High Adult Survival Research Articles

Predictability of demographic rates based on phylogeny and biological similarity.

Lack of demographic data for most of the world's threatened species is a widespread problem that precludes viability-based status assessments for species conservation. A commonly suggested solution is to use data from species that are closely related or biologically similar to the focal species. This approach assumes similar species and populations of the same species have similar demographic rates, an assumption that has yet to be thoroughly tested. We constructed a Bayesian hierarchical model with data on 425 plant species to predict demographic rates (intrinsic rate of population growth, recruit survival, juvenile survival, adult survival, and fecundity) based on biological traits and phylogenetic relatedness. Generally, we found small effects of species-level traits (except woody polycarpic species tended to have high adult survival rates that increased with plant height) and a weak phylogenetic signal for 4 of the 5 demographic parameters examined. Patterns were stronger in adult survival and fecundity than other demographic rates; however, the unexplained variances at both the species and population levels were high for all demographic rates. For species lacking demographic data, our model produced large, often inaccurate, prediction intervals that may not be useful in a management context. Our findings do not support the assumption that biologically similar or closely related species have similar demographic rates and provide further evidence that direct monitoring of focal species and populations is necessary for informing conservation status assessments.

Ecology and breeding biology of a tropical bird, the Lovely Fairy-Wren (Malurus amabilis)

ABSTRACTThe Lovely Fairy-Wren (Malurus amabilis) is endemic to the wet tropics of Australia and is one of 11 species in the genus Malurus. Despite the large number of studies on fairy-wrens, little is known about the Lovely Fairy-Wren. This study provides the first detailed description of its ecology, behaviour, and breeding biology. Lovely Fairy-Wrens displayed breeding behaviour characteristic of tropical birds, with groups maintaining territories and breeding year-round, small clutch size (two to three eggs), long juvenile dependence (2 months) and high adult breeder survival (86%). They breed cooperatively, and groups formed when male (but not female) offspring delayed dispersal and remained in their natal group as subordinates. Groups were typically small (2.5 ± 0.8 individuals), possibly because productivity was low: 29% of the monitored groups produced at least one fledgling per year. Males provided high levels of parental care and this, together with low extra-pair courtship and petal displays, suggests that this species may not be as promiscuous as other fairy-wrens. Unlike other Australian fairy-wrens, males maintained their brightly coloured adult plumage year-round after initial acquisition. This lack of seasonal moult into dull plumage, coupled with the unusually colourful plumage of females in this species, suggests that the impact of natural selection on the plumage colour of both sexes may be lower in this species than in their congeners. We discuss similarities and differences in life-history and morphological traits between the Lovely Fairy-Wren and other Malurus species.

A review of predation as a limiting factor for bird populations in mesopredator-rich landscapes: a case study of the UK.

The impact of increasing vertebrate predator numbers on bird populations is widely debated among the general public, game managers and conservationists across Europe. However, there are few systematic reviews of whether predation limits the population sizes of European bird species. Views on the impacts of predation are particularly polarised in the UK, probably because the UK has a globally exceptional culture of intensive, high-yield gamebird management where predator removal is the norm. In addition, most apex predators have been exterminated or much depleted in numbers, contributing to a widely held perception that the UK has high numbers of mesopredators. This has resulted in many high-quality studies of mesopredator impacts over several decades. Here we present results from a systematic review of predator trends and abundance, and assess whether predation limits the population sizes of 90 bird species in the UK. Our results confirm that the generalist predators Red Fox (Vulpes vulpes) and Crows (Corvus corone and C. cornix) occur at high densities in the UK compared with other European countries. In addition, some avian and mammalian predators have increased numerically in the UK during recent decades. Despite these high and increasing densities of predators, we found little evidence that predation limits populations of pigeons, woodpeckers and passerines, whereas evidence suggests that ground-nesting seabirds, waders and gamebirds can be limited by predation. Using life-history characteristics of prey species, we found that mainly long-lived species with high adult survival and late onset of breeding were limited by predation. Single-brooded species were also more likely to be limited by predation than multi-brooded species. Predators that depredate prey species during all life stages (i.e. from nest to adult stages) limited prey numbers more than predators that depredated only specific life stages (e.g. solely during the nest phase). The Red Fox and non-native mammals (e.g. the American Mink Neovison vison) were frequently identified as numerically limiting their prey species. Our review has identified predator-prey interactions that are particularly likely to result in population declines of prey species. In the short term, traditional predator-management techniques (e.g. lethal control or fencing to reduce predation by a small number of predator species) could be used to protect these vulnerable species. However, as these techniques are costly and time-consuming, we advocate that future research should identify land-use practices and landscape configurations that would reduce predator numbers and predation rates.

