas. The latter is likely to be declining given increasing levels of environmental degradation throughout Africa. Large‐scale migratory connectivity also has implications for the evolutionary ecology of migrants, generally because this is likely to lead to selection for generalist traits.

Methods for estimating spatial trends in Steller sea lion pup production using the Kalman filter

Many species exhibit spatially varying trends in population size and status, often driven by differences among factors affecting individual subpopulations. Estimation and differentiation of such trends may be important for management, and a driving force for monitoring programs. The ability to estimate spatial differences in population trend may depend on assumptions regarding connectivity among subpopulations (stock structure or spatial overlap in stressors), information that is often poorly known. Linear state-space models using the Kalman filter were developed, tested, and applied for trend estimation of pup production for the western Alaska stock of Steller sea lions (Eumetopias jubatus), given only count data. Models were able to estimate trends and abundance even when data were missing. Models that assumed spatial correlation in trend among rookeries were more robust to stock structure assumptions when the stock structure was potentially mis-specified. High levels of spatial correlation among rookeries estimated from Steller sea lion pup count data are consistent with large-scale covariance of population trend within the Steller sea lion metapopulation.