How does a widespread reef coral maintain a population in an isolated environment?

In a changing global environment, previously suboptimal habitats may become climate refuges for species. For instance, the ranges of some tropical reef corals are already expanding poleward. Understanding the demographic strategies by which isolated or marginal populations persist is therefore important, especially since such populations are often both vulnerable to local extinction and sources of evolutionary novelty. This study builds an integral projection model from individual-level demographic rates for a genetically isolated population of a reef coral, Plesiastrea versipora, in Sydney Harbour, Australia, in order to understand the population-level demographic characteristics allowing its persistence. We show that this population is thriving, with the potential to rapidly increase in benthic cover, due to high adult survivorship and at least sporadic high recruitment. Medium-sized colonies are the most important for long-term population viability due to their reproductive potential. Nonetheless, the population's persistence is sensitive to recruitment and growth rates, and protecting it from factors that affect these processes is likely to be crucial for its longer-term survival.

Distribution, movements, and survival of the critically endangered Bengal Florican Houbaropsis bengalensis in India and Nepal

We undertook field surveys of the critically endangered Bengal Florican throughout its range in India and Nepal and used the results to develop models of distribution to identify new populations. We also tagged 11 birds with satellite transmitters to assess their distribution and habitat use during the non-breeding season, about which nothing is known. The models suggest that the distribution is now extremely fragmented in the west, although potentially sizeable populations may await discovery in eastern parts of the species’ range, particularly along the Brahmaputra River. After breeding, tagged birds left their breeding sites inside protected areas (PAs) and moved up to 80 km into landscapes characterised by relatively low-intensity agriculture along rivers with lower than average human population densities. Many birds spent more than six months away from their breeding grounds outside PAs. Models of non-breeding distribution suggest that some breeding areas become unsuitable at that time of the year, and therefore that birds may be forced to leave PAs at that time. Tagged birds had high annual adult survival rates (0.92, 95% confidence interval 0.858–0.953). Home ranges during the non-breeding season were significantly larger than breeding season home ranges. The results suggest that the conservation of this species needs to account for the species’ use outside the breeding season of less intensively cultivated floodplain-agricultural landscapes, as well as protecting breeding grassland sites.

Mimetic asociations in natural populations of tropical papilionid butterflies. I. Life history and structure of a tropical dry forest breeding population of Battus polydamus polydamus

A small breeding population of the butterfly Battus polydamus polydamus Linnaeus was studied at a tropical dry forest site in northwestern (Guanacaste Province), Costa Rica, from March through June, 1970. Life history, adult population size, adult turnover, adult dispersal, breeding behavior, territorial behavior and biotic mortality in larval populations were studied. It was condud­ ed that the apparent patchy distribution of the larval foodplant ( Aristolochia vines ) results in a very patchy distribution of breeding populations of this but terfly; low vagility, high adult survivorship and localized breeding interactions at the larval foodplant account for the apparent high population cohesiveness in this species, despite high levels of parasitism during the larval stage. Males eclose before females and establish territories at the breeding site and adult numbers remain consistent over long periods of time. The latter is believed to be a result of high adult survivorship (from predation by birds), with low mor­ tality associated with old age being counterbalanced with low recruitment of new adults to the population. The relation of such a population structure to mimicry theory is also discussed.

Weakening of the subpolar gyre as a key driver of North Atlantic seabird demography: a case study with Brünnich’s guillemots in Svalbard

The Arctic is experiencing environmental changes at unprecedented rates. These changes are spreading throughout the entire food web, affecting apex predators such as seabirds. Brunnich’s guillemot Uria lomvia populations in Svalbard archipelago have significantly declined since the mid-1990s. For long-lived species such as seabirds, population growth rate is highly sensitive to changes in adult survival rates, and slight changes in survival may have large consequences at the population level. Adult survival rates, were estimated for Brunnich’s guillemots individually marked and monitored from 1986 to 2011 at Bjornoya, Svalbard. While survival appeared to be repeatedly high (mean ± SE; 95 ± 1%) from 1986 to 1995-98 (transitional years, when Svalbard guillemot colonies started to decline), it dropped by 9-12% over the period 1995-98 to 2011. This decline coincided with the occurrence of an abrupt ecosystem shift in the North Atlantic Ocean in the mid-1990s and the weakening of the Atlantic subpolar gyre. Variations in the subpolar gyre index (SGI) were significantly associated with inter-annual variation in guillemot annual survival, and a strong gyre (i.e. cold waters on guillemot wintering grounds) was associated with high adult survival. Our results, combined with other studies, suggest that the SGI may be an important global proxy to assess oceanographic conditions and changes in marine ecosystems in the North Atlantic.

Life tables and elasticity analyses of Yangtze River fish species with implications for conservation and management

In conservation biology, knowing the life history strategy of a species is crucial for deciding which stage needs the greatest protection: reproduction, juveniles, or adults. Here, we compiled biological data for 83 Yangtze River fish species, constructed their life tables and conducted elasticity analyses, which calculates the proportional contribution of each vital rate (age-specific survival and fecundity) to the annual population multiplication rate. Life tables showed that, for our analyzed species, the survival rate of age 0 fish was extremely low, ranging from 1.25 × 10−6 to 1.74 × 10−2 year−1. All species showed a type III survivorship curve. Elasticity analysis revealed slow–fast continuum life histories ranging from species with a high contribution of fertility elasticity to the population growth rate, but lower juvenile and adult survival elasticity, as well as early maturation and short generation time to species that mature late, possess a long generation time, exhibit low fertility elasticity, and a high adult or juvenile survival elasticity. In addition, the analysis of all the species showed that fertility elasticity was significantly smaller than the sum of juvenile and adult survival elasticity, indicating the need to increase the juvenile and adult survival rates of Yangtze fish rather than focusing only on protecting reproduction and age 0 survival via a breeding season fishing ban which is the current conservation practice. Since overfishing has been proposed as the major factor responsible for the decline of Yangtze fish populations, we further suggest that controlling fishing pressure on juvenile and adult fish is another key conservation requirement.

Extreme migration and the individual quality spectrum

Costs of migration, in terms of time, energy, and mortality risk, have a strong theoretical and empirical foundation in the study of birds. We expect these costs to be most severe for extreme long‐distance migratory landbirds, whose demanding annual routines (e.g. non‐stop flights > 8000 km and return journeys > 30 000 km) may approach their maximum physiological capabilities. To explore whether this is true, we review evidence in long‐jump migratory shorebirds (Scolopacidae), focusing most on the prototypical example, the Alaska‐breeding bar‐tailed godwit Limosa lapponica baueri. Contrary to expectations, these and similar birds demonstrate high adult survival, little evidence for elevated mortality during migration, no apparent minimisation of non‐stop flight distances, and low inter‐ and intra‐individual variation in migration performance. Two key aspects of extreme migrants may explain these findings: 1) a counter‐intuitively conservative annual‐cycle strategy, which minimises risks and enables dissipation of carry‐over effects before fitness consequences arise; and 2) selection pressure during early life, which quickly removes low‐performing individuals from the population. We hypothesise that these two factors, applicable to extreme strategies in a wide range of taxa, act to truncate the range of individual quality in a population, and decrease the prevalence and detectability of carry‐over effects. Testing these hypotheses is challenging, as it requires comparative studies of demography and individual quality spectra along a continuum of extremeness. However, it has important potential implications for interpreting individual variation, designing studies of cross‐seasonal interactions or costs of migration, and recognising early‐warning signs of population decline. For example, the most extreme shorebird migrations rely on abundant but difficult‐to‐access resources; the high minimum individual performance required for survival predicts that degradation of these resource hot‐spots will propel rapid population collapse, rather than incremental declines in condition or performance. Therefore, in extreme migrants, we may paradoxically view populations as operating close to the edge, even while individuals are not.

Modeled Impacts of Chronic Wasting Disease on White-Tailed Deer in a Semi-Arid Environment.

White-tailed deer are a culturally and economically important game species in North America, especially in South Texas. The recent discovery of chronic wasting disease (CWD) in captive deer facilities in Texas has increased concern about the potential emergence of CWD in free-ranging deer. The concern is exacerbated because much of the South Texas region is a semi-arid environment with variable rainfall, where precipitation is strongly correlated with fawn recruitment. Further, the marginally productive rangelands, in combination with erratic fawn recruitment, results in populations that are frequently density-independent, and thus sensitive to additive mortality. It is unknown how a deer population in semi-arid regions would respond to the presence of CWD. We used long-term empirical datasets from a lightly harvested (2% annual harvest) population in conjunction with 3 prevalence growth rates from CWD afflicted areas (0.26%, 0.83%, and 2.3% increases per year) via a multi-stage partially deterministic model to simulate a deer population for 25 years under four scenarios: 1) without CWD and without harvest, 2) with CWD and without harvest, 3) with CWD and male harvest only, and 4) with CWD and harvest of both sexes. The modeled populations without CWD and without harvest averaged a 1.43% annual increase over 25 years; incorporation of 2% annual harvest of both sexes resulted in a stable population. The model with slowest CWD prevalence rate growth (0.26% annually) without harvest resulted in stable populations but the addition of 1% harvest resulted in population declines. Further, the male age structure in CWD models became skewed to younger age classes. We incorporated fawn:doe ratios from three CWD afflicted areas in Wisconsin and Wyoming into the model with 0.26% annual increase in prevalence and populations did not begin to decline until ~10%, ~16%, and ~26% of deer were harvested annually. Deer populations in variable environments rely on high adult survivorship to buffer the low and erratic fawn recruitment rates. The increase in additive mortality rates for adults via CWD negatively impacted simulated population trends to the extent that hunter opportunity would be greatly reduced. Our results improve understanding of the potential influences of CWD on deer populations in semi-arid environments with implications for deer managers, disease ecologists, and policy makers.

Life at the top: Long-term demography, microclimatic refugia, and responses to climate change for a high-elevation southern Appalachian endemic plant

Plants existing in small and isolated populations often depend on microclimatic refugia that create local environments buffered from macroclimatic conditions. Currently much effort is devoted toward identifying features that create refugial conditions in the expectation that they will continue to serve as refugia into the future. However, the ability of a refuge to resist macroclimatic change is a biological question, not an abiotic one, since species can persist in these conditions while suffering slow decline. Here we test the ability of current refugial habitats of Geum radiatum, a narrowly endemic perennial herb specializing in cool, humid, high elevation sites, to continue to serve as refugia under present and future climatic conditions. We constructed integral projection models to characterize demography, and macro- and topoclimatic niche models to predict dynamics given climate change through 2070. This species' demography is characterized by high adult survival (about 97% annually), variable growth, frequent flowering, and rare seedling recruitment. Site relative humidity affected survival and reproduction, but predicted population growth rates under current conditions were similar for dry, wet, sheltered, and exposed sites (λ=0.994–0.998). Augmentation by planting 20–70 seedlings annually would raise population growth rates to 1. Demographic modeling under future lower relative humidity predicted further reductions in population growth. Models of the species' macro- and microclimatic niche indicated that all populations had reduced climatic suitability by 2050 or 2080, with 58–83% falling below minimum suitability levels, depending on the climate scenario. G. radiatum's stable demography and habitat protection mean that, barring catastrophes, most populations are not facing extinction under current conditions. However, this species is extremely vulnerable to projected climate change even within its current refugial habitats. This study demonstrates that climate refugia that currently buffer rare species from macroclimatic extremes may not be able to do so under anticipated climate change.

Natal philopatry varies with larval condition in salamanders

An individual’s physiological condition early in ontogeny often regulates natal dispersal and philopatry decisions; however, increased condition promotes dispersal in some organisms and philopatry in others. These disparate findings likely arise from interactions among an individual’s early life stage physiological condition, its likelihood of surviving a dispersal event (i.e., dispersal capacity), and its motivation to leave its natal site (i.e., dispersal propensity). Due to the broad importance of reproductive site selection to population structure and dynamics, studies disentangling these various phenotype-dependent effects are critical. We evaluated the relationships between two aspects of larval physiological condition and natal philopatry in Arizona tiger salamanders (Ambystoma tigrinum nebulosum) in an isolated pond system. In this population, geographic distance between ponds is small, adult survivorship is very high, and thus the likelihood of a successful breeding event should mediate reproductive site selection as opposed to the likelihood of surviving the dispersal event. We found that natal philopatry increased with an estimate of long-term body condition in males, but there was no relationship in females. However, natal philopatry decreased with an estimate of short-term body condition. We also found that an individual’s natal pond had effects on philopatry that influenced both sexes and were independent of the pond’s direct effects on body condition. Together, these findings strongly support the importance of an individual’s early developmental experience in the natal environment to its reproductive behaviors across its lifespan, and further highlight the value of considering how phenotype-dependent dispersal mechanisms may vary between the sexes. Previous research has not discerned a generalizable relationship between larval physiological condition and natal philopatry, likely because of the complex interaction between an individual’s ability (dispersal capacity) and its motivation (dispersal propensity) to reproduce in its natal habitat. Using a salamander population with small inter-pond distances and high adult survival, we isolated the effects of two aspects of physiological condition on dispersal propensity. We found that increased long-term larval physiological condition was associated with natal philopatry in male, but not female, tiger salamanders, as well as differences in philopatry based on natal pond. In contrast, short-term larval physiological condition was negatively associated with philopatry. Our findings suggest an important, long-lasting role of the natal environment on reproductive site selection, and further implicate that the conditions experienced in early development can strongly affect reproductive behaviors across the life cycle.

Feasibility and pitfalls of ex situ management to mitigate the effects of an environmentally persistent pathogen

AbstractEx situ (captive) management can facilitate species recovery, but this approach is invasive and is not universally appropriate. Evidence‐based approaches are critical to determining whether ex situ approaches will be effective, but in many cases biological and ecological data from threatened populations are scarce. We generated a structured set of general biological and social/logistical criteria required for captive management to benefit threatened, free‐ranging populations. We illustrate how these criteria can be applied using a case study where populations are severely threatened, but demographic data are scarce (white‐nose syndrome in Canadian bats). Using (1) population viability modelling (PVA), (2) a survey of Canadian zoos and wildlife rehabilitators, and (3) literature reviews, we identified two of our five initial target species as potential candidates for captive management. PVA revealed that sustainable captive colonies require high adult survivorship relative to free‐ranging populations. Our survey and literature reviews showed that Canadian zoos and wildlife rehabilitators are enthusiastic about bat conservation. However, none could currently maintain the target species, due to limited infrastructure and/or knowledge gaps related to husbandry and reintroduction of captive bats to the wild. Captive management is unlikely to stabilize target populations because released bats risk re‐infection. We conclude that ex situ management is not an appropriate tool in our case study, and would represent ineffective use of available conservation resources. However, development of captive husbandry and re‐introduction methods for hibernating, insectivorous bats would contribute to our global capacity to conserve similar species.

Annual Variation in Breeding Numbers of Two Gull Species in Response to Regional Stock Size and Local Availability of Japanese Sand Lance on Rishiri Island, Northern Japan

Abstract Breeding population abundance such as colony size of seabirds is not generally considered to be particularly sensitive to the annual dynamics of the food conditions because of the long life-span and high adult survival rate. However, in seabird species in which adults decide to breed or not depending on the food conditions, population abundance can respond sensitively to the annual variation in the food conditions. Here, we examine the effects of the regional annual stock abundance of Japanese Sand Lance Ammodytes personatus, and their local temporal availability during the egg-laying period on the size of a Black-tailed Gull Larus crassirostris and Slaty-backed Gull L. schistisagus, breeding colony over 12 years on Rishiri Island, northern Japan. The total number of nests of both gull species increased significantly with the regional annual stock abundance, but not with the local temporal availability of the sand lance. The number of Black-tailed Gull nests without eggs was significantly higher ...

Fledgling survival increases with development time and adult survival across north and south temperate zones

Slow life histories are characterized by high adult survival and few offspring, which are thought to allow increased investment per offspring to increase juvenile survival. Consistent with this pattern, south temperate zone birds are commonly longer‐lived and have fewer young than north temperate zone species. However, comparative analyses of juvenile survival, including during the first few weeks of the post‐fledging period when most juvenile mortality occurs, are largely lacking. We combined our measurements of fledgling survival for eight passerines in South Africa with estimates from published studies of 57 north and south temperate zone songbird species to test three predictions: (1) fledgling survival increases with length of development time in the nest; (2) fledgling survival increases with adult survival and reduced brood size controlled for development time; and (3) south temperate zone species, with their higher adult survival and smaller brood sizes, exhibit higher fledgling survival than north temperate zone species controlled for development time. We found that fledgling survival was higher among south temperate zone species and generally increased with development time and adult survival within and between latitudinal regions. Clutch size did not explain additional variation, but was confounded with adult survival. Given the importance of age‐specific mortality to life history evolution, understanding the causes of these geographical patterns of mortality is important.

Arrested recovery of Diadema antillarum population: Survival or recruitment limitation?

Densities of the long-spined sea urchin Diadema antillarum remain significantly below pre mass-mortality levels at most Caribbean localities. The arrested recovery of this formerly abundant herbivore has been attributed to low supply of recruits and high post settlement mortality. There is, however, some debate as to which of these factors is determinant of the local dynamics of this echinoid. In this study, we use demographic modeling to analyze the contribution of recruitment and post settlement survival on the dynamics of D. antillarum in four localities of Puerto Rico Archipelago. Our results indicate relatively high adult survival, and low stasis but high growth transition in the small individuals. Recruitment rates were low and exhibited high spatial and temporal variability. The four populations exhibited asymptotic growth rates (λ) below 1.0, with λ varying from 0.918 to 0.964. The elasticity analysis showed that the survival of large-sized Diadema can potentially contribute most to the changes in λ for all sites. Numerical projections of the populations indicate that no site would exhibit an increase in density under current recruitment rates, but doubling recruitment would produce an increase in sea urchin density in three of the four sites. Recovery of D. antillarum populations would require the spatial and temporal co-occurrence of high recruitment and survival rates.

Maya paleodemographics: what do we know?

We present a review of what is known about the population dynamics from Classic and Post-Classic Maya settlements in coastal areas of the Yucatan Peninsula such as Jaina, Chac Mool, El Meco and Xcambó and two other urban centers, Palenque and Copan. This contribution discusses the available data on mortality, survival, life expectancy, fertility and migration, obtained by paleodemographic methodology. Data for Xcambó and El Meco were obtained from Tiesler Bloss et al., (2005) and Ortega (2007); information from other sites was obtained from previous work conducted by the authors. This review proposes that the demographic dynamics of the Classical period are typical of densely populated and developing areas with overall average birth rates of six children per woman and a life expectancy at birth of between 20 and 42.2 years, which is equivalent to birth rates above 40 per thousand inhabitants. Post-Classic settlements show evidence of great population mobility with unfavorable changes in living conditions that lead us to think of fertility decrease and low life expectancies at birth. There are indications of a demographic change between the Late-Terminal Classic and Post-Classic periods. Life expectancies are lower than 30 years, a high infant mortality and low adult survival after 50 years is shown. The Post-Classic period is characterized by population rearrangements and mobility. Results obtained for both Chac Mool series showed deterioration in health and reduced life expectancy and fertility levels from one period to another. El Meco and Xcambó series showed differences with Chac Mool's due to higher growth rates.

Age specific survival rates of Steller sea lions at rookeries with divergent population trends in the Russian Far East.

After a dramatic population decline, Steller sea lions have begun to recover throughout most of their range. However, Steller sea lions in the Western Aleutians and Commander Islands are continuing to decline. Comparing survival rates between regions with different population trends may provide insights into the factors driving the dynamics, but published data on vital rates have been extremely scarce, especially in regions where the populations are still declining. Fortunately, an unprecedented dataset of marked Steller sea lions at rookeries in the Russian Far East is available, allowing us to determine age and sex specific survival in sea lions up to 22 years old. We focused on survival rates in three areas in the Russian range with differing population trends: the Commander Islands (Medny Island rookery), Eastern Kamchatka (Kozlov Cape rookery) and the Kuril Islands (four rookeries). Survival rates differed between these three regions, though not necessarily as predicted by population trends. Pup survival was higher where the populations were declining (Medny Island) or not recovering (Kozlov Cape) than in all Kuril Island rookeries. The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there. However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends. High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas.

Individual traits and extrinsic factors influence survival of the threatened pin-tailed sandgrouse (Pterocles alchata) in Europe

Survival and the underlying causes of mortality are key demographic parameters for understanding animal population dynamics and identifying conservation needs. Here we use a large data set of tagged wild pin-tailed sandgrouse (Pterocles alchata) to examine the influence of individual traits (age, sex, size, movements and reproduction), and of temporal and spatial variations on the survival of this steppe-bird of conservation concern in Europe. Annual survival for adults and juveniles was estimated at 0.60 and 0.61, respectively. Survival rate tended to be lower towards the northern margin of the European distribution. In the core distribution area (central Spain) mortality was more frequent during the non-breeding season due to higher predation rates. Survival rate was slightly higher in males than females, which may explain male skewed population sex-ratios. Sedentary birds had lower survival than birds using different areas for breeding and wintering, indicating that high mobility, as a possible behavioural response to varying conditions, could eventually increase fitness. Predation was the main cause of mortality, but illegal hunting was also recorded, indicating a need for stricter law enforcement and regulation plans. Sandgrouse can be characterized by a relatively slow life history (medium–high adult survival and low reproductive rate), with lower survival rates than other sympatric steppe birds of larger size. Management and conservation efforts should focus on maintaining a high adult survival within protected areas. Sandgrouse mobility, which positively influenced survival, should also be taken into account in conservation plans, especially when considering the size and connectivity of protected areas.

Modeling the demography and population dynamics of a subtropical seabird, and the influence of environmental factors

ABSTRACT The use of long-term ecological datasets to explore the importance of the effects of environmental variability on higher predator populations has been focused mainly on high-latitude areas. We modeled the population dynamics of the Westland Petrel (Procellaria westlandica), which spends its time mostly in subtropical waters during both breeding and the interbreeding migration across the Pacific Ocean. We found that the population has slowly increased since the early 1970s, a result of high adult survival, high fecundity (0.6 of all eggs laid survived to fledge) and moderate mean age at first return to the colony (7.7 yr; a recruitment age typical for this genus), strong recruitment rate of juveniles, and negligible emigration. The modeled population trends were supported by similar rates of increase in nest occupancy since 2001 and nest density since 2007. Annual adult survival for breeders was the same for both sexes (0.954, 95% CI: 0.918–0.975) and constant across years. However, nonbreeders ha